MIT News - Nuclear science and engineering - Laboratory for Nuclear Science http://news.mit.edu/rss/topic/nuclear-engineering MIT News is dedicated to communicating to the media and the public the news and achievements of the students, faculty, staff and the greater MIT community. en Thu, 05 Mar 2020 23:59:59 -0500 Novel method for easier scaling of quantum devices http://news.mit.edu/2020/scaling-quantum-devices-quibits-0306 System “recruits” defects that usually cause disruptions, using them to instead carry out quantum operations. Thu, 05 Mar 2020 23:59:59 -0500 Rob Matheson | MIT News Office http://news.mit.edu/2020/scaling-quantum-devices-quibits-0306 <p>In an advance that may help researchers scale up quantum devices, an MIT team has developed a method to “recruit” neighboring quantum bits made of nanoscale defects in diamond, so that instead of causing disruptions they help carry out quantum operations.</p> <p>Quantum devices perform operations using quantum bits, called “qubits,” that can represent the two states corresponding to classic binary bits — a 0 or 1 — or a “quantum superposition” of both states simultaneously. The unique superposition state can enable quantum computers to solve problems that are practically impossible for classical computers, potentially spurring breakthroughs in biosensing, neuroimaging, machine learning, and other applications.</p> <p>One promising qubit candidate is a defect in diamond, called a nitrogen-vacancy (NV) center, which holds electrons that can be manipulated by light and microwaves. In response, the defect emits photons that can carry quantum information. Because of their solid-state environments, however, NV centers are always surrounded by many other unknown defects with different spin properties, called “spin defects.” When the measurable NV-center qubit interacts with those spin defects, the qubit loses its coherent quantum state — “decoheres”—&nbsp;and operations fall apart. Traditional solutions try to identify these disrupting defects to protect the qubit from them.</p> <p>In a paper published Feb. 25 in <em>Physical Letters Review</em>, the researchers describe a method that uses an NV center to probe its environment and uncover the existence of several nearby spin defects. Then, the researchers can pinpoint the defects’ locations and control them to achieve a coherent quantum state — essentially leveraging them as additional qubits.</p> <p>In experiments, the team generated and detected quantum coherence among three electronic spins — scaling up the size of the quantum system from a single qubit (the NV center) to three qubits (adding two nearby spin defects). The findings demonstrate a step forward in scaling up quantum devices using NV centers, the researchers say. &nbsp;</p> <p>“You always have unknown spin defects in the environment that interact with an NV center. We say, ‘Let’s not ignore these spin defects, which [if left alone] could cause faster decoherence. Let’s learn about them, characterize their spins, learn to control them, and ‘recruit’ them to be part of the quantum system,’” says the lead co-author Won Kyu Calvin Sun, a graduate student in the Department of Nuclear Science and Engineering and a member of the Quantum Engineering group. “Then, instead of using a single NV center [or just] one qubit, we can then use two, three, or four qubits.”</p> <p>Joining Sun on the paper are lead author Alexandre Cooper ’16 of Caltech; Jean-Christophe Jaskula, a research scientist in the MIT Research Laboratory of Electronics (RLE) and member of the Quantum Engineering group at MIT; and Paola Cappellaro, a professor in the Department of Nuclear Science and Engineering, a member of RLE, and head of the Quantum Engineering group at MIT.</p> <p><strong>Characterizing defects</strong></p> <p>NV centers occur where carbon atoms in two adjacent places in a diamond’s lattice structure are missing — one atom is replaced by a nitrogen atom, and the other space is an empty “vacancy.” The NV center essentially functions as an atom, with a nucleus and surrounding electrons that are extremely sensitive to tiny variations in surrounding electrical, magnetic, and optical fields. Sweeping microwaves across the center, for instance, makes it change, and thus control, the spin states of the nucleus and electrons.</p> <p>Spins are measured using a type of magnetic resonance spectroscopy. This method plots the frequencies of electron and nucleus spins in megahertz as a “resonance spectrum” that can dip and spike, like a heart monitor. Spins of an NV center under certain conditions are well-known. But the surrounding spin defects are unknown and difficult to characterize.</p> <p>In their work, the researchers identified, located, and controlled two electron-nuclear spin defects near an NV center. They first sent microwave pulses at specific frequencies to control the NV center. Simultaneously, they pulse another microwave that probes the surrounding environment for other spins. They then observed the resonance spectrum of the spin defects interacting with the NV center.</p> <p>The spectrum dipped in several spots when the probing pulse interacted with nearby electron-nuclear spins, indicating their presence. The researchers then swept a magnetic field across the area at different orientations. For each orientation, the defect would “spin” at different energies, causing different dips in the spectrum. Basically, this allowed them to measure each defect’s spin in relation to each magnetic orientation. They then plugged the energy measurements into a model equation with unknown parameters. This equation is used to describe the quantum interactions of an electron-nuclear spin defect under a magnetic field. Then, they could solve the equation to successfully characterize each defect.</p> <p><strong>Locating and controlling</strong></p> <p>After characterizing the defects, the next step was to characterize the interaction between the defects and the NV, which would simultaneously pinpoint their locations. To do so, they again swept the magnetic field at different orientations, but this time looked for changes in energies describing the interactions between the two defects and the NV center. The stronger the interaction, the closer they were to one another. They then used those interaction strengths to determine where the defects were located, in relation to the NV center and to each other. That generated a good map of the locations of all three defects in the diamond.</p> <p>Characterizing the defects and their interaction with the NV center allow for full control, which involves a few more steps to demonstrate. First, they pump the NV center and surrounding environment with a sequence of pulses of green light and microwaves that help put the three qubits in a well-known quantum state. Then, they use another sequence of pulses that ideally entangles the three qubits briefly, and then disentangles them, which enables them to detect the three-spin coherence of the qubits.</p> <p>The researchers verified the three-spin coherence by measuring a major spike in the resonance spectrum. The measurement of the spike recorded was essentially the sum of the frequencies of the three qubits. If the three qubits for instance had little or no entanglement, there would have been four separate spikes of smaller height.</p> <p>“We come into a black box [environment with each NV center]. But when we probe the NV environment, we start seeing dips and wonder which types of spins give us those dips. Once we [figure out] the spin of the unknown defects, and their interactions with the NV center, we can start controlling their coherence,” Sun says. “Then, we have full universal control of our quantum system.”</p> <p>Next, the researchers hope to better understand other environmental noise surrounding qubits. That will help them develop more robust error-correcting codes for quantum circuits. Furthermore, because on average the process of NV center creation in diamond creates numerous other spin defects, the researchers say they could potentially scale up the system to control even more qubits. “It gets more complex with scale. But if we can start finding NV centers with more resonance spikes, you can imagine starting to control larger and larger quantum systems,” Sun says.</p> An MIT team found a way to “recruit” normally disruptive quantum bits (qubits) in diamond to, instead, help carry out quantum operations. This approach could be used to help scale up quantum computing systems. Image: Christine Daniloff, MITResearch, Computer science and technology, Quantum computing, Nuclear science and engineering, Nanoscience and nanotechnology, Sensors, Research Laboratory of Electronics, Materials Science and Engineering, Physics, School of Engineering Thomas Dupree, professor emeritus of nuclear science and engineering and physics, dies at 86 http://news.mit.edu/2020/thomas-dupree-professor-emeritus-nuclear-science-and-engineering-and-physics-dies-0228 Highly regarded physicist was well-known for studying plasma turbulence in terms of coherent structures. Fri, 28 Feb 2020 11:15:01 -0500 Paul Rivenberg | Plasma Science and Fusion Center http://news.mit.edu/2020/thomas-dupree-professor-emeritus-nuclear-science-and-engineering-and-physics-dies-0228 <p>Thomas H. Dupree, a professor emeritus in both the Department of Nuclear Science and Engineering and the Department of Physics, passed away on Feb. 11 at the age of 86.</p> <p>Focusing on theoretical plasma physics, Dupree was well-known for studying plasma turbulence in terms of coherent structures. Understanding plasma’s unpredictable behavior has been a continuing challenge in the pursuit of fusion energy. Dupree’s articles published in the 1980s and 90s continue to be cited in support of current research.</p> <p>Professor of nuclear science and engineering Ian Hutchinson remembers Dupree as highly regarded among plasma scientists: “He gained a reputation throughout the plasma community as having formidable powers of algebra and analytic theory. He was driven by the intellectual challenge of these very deep theoretical questions.”</p> <p>Born in Santa Monica, California, in 1933, Dupree began his career at MIT as an undergraduate, completing his BS in 1955 and his PhD in physics in 1960. He joined the MIT faculty in 1961, receiving his double appointment as full professor in 1969.</p> <p>Professor emeritus of nuclear science and engineering Kent Hansen met Dupree as a fellow undergraduate physics major at MIT, maintaining a friendship with him through graduate school and later as a professional colleague. He remembers the young Dupree as “very bright, very well-spoken, very reserved but engaged, with a good sense of humor,” as well as being “a superb tennis player.” The two friends acted as ushers for each other’s weddings.</p> <p>Dupree married Andrea Kundsin in 1961. They met at a mixer for students from MIT and Wellesley College, where Kundsin was studying astronomy. She would later earn a PhD in astrophysics from Harvard University, and serve as president of the American Astronomical Society, as well as associate director of the Harvard-Smithsonian Center for Astrophysics.</p> <p>Dupree’s teaching abilities were honored in 1987 with an MIT Graduate Student Council Teaching Award. He retired from teaching one year later at the age of 55, though he continued to do research.</p> <p>In parallel with his academic career, Dupree was engaged in real estate development with his brother, Fred. Their first project in 1962 was 1010 Memorial Drive in Cambridge, Massachusetts, a now-iconic residential tower on the banks of the Charles River. He and his wife lived there themselves until they needed more room for a growing family. Their son, Tom Jr., was born in 1970 and their daughter, Catherine, in 1973.</p> <p>Thomas Dupree is survived by his wife, son, and daughter, and his four grandchildren: Andrew, Caroline, Aoife, and Lochlann. The family has requested that donations in Thomas Dupree’s memory may be made to the MIT Department of Physics.</p> Thomas DupreeImage: C. DupreePlasma Science and Fusion Center, Nuclear science and engineering, Obituaries, Physics, Plasma, Faculty, School of Science, School of Engineering From culinary arts to nuclear engineering http://news.mit.edu/2020/from-culinary-arts-to-nuclear-engineering-0226 Ciara Sivels ’13 takes unusual path to a research career in nuclear engineering for national security. Wed, 26 Feb 2020 15:05:01 -0500 Leda Zimmerman | Department of Nuclear Science and Engineering http://news.mit.edu/2020/from-culinary-arts-to-nuclear-engineering-0226 <p>No one could be more astonished to find Ciara Sivels ’13 where she is today than Ciara Sivels herself. “Never in a million years would I have predicted that I’d be working as a nuclear engineer in a major research laboratory,” says Sivels. “My original dream was to be a pastry chef.”</p> <p>Instead, Sivels, who grew up in rural Virginia, went to MIT and majored in nuclear science and engineering with a focus on nuclear nonproliferation, and a concentration in middle school education. She then earned a PhD from the University of Michigan in nuclear engineering and radiological sciences, where she was the first African-American woman to graduate from this program.</p> <p>Today, Sivels is on staff at the Johns Hopkins University Applied Physics Laboratory (APL), engaged in projects related to national security. While details about her research remain classified, Sivels&nbsp;can&nbsp;reveal that she works on radiation transport simulations focusing on materials effects: “In lay terms, I look at how radiation interacts with and changes the properties of various types of materials.”</p> <p>Sivels’ expertise in this area evolved during her graduate study and national security internships at Pacific Northwest National Laboratory, where she helped develop a unique detection system for radioxenon, a gas linked to explosions from nuclear weapons testing.</p> <p>Although she must maintain a shroud of secrecy around her current work life, Sivels readily shares details of the remarkable journey she has traveled from her home in Hickory, Virginia, to a prestigious national defense lab. It has been a trek marked by some lucky breaks, hard-won battles, a fascination for problem solving, and an abiding passion to give back to others.</p> <p><strong>Not the engineering type</strong></p> <p>“I didn’t have a traditional engineering past,” says Sivels. “I wasn’t interested in tinkering or building things, and I was all over the place in high school, doing things like culinary arts and church-related activities like praise dancing.”</p> <p>No academic subjects resonated with Sivels until she tried chemistry. Her teacher, taking note of both her engagement and good grades, suggested she think about chemical engineering in college. “I was making a list of schools all related to culinary careers, and he was telling me to think about much better colleges, places I’d never heard about.”</p> <p>With her chemistry teacher’s help, she applied to several, including MIT. Unfamiliar with the admissions process, she missed learning about her acceptance on Pi Day. “I assumed I was going to Virginia Commonwealth University when one of my classmates told me to check my email,” she recalls.</p> <p>Sivels was sold on MIT after Campus Preview Weekend. “I thought it would be a great experience to attend a university far away from home,” she says. She also decided to shift her major that weekend, after learning that chemical engineering involved “polymers and plastics and manufacturing things,” which didn’t appeal to Sivels. “My weekend host thought nuclear engineering might be a better match for my interests, and I thought the field seemed really interesting, so I decided to major in it.”</p> <p>Before Sivels officially started, she completed MIT’s <a href="https://ome.mit.edu/programs-services/interphase-edge-empowering-discovery-gateway-excellence">Interphase EDGE</a> program, a summer school that helps admitted students fill academic gaps prior to their first year. “I had previously taken physics, but Interphase made me realize I didn’t know what vectors were, and I wasn’t up to speed on math,” she says. “I struggled, but the program was pivotal for me, because it helped me assimilate to the academics faster than I would have, and introduced me to a new group of friends.”</p> <p>Sivels’ academic challenges were not over, though. “Growing up, learning had come naturally to me, but at MIT, things were really hard for the first time — I felt I might even fail a class,” says Sivels. “It wasn’t until junior year, after learning new study skills, and thinking beyond cookie-cutter solutions, that I could take the tools I was given and really figure out how to solve problems.” Says Sivels, “MIT is where I became myself — a thinker and an engineer.”</p> <p>Her social experiences at MIT also proved formative. “I was thrown into a melting pot full of highly motivated people who held different perspectives from me, and at a human level, I grew.”</p> <p>Part of that growth came from Sivels’ immersion in secondary-school teaching during her undergraduate years. In high school, she routinely tutored younger students, and thought a career in education might ultimately prove rewarding. While earning her NSE degree Sivels pursued a middle school general science teaching degree, and worked directly with students at a Cambridge, Massachusetts, school. “I saw how important it was for students to learn from someone who looked like them — young, black, female — someone they could relate to,” she says.</p> <p><strong>Pushed toward nuclear engineering</strong></p> <p>Sivels pivoted from a teaching career on to the advice of her advisor, Richard K. Lester, then department head and now associate provost. “He knew I wanted to teach, but he told me I hadn’t really given nuclear engineering a chance, that I’d just taken the classes but not tried research,” recalls Sivels, whose summers had exclusively been occupied by teaching internships. Lester pointed her toward opportunities that would “show me what nuclear engineering was really about,” she says. “I was lucky he was my advisor; he changed the course of my career.”</p> <p>One of those opportunities included an internship at Pacific Northwest National Laboratory, just after graduation from MIT. There Sivels became engaged in experimental studies to detect the release of radioxenon gas from underground nuclear weapons testing, an effort driven by the Comprehensive Nuclear Test Ban Treaty. This research expanded to become the foundation of her graduate school studies at the University of Michigan.</p> <p>“I helped develop a novel device to improve monitoring stations all over the world, where detectors run 24/7,” she says. “We fabricated something that could plug and play in existing technology at these stations.”</p> <p>Now at APL, she leverages the knowledge and problem-solving skills she acquired at MIT and Michigan to make “critical contributions to critical challenges that face the nation,” Sivels says. But she also makes contributions in other areas important to her. She was recently named one of the nation’s 125 American Association for the Advancement of Science <a href="https://www.aaas.org/page/ifthen-ambassadors">If/Then ambassadors</a>, an initiative aimed at middle-school girls to further women in STEM fields. Also, she serves as a math mentor for elementary kids. “Working with students is a highlight for me,” she says. “Maybe if they see someone like me doing something they never knew was possible, it might change their lives.”</p> "MIT is where I became myself — a thinker and an engineer," says Ciara Sivels ’13.Photo courtesy of Johns Hopkins University Applied Physics Laboratory.Nuclear science and engineering, School of Engineering, Diversity and inclusion, Alumni/ae, STEM education, Nuclear security and policy, Government, Women in STEM, Mentoring, Profile, Education, teaching, academics The force is strong in neutron stars http://news.mit.edu/2020/force-strong-neutron-stars-0226 Study identifies a transition in the strong nuclear force that illuminates the structure of a neutron star’s core. Wed, 26 Feb 2020 11:39:17 -0500 Jennifer Chu | MIT News Office http://news.mit.edu/2020/force-strong-neutron-stars-0226 <p>Most ordinary matter is held together by an invisible subatomic glue known as the strong nuclear force — one of the four fundamental forces in nature, along with gravity, electromagnetism, and the weak force. The strong nuclear force is responsible for the push and pull between protons and neutrons in an atom’s nucleus, which keeps an atom from collapsing in on itself.</p> <p>In atomic nuclei, most protons and neutrons are far enough apart that physicists can accurately predict their interactions. However, these predictions are challenged when the subatomic particles are so close as to be practically on top of each other.</p> <p>While such ultrashort-distance interactions are rare in most matter on Earth, they define the cores of neutron stars and other extremely dense astrophysical objects. Since scientists first began exploring nuclear physics, they have struggled to explain how the strong nuclear force plays out at such ultrashort distances.</p> <p>Now physicists at MIT and elsewhere have for the first time characterized the strong nuclear force, and the interactions between protons and neutrons, at extremely short distances.</p> <p>They performed an extensive data analysis on previous particle accelerator experiments, and found that as the distance between protons and neutrons becomes shorter, a surprising transition occurs in their interactions. Where at large distances, the strong nuclear force acts primarily to attract a proton to a neutron, at very short distances, the force becomes essentially indiscriminate: Interactions can occur not just to attract a proton to a neutron, but also to repel, or push apart pairs of neutrons.</p> <p>“This is the first very detailed look at what happens to the strong nuclear force at very short distances,” says Or Hen, assistant professor of physicst at MIT. “This has huge implications, primarily for neutron stars and also for the understanding of nuclear systems as a whole.”</p> <p>Hen and his colleagues have published their results today in the journal <em>Nature.</em> His co-authors include first author Axel Schmidt PhD ’16, a former graduate student and postdoc, along with graduate student Jackson Pybus, undergraduate student Adin Hrnjic and additional colleagues from MIT, the Hebrew University, Tel-Aviv University, Old Dominion University, and members of the CLAS Collaboration, a multi-institutional group of scientists involved with the CEBAF Large Accelerator Spectrometer (CLAS), a particle accelerator at Jefferson Laboratory in Newport News, Virginia.</p> <p><strong>Star drop snapshot</strong></p> <p>Ultra-short-distance interactions between protons and neutrons are rare in most atomic nuclei. Detecting them requires pummeling atoms with a huge number of extremely high-energy electrons, a fraction of which might have a chance of kicking out a pair of nucleons (protons or neutrons) moving at high momentum — an indication that the particles must be interacting at extremely short distances.</p> <p>“To do these experiments, you need insanely high-current particle accelerators,” Hen says. “It’s only recently where we have the detector capability, and understand the processes well enough to do this type of work.”</p> <p>Hen and his colleagues looked for the interactions by mining data previously collected by CLAS, a house-sized particle detector at Jefferson Laboratory; the JLab accelerator produces unprecedently high intensity and high-energy beams of electrons. The CLAS detector was operational from 1988 to 2012, and the results of those experiments have since been available for researchers to look through for other phenomena buried in the data.</p> <p>In their new study, the researchers analyzed a trove of data, amounting to some quadrillion electrons hitting atomic nuclei in the CLAS detector. The electron beam was aimed at foils made from carbon, lead, aluminum, and iron, each with atoms of varying ratios of protons to neutrons. When an electron collides with a proton or neutron in an atom, the energy at which it scatters away is proportional to the energy and momentum of the corresponding nucleon.</p> <p>“If I know how hard I kicked something and how fast it came out, I can reconstruct the initial momentum of the thing that was kicked,” Hen explains.</p> <p>With this general approach, the team looked through the quadrillion electron collisions and managed to isolate and calculate the momentum of several hundred pairs of high-momentum nucleons. Hen likens these pairs to “neutron star droplets,” as their momentum, and their inferred distance between each other, is similar to the extremely dense conditions in the core of a neutron star.</p> <p>They treated each isolated pair as a “snapshot” and organized the several hundred snapshots along a momentum distribution. At the low end of this distribution, they observed a suppression of proton-proton pairs, indicating that the strong nuclear force acts mostly to attract protons to neutrons at intermediate high-momentum, and short distances.</p> <p>Further along the distribution, they observed a transition: There appeared to be more proton-proton and, by symmetry, neutron-neutron pairs, suggesting that, at higher momentum, or increasingly short distances, the strong nuclear force acts not just on protons and neutrons, but also on protons and protons and neutrons and neutrons. This pairing force is understood to be repulsive in nature, meaning that at short distances, neutrons interact by strongly repelling each other.</p> <p>“This idea of a repulsive core in the strong nuclear force is something thrown around as this mythical thing that exists, but we don’t know how to get there, like this portal from another realm,” Schmidt says. “And now we have data where this transition is staring us in the face, and that was really surprising.”</p> <p>The researchers believe this transition in the strong nuclear force can help to better define the structure of a neutron star. Hen previously <a href="http://news.mit.edu/2018/neutron-stars-protons-may-do-heavy-lifting-0813">found evidence</a> that in the outer core of neutron stars, neutrons mostly pair with protons through the strong attraction. With their new study, the researchers have found evidence that when particles are packed in much denser configurations and separated by shorter distances, the strong nuclear force creates a repulsive force between neutrons that, at a neutron star’s core, helps keep the star from collapsing in on itself.</p> <p><strong>Less than a bag of quarks</strong></p> <p>The team made two additional discoveries. For one, their observations match the predictions of a surprisingly simple model describing the formation of short-ranged correlations due to the strong nuclear force. For another, against expectations, the core of a neutron star can be described strictly by the interactions between protons and neutrons, without needing to explicitly account for more complex interactions between the quarks and gluons that make up individual nucleons.</p> <p>When the researchers compared their observations with several existing models of the strong nuclear force, they found a remarkable match with predictions from Argonne V18, a model developed by a research group at Argonne National Laboratory, that considered 18 different ways nucleons may interact, as they are separated by shorter and shorter distances.</p> <p>This means that if scientists want to calculate properties of a neutron star, Hen says they can use this particular Argonne V18 model to accurately estimate the strong nuclear force interactions between pairs of nucleons in the core. The new data can also be used to benchmark alternate approaches to modeling the cores of neutron stars.</p> <p>What the researchers found most exciting was that this same model, as it is written, describes the interaction of nucleons at extremely short distances, without explicitly taking into account quarks and gluons. Physicists had assumed that in extremely dense, chaotic environments such as neutron star cores, interactions between neutrons should give way to the more complex forces between quarks and gluons. Because the model does not take these more complex interactions into account, and because its predictions at short distances match the team’s observations, Hen says it’s likely that a neutron star’s core can be described in a less complicated manner.</p> <p>“People assumed that the system is so dense that it should be considered as a soup of quarks and gluons,” Hen explains. “But we find even at the highest densities, we can describe these interactions using protons and neutrons; they seem to keep their identities and don’t turn into this bag of quarks. So the cores of neutron stars could be much simpler than people thought. That’s a huge surprise.”</p> <p>This research was supported, in part, by the Office of Nuclear Physics in the U.S. Department of Energy’s Office of Science.</p> Researchers from MIT and elsewhere have compared “snapshots” of pairs of nucleons separated by various distances, and for the first time observed a key transition in the behavior of the strong nuclear force — the glue that binds the building blocks of matter.Image credit: JLabLaboratory for Nuclear Science, Physics, Stars, Research, Nuclear science and engineering, School of Science, Department of Energy (DoE) A new way to prepare graduate students to lead in tech http://news.mit.edu/2020/new-way-prepare-graduate-students-lead-tech-0226 A new graduate certificate offered through the Bernard M. Gordon-MIT Engineering Leadership Program will launch this fall. Wed, 26 Feb 2020 11:20:01 -0500 School of Engineering http://news.mit.edu/2020/new-way-prepare-graduate-students-lead-tech-0226 <p>Before coming to MIT, Benjamin Lienhard focused most of his energy exploring fragile quantum states, dwelling in the world of nanotechnology and filling in gaps in the research to help steer and stabilize new technologies. Now that he’s a fifth-year graduate student in electrical engineering and computer science, he’s still investigating tiny quantum bits, looking for novel ways to support enormous breakthroughs in quantum computing.</p> <p>But for all his advanced technical knowledge and forward-thinking momentum, Lienhard found himself suddenly in a tenuous state in 2017. Asked to coordinate a conference, he realized developing leadership skills was an aspect of his work that he’d overlooked through all those years investigating quantum states at exceptionally small scales.</p> <p>Not wanting to miss an opportunity, Lienhard accepted the conference role and other leadership roles like it, and each time he agreed to step in to lead, he arrived at the same uneasy conclusion. “I really noticed the only way to improve yourself and learn [leadership] is by actually experiencing it, executing it yourself and seeing how the people around you react to your leadership style,” Lienhard says. A background in theoretical leadership skills could’ve made that transition smoother, recognizing new situations on the job to adjust at a faster pace.</p> <p>Since then, Lienhard has joined the <a href="http://news.mit.edu/2019/gradsage-leadership-engineering-0904">Graduate Student Advisory Group</a> (GradSAGE) in the School of Engineering, a group established by Anantha P. Chandrakasan, dean of the School of Engineering and the Vannevar Bush Professor of Electrical Engineering and Computer Science, to hear from students and bolster initiatives. Through GradSAGE, Lienhard is positioned to help other MIT students. On the GradSAGE Leadership Sub-Committee with engineering graduate students Vamsi Mangena, Laureen Meroueh, Lucio Milanese, Clinton Wang, and Elise Wilcox, he’s provided input that has helped pave the way for a new MIT offering this spring, designed to make those transitions from lab research into leadership roles less of a shock to the system for MIT graduate students<strong>.</strong></p> <p>Becoming a leader is nearly inevitable for engineering students, says Milanese, a fourth-year nuclear science and engineering graduate student. Even for those planning to remain in academia. “In most cases, MIT graduate students will be leading,” Milanese says. “If you become a professor, the first thing you do is set up your lab. You hire a couple graduate students, you hire a couple postdocs, and you are already, early in your 30s, essentially a manager of a small research enterprise.”</p> <p>Meroueh, a fifth-year mechanical engineering graduate student and entrepreneur, puts it another way: “It’s not just our technical skills we need to make a change in the real world.” She became interested in thinking beyond the tech after co-founding a startup company called MetaStorage during her master’s program. She plans to launch a new startup after graduating, and advancing her leadership skills is part of that plan.</p> <p>Recognizing how many engineering graduate students were lacking a leadership program that catered to their future goals, GradSAGE Leadership Sub-Committee approached the Bernard M. Gordon-MIT Engineering Leadership Program (GEL). This led to the creation of a new interim MIT Graduate Certificate in Technical Leadership, which will launch in a permanent form this fall. Completing the certificate requires that students complete a course called Leading Creative Teams and an additional 12 units of graduate leadership courses, plus attendance of four workshops. It’s designed to deliver both leadership theory and practical experience to engineering students by providing technical leadership-focused courses alongside hands-on workshops required to complete the certificate.</p> <p>For engineering students, the GEL courses cover how to conduct multi-stakeholder negotiations, influence others, and provide leadership in the age of artificial intelligence — with coursework all contextualized within tech companies. The program also offers custom paths for graduate students in any program to create a leadership certificate that suits different career goals, with the only required course GEL’s Leading Creative Teams. It’s taught by David Niño, who has been piloting Leading Creative Teams for the past three years. For the GradSAGE students enrolled, taking Niño’s course served as inspiration for building the certificate, and forms its essential core. To complete the additional units, students from any program can choose from dozens of graduate courses from across MIT to build their own certificate, including subjects in building successful careers and organizations; advanced leadership communications; and science, technology, and public policy. “We envision it as being for everybody,” Milanese says of the certificate in technical leadership.</p> <p>This spring, there are six workshops available, <a href="https://gelp.mit.edu/grad-students/graduate-certificate-technical-leadership-interim-requirements" target="_blank">scheduled at different dates and times</a> to accommodate a range of student schedules. Workshops will cover topics like how to deliver objectives in technical organizations, leadership paths in technical organizations, what to do during your first 90 days in a new professional role, and what happens when technical leaders fail to stand up to unrealistic or unethical pressures.</p> <p>“If you want to improve your leadership skills, you need to exercise them in practice,” Lienhard says, adding that the workshops are not simply extensions of these courses, but immersive experiences of their own.</p> <p>In addition to delivering educational value, another goal of the workshops is to build a community among graduate students interested in technical leadership. Meroueh says the workshops present an opportunity to meet students with different engineering backgrounds. “We wanted to create a sense of community,” she says. Their plan seems to be working (or perhaps it’s the free pizza). Earlier this month, Meroueh and Wilcox both attended the first workshop on technical leadership and finance, led by Olivier L. de Weck, professor of aeronautics and astronautics and engineering systems, and faculty co-director of GEL. The workshop drew twice as many attendees as the GradSAGE sub-committee had predicted.</p> <p>Wilcox, a fifth-year graduate student in medical engineering and medical physics, says she left de Weck’s workshop with a fresh perspective on approaching the job market, taking away actionable advice like how to check a company’s financial health before agreeing to come onboard. She also learned how companies make decisions based on finances, a way of thinking she says will help her better pitch her ideas. Citing a need for female leadership in engineering, Meroueh adds that participating in leadership programs can help women navigate to the top in a male-dominated field.</p> <p>To earn the certificate, students must complete four out of six workshops, attendance of which can be spread out over different semesters. The workshops take two hours to complete, with registration required and food and drinks provided to attendees.</p> <p>Although half of engineering graduate students that GradSAGE sub-committee surveyed indicated an interest in a leadership certificate like GEL’s new initiative, two-thirds of respondents were concerned they wouldn’t have time to hone leadership skills during their graduate degree program. Lienhard says for doctoral programs that require minors, the leadership certificate’s courses can be simultaneously used to meet that requirement, which provides the further benefit of acquiring leaderships skills while working closely with an advisor.</p> <p>This spring, an Interim Certificate in Technical Leadership will be available through the Graduate Program in Engineering Leadership. Any eligible courses completed can be retroactively applied once the certificate debuts next fall. For Lienhard, this bundling of tailored courses combined with practical workshops gives MIT graduate students a “less painful” and more productive adjustment period on the path to specific ambitions, so somebody who is gunning to be chief technology officer doesn’t waste time learning insights more appropriate for tomorrow’s next top CEO.</p> <p>Milanese says the first thing the GradSAGE subcommittee did when they met was land on their own definition of leadership, which serves as a simple summation of the wide array of ambitions being pursued by aspiring tech leaders at MIT. According to Milanese, GradSAGE hopes the new certificate instills in graduate students interested in developing leadership skills “the ability to work with others to create great things.”</p> GradSAGE Leadership Sub-Committee members (left to right): Vamsi Mangena, Elise Wilcox, Benjamin Lienhard, Lucio Milanese, Laureen Meroueh, and Clinton WangPhoto: Lillie Paquette/School of EngineeringElectrical engineering and computer science (EECS), Nuclear science and engineering, Mechanical engineering, Leadership, Aeronautical and astronautical engineering, Classes and programs, School of Engineering, GEL Program A material’s insulating properties can be tuned at will http://news.mit.edu/2020/materials-insulating-properties-can-be-tuned-at-will-0224 Most materials have a fixed ability to conduct heat, but applying voltage to this thin film changes its thermal properties drastically. Mon, 24 Feb 2020 14:50:23 -0500 David Chandler | MIT News Office http://news.mit.edu/2020/materials-insulating-properties-can-be-tuned-at-will-0224 <p>Materials whose electronic and magnetic properties can be significantly changed by applying electrical inputs form the backbone of all of modern electronics. But achieving the same kind of tunable control over the thermal conductivity of any material has been an elusive quest.</p> <p>Now, a team of researchers at MIT have made a major leap forward. They have designed a long-sought device, which they refer to as an “electrical heat valve,” that can vary the thermal conductivity on demand. They demonstrated that the material’s ability to conduct heat can be “tuned” by a factor of 10 at room temperature.</p> <p>This technique could potentially open the door to new technologies for controllable insulation in smart windows, smart walls, smart clothing, or even new ways of harvesting the energy of waste heat.&nbsp;</p> <p>The findings are reported today in the journal <em>Nature Materials</em>, in a paper by MIT professors Bilge Yildiz and Gang Chen, recent graduates Qiyang Lu PhD ’18 and Samuel Huberman PhD ’18, and six others at MIT and at Brookhaven National Laboratory.</p> <p>Thermal conductivity describes how well heat can transfer through a material. For example, it’s the reason you can easily pick up a hot frying pan with a wooden handle, because of wood’s low thermal conductivity, but you might get burned picking up a similar frying pan with a metal handle, which has high thermal conductivity.</p> <p>The researchers used a material called strontium cobalt oxide (SCO), which can be made in the form of thin films. By adding oxygen to SCO in a crystalline form called brownmillerite, thermal conductivity increased. Adding hydrogen to it caused conductivity to decrease.</p> <p>The process of adding or removing oxygen and hydrogen can be controlled simply by varying a voltage applied to the material. In essence, the process is electrochemically driven. Overall, at room temperature, the researchers found this process provided a tenfold variation in the material’s heat conduction. Such an order-of-magnitude range of electrically controllable variation has never been seen in any material before, the researchers say.</p> <p>In most known materials, thermal conductivity is invariable — wood never conducts heat well, and metals never conduct heat poorly. As such, when the researchers found that adding certain atoms into the molecular structure of a material could actually increase its thermal conductivity, it was an unexpected result. If anything, adding the extra atoms — or, more specifically, ions, atoms stripped of some electrons, or with excess electrons, to give them a net charge — should make conductivity worse (which, it turned out, was the case when adding hydrogen, but not oxygen).</p> <p>“It was a surprise to me when I saw the result,” Chen says. But after further studies of the system, he says, “now we have a better understanding” of why this unexpected phenomenon happens.</p> <p>It turns out that inserting oxygen ions into the structure of the brownmillerite SCO transforms it into what’s known as a perovskite structure — one that has an even more highly ordered structure than the original. “It goes from a low-symmetry structure to a high-symmetry one. It also reduces the amount of so-called oxygen vacancy defect sites. These together lead to its higher heat conduction,” Yildiz says.</p> <p>Heat is conducted readily through such highly ordered structures, while it tends to be scattered and dissipated by highly irregular atomic structures. Introducing hydrogen ions, by contrast, causes a more disordered structure.</p> <p>“We can introduce more order, which increases thermal conductivity, or we can introduce more disorder, which gives rise to lower conductivity. We could figure this out by performing computational modeling, in addition to our experiments,” Yildiz explains.</p> <p>While the thermal conductivity can be varied by about a factor of 10 at room temperature, at lower temperatures the variation is even greater, she adds.</p> <p>The new method makes it possible to continuously vary that degree of order, in both directions, simply by varying a voltage applied to the thin-film material. The material is either immersed in an ionic liquid (essentially a liquid salt) or in contact with a solid electrolyte, that supplies either negative oxygen ions or positive hydrogen ions (protons) into the material when the voltage is turned on. In the liquid electrolyte case, the source of oxygen and hydrogen is hydrolysis of water from the surrounding air.</p> <p>“What we have shown here is really a demonstration of the concept,” Yildiz explains. The fact that they require the use of a liquid electrolyte medium for the full range of hydrogenation and oxygenation makes this version of the system “not easily applicable to an all-solid-state device,” which would be the ultimate goal, she says. Further research will be needed to produce a more practical version. “We know there are solid-state electrolyte materials” that could theoretically be substituted for the liquids, she says. The team is continuing to explore these possibilities, and have demonstrated working devices with solid electrolytes as well.</p> <p>Chen says “there are many applications where you want to regulate heat flow.” For example, for energy storage in the form of heat, such as from a solar-thermal installation, it would be useful to have a container that could be highly insulating to retain the heat until it’s needed, but which then could be switched to be highly conductive when it comes time to retrieve that heat. “The holy grail would be something we could use for energy storage,” he says. “That’s the dream, but we’re not there yet.”</p> <p>But this finding is so new that there may also be a variety of other potential uses. This approach, Yildiz says, “could open up new applications we didn’t think of before.” And while the work was initially confined to the SCO material, “the concept is applicable to other materials, because we know we can oxygenate or hydrogenate a range of materials electrically, electrochemically” she says. In addition, although this research focused on changing the thermal properties, the same process actually has other effects as well, Chen says: “It not only changes thermal conductivity, but it also changes optical properties.”</p> <p>“This is a truly innovative and novel way for using ion insertion and extraction in solids to tune or switch thermal conductivity,” says Juergen Fleig, a professor of chemical technology and analytics at the University of Vienna, Austria, who was not involved in this work. “The measured effects (caused by two phase transitions) are not only quite large but also bi-directional, which is exciting. I’m also impressed that the processes work so well at room temperature, since such oxide materials are usually operated at much higher temperatures.”</p> <p>Yongjie Hu, an associate professor of mechanical and aerospace engineering at the University of California at Los Angeles, who also was not involved in this work, says “Active control over thermal transport is fundamentally challenging. This is a very exciting study and represents an important step to achieve the goal. It is the first report that has looked in detail at the structures and thermal properties of tri-state phases, and may open up new venues for thermal management and energy applications.”</p> <p>The research team also included Hantao Zhang, Qichen Song, Jayue Wang and Gulin Vardar at MIT, and Adrian Hunt and Iradwikanari Waluyo at Brookhaven National Laboratory in Upton, New York. The work was supported by the National Science Foundation and the U.S. Department of Energy.</p> Researchers found that strontium cobalt oxide (SCO) naturally occurs in an atomic configuration called brownmillerite (center), but when oxygen ions are added to it (right), it becomes more orderly and more heat conductive, and when hydrogen ions are added (left) it becomes less orderly and less heat conductive.Image: courtesy of the researchersMechanical engineering, Nuclear science and engineering, DMSE, Materials Science and Engineering, Research, Energy, Renewable energy, Nanoscience and nanotechnology, School of Engineering Fusor workshop inaugurates nuclear makerspace http://news.mit.edu/2020/mit-fusor-workshop-inaugurates-nuclear-makerspace-0224 Building devices to study fusion at the new (and highly controlled) “MIT Nucleus” makerspace generates enthusiasm — and a purple glow. Mon, 24 Feb 2020 13:30:01 -0500 Paul Rivenberg | Plasma Science and Fusion Center http://news.mit.edu/2020/mit-fusor-workshop-inaugurates-nuclear-makerspace-0224 <p>Willy Burke had never heard of a “fusor.” Until three years ago, the research engineer from MIT’s Plasma Science and Fusion Center (PSFC) was not familiar with the portable device that uses an electric field to accelerate ions to energies high enough to fuse nuclei. These had lately gained popularity as fusion equipment you could “<a href="https://makezine.com/projects/make-36-boards/nuclear-fusor/" target="_blank">build in your basement</a>.” Then he met MIT undergraduate Alex Calburean ’19 and agreed to oversee his research project. With an enthusiastic and knowledgeable student at his side, Burke learned how to build his first fusor, step by step.</p> <p>Now, after IAP 2020, he has guided the successful creation of 14 fusors, in the process inaugurating a new makerspace sponsored by the Department of Nuclear Science and Engineering (NSE), the PSFC, and MIT’s Environment, Health and Safety Office.</p> <p>This nuclear makerspace, dubbed “MIT Nucleus,” was proposed by NSE professors Mike Short and Anne White, head of NSE, as a way of using hands-on learning to nurture student curiosity about the fast-paced, international field of nuclear energy. Because nuclear engineering and plasma science experiments require high voltages, high vacuum, high magnetic fields, and the ability to deal with and measure ionizing radiation, they needed a dedicated and uniquely equipped makerspace — one where, for example, fusors could be built.</p> <p>One of the major issues for a fusor, or any fusion device, is how to keep the hot plasma fuel energized and confined in its container. The PSFC’s <a href="http://www.psfc.mit.edu/sparc" target="_blank">SPARC</a> tokamak is being designed with magnets to keep the fusing plasma in place, a method known as magnetic confinement. The fusor instead confines the plasma with electric fields (inertial electrostatic confinement). Inside a vacuum chamber, a small wire cage with a negative charge is positioned in the center of a larger, grounded cage. When voltage is applied ions are drawn to the center, where they can collide and possibly fuse, creating a purple glow around the wire cage.</p> <p>Alex Calburean reunited with Burke to design the simple IAP fusor, similar to one <a href="https://makezine.com/projects/make-36-boards/nuclear-fusor/" target="_blank">published by <em>Make</em> magazine</a> in 2013. Because the time to build that device was estimated at 20 hours, they broke the job into two parts. The PSFC machine shop would build the launch pad — essentially a bottom flange with connections for the vacuum pump, a pressure gauge, and the gas feed system. The students would build the vacuum chamber, including the top flange with an electrical feed-through, and the fusor grid. Participants worked in teams of two to further economize on the time and space.</p> <p>The six-hour course, which met for two hours a week, offered a Tuesday and a Thursday session. It attracted undergraduates and graduate students from five departments, as well as staff, and even one alumnus, all teaming up and rotating from one work station to the next. Noise levels increased as some participants fashioned the vacuum chamber, using rotary sanders to smooth rough-cut aluminum discs, while others hand-sanded polycarbonate tubes on a series of increasingly fine squares of sandpaper. At other times, students were drilling a hole in the flange for the feed-through that would supply electricity to the grid.</p> <p>Thursday’s class benefited from the way Tuesday’s class managed unforeseen mechanical and technical problems to creating the fusor. “We had vacuum problems and power supply problems the Tuesday class helped solve,” says Burke. “Yeah, they were guinea pigs.”</p> <p>During the final session of both courses, each team was able to produce a glowing plasma in their fusor. Most were also able to take data showing the effects of pressure on plasma voltage and observe the differences between air and deuterium plasmas. The experience provided a taste of the fundamental physics and engineering that supports PSFC fusion projects like SPARC.</p> <p>Burke notes that some in the class had wanted to build fusors in high school but had run into administrative problems or objections. He says that the fusors built during the IAP course are safer because the vacuum is poor and the voltage is relatively low, a nonstarter for neutrons. “If you want to get it to fuse, you have to get a better vacuum and a higher voltage, and before you get to fusion you are generating dangerous amounts of X-rays. That is why the radiation safety office is heavily involved in this space.”</p> <p>With the first real test of the space successfully passed, professors Short and White envision the space will open up opportunities for students in courses across the Institute to propose innovative projects that require “NSE-specific” equipment.</p> <p>“It was very exciting to see the nuclear makerspace coming to life during this IAP course,” comments White. “Our undergraduate program in Course 22 now includes a flexible degree, a <a href="https://neet.mit.edu/" target="_blank">NEET</a> thread, a first-year <a href="https://www.edx.org/school/mitx" target="_blank">MOOC</a>, and many hands-on classes — the nuclear makerspace greatly adds to the unique educational experience that NSE can offer to MIT students.”</p> <p>Participants in the course were enthusiastic about the experience. First-year Kyle Thompson, double-majoring in NSE and mechanical engineering, had been looking for hands-on IAP activities when he came across the fusor opportunity.</p> <p>“I think this was actually my favorite IAP class,” says Thompson, “because there were a lot of different things, from polishing the aluminum to sealing the vacuum. Just a lot of stuff I had never used before. And it was cool, they would say ‘Do you know how to use this,’ and I’d say ‘no’ and they would say, ‘OK, then we’ll show you.’ Instead of taking it out of your hands and doing it for you, they let you do it with them. We did it all in parts; and then operating it and seeing the glow … I was not expecting that whatsoever!”</p> <p>Leanne Galanek, a junior majoring in NSE, was familiar with fusors, having seen one constructed and tested by a group of students in her high school. But she had never built one herself.&nbsp;</p> <p>“I especially enjoyed how we built our fusors using very regular materials and pretty simple techniques, and yet it made a really amazing thing. I think my biggest takeaway was that small maker projects like these are a really good way to learn more about things that interest you, and to bridge the gap between the theoretical and the physical.”</p> <p>Burke agrees. “You probably can’t get it to fuse without doing a lot more work,” he admits, “but you get to see plasma and plasma effects. You get to play with the knobs and actually make real measurements — real science with just a simple device.”</p> At an IAP workshop in the new nuclear makerspace, "MIT Nucleus," participants created fusors, devices that use an electric field to accelerate ions to energies high enough to fuse nuclei, giving off a purple glow. Photo: Paul Rivenberg/PSFCPlasma Science and Fusion Center, Nuclear science and engineering, Physics, Mechanical engineering, Fusion, Plasma, Independent Activities Period, Classes and programs, School of Engineering, School of Science Correcting the “jitters” in quantum devices http://news.mit.edu/2020/correcting-errors-quantum-devices-0218 A new study suggests a path to more efficient error correction, which may help make quantum computers and sensors more practical. Tue, 18 Feb 2020 00:00:00 -0500 David L. Chandler | MIT News Office http://news.mit.edu/2020/correcting-errors-quantum-devices-0218 <p>Labs around the world are racing to develop new computing and sensing devices that operate on the principles of quantum mechanics and could offer dramatic advantages over their classical counterparts. But these technologies still face several challenges, and one of the most significant is how to deal with “noise” — random fluctuations that can eradicate the data stored in such devices.</p> <p>A new approach developed by researchers at MIT could provide a significant step forward in quantum error correction. The method involves fine-tuning the system to address the kinds of noise that are the most likely, rather than casting a broad net to try to catch all possible sources of disturbance.</p> <p>The analysis is described in the journal <em>Physical Review Letters</em>, in a paper by MIT graduate student David Layden, postdoc Mo Chen, and professor of nuclear science and engineering Paola Cappellaro.</p> <p>“The main issues we now face in developing quantum technologies are that current systems are small and noisy,” says Layden. Noise, meaning unwanted disturbance of any kind, is especially vexing because many quantum systems are inherently highly sensitive, a feature underlying some of their potential applications.</p> <p>And there’s another issue, Layden says, which is that quantum systems are affected by any observation. So, while one can detect that a classical system is drifting and apply a correction to nudge it back, things are more complicated in the quantum world. “What's really tricky about quantum systems is that when you look at them, you tend to collapse them,” he says.</p> <p>Classical error correction schemes are based on redundancy. For example, in a communication system subject to noise, instead of sending a single bit (1 or 0), one might send three copies of each (111 or 000). Then, if the three bits don’t match, that shows there was an error. The more copies of each bit get sent, the more effective the error correction can be.</p> <p>The same essential principle could be applied to adding redundancy in quantum bits, or “qubits.” But, Layden says, “If I want to have a high degree of protection, I need to devote a large part of my system to doing these sorts of checks. And this is a nonstarter right now because we have fairly small systems; we just don’t have the resources to do particularly useful quantum error correction in the usual way.” So instead, the researchers found a way to target the error correction very narrowly at the specific kinds of noise that were most prevalent.</p> <p>The quantum system they’re working with consists of carbon nuclei near a particular kind of defect in a diamond crystal called a nitrogen vacancy center. These defects behave like single, isolated electrons, and their presence enables the control of the nearby carbon nuclei.</p> <p>But the team found that the overwhelming majority of the noise affecting these nuclei came from one single source: random fluctuations in the nearby defects themselves. This noise source can be accurately modeled, and suppressing its effects could have a major impact, as other sources of noise are relatively insignificant.</p> <p>“We actually understand quite well the main source of noise in these systems,” Layden says. “So we don't have to cast a wide net to catch every hypothetical type of noise.”</p> <p>The team came up with a different error correction strategy, tailored to counter this particular, dominant source of noise. As Layden describes it, the noise comes from “this one central defect, or this one central ‘electron,’ which has a tendency to hop around at random. It jitters.”</p> <p>That jitter, in turn, is felt by all those nearby nuclei, in a predictable way that can be corrected.</p> <p>“The upshot of our approach is that we’re able to get a fixed level of protection using far fewer resources than would otherwise be needed,” he says. “We can use a much smaller system with this targeted approach.”</p> <p>The work so far is theoretical, and the team is actively working on a lab demonstration of this principle in action. If it works as expected, this could make up an important component of future quantum-based technologies of various kinds, the researchers say, including quantum computers that could potentially solve previously unsolvable problems, or quantum communications systems that could be immune to snooping, or highly sensitive sensor systems.</p> <p>“This is a component that could be used in a number of ways,” Layden says. “It’s as though we’re developing a key part of an engine. We’re still a ways from building a full car, but we’ve made progress on a critical part.”</p> <p>"Quantum error correction is the next challenge for the field," says Alexandre Blais, a professor of physics at the University of Sherbrooke, in Canada, who was not associated with this work. "The complexity of current quantum error correcting codes is, however, daunting as they require a very large number of qubits to robustly encode quantum information."</p> <p>Blais adds, "We have now come to realize that exploiting our understanding of the devices in which quantum error correction is to be implemented can be very advantageous.&nbsp;This work makes an important contribution in this direction by showing that a common type of error can be corrected for in a much more efficient manner than expected. For quantum computers to become practical we need more ideas like this.​"</p> <p>The research was supported by the U.S. Army Research Office and the National Science Foundation.</p> In a diamond crystal, three carbon atom nuclei (shown in blue) surround an empty spot called a nitrogen vacancy center, which behaves much like a single electron (shown in red). The carbon nuclei act as quantum bits, or qubits, and it turns out the primary source of noise that disturbs them comes from the jittery “electron” in the middle. By understanding the single source of that noise, it becomes easier to compensate for it, the researchers found.Image: David LaydenStudents, Research, Graduate, postdoctoral, School of Engineering, Nuclear science and engineering, Quantum computing, Research Laboratory of Electronics, Nanoscience and nanotechnology, National Science Foundation (NSF) Analyce Hernandez: Uncloaking big mysteries http://news.mit.edu/2020/analyce-hernandez-uncloaking-big-mysteries-0212 Junior double major seeks to piece together puzzles of the universe, particle by particle. Wed, 12 Feb 2020 16:10:01 -0500 Leda Zimmerman | Department of Nuclear Science and Engineering http://news.mit.edu/2020/analyce-hernandez-uncloaking-big-mysteries-0212 <p>For Analyce Hernandez, there are few greater pleasures than venturing into the unknown. Take her experience during January’s Independent Activities Period, for instance. Hernandez, a double major in Course 8 (physics) and Course 22-ENG (nuclear science and engineering), signed up for “Build your own Fusor,” a class taught by Research Engineer William M. Burke Jr. of the MIT Plasma Science and Fusion Center.</p> <p>“I had no idea what the outcome would be of trying to make my own mini-fusion reactor, but the project was hands-on and high-voltage,” recalls Hernandez. “Nuclides were smashing into each other and producing plasma with different colors — it was a lot of fun, and I loved it.”</p> <p>Hernandez’s joyful pursuit of novel learning experiences has powered her personal and academic journey, and lent her resilience during some challenging times.</p> <p><strong>A flexible second major</strong></p> <p>Last year, as a sophomore, Hernandez was among the first students to sign up for&nbsp;22-ENG, a new nuclear science and engineering program that offers a more flexible path for students interested in the field.</p> <p>“At a dorm event, an upperclassman described the versatility of Course 22, with its inclusion of subjects like medicine and materials science, which I found very attractive,” says Hernandez, who had arrived at MIT determined to major in physics, but also interested in a supplementary area of study.</p> <p>Then, after taking 22.01 (Introduction to Nuclear Engineering and Ionizing Radiation), taught by&nbsp;<a href="http://web.mit.edu/nse/people/faculty/short.html">Michael Short</a>, Class of ’42 Associate Professor of Nuclear Science and Engineering, Hernandez was hooked by the field. The emergence of the new 22-ENG flex degree, which allowed her to incorporate classes relevant to her core physics interest, particle physics, made a double major possible.</p> <p>Between physics and her 22-ENG concentration in quantum science, Hernandez is investigating some very fundamental questions. “In quantum mechanics class, we try to understand how particles work together in bizarre ways, using probabilities to think about how the universe works,” she says. “The ambiguity of quantum mechanics can be confusing or frustrating, but looking at the world this way is also almost beautiful.”</p> <p><strong>Detecting dark matter</strong></p> <p>Hernandez has just begun an Undergraduate Research Opportunities Program (UROP) project that seems a perfect match for her keen curiosity about the workings of the universe. She will be assisting on an experiment called GAPS (for General AntiParticle Spectrometer), which will fly a balloon high over the Antarctic in 2021 to detect particles of dark matter. GAPS is the product of an international consortium of universities and other research institutions; the MIT contingent is led by Kerstin Perez, Class of 1948 Career Development Assistant Professor of Physics.</p> <p>“Dark matter is a big mystery, a black blob of mass out in space that we know must be there, but somehow remains concealed,” says Hernandez. The main goal of the project is to identify and measure what may be indicators of dark matter — low-energy cosmic-ray antinuclei — such as antideuterons, antiprotons and antihelium. The GAPS balloon tracker, powered by solar panels during the Antarctic’s endless summer days, carries technology that can capture these particles. “In the experiment, the particle will strike the balloon, slow down, direct its energy into a detector and create an exotic atom before it decays away, releasing X-rays,” says Hernandez.</p> <p>During spring semester and next summer, Hernandez will do the painstaking work of calibrating thousands of detectors that will be borne aloft by the balloon. “The technology requires individual testing, to ensure detectors achieve the kind of fine sensitivity and efficiency required,” she says.</p> <p><strong>Boosting MIT and mental health</strong></p> <p>While the UROP and her double major demand a significant portion of her waking hours, Hernandez remains committed to a job she assumed when she first arrived at MIT. First as a caller, and now a call center supervisor, she reaches out to MIT alumni to help raise funds for the Institute. “I like talking to people and hearing their stories, and my passion for MIT reminds them about what they got out of being here, so I’m paying it forward so future students have the same opportunities,” she says.</p> <p>Hernandez describes falling in love with MIT at her first visit during a Weekend Immersion in Science and Engineering, a program for students of color and of low socioeconomic means. Her Pittsburgh-based parents, both high school drop outs, encouraged her ambition to pursue science, and particularly physics, wherever it led. As a first-generation college student, though, things did not come easy for Hernandez.</p> <p>“It was really hard to be away from my family, and faced with coursework that was very difficult for me, I tried to brute-force my way through everything,” she says. Before MIT, she had been diagnosed with depression and anxiety, which made this first year even more trying. But by drawing on support from MIT’s health and counseling system, and learning to ask for help from academic mentors, she cleared a path forward.</p> <p>Today, as a member of the Active Minds Club, Hernandez gets the word out to fellow students: “The mental-health help I received made it possible for me to do all the things I do here, and thrive,” she says. “It’s important that those top-of-class high school kids who might feel overwhelmed and stressed out here know not to feel shame or guilt, and that there are resources here for them.”</p> <p>For Hernandez, an important pressure valve is movie watching. She has taken two film courses at MIT, but really loves kicking back and screening horror films on Netflix. “I especially love Wes Craven’s&nbsp;Scream&nbsp;series, where they’re aware of clichés, and break the fourth wall so there’s a lot of parody,” she says.</p> <p>With a life full of classwork, jobs, extracurriculars, and research projects, Hernandez contemplates a post-graduate future in academia, one that will give her regular opportunities for experimentation. “Assuming I continue to graduate school, I think I would like to be involved in a research effort, like the one I’m working on in dark matter, where I uncloak big mysteries and discover something fundamental about the way the universe works.”</p> “Assuming I continue to graduate school, I think I would like to be involved in a research effort," says MIT junior Analyce Hernandez, "like the one I’m working on in dark matter, where I uncloak big mysteries and discover something fundamental about the way the universe works.”Photo: Gretchen ErtlNuclear science and engineering, Plasma Science and Fusion Center, Physics, Independent Activities Period, Undergraduate Research Opportunities Program (UROP), School of Engineering, Students, Undergraduate, Plasma Aron Bernstein, professor emeritus of physics, dies at 88 http://news.mit.edu/2020/aron-bernstein-professor-emeritus-physics-dies-0203 Bernstein was a member of the Hadronic Physics Group in the Laboratory for Nuclear Science, and a longtime anti-nuclear weapons activist. Mon, 03 Feb 2020 16:50:01 -0500 Sandi Miller | Department of Physics http://news.mit.edu/2020/aron-bernstein-professor-emeritus-physics-dies-0203 <p>Aron Bernstein, professor emeritus of physics and longtime anti-nuclear proliferation activist, died on Jan. 14 after a short battle with cancer. He was 88.</p> <p>Aron Bernstein joined MIT in 1961, and taught a broad range of physics courses from first-year to graduate level for 40 years. A member of <a href="http://web.mit.edu/lns/research/hpg.html" target="_blank">The Hadronic Physics Group</a> in the Laboratory for Nuclear Science, his research was in intermediate energy physics, including nuclear and particle physics, with an emphasis on studying the basic structure of matter. He was also active in the anti-nuclear weapons movement with the <a href="https://livableworld.org/" target="_blank">Council for a Livable World</a>, the&nbsp;<a href="https://en.wikipedia.org/wiki/Union_of_Concerned_Scientists" target="_blank" title="Union of Concerned Scientists">Union of Concerned Scientists</a>, and the <a href="https://nuclearweaponsedproj.mit.edu/" target="_blank">Nuclear Weapons Education Project.</a></p> <p>“Aron was one of those rare beings — a thoughtful scholar, a good and cheerful person, and someone who worked with a lightness of being to make the world a better place,” said Jim Walsh, a senior research associate in MIT’s <a href="https://ssp.mit.edu/">Security Studies Program</a><strong>, </strong>who worked with Aron in the classroom and<strong> </strong>on the board of the Council for a Livable World<strong>. </strong>“He was a gentle soul, but also a persistent, if humble, instigator.&nbsp;He had a deep commitment and boundless energy for university students and for efforts to eliminate nuclear weapons.”</p> <p>Born April 6, 1931, he grew up in Brooklyn and Queens, the son of Abraham and Lillian (Dashevsky) Bernstein, and the older brother of Grace. His father owned an engraving business specializing in mercury-and-glass thermometers. A physics major at Queens College, he was inspired by his professor Banesh Hoffman, who had worked with Albert Einstein. Bernstein recalled Hoffman promising an instant A if the class could solve a difficult math problem. “Aron and one of his friends worked on it for days,” recalled Bernstein’s wife, Susan Goldhor. “They took it very seriously and they actually came up with a solution. I don’t know if he got an A, but from the professor’s viewpoint there was an elegant solution, and theirs was a cobbled-together solution. Aron was like that, he would work on something and would not give up.”</p> <p>However, Bernstein was stumped by foreign languages, which was a requirement, so he switched to Union College, where he received a bachelor’s in physics in 1953. He then pursued his doctorate at the University of Pennsylvania, where he recalled a memorable colloquium featuring MIT Professor Victor “Viki” Weisskopf. “His physical intuition made a vivid impression on me, and I still remember him rubbing his fingers together to show his pleasure at getting to the nub of things,” said Bernstein.</p> <p>After receiving his PhD in 1958, Bernstein became a postdoc at Princeton University. He recalled asking his advisor Donald Hamilton to let him attend a summer program on nuclear physics in Colorado that featured Weisskopf. “I decided to present&nbsp;a project&nbsp;I’d done with my fellow postdoc Max Brennan,” Bernstein recalled. “I remember pacing the streets the evening before, wondering what Viki would ask me. After a few hours pacing around, I realized that Viki would say, ‘Very nice, but please explain how it works.’ I would then smile and explain on my fingers. Amazingly, that’s exactly what happened.”</p> <p>Soon after, Bernstein was drawn to interview at MIT. “He sort of fell in love with MIT and Cambridge,” recalled his wife. “He had a dream that was linked to MIT, where he was on the subway and every single person had a white coat and was a scientist.” &nbsp;</p> <p>He started in 1961 as an assistant professor of physics, and used accelerators around the world to study the structure of atomic nuclei by looking at reactions started by beams of particle accelerators. His first accelerator at MIT was the Markle cyclotron, an atom-smasher built in 1938 for nuclear and medical research, and newly refurbished. Bernstein saw it as an underutilized workhorse, and used its 30 MeV alpha particle beam to perform low-energy nuclear physics experiments. “We could get a lot of experiments done with the cyclotron,” he said. “We were quite active using a solid-state detector, so we had decent resolution. We made a lot of physics hay, so to speak, with this beam.” &nbsp;</p> <p>When Bernstein and four others came up for tenure in the mid-’70s, he had Weisskopf in his corner. “All four (other) physics candidates for promotion that year were turned down, but I was the one Viki successfully fought for,” recalled Bernstein.</p> <p>Bernstein was an experimental nuclear scientist but also worked on the theoretical side of physics. He collaborated with multiple laboratories at home and abroad, including France as a Guggenheim fellow, Germany as a Humboldt fellow, and in an exchange program with the physics and political science departments at Oxford’s Baliol College.</p> <p>“He covered a lot of ground,” said his colleague, professor of physics Robert Redwine. “He was highly esteemed.” Redwine and Bernstein wrote papers together, and alternated on round-the-clock shifts for weeks during accelerator experiments, most often at the former <a href="http://web.mit.edu/lns/research/bates.html" target="_blank">Bates Linear Accelerator Center</a> in Middleton, Massachusetts. “We would work rather intensely together,” Redwine said.&nbsp;</p> <p>Bernstein organized an internationally recognized chiral dynamics workshop in 1994. After the first two workshops, he stepped back to serve on its advisory committee. “He spent a lot of time to make sure it was useful, not just a bunch of senior people talking, and it was so successful they are still held every three years,” said Susan. “His attitude was ‘Let the young people run it.’ Some people are always angling to be senior author or to get more credit. Aron didn’t care about that. He only cared about the physics and mentoring young people.”</p> <p>Bernstein’s family used to tease him for not winning a Nobel prize like many of his physics colleagues. But as the saying goes, to be rich in friends is to be poor in nothing. And Bernstein had a talent for making friends among colleagues, students, and others around the world. After his death, Susan received condolence emails from many of Bernstein’s former students and colleagues, and they all expressed how much he had touched their lives.</p> <p>“Aron was the colleague I talked the most with about physics and also learned from the most about science,” said one former colleague, Haiyan Gao. “Aron's passion for physics is contagious and tremendously inspiring. He has always been so nurturing to young scientists and extremely generous in sharing his physics insight, knowledge, and wisdom.”</p> <p>“He was a dedicated classroom teacher who knew what he was talking about,” said Redwine. “He really liked to connect to people. He was good at making what he was saying relevant to you.”</p> <p>Victor F. Weisskopf Professor of Physics Alan Guth was an MIT first-year in 1964 when he took Bernstein’s 8.01 class, and he also chose Bernstein for his junior lab 8.14 (Experimental Physics II). That project extended into a senior thesis, and then a master's thesis.&nbsp;“From the beginning of this project, Aron made me feel for the first time like I was a physicist, and not just a student,” said Guth.&nbsp;“He always made the people he was speaking to feel important. When I was still an undergraduate, but had started working with him, he always invited me to the meetings of his research group, treating me like any other member of the group.”</p> <p>Bernstein’s former grad student and Jefferson Lab worker Peter Bosted recalled Bernstein’s “twinkle in his eye” and his generosity with his time. Bernstein’s former grad student Itaru Nakagawa said that “research with Aron was a joy for me.” Bernstein’s postdoc Cesar Fernandez-Ramirez said, “Aron became a mentor to me and showed me how I should conduct myself as a scientist and a human being. The world is a better place, thanks to people like him.”</p> <p>Bernstein was a member of Phi Beta Kappa and Sigma Xi, and a fellow of the American Physical Society and the American Association for the Advancement of Science. He retired from the physics department in 2001 after 40 years.</p> <p><strong>Nuclear arms control activist</strong></p> <p>Bernstein never retired from keeping an eye on the hands of the Doomsday Clock. “The disarmament project is his capstone project, because it married his political and research passions,” said his son, Dan Bernstein MCP ’86. “He was really a peace activist.”</p> <p>Among those he teamed up with were fellow peace advocates Weisskopf and Phil Morrison, both Manhattan Project veterans; future Nobel laureate and professor of physics Henry Kendall; microbiologist Salvador “Salva”&nbsp;Luria; Center for Theoretical Physics&nbsp;founder Herman Feshbach; and professor of linguistics Noam Chomsky.</p> <p>“I was always aware of the fact that if I had been 20 years older, I would have been in the Manhattan Project,” Bernstein said. “I was fortunate in my career to have worked closely with, and to have been inspired by, three such extraordinary people as Viki, Salva, and Phil. I regularly got phone calls from Salva commanding me to “get&nbsp;your head out of the cyclotron and come to my office and do something important. Viki … was a tremendous sounding board and a moral force that I greatly benefitted from.”</p> <p>In 1969, Bernstein helped form the&nbsp;Union of Concerned Scientists and participated in its “Scientists Strike for Peace,” which disrupted research and classes to protest U.S. and MIT involvement in the Vietnam War. The strike led MIT to the divestment of the Instrumentation Laboratory (now Draper Laboratory), a U.S. Department of Defense contractor.</p> <p>“The organizers were distressed, on the one hand, with the low level of political engagement of the scientific community, and more specifically with the role of military research on university campuses,” Bernstein wrote in a <a href="https://web.mit.edu/fnl/volume/314/king_bernstein.html">50-year retrospective</a> on the strike.</p> <p>Years later, Bernstein joined a similar campaign to reject research funds for work related to President Ronald Reagan’s “Star Wars” space-based missile defense system.</p> <p>He served on the National Advisory Board of the Council for a Livable World, an organization aimed at educating Congress on issues of arms control. “He was quick to offer advice, and just as quick to offer and provide help,” said Executive Director John Tierney.</p> <p>Bernstein chaired a Federation of American Scientists chapter at MIT and the MIT Faculty Disarmament Study Group, and was the advisor to a student group on arms control, MIT’s <a href="http://globalzero.mit.edu/">Global Zero</a>.</p> <p>Bernstein and his contemporaries grew up prepared for a Russian nuclear attack, practicing classroom duck-and-cover exercises, and working in buildings set up with basement bomb shelters. But he soon became aware that his post-Cold War students didn’t quite understand this nuclear threat. He gathered a group of volunteers, including Redwine and Los Alamos weapons program veteran Mike Hynes, to launch the <a href="http://nuclearweaponsedproj.mit.edu/">Nuclear Weapons Education Project</a>. The idea was to supplement curriculums to increase nuclear-weapon literacy, and to set up a website to share information.</p> <p>In his final years, Bernstein continued to visit universities, and cultivated a network of physicists around the country on behalf of this project. “We were still having meetings and discussions on this a few months ago,” said Redwine. “It became more difficult for him because of health reasons, but he was still involved.” Guth added that Bernstein possessed an “inexhaustible concern for helping to make the world a better place.”</p> <p><strong>Family life</strong></p> <p>Bernstein married Marlene Reshall in 1956, and raised two children, Dan and Amy. The couple divorced in 1975.</p> <p>His family benefited from Bernstein’s ability to combine his work with travel and a love of the outdoors. In 1968, he took them on his sabbaticals to France and New Mexico. When China opened up to the West in the late ’70s, he not only wanted to make connections with Chinese physicists, he took Dan with him, with detours to Japan, India, Germany, and England. Wherever he traveled for work, he’d find a spot to go hiking. He enjoyed living in Cambridge, Massachusetts, so he could bike to work and take his family sailing on the MIT boats, and family time was spent snowshoeing, cross-country skiing, or sailing.</p> <p>Bernstein met second wife Susan Goldhor through mutual friends. “I thought he was kind of cute and had a really nice smile,” she recalled. Susan, a biologist with an interest in mycology, recalled Bernstein joking that “I did mushrooms, and he did mushroom clouds.” On their first date, they hiked the White Mountains. Then they planned a longer hike. “I didn’t have the right socks, and I got blisters. These were big hikes every day. I was really having a hard time, I was in pain, I was exhausted, and so I complained to Aron about this. Aron hated whiners, so he wrote me a letter afterward that it wasn’t going to work out, that he wasn’t going to deal with whiners. He was a very, very straightforward person — he didn’t play games.”</p> <p>She convinced him that she wasn’t actually a whiner, and he took her to a Mozart concert at Jordan Hall. Bernstein loved music, “nothing later than Schubert, and preferably a lot earlier— I couldn’t get him to go to a Mahler concert.” They married in 1990. Hiking was a shared passion, and they bought a vacation home in the White Mountains. “We hiked in summer, fall, and winter — I remember hiking in a blizzard. Until Aron was 86, we were still hiking and snowshoeing together. The hikes got shorter but the pleasure was still there.”</p> <p>And he was still biking into MIT until the last couple of years, to work on his anti-nuclear projects or meet with friends.</p> <p>Bernstein “was the kind of person to whom it is quite difficult to say no, even when you should,” said Walsh. “He cared about you, the person sitting across from him in his office, and cared about the fate of humanity, and both are the better for it.”</p> <p>“Aron was certainly one of the most wonderful people I've known,” said Guth.&nbsp;“His dedication to helping to build a better world was unbounded.”</p> <p>Bernstein is survived by his wife, Susan Goldhor; daughter Amy Bernstein; son Dan Bernstein and daughter-in-law Efrat Levy; and three granddaughters, Dara, Meirav, and Tali. &nbsp;</p> <p>The Department of Physics is planning a memorial celebration later this year in honor of Aron Bernstein.</p> Aron Bernstein in 2015, on the fire tower at the top of Mt. Chocorua in New HampshirePhoto courtesy of the Bernstein family.Physics, Obituaries, Laboratory for Nuclear Science, Faculty, School of Science, Government, STEM education, Education, teaching, academics" New electrode design may lead to more powerful batteries http://news.mit.edu/2020/solid-batteries-lithium-metal-electrode-0203 An MIT team has devised a lithium metal anode that could improve the longevity and energy density of future batteries. Mon, 03 Feb 2020 10:59:59 -0500 David L. Chandler | MIT News Office http://news.mit.edu/2020/solid-batteries-lithium-metal-electrode-0203 <p>New research by engineers at MIT and elsewhere could lead to batteries that can pack more power per pound and last longer, based on the long-sought goal of using pure lithium metal as one of the battery’s two electrodes, the anode. &nbsp;</p> <p>The new electrode concept comes from the laboratory of Ju Li, the Battelle Energy Alliance Professor of Nuclear Science and Engineering and professor of materials science and engineering. It is described today in the journal <em>Nature</em>, in a paper co-authored by Yuming Chen and Ziqiang Wang at MIT, along with 11 others at MIT and in Hong Kong, Florida, and Texas.</p> <p>The design is part of a concept for developing safe all-solid-state batteries, dispensing with the liquid or polymer gel usually used as the electrolyte material between the battery’s two electrodes. An electrolyte allows lithium ions to travel back and forth during the charging and discharging cycles of the battery, and an all-solid version could be safer than liquid electrolytes, which have high volatilility and have been the source of explosions in lithium batteries.</p> <p>“There has been a lot of work on solid-state batteries, with lithium metal electrodes and solid electrolytes,” Li says, but these efforts have faced a number of issues.</p> <p>One of the biggest problems is that when the battery is charged up, atoms accumulate inside the lithium metal, causing it to expand. The metal then shrinks again during discharge, as the battery is used. These repeated changes in the metal’s dimensions, somewhat like the process of inhaling and exhaling, make it difficult for the solids to maintain constant contact, and tend to cause the solid electrolyte to fracture or detach.</p> <p>Another problem is that none of the proposed solid electrolytes are truly chemically stable while in contact with the highly reactive lithium metal, and they tend to degrade over time.</p> <p>Most attempts to overcome these problems have focused on designing solid electrolyte materials that are absolutely stable against lithium metal, which turns out to be difficult.&nbsp; Instead, Li and his team adopted an unusual design that utilizes two additional classes of solids, “mixed ionic-electronic conductors” (MIEC) and “electron and Li-ion insulators” (ELI), which are absolutely chemically stable in contact with lithium metal.</p> <p>The researchers developed a three-dimensional nanoarchitecture in the form of a honeycomb-like array of hexagonal MIEC tubes, partially infused with the solid lithium metal to form one electrode of the battery, but with extra space left inside each tube. When the lithium expands in the charging process, it flows into the empty space in the interior of the tubes, moving like a liquid even though it retains its solid crystalline structure. This flow, entirely confined inside the honeycomb structure, relieves the pressure from the expansion caused by charging, but without changing the electrode’s outer dimensions or the boundary between the electrode and electrolyte. The other material, the ELI, serves as a crucial mechanical binder between the MIEC walls and the solid electrolyte layer.</p> <p>“We designed this structure that gives us three-dimensional electrodes, like a honeycomb,” Li says. The void spaces in each tube of the structure allow the lithium to “creep backward” into the tubes, “and that way, it doesn’t build up stress to crack the solid electrolyte.” The expanding and contracting lithium inside these tubes moves in and out, sort of like a car engine’s pistons inside their cylinders. Because these structures are built at nanoscale dimensions (the tubes are about 100 to 300 nanometers in diameter, and tens of microns in height), the result is like “an engine with 10 billion pistons, with lithium metal as the working fluid,” Li says.</p> <p>Because the walls of these honeycomb-like structures are made of chemically stable MIEC, the lithium never loses electrical contact with the material, Li says. Thus, the whole solid battery can remain mechanically and chemically stable as it goes through its cycles of use. The team has proved the concept experimentally, putting a test device through 100 cycles of charging and discharging without producing any fracturing of the solids.</p> <p><img alt="" src="/sites/mit.edu.newsoffice/files/images/anodes-cathodes.gif" style="width: 500px; height: 440px;" /></p> <p><em><span style="font-size:10px;">Reversible Li metal plating and stripping in a carbon tubule with&nbsp;an inner diameter of 100nm. Courtesy of the researchers.</span></em></p> <p>Li says that though many other groups are working on what they call solid batteries, most of those systems actually work better with some liquid electrolyte mixed with the solid electrolyte material. “But in our case,” he says, “it’s truly all solid. There is no liquid or gel in it of any kind.”&nbsp;&nbsp;</p> <p>The new system could lead to safe anodes that weigh only a quarter as much as their conventional counterparts in lithium-ion batteries, for the same amount of storage capacity. If combined with new concepts for lightweight versions of the other electrode, the cathode, this work could lead to substantial reductions in the overall weight of lithium-ion batteries. For example, the team hopes it could lead to cellphones that could be charged just once every three days, without making the phones any heavier or bulkier.</p> <p>One new concept for a lighter cathode was described by another team led by Li, in a paper that appeared last month in the journal <em>Nature Energy</em>, co-authored by MIT postdoc Zhi Zhu and graduate student Daiwei Yu. The material would reduce the use of nickel and cobalt, which are expensive and toxic and used in present-day cathodes. The new cathode does not rely only on the capacity contribution from these transition-metals in battery cycling. Instead, it would rely more on the redox capacity of oxygen, which is much lighter and more abundant. But in this process the oxygen ions become more mobile, which can cause them to escape from the cathode particles. The researchers used a high-temperature surface treatment with molten salt to produce a protective surface layer on particles of manganese- and lithium-rich metal-oxide, so the amount of oxygen loss is drastically reduced.</p> <p>Even though the surface layer is very thin, just 5 to 20 nanometers thick on a 400 nanometer-wide particle, it provides good protection for the underlying material. “It’s almost like immunization,” Li says, against the destructive effects of oxygen loss in batteries used at room temperature. The present versions provide at least a 50 percent improvement in the amount of energy that can be stored for a given weight, with much better cycling stability.</p> <p>The team has only built small lab-scale devices so far, but “I expect this can be scaled up very quickly,” Li says. The materials needed, mostly manganese, are significantly cheaper than the nickel or cobalt used by other systems, so these cathodes could cost as little as a fifth as much as the conventional versions.</p> <p>The research teams included researchers from MIT, Hong Kong Polytechnic University, the University of Central Florida, the University of Texas at Austin, and Brookhaven National Laboratories in Upton, New York. The work was supported by the National Science Foundation.</p> New research by engineers at MIT and elsewhere could lead to batteries that can pack more power per pound and last longer.Credit: MIT NewsResearch, Research Laboratory of Electronics, Nuclear science and engineering, School of Engineering, Materials Science and Engineering, DMSE, Batteries, Energy storage, Energy, National Science Foundation (NSF), Nanoscience and nanotechnology Nathan Howard wins Nuclear Fusion Award http://news.mit.edu/2020/nathan-howard-wins-nuclear-fusion-award-0129 Researcher unravels the mystery of heat loss in turbulent fusion plasmas. Wed, 29 Jan 2020 13:50:01 -0500 Paul Rivenberg | Plasma Science and Fusion Center http://news.mit.edu/2020/nathan-howard-wins-nuclear-fusion-award-0129 <p>Nathan Howard, research scientist at MIT’s Plasma Science and Fusion Center (PSFC), has won the 2019 Nuclear Fusion Award from the International Atomic Energy Agency (IAEA) for a&nbsp;<a href="https://iopscience.iop.org/article/10.1088/0029-5515/56/1/014004" target="_blank">paper</a>&nbsp;that explains heat losses due to turbulence in the core of magnetically confined fusion plasmas.</p> <p>Understanding and predicting plasma turbulence has been a key challenge for fusion researchers. Simulations of turbulent plasma conditions have not always been able to match experimental observations of heat loss in magnetically confined plasmas, making it impossible for researchers to be confident predicting the performance of future tokamaks, like&nbsp;<a href="https://www.iter.org/">ITER</a>, the next-step fusion reactor being built in France. In collaboration with colleagues from MIT, the University of California at San Diego, and General Atomics, Howard discovered that only by performing multiscale simulations, which simultaneously capture both short wavelength (electron scale) and long wavelength (ion scale) plasma turbulence, could he match the experimental observations.</p> <p>Before this, many researchers had assumed that the turbulence caused by electrons would be negligible in relation to the greater turbulence caused by ions, which is 60 times larger. In fact, this work found that the smaller-scale electron-scale turbulence interacts with the ion-scale turbulence in a way that contributes significantly to the experimental results and would need to be considered in any simulation.</p> <p>The multiscale simulations took approximately 120 million CPU hours and roughly a year to run on the Edison supercomputer at the National Energy Research Scientific Computing Center (NERSC), requiring Howard to get increases from the U.S. Department of Energy to his already-large allocation. Additionally, while the NERSC system only allows jobs to run without interruption for 36 hours, Howard's simulations took months to complete, necessitating frequent restarts.</p> <p>“I’d wake up in the middle of the night and basically switch jobs around so I could keep the simulation running as frequently as possible because I wanted the answer faster. They still took months and months to do.”</p> <p>What most excites Howard about the research is that the multiscale results of his paper have been incorporated into a reduced transport model called Trapped Gyro-Landau Fluid (TGLF), a model that provides results in a fraction of the time of a supercomputer.</p> <p>“This allows you to predict the electron temperature, electron density, ion temperature profiles that you see in the experiment, but do it in a matter of minutes, not years,” says Howard. “That’s really what was cool about this work: Not only did it show that you can match these experiments with these large-scale simulations, but the results were fed back into TGLF and created a slightly different TGLF model that is now used to predict performance and interpret results on a number of fusion devices.”</p> <p>Noting that the reduced model is now being used to predict performance of the PSFC’s proposed path to fusion, SPARC, Howard says, “It’s come full circle.”</p> <p>Howard continues to explore similar simulations, but is looking at higher performance discharges than before, to see if the observed multiscale interactions still exist and to gain greater insight into how and when turbulence occurs.</p> <p>Inaugurated in 2006, The Nuclear Fusion Award is given annually to recognize work published in the journal <em>Nuclear Fusion</em> that has made the largest scientific impact. Past recipients have included other members of the PSFC community: Senior Research Scientist John Rice (2010) and Director Dennis Whyte (2013).</p> <p>Howard authored the winning paper as a postdoc supported by the Oak Ridge Institute for Science and Education (ORISE), using data from the PSFC’s Alcator C-Mod tokamak. He credits co-authors Chris Holland (University of California at San Diego), and Jeff Candy (General Atomics), as well as MIT colleagues Anne White, head of the Department of Nuclear Science and Engineering, and Martin Greenwald, PSFC deputy director. He is also grateful for significant support and encouragement from program managers at the Department of Energy.</p> <p>“There is support for good science wherever it goes. And I think that is one thing that is great about the PSFC. It allows you to pursue what you feel is interesting research, and let it take you in a direction that you think might be most interesting and impactful. Working here, combined with the ORISE, really allowed me to do that.”</p> <p>Howard will receive the award at the&nbsp;<a href="https://www.iaea.org/events/fec-2020">IAEA Fusion Energy Conference </a>to be held in France in 2020.</p> <p>The research was supported by the U.S. Department of Energy.</p> Research Scientist Nathan Howard used data from MIT's Alcator C-Mod tokamak as the basis for an award-winning paper.Photo: Paul RivenbergPlasma Science and Fusion Center, Nuclear science and engineering, Physics, School of Engineering, Plasma, Fusion, Awards, honors and fellowships, Staff Zeroing in on decarbonization http://news.mit.edu/2020/zeroing-decarbonization-nestor-sepulveda-0115 Wielding complex algorithms, nuclear science and engineering doctoral candidate Nestor Sepulveda spins out scenarios for combating climate change. Wed, 15 Jan 2020 00:00:00 -0500 Leda Zimmerman | Department of Nuclear Science and Engineering http://news.mit.edu/2020/zeroing-decarbonization-nestor-sepulveda-0115 <p>To avoid the most destructive consequences of climate change, the world’s electric energy systems must stop producing carbon by 2050. It seems like an overwhelming technological, political, and economic challenge — but not to Nestor Sepulveda.</p> <p>“My work has shown me that we&nbsp;do&nbsp;have the means to tackle the problem, and we can start now,” he says. “I am optimistic.”</p> <p>Sepulveda’s research, first as a master’s student and now as a doctoral candidate in the MIT Department of Nuclear Science and Engineering (NSE), involves complex simulations that describe potential pathways to decarbonization. In work published last year in the journal&nbsp;<em>Joule,&nbsp;</em>Sepulveda and his co-authors made a powerful case for using a mix of renewable and “firm” electricity sources, such as nuclear energy, as the least costly, and most likely, route to a low- or no-carbon grid.</p> <p>These insights, which flow from a unique computational framework blending optimization and data science, operations research, and policy methodologies, have attracted interest from&nbsp;<em>The New York Times&nbsp;</em>and&nbsp;<em>The Economist,&nbsp;</em>as well as from such notable players in the energy arena as Bill Gates. For Sepulveda, the attention could not come at a more vital moment.</p> <p>“Right now, people are at extremes: on the one hand worrying that steps to address climate change might weaken the economy, and on the other advocating a Green New Deal to transform the economy that depends solely on solar, wind, and battery storage,” he says. “I think my data-based work can help bridge the gap and enable people to find a middle point where they can have a conversation.”</p> <p><strong>An optimization tool</strong></p> <p>The computational model Sepulveda is developing to generate this data, the centerpiece of his dissertation research, was sparked by classroom experiences at the start of his NSE master’s degree.</p> <p>“In courses like Nuclear Technology and Society [22.16], which covered the benefits and risks of nuclear energy, I saw that some people believed the solution for climate change was definitely nuclear, while others said it was wind or solar,” he says. “I began wondering how to determine the value of different technologies.”</p> <p>Recognizing that “absolutes exist in people’s minds, but not in reality,” Sepulveda sought to develop a tool that might yield an optimal solution to the decarbonization question. His inaugural effort in modeling focused on weighing the advantages of utilizing advanced nuclear reactor designs against exclusive use of existing light-water reactor technology in the decarbonization effort.</p> <p>“I showed that in spite of their increased costs, advanced reactors proved more valuable to achieving the low-carbon transition than conventional reactor technology alone,” he says. This research formed the basis of Sepulveda’s master’s thesis in 2016, for a degree spanning NSE and the Technology and Policy Program. It also informed the MIT Energy Initiative’s report,&nbsp;“The Future of Nuclear Energy in a Carbon-Constrained World.”</p> <p><strong>The right stuff</strong></p> <p>Sepulveda comes to the climate challenge armed with a lifelong commitment to service, an appetite for problem-solving, and grit. Born in Santiago, he enlisted in the Chilean navy, completing his high school and college education at the national naval academy.</p> <p>“Chile has natural disasters every year, and the defense forces are the ones that jump in to help people, which I found really attractive,” he says. He opted for the most difficult academic specialty, electrical engineering, over combat and weaponry. Early in his career, the climate change issue struck him, he says, and for his senior project, he designed a ship powered by hydrogen fuel cells.</p> <p>After he graduated, the Chilean navy rewarded his performance with major responsibilities in the fleet, including outfitting a $100 million amphibious ship intended for moving marines and for providing emergency relief services. But Sepulveda was anxious to focus fully on sustainable energy, and petitioned the navy to allow him to pursue a master’s at MIT in 2014.</p> <p>It was while conducting research for this degree that Sepulveda confronted a life-altering health crisis: a heart defect that led to open-heart surgery. “People told me to take time off and wait another year to finish my degree,” he recalls. Instead, he decided to press on: “I was deep into ideas about decarbonization, which I found really fulfilling.”</p> <p>After graduating in 2016, he returned to naval life in Chile, but “couldn’t stop thinking about the potential of informing energy policy around the world and making a long-lasting impact,” he says. “Every day, looking in the mirror, I saw the big scar on my chest that reminded me to do something bigger with my life, or at least try.”</p> <p>Convinced that he could play a significant role in addressing the critical carbon problem if he continued his MIT education, Sepulveda successfully petitioned naval superiors to sanction his return to Cambridge, Massachusetts.</p> <p><strong>Simulating the energy transition</strong></p> <p>Since resuming studies here in 2018, Sepulveda has wasted little time. He is focused on refining his modeling tool to play out the potential impacts and costs of increasingly complex energy technology scenarios on achieving deep decarbonization. This has meant rapidly acquiring knowledge in fields such as economics, math, and law.</p> <p>“The navy gave me discipline, and MIT gave me flexibility of mind — how to look at problems from different angles,” he says.</p> <p>With mentors and collaborators such as Associate Provost and Japan Steel Industry Professor Richard Lester and MIT Sloan School of Management professors Juan Pablo Vielma and Christopher Knittel, Sepulveda has been tweaking his models. His simulations, which can involve more than 1,000 scenarios, factor in existing and emerging technologies, uncertainties such as the possible emergence of fusion energy, and different regional constraints, to identify optimal investment strategies for low-carbon systems and to determine what pathways generate the most cost-effective solutions.</p> <p>“The idea isn’t to say we need this many solar farms or nuclear plants, but to look at the trends and value the future impact of technologies for climate change, so we can focus money on those with the highest impact, and generate policies that push harder on those,” he says.</p> <p>Sepulveda hopes his models won’t just lead the way to decarbonization, but do so in a way that minimizes social costs. “I come from a developing nation, where there are other problems like health care and education, so my goal is to achieve a pathway that leaves resources to address these other issues.”</p> <p>As he refines his computations with the help of MIT’s massive computing clusters, Sepulveda has been building a life in the United States. He has found a vibrant Chilean community at MIT&nbsp;and discovered local opportunities for venturing out on the water, such as summer sailing on the Charles.</p> <p>After graduation, he plans to leverage his modeling tool for the public benefit, through direct interactions with policy makers (U.S. congressional staffers have already begun to reach out to him), and with businesses looking to bend their strategies toward a zero-carbon future.</p> <p>It is a future that weighs even more heavily on him these days: Sepulveda is expecting his first child. “Right now, we’re buying stuff for the baby, but my mind keeps going into algorithmic mode,” he says. “I’m so immersed in decarbonization that I sometimes dream about it.”</p> “In courses like Nuclear Technology and Society, which covered the benefits and risks of nuclear energy, I saw that some people believed the solution for climate change was definitely nuclear, while others said it was wind or solar,” says doctoral student Nestor Sepulveda. “I began wondering how to determine the value of different technologies.”Photo: Gretchen ErtlNuclear science and engineering, MIT Energy Initiative, School of Engineering, Technology and policy, Students, Research, Alternative energy, Energy, Energy storage, Greenhouse gases, Climate change, Global Warming, Sustainability, Emissions, Renewable energy, Economics, Policy, Nuclear power and reactors, Profile, graduate, Graduate, postdoctoral A new way to remove contaminants from nuclear wastewater http://news.mit.edu/2019/remove-contaminants-nuclear-plant-wastewater-1219 Method concentrates radionuclides in a small portion of a nuclear plant’s wastewater, allowing the rest to be recycled. Thu, 19 Dec 2019 09:23:05 -0500 David L. Chandler | MIT News Office http://news.mit.edu/2019/remove-contaminants-nuclear-plant-wastewater-1219 <p>Nuclear power continues to expand globally, propelled, in part, by the fact that it produces few greenhouse gas emissions while providing steady power output. But along with that expansion comes an increased need for dealing with the large volumes of water used for cooling these plants, which becomes contaminated with radioactive isotopes that require special long-term disposal.</p> <p>Now, a method developed at MIT provides a way of substantially reducing the volume of contaminated water that needs to be disposed of, instead concentrating the contaminants and allowing the rest of the water to be recycled through the plant’s cooling system. The proposed system is described in the journal <em>Environmental Science and Technology</em>, in a paper by graduate student Mohammad Alkhadra, professor of chemical engineering Martin Bazant, and three others.</p> <p>The method makes use of a process called shock electrodialysis, which uses an electric field to generate a deionization shockwave in the water. The shockwave pushes the electrically charged particles, or ions, to one side of a tube filled with charged porous material, so that concentrated stream of contaminants can be separated out from the rest of the water. The group discovered that two radionuclide contaminants — isotopes of cobalt and cesium — can be selectively removed from water that also contains boric acid and lithium. After the water stream is cleansed of its cobalt and cesium contaminants, it can be reused in the reactor.</p> <p>The shock electrodialysis process was initially developed by Bazant and his co-workers as a general method of removing salt from water, as demonstrated in their <a href="http://news.mit.edu/2015/shockwave-process-desalination-water-1112">first scalable prototype</a> four years ago. Now, the team has focused on this more specific application, which could help improve the economics and environmental impact of working nuclear power plants. In ongoing research, they are also continuing to develop a system for removing other contaminants, including lead, from drinking water.</p> <p>Not only is the new system inexpensive and scalable to large sizes, but in principle it also can deal with a wide range of contaminants, Bazant says. “It’s a single device that can perform a whole range of separations for any specific application,” he says.</p> <p>In their earlier desalination work, the researchers used measurements of the water’s electrical conductivity to determine how much salt was removed. In the years since then, the team has developed other methods for detecting and quantifying the details of what’s in the concentrated radioactive waste and the cleaned water.</p> <p>“We carefully measure the composition of all the stuff going in and out,” says Bazant, who is the E.G. Roos Professor of Chemical Engineering as well as a professor of mathematics. “This really opened up a new direction for our research.” They began to focus on separation processes that would be useful for health reasons or that would result in concentrating material that has high value, either for reuse or to offset disposal costs.</p> <p>The method they developed works for sea water desalination, but it is a relatively energy-intensive process for that application. The energy cost is dramatically lower when the method is used for ion-selective separations from dilute streams such as nuclear plant cooling water. For this application, which also requires expensive disposal, the method makes economic sense, he says. It also hits both of the team’s targets: dealing with high-value materials and helping to safeguard health. The scale of the application is also significant — a single large nuclear plant can circulate about 10 million cubic meters of water per year through its cooling system, Alkhadra says.</p> <p>For their tests of the system, the researchers used simulated nuclear wastewater based on a recipe provided by Mitsubishi Heavy Industries, which sponsored the research and is a major builder of nuclear plants. In the team’s tests, after a three-stage separation process, they were able to remove 99.5 percent of the cobalt radionuclides in the water while retaining about 43 percent of the water in cleaned-up form so that it could be reused. As much as two-thirds of the water can be reused if the cleanup level is cut back to 98.3 percent of the contaminants removed, the team found.</p> <p>While the overall method has many potential applications, the nuclear wastewater separation, is “one of the first problems we think we can solve [with this method] that no other solution exists for,” Bazant says. No other practical, continuous, economic method has been found for separating out the radioactive isotopes of cobalt and cesium, the two major contaminants of nuclear wastewater, he adds.</p> <p>While the method could be used for routine cleanup, it could also make a big difference in dealing with more extreme cases, such as the millions of gallons of contaminated water at the damaged Fukushima Daichi power plant in Japan, where the accumulation of that contaminated water has threatened to overpower the containment systems designed to prevent it from leaking out into the adjacent Pacific. While the new system has so far only been tested at much smaller scales, Bazant says that such large-scale decontamination systems based on this method might be possible “within a few years.”</p> <p>The research team also included MIT postdocs Kameron Conforti and Tao Gao and graduate student Huanhuan Tian.</p> A small-scale device, seen here, was used in the lab to demonstrate the effectiveness of the new shockwave-based system for removing radioactive contaminants from the cooling water in nuclear powerplants.Image courtesy of the researchers Research, School of Engineering, Chemical engineering, Energy, Water, Desalination, Mathematics, Nuclear science and engineering Anoushka Bose: Targeting a career in security studies and diplomacy http://news.mit.edu/2019/mit-anoushka-bose-career-security-studies-diplomacy-1217 Nuclear science and engineering and physics met political science to illuminate a new path. Tue, 17 Dec 2019 15:25:01 -0500 Leda Zimmerman | MIT Political Science http://news.mit.edu/2019/mit-anoushka-bose-career-security-studies-diplomacy-1217 <div> <p>Anoushka Bose arrived at MIT in 2016 intent on pursuing problems related to climate change and energy. But two years later, she found herself discussing arms control and international security with Russian foreign minister Sergei Lavrov during a policy forum connecting American and Russian students.</p> <p>“It was eye-opening for me,” says Bose, a double major in political science and physics. “I thought it was fascinating to see how politics and diplomacy work between countries that don't share the same motivations.”</p> <p>In the wake of this experience and a set of equally transformative internships, Bose is now on a new trajectory, moving purposefully toward a public-service career in nuclear policy and diplomacy.</p> <p><strong>Passion for policy and science</strong></p> <p>Growing up in the San Diego, California, area, Bose gravitated toward physics and chemistry in her STEM-oriented high school. But the extracurricular project that completely captivated her was her community's yearlong research and writing competition that traditionally focused on a historical topic. Bose's subject: the Clean Air Act.</p> <p>“This project substantively shaped my interests,” she says. Bose found it “enlightening” to study both the science behind air pollution and the political movement that helped nail down the legislation. “I realized I had passions for both the social sciences and science.”</p> <p>Bose inclined initially toward nuclear science and engineering at MIT because she saw “nuclear energy as the pinnacle solution to climate problems.” She later migrated toward physics, where she hoped to gain more latitude to pursue clean-energy policy questions as well.</p> <p>But it was her engagement with political science that propelled Bose on her current academic path.</p> <p>Venturing into 17.581 (Riots, Rebellions and Revolutions), taught by Roger Petersen, the Arthur and Ruth Sloan Professor of Political Science, Bose says “a gate opened for me into national security.” With its hybrid focus on American and international politics, the class “gave me both knowledge and respect for the entire security enterprise of the U.S.”</p> <p>This class, along with 17.482-3 (U.S. Military Power), taught by Barry R. Posen, the Ford International Professor of Political Science, “kicked off several semesters dedicated to security studies,” says Bose. “This area seemed like it might be really fulfilling as a career.” The summer after her sophomore year, she grabbed a chance to test her premise.</p> <p><strong>The Washington experience</strong></p> <p>With the help of the MIT Washington DC Summer Internship Program, and Ernest J. Moniz, former U.S. Secretary of Energy and Cecil and Ida Green Professor of Physics and Engineering Systems, Bose landed an internship at the Nuclear Threat Initiative. Plunging into research about safeguarding nuclear materials in central Asia, protecting against radiological challenges, and the potential impacts of a nuclear winter after a small-scale nuclear exchange, Bose strongly felt, “This is the kind of place where I want to be.”</p> <p>The initiative's mission also made an impact on Bose: “I thought maybe I should be exploring global nuclear safety, proliferation, and security issues, rather than energy,” she says. With this in mind, she seized an opportunity to dive even deeper into this area, applying for one of 20 U.S. spots in the Stanford-U.S. Russia Forum.</p> <p>Running September 2018 through April 2019, this project brought Bose together with a small group of U.S. and Russian students to discuss the Intermediate-Range Nuclear Forces (INF) Treaty, from which the Trump administration had decided to withdraw. Meeting virtually and then in person (in both Moscow and Washington) to present policy ideas, Bose and her partners tried to offer solutions that might prove mutually, politically beneficial.</p> <p>“From the policy-making side, I hadn't understood the power of individuals to shape what gets done,” she says. “It was really interesting working with the Russians, who often spoke bluntly, and who did not routinely view the U.S. as having pure motivations.”</p> <p>While laboring over the research and writing for this policy project, Bose continued to delve deeper into security studies at MIT. “I needed to gain knowledge and confidence in understanding international crises,” says Bose.</p> <p>Increasingly sure that she “wanted to do something involving diplomacy and international relations,” Bose secured another internship in Washington last summer, working on nuclear energy policy at the State Department. Even though she hoped to concentrate on weapons and proliferation, Bose was eager “to learn about the processes of government and bureaucracy.”</p> <p>The internship did not disappoint. Bose worked on bolstering U.S. nuclear energy business in countries around the world seeking nuclear power. “I had not internalized how the State Department on a daily basis uses nuclear energy as a policy thrust,” she says. She also helped develop U.S. nuclear cooperation accords with Argentina and Romania. “I was so excited to see something come out of my advocacy,” she says.</p> <p>These real-world experiences “sealed the deal" for Bose. “After last summer I knew I wanted to work in nuclear policy, focusing on security,” she says. Today, under the direction of political science Associate Professor Vipin Narang, she is delving into the issue of global noncompliance with nuclear materials — work for which she has been named a presidential fellow at the Center for the Study of the Presidency and Congress.</p> <p>She hasn't abandoned energy, though. She serves as president of the MIT Energy Club, devoting considerable time to hosting events as she finishes coursework for her double major. She is applying both to law school, and for a full-time job next year in Washington in policy and/or diplomacy.</p> <p>In a world challenged by nationalism and conflict, Bose retains a sense of optimism and commitment to a larger goal — a safer world. “It's simple for me to believe in the power of cooperation and trust, especially after working alongside Russian students all year,” she says. “I learned that both sides deeply value nuclear security, and neither side wants a much more dangerous world where no one wins,” she says.</p> </div> Anoushka Bose is moving purposefully toward a public-service career in nuclear policy and diplomacy.Political science, School of Humanities Arts and Social Sciences, Physics, Policy, Nuclear security and policy, Energy, International relations, Students, Undergraduate, School of Science, Government, Profile, Nuclear science and engineering, Global Is there dark matter at the center of the Milky Way? http://news.mit.edu/2019/center-milky-way-dark-matter-gce-1211 A new analysis puts dark matter back in the game as a possible source of energy excess at the galactic center. Tue, 10 Dec 2019 23:59:59 -0500 Jennifer Chu | MIT News Office http://news.mit.edu/2019/center-milky-way-dark-matter-gce-1211 <p>MIT physicists are reigniting the possibility, which they previously had snuffed out, that a bright burst of gamma rays at the center of our galaxy may be the result of dark matter after all.</p> <p>For years, physicists have known of a mysterious surplus of energy at the Milky Way’s center, in the form of gamma rays — the most energetic waves in the electromagnetic spectrum. These rays are typically produced by the hottest, most extreme objects in the universe, such as supernovae and pulsars.</p> <p>Gamma rays are found across the disk of the Milky Way, and for the most part physicists understand their sources. But there is a glow of gamma rays at the Milky Way’s center, known as the galactic center excess, or GCE, with properties that are difficult for physicists to explain given what they know about the distribution of stars and gas in the galaxy.</p> <p>There are two leading possibilities for what may be producing this excess: a population of high-energy, rapidly rotating neutron stars known as pulsars, or, more enticingly, a concentrated cloud of dark matter, colliding with itself to produce a glut of gamma rays.</p> <p>In 2015, an MIT-Princeton University team, including associate professor of physics Tracy Slatyer and postdocs Benjamin Safdi and Wei Xue, came down in favor of pulsars. The researchers had analyzed observations of the galactic center taken by the Fermi Gamma-ray Space Telescope, using a “background model” that they developed to describe all the particle interactions in the galaxy that could produce gamma rays. They concluded, rather definitively, that the GCE was most likely a result of pulsars, and not dark matter.</p> <p>However, in new work, led by MIT postdoc Rebecca Leane, Slatyer has since reassessed this claim. In trying to better understand the 2015 analytical method, Slatyer and Leane found that the model they used could in fact be “tricked” to produce the wrong result. Specifically, the researchers ran the model on actual Fermi observations, as the MIT-Princeton team did in 2015, but this time they added a fake extra signal of dark matter. They found that the model failed to pick up this fake signal, and even as they turned the signal up, the model continued to assume pulsars were at the heart of the excess.</p> <p>The results, published today in the journal <em>Physical Review Letters</em>, highlight a “mismodeling effect” in the 2015 analysis and reopen what many had thought was a closed case.</p> <p>“It’s exciting in that we thought we had eliminated the possibility that this is dark matter,” Slatyer says. “But now there’s a loophole, a systematic error in the claim we made. It reopens the door for the signal to be coming from dark matter.”</p> <p><strong>Milky Way’s center: grainy or smooth?</strong></p> <p>While the Milky Way galaxy more or less resembles a flat disk in space, the excess of gamma rays at its center occupies a more spherical region, extending about 5,000 light years in every direction from the galactic center.</p> <p>In their 2015 study, Slatyer and her colleagues developed a method to determine whether the profile of this spherical region is smooth or “grainy.” They reasoned that, if pulsars are the source of the gamma ray excess, and these pulsars are relatively bright, the gamma rays they emit should inhabit a spherical region that, when imaged, looks grainy, with dark gaps between the bright spots where the pulsars sit.</p> <p>If, however, dark matter is the source of the gamma ray excess, the spherical region should look smooth: “Every line of sight toward the galactic center probably has dark matter particles, so I shouldn’t see any gaps or cold spots in the signal,” Slatyer explains.</p> <p>She and her team used a background model of all the matter and gas in the galaxy, and all the particle interactions that could occur to produce gamma rays. They considered models for the GCE’s spherical region that were grainy on one hand or smooth on the other, and devised a statistical method to tell the difference between them. They then fed into the model actual observations of the spherical region, taken by the Fermi telescope, and looked to see if these observations fit more with a smooth or grainy profile.</p> <p>“We saw it was 100 percent grainy, and so we said, ‘oh, dark matter can’t do that, so it must be something else,’” Slatyer recalls. “My hope was that this would be just the first of many studies of the galactic center region using similar techniques. But by 2018, the main cross-checks of the method were still the ones we’d done in 2015, which made me pretty nervous that we might have missed something.”</p> <p><strong>Planting a fake</strong></p> <p>After arriving at MIT in 2017, Leane became interested in analyzing gamma-ray data. Slatyer suggested they try to test the robustness of the statistical method used in 2015, to develop a deeper understanding of the result. The two researchers asked the difficult question: Under what circumstances would their method break down? If the method withstood interrogation, they could be confident in the original 2015 result. If, however, they discovered scenarios in which the method collapsed, it would suggest something was amiss with their approach, and perhaps dark matter could still be at the center of the gamma ray excess.</p> <p>Leane and Slatyer repeated the approach of the MIT-Princeton team from 2015, but instead of feeding into the model Fermi data, the researchers essentially drew up a fake map of the sky, including a signal of dark matter, and pulsars that were not associated with the gamma ray excess. They fed this map into the model and found that, despite there being a dark matter signal within the spherical region, the model concluded this region was most likely grainy and therefore dominated by pulsars. This was the first clue, Slatyer says, that their method “wasn’t foolproof.”</p> <p>At a conference to present their results thus far, Leane entertained a question from a colleague: What if she added a fake signal of dark matter that was combined with real observations, rather than with a fake background map?</p> <p>The team took up the challenge, feeding the model with data from the Fermi telescope, along with a fake signal of dark matter. Despite the deliberate plant, their statistical analysis again missed the dark matter signal and returned a grainy, pulsar-like picture. Even when they turned up the dark matter signal to four times the size of the actual gamma ray excess, their method failed to see it.</p> <p>“By that stage, I was pretty excited, because I knew the implications were very big — it meant that the dark matter explanation was back on the table,” Leane says.</p> <p>She and Slatyer are working to better understand the bias in their approach, and hope to tune out this bias in the future.</p> <p>“If it’s really dark matter, this would be the first evidence of dark matter interacting with visible matter through forces other than gravity,” Leane says. “The nature of dark matter is one of the biggest open questions in physics at the moment. Identifying this signal as dark matter may allow us to finally expose the fundamental identity of dark matter. No matter what the excess turns out to be, we will learn something new about the universe.”</p> <p>This research was funded in part by the Office of High Energy Physics of the U.S. Department of Energy. This research was conducted in part while Slatyer was a visiting junior professor at the Institute for Advanced Study’s School of Natural Sciences, during which she was supported by the Institute for Advanced Study's John N. Bahcall Fellowship.</p> A map of gamma ray emissions throughout the Milky Way galaxy, based on observations from the Fermi Gamma-ray Space Telescope. The inset depicts the Galactic Center Excess – an unexpected, spherical region of gamma ray emissions at the center of our galaxy, of unknown origin.Credit: NASA/T. Linden, U.ChicagoAstronomy, Astrophysics, Center for Theoretical Physics, Laboratory for Nuclear Science, Physics, Research, School of Science, Space, astronomy and planetary science, Department of Energy (DoE) School of Engineering third quarter 2019 awards http://news.mit.edu/2019/school-engineering-third-quarter-2019-awards-1127 Faculty members recognized for excellence via a diverse array of honors, grants, and prizes over the last quarter. Wed, 27 Nov 2019 11:35:01 -0500 School of Engineering http://news.mit.edu/2019/school-engineering-third-quarter-2019-awards-1127 <p>Members of the MIT engineering faculty receive many awards in recognition of their scholarship, service, and overall excellence. Every quarter, the School of Engineering publicly recognizes their achievements by highlighting the honors, prizes, and medals won by faculty working in our academic departments, labs, and centers.</p> <p>Richard Braatz, of the Department of Chemical Engineering, won the <a href="https://www.aiche.org/community/awards/separations-division-innovation-award">AIChE 2019 Separations Division Innovation Award</a> on Oct. 1.</p> <p>Michael Carbin, of the Department of Electrical Engineering and Computer Science, <a href="https://iclr.cc/Conferences/2019/Awards">won the Best Paper Award</a> at the International Conference on Learning Representations on May 8. He also <a href="https://icfp19.sigplan.org/details/icfp-2019-papers/15/Sound-and-robust-solid-modeling-via-exact-real-arithmetic-and-continuity">won the Distinguished Paper Award</a> at the International Conference on Functional Programming on Aug. 20.</p> <p>Vincent W. S. Chan, of the Department of Electrical Engineering and Computer Science, was elected <a href="https://www.comsoc.org/vincent-ws-chan">2020-21 president of the IEEE Communication Society</a> on Sept. 5.</p> <p>Victor Chernozhukov, of the Institute for Data, Systems, and Society, was <a href="http://bulletin.imstat.org/2019/05/congratulations-to-the-2019-ims-fellows/">named a fellow of the Institute of Mathematical Statistics</a> on May 15.</p> <p>Michael Cima, of the Department of Materials Science and Engineering, won the&nbsp;<a href="https://ceramics.org/award-winners/michael-cima">W. David Kingery Award</a> from the American Ceramic Society on Oct. 16.</p> <p>James Collins, of the Institute for Medical Engineering and Science, won the <a href="https://www.aps.org/programs/honors/prizes/delbruck.cfm">2020 Max Delbrück Prize in Biological Physics</a> from the American Physical Society on Sept. 26.</p> <p>Areg Danagoulian, of the Department of Nuclear Science and Engineering, won the <a href="http://www.ans.org/honors/recipients/">2019 Radiation Science and Technology Award</a> from the American Nuclear Society on Nov. 17.</p> <p>Peter Dedon and Eric Alm, of the Department of Biological Engineering, won the <a href="https://commonfund.nih.gov/TRA/recipients">NIH Director’s Transformative Research Award</a> on Oct. 1.</p> <p>Esther Duflo, of the Institute for Data, Systems, and Society, won the <a href="https://www.nobelprize.org/prizes/economic-sciences/2019/press-release/">Nobel Prize for economics</a> on Oct. 14.</p> <p>Ruonan Han, of the Department of Electrical Engineering and Computer Science, was <a href="https://www.mtt.org/mtt-s-dmls-class-2020-2022/">named the 2020-22 Distinguished Lecturer</a> by the IEEE Microwave Theory and Technique Society on Sept. 11.</p> <p>James M. LeBeau, of the Department of Materials Science and Engineering, won the <a href="https://www.whitehouse.gov/briefings-statements/president-donald-j-trump-announces-recipients-presidential-early-career-award-scientists-engineers/">Presidential Early Career Award for Scientists and Engineers</a> on July 2.</p> <p>Nancy Lynch, of the Department of Electrical Engineering and Computer Science, was <a href="https://www.sorbonne-universite.fr/en/newsroom/actualites/doctors-honoris-causa-ceremony">given a doctor honoris causa</a> (honorary doctorate) from the Sorbonne University on Sept. 11.</p> <p>Karthish Manthiram, of the Department of Chemical Engineering, won the <a href="https://www.nsf.gov/funding/pgm_summ.jsp?pims_id=503214">2019 NSF Faculty Early Career Development (CAREER) Award</a> on Nov. 15.</p> <p>Devavrat Shah, of the Department of Electrical Engineering and Computer Science,&nbsp;won the <a href="https://www.sigmetrics.org/awards.shtml#testoftime">ACM Sigmetrics Test of Time Paper Award</a> on July 22.</p> <p>Suvrit Sra, of the Department of Electrical Engineering and Computer Science, won the <a href="https://nsf.gov/awardsearch/showAward?AWD_ID=1846088&amp;HistoricalAwards=false">NSF CAREER Award</a> on July 24.</p> <p>Anne White, of the Department of Nuclear Science and Engineering,&nbsp;was named a <a href="https://www.aps.org/newsroom/pressreleases/fellows2019.cfm">fellow of the American Physical Society</a> on Nov. 17.</p> <p>Cathy Wu, of the Institute for Data, Systems, and Society, won the <a href="https://www.ieee-itss.org/awards-best-dissertation">Best PhD Dissertation Award first prize</a> from the IEEE Intelligent Transportation Systems Society on Nov. 12.</p> Photo: Lillie Paquette/School of EngineeringSchool of Engineering, Chemical engineering, Electrical engineering and computer science (EECS), Materials Science and Engineering, Institute for Data, Systems, and Society, Institute for Medical Engineering and Science (IMES), Nuclear science and engineering, Biological engineering, Awards, honors and fellowships, Faculty Heating by cooling http://news.mit.edu/2019/heating-cooling-mit-pablo-rodriguez-fernandez-1127 Pablo Rodriguez-Fernandez resolves a fusion paradox to receive Del Favero Prize. Wed, 27 Nov 2019 11:30:01 -0500 Paul Rivenberg | Plasma Science and Fusion Center http://news.mit.edu/2019/heating-cooling-mit-pablo-rodriguez-fernandez-1127 <p>The field of magnetic fusion research has mysteries to spare. How to confine turbulent plasma fuel in a donut-shaped vacuum chamber, making it hot and dense enough for fusion to take place, has generated questions — and answers — for decades.&nbsp;</p> <p>As a graduate student under the direction of Department of Nuclear Science and Engineering Professor Anne White, Pablo Rodriguez-Fernandez PhD ’19 became intrigued by a fusion research mystery that had remained unsolved for 20 years. His novel observations and subsequent modeling helped provide the answer, earning him the Del Favero Prize.</p> <p>The focus of his thesis is plasma turbulence, and how heat is transported from the hot core to the edge of the plasma in a tokamak. Experiments over 20 years have shown that, in certain circumstances, cooling the edge of the plasma results in the core becoming hotter.&nbsp;</p> <p>“When you cool the edge of the plasma by injecting impurities, what every standard theory and intuition would tell you is that a cold pulse propagates in, so that eventually the core temperature will drop as well. But what we observed is that, in certain conditions when we drop the temperature of the edge, the core got hotter. It’s sort of heating by cooling.”</p> <p>The counterintuitive observation was not supported by any existing theory for plasma behavior.&nbsp;</p> <p>“The fact that our theory cannot explain something that happens so often in experiments makes us question those models,” Rodriquez-Fernandez says. “Should we trust them to predict what will happen in future fusion devices?”&nbsp;</p> <p>These models were the basis for predicting performance in the Plasma Science and Fusion Center’s Alcator C-Mod tokamak, which is no longer in operation. They are currently used for <a href="https://www.iter.org/">ITER</a>, the next-generation machine being constructed in France, and SPARC, the tokamak the PSFC is pursuing with <a href="https://cfs.energy/">Commonwealth Fusion Systems</a>.&nbsp;</p> <p>To solve the mystery, Rodriguez-Fernandez learned complex coding that would allow him to run simulations of the edge-cooling experiments. When he manually cooled the edge in his early simulations, however, his models failed to reproduce the core heating observed in the actual experiments.</p> <p>Carefully studying data from Alcator C-Mod experiments, Rodriguez-Fernandez realized that the impurities injected to cool the plasma perturb not only the temperature, but every parameter, including the density.&nbsp;</p> <p>“We are perturbing the density because we are introducing more particles into the plasma. I was looking at the Alcator C-Mod data and I was seeing all the time these bumps in density. People have been disregarding them forever.”</p> <p>With new density perturbations to introduce into his simulation, he was able to simulate the core heating that had been observed in so many experiments around the world for more than two decades. These findings became the basis for an <a href="https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.120.075001" target="_blank">article</a> in <em>Physical&nbsp;Review Letters (PRL)</em>.</p> <p>To strengthen his thesis, Rodriguez-Fernandez wanted to use the same model to predict the response to edge cooling in a very different tokamak — DIII-D in San Diego, California. At the time, this tokamak did not have the capability to run such an experiment, but the MIT team, led by Research Scientist Nathan Howard, installed a new laser ablation system for injecting impurities and cold pulses into the machine. The subsequent experiments run on DIII-D showed the predictions to be accurate.</p> <p>“This was further support that my answer to the mystery and my predictive simulations were correct,” says Rodriguez-Fernandez. “The fact that we can reproduce core heating by edge cooling in a simulation, and for more than one tokamak, means that we can understand the physics behind the phenomenon. And what is more important, it gives us confidence that the models we have for C-Mod and SPARC are not wrong.”</p> <p>Rodriquez-Fernandez notes the excellent collegial environment&nbsp;at the PSFC, as well as a strong external collaboration network. His collaborators include Gary Staebler at General Atomics, home to DIII-D, who authored the Trapped Gyro-Landau Fluid transport model used for his simulations; Princeton Plasma Physics Laboratory researchers Brian Grierson and Xingqiu Yuan, who are experts at a modeling tool called TRANSP that was invaluable to his work; and Clemente Angioni at the Max-Planck Institute for Plasma Physics in Garching, Germany, whose experiments on the ASDEX Upgrade tokamak supported the findings from the PRL article.</p> <p>Now a postdoc at the PSFC, Rodriguez-Fernandez devotes half of his time to SPARC and half to DIII-D and ASDEX Upgrade. With all these projects, he is using the simulations from his PhD thesis to develop techniques for predicting and optimizing tokamak performance.&nbsp;</p> <p>The postdoc admits that the timing of his thesis could not have been better, just as the SPARC project was ramping up. He quickly joined the team that is designing the device and working on the physics basis.&nbsp;</p> <p>As part of the <a href="http://calendar.mit.edu/event/2019_del_favero_award_lecture_-_pablo_rodriguez_fernadez#.XdfzuJNKg7x">Dec. 5 ceremony</a> where Rodriguez Fernandez will receive the Del Favero Thesis Prize, he will discuss his how his thesis research is connected to his current work on predicting SPARC performance. Established in 2014 with a generous gift from alum James Del Favero SM ’84, the prize is awarded annually to a PhD graduate in NSE whose thesis is judged to have made the most innovative advance in the field of nuclear science and engineering.&nbsp;</p> <p>“It’s very exciting,” he says. “The SPARC project really drives me. I see a future here for me, and for fusion.”&nbsp;</p> <p>This research is supported by the U.S. Department of Energy Office of Fusion Energy Sciences.</p> For his prize-winning thesis, Pablo Rodriguez-Fernandez examined data from MIT's Alcator C-Mod tokamak (background).Photo: Paul Rivenberg/PSFCPlasma Science and Fusion Center, Nuclear science and engineering, School of Engineering, Physics, Fusion, Awards, honors and fellowships, Graduate, postdoctoral, Staff, Department of Energy (DoE) Advancing nuclear detection and inspection http://news.mit.edu/2019/advancing-nuclear-detection-and-inspection-areg-danagoulian-1114 Assistant professor of nuclear science and engineering Areg Danagoulian probes deep inside cargo containers and ballistic warheads to ferret out fissile materials. Thu, 14 Nov 2019 11:25:01 -0500 Leda Zimmerman | Nuclear science and engineering http://news.mit.edu/2019/advancing-nuclear-detection-and-inspection-areg-danagoulian-1114 <p>If not for an episode of soul-searching at Los Alamos National Laboratory, Areg Danagoulian ’99 might have remained content pummeling protons with photons and advancing experimental nuclear physics. Instead, the assistant professor of nuclear science and engineering took off on a different trajectory.</p> <p>“At Los Alamos, where I worked after my doctoral research, I began learning about the scale of the problem of nuclear weapons,” he recounts. “With two children, I was newly sensitive to the issue, and began wondering if I could apply what I had learned in nuclear physics to address such urgent challenges as nuclear terrorism and accidental nuclear war.”</p> <p>Since 2008, Danagoulian has committed himself to these challenges, generating new technologies that reduce nuclear security threats in the near term and that offer game-changing options in the arena of nuclear nonproliferation and treaty verification.</p> <p>This work has brought significant notice. This year the U.S. Department of Energy named him as a member of its Consortium of Monitoring, Technology, and Verification. And for scientific and engineering achievements that bear important implications for the field, he was just awarded the 2019 Radiation Science and Technology Award from the American Nuclear Society.</p> <p><strong>Verify, then trust</strong></p> <p>One of Danagoulian’s key research thrusts is development of a method for verifying the authenticity of nuclear warheads. His most recent work in the area, <a href="http://www.nature.com/articles/s41467-019-12386-0" target="_blank">published</a> in the Sept. 30 <em>Nature Communications</em>&nbsp;and coauthored by nuclear science and engineering graduate student Ezra M. Engel, may open up new paths to reducing nuclear stockpiles and reaching new treaties on deployed nuclear weaponry.</p> <p>“Up to now, there have been no ways to verify warheads, or to verify dismantlement of warheads,” says Danagoulian. For security reasons, nuclear powers don’t let inspectors get close to their warheads, and the conventional method for offering proof of dismantlement relies on destroying weapons delivery systems — e.g., cutting wings off B-52 bombers.</p> <p>And even where disarmament treaties exist, “there is an incentive to cheat and maintain an advantage,” says Danagoulian. Without the capacity to determine whether the other side’s warhead is real, or if its warhead has actually been dismantled, a nation might well view a current or future treaty as toothless.</p> <p>But Danagoulian has found a technical solution to this problem. His approach uses neutron resonance transmission spectroscopy to capture a unique fingerprint of the relevant isotopes in a nuclear weapon, as well as its geometry. During this process, information describing these key identifiers for a nuclear object becomes encrypted physically in a special filter. This encrypted, master version of data can be used as the basis for comparison of other warheads. If their nuclear signatures don't match this template, warheads may be deemed hoaxes.</p> <p>This technology offers two major advances: First, the physical encryption, unlike a digitally stored, computational record, cannot be hacked. And second, the process around this technology makes it possible for weapons inspectors to determine the nature of a weapon without ascertaining its engineering makeup.</p> <p>“This is a way to verify that something is a warhead, and find out nothing about it,” says Danagoulian. The capacity to protect proprietary nuclear weapon design while verifying the dismantlement of its treaty partner’s nuclear stockpile makes it more likely that nations will submit to inspections, and potentially sign new treaties.</p> <p>“By reducing technological barriers, our approach might catalyze future treaties,” says Danagoulian. While he knows that “without political will, even the coolest technology won’t come into play,” he wants the right technology in hand if and when the political door opens. “Our research is high risk, high reward: If and when the politics lines up, the impact will be enormous.”</p> <p><strong>Evolving nuclear concerns</strong></p> <p>Danagoulian was born in Soviet-era Armenia, the child of two physicists. While he grew up during the Cold War, he says that most of the Soviet public didn’t perceive nuclear weapons as an existential threat. “The party regulated all debate, and while my own father knew a lot and discussed with me the devastating power of the bomb, most people knew little about fallout and nuclear winter,” he recalls. “Then suddenly, in the late 1980s, the Soviet Union was all about peace, but no one could really say what it meant to try to prevent nuclear war.”</p> <p>Smitten with math, he decided to become a physicist. After moving to the United States with his family in 1993, he attended first North Carolina State University, then MIT as an undergraduate, where he was warmly welcomed by the nuclear physics group.</p> <p>Then came doctoral studies at the University of Illinois at Urbana-Champaign, where he investigated the interactions of fundamental particles, and next, his career-changing time at Los Alamos. “People there were working on nuclear detection and others on nuclear terrorism,” he says. “But not everyone shared my sense of the dangers of nuclear weapons, or the urgency to get rid of them.”</p> <p>Eager to pursue technological solutions to nuclear threats where he could employ his physics expertise, Danagoulian took a job at Passport Systems starting in 2009. Over the next five years, he helped spearhead a new process for detecting bomb-worthy nuclear materials concealed in large shipping containers. “We wanted to be able to find a tiny amount of material, maybe a two-inch cube representing a two- to three-kilogram uranium or plutonium weapon, inside a jammed 20-ton container,” he says.</p> <p>The technology he helped develop finds radioactive material by subjecting a container to a beam of photons. These energetic particles catalyze fission and breakup of elements like uranium and plutonium, releasing a flood of neutrons. “If we see a sudden increase in the count of fast neutrons in our detector, we know something weird is going on inside,” he says. This technology for sniffing out radioactive weapons has been put into practice at such sites as South Boston’s Conley terminal.</p> <p><strong>Contending with an existential threat</strong></p> <p>While bringing this technology to commercial fruition was rewarding, Danagoulian felt drawn back to academia. “I was more interested in focusing fully on research and the opportunity to work with students,” he says. Returning to MIT in 2014, he encountered an eager and engaged pool of young people.</p> <p>“Today’s students, even though they didn’t grow up in the shadow of the mushroom cloud, are imaginative and curious enough to understand the scale of the problem,” he says. “Many come to MIT motivated to adopt a mission, which is more important than a good job to them.”</p> <p>Danagoulian is happy for such motivated recruits, given the immensity of his cause. “We use abstract and technical language like deterrence and strategic balance to talk about these weapons, when what we’re really talking about are instruments of global genocide,” he says. “I’d like to see a world with no nuclear weapons at all.”</p> Areg Danagoulian has committed himself to generating new technologies that reduce nuclear security threats and that offer game-changing options in the arena of nuclear nonproliferation and treaty verification.Photo: Gretchen ErtlNuclear science and engineering, Research, Nuclear security and policy, Security studies and military, School of Engineering, Physics, International relations, Cryptography, Profile, Alumni/ae, Policy, Faculty American Physical Society honors three MIT professors for physics research http://news.mit.edu/2019/aps-honors-three-mit-professors-physics-research-1024 James Collins, Pablo Jarillo-Herrero, and Richard Milner have won top prizes for their work. Thu, 24 Oct 2019 14:55:01 -0400 Sandi Miller | Department of Physics http://news.mit.edu/2019/aps-honors-three-mit-professors-physics-research-1024 <p>MIT professor of biological engineering <a href="http://be.mit.edu/directory/james-j-collins" target="_blank">James Collins</a> and professors of physics <a href="http://web.mit.edu/physics/people/faculty/jarillo-herrero_pablo.html" target="_blank">Pablo Jarillo-Herrero</a> and <a href="http://web.mit.edu/physics/people/faculty/milner_richard.html" target="_blank">Richard Milner</a> have been awarded top prizes from the American Physical Society.</p> <p>Jarillo-Herrero, the Cecil and Ida Green Professor of Physics, received the 2020 <a href="https://www.aps.org/programs/honors/prizes/buckley.cfm">Oliver E. Buckley Condensed Matter Physics Prize</a> for the discovery of superconductivity in twisted bilayer graphene. Milner has been awarded the 2020 <a href="https://www.aps.org/programs/honors/prizes/bonner.cfm">Tom W. Bonner Prize in Nuclear Physics</a> for pioneering work developing and using polarized internal targets in storage rings, and his leadership role in studying the structure of the nucleon in a wide range of electronuclear experiments. Collins, the Termeer Professor of Medical Engineering and Science, received the 2020 <a href="https://www.aps.org/programs/honors/prizes/delbruck.cfm">Max Delbruck Prize in Biological Physics</a> “for pioneering contributions at the interface of physics and biology, in particular the establishment of the field of synthetic biology and applications of statistical physics and nonlinear dynamics in biology and medicine.”</p> <p><strong>Pablo Jarillo-Herrero</strong></p> <p>When his team of physicists at MIT and collaborators at Harvard University stacked two sheets of atomic-thick carbon (graphene), and twisted them to 1.1 degrees to form what they call “magic-angle graphene,” the sheets exhibited nonconducting behavior, similar to a class of materials known as Mott insulators. And when they applied voltage to this twisted graphene, electrons flowed without resistance, displaying an unconventional superconductivity at 1.7 kelvins.</p> <p>Graphene is light and flexible, stronger than steel, and more electrically conductive than copper. Jarillo-Herrero believes that this newly discovered superconducting behavior could be used to create a superconductor transistor useful for quantum devices. Since this discovery, he says, “These systems are quickly becoming an ever-growing platform to investigate new physics. By now, many physicists are using other experimental techniques to investigate magic angle graphene and other related systems.”</p> <p>Although his discovery earned him <em>Physics World’s </em>2018 Breakthrough of the Year award, receiving this prize from APS so relatively quickly caught him off guard. “Our discovery was published just last year; so, in that sense, getting the Oliver E. Buckley Award this early is very surprising, as it is the most prestigious award worldwide in the field of condensed matter physics,” says Jarillo-Herrero, who also noted that he is the first Spaniard to receive the award, and among the youngest. “I feel truly humbled, both by the recognition and the early stage at which it has come. Having been myself a first-generation college student, I also hope this prize will help encourage young people to pursue careers in physics and quantum materials research."</p> <p>The Buckley Prize recognizes outstanding theoretical or experimental contributions to condensed matter physics, and includes a $20,000 award. Ten other MIT physicists have received this award, including Xiaogang-Wen (2017), Jagadeesh Moodera, Paul Tedrow and Robert Mersevey (2009), and Mildred Dresselhaus (2008). "I never imagined I would be seeing my name in a list with the distinguished colleagues and friends that got this award earlier,” he said.</p> <p>Jarillo-Herrero joined MIT in 2008 and was promoted to full professor in 2018. He received his "licenciatura" in physics from the University of Valencia in Spain, in 1999; a master of science degree from the University of California at San Diego in 2001; and his PhD from the Delft University of Technology in the Netherlands, in 2005.&nbsp;</p> <p><strong>Richard Milner</strong></p> <p>Milner’s research group performed a series of experiments carried out over three decades at electron storage rings at the Deutsches Elektronen-Synchrotron (DESY) laboratory in Hamburg, Germany, and at the MIT-owned Bates Research and Engineering Center.</p> <p>“The scientific focus was to use electron scattering from internal gas targets to gain insight into the origin of spin and charge in the nucleon, as well as to understand fundamental aspects of the quantum mechanics of electron-proton scattering,” says Milner.</p> <p>Milner’s experimental work with internal polarized targets include the HERMES and Olympus projects at DESY, BLAST at the Bates Lab South Hall Ring, and the Darklight collaboration at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility (Jefferson Lab).</p> <p>The Bonner Prize recognizes outstanding experimental research in nuclear physics, including the development of a method, technique, or device that significantly contributes in a general way to nuclear physics research, and includes a $10,000 award.&nbsp;</p> <p>“Richard is an experimental nuclear physicist who has made contributions to the field at all levels, from the most technical to providing leadership for the nuclear physics community,” physics department head Peter Fisher said in his nomination letter.</p> <p>Milner was a co-organizer of the Electron Ion Collider (EIC) collaboration that played a key role in the years 2005-10 in developing the EIC science case and in stimulating the involvement of users across the worldwide quantum chromodynamics community. He also has been a longtime proponent for the EIC, which would be the largest accelerator facility in the United States, second only to CERN’s Large Hadron Collider. The EIC would smash together beams of protons and electrons to provide “snapshots” into the fundamental structure of matter.&nbsp;&nbsp;</p> <p>Fisher cited Milner’s leadership in the physics community, such as transitioning the Bates Lab from a national user facility to a research and engineering center to attract companies such as Raytheon and Passport. As former director of the MIT Laboratory for Nuclear Science (LNS), he attracted new faculty, and worked with the U.S. Department of Energy on several projects.</p> <p>Milner credits his physics colleagues Professor Robert Redwine, former director of the Bates Research and Engineering Center, and theoretical Senior Research Scientist T. William Donnelly; and, at LNS, Principal Research Scientist Douglas Hasell and Principal Research Engineer James Kelsey, “with essential contributions vital to the success of the experiments recognized by the&nbsp;Bonner Prize.”</p> <p>He joined the Department of Physics in 1988, was director of the then-called MIT-Bates Linear Accelerator Center from 1998 to 2006, and served as director of MIT LNS from 2006 to 2015. He is also collaborating on the Arts at MIT’s “<a href="https://arts.mit.edu/artists/richard-milner-visualizing-the-proton/#about-the-project">Visualizing the Proton</a>” project — a video for middle and high school science students that highlights physicists’ current understanding of the structure of the proton in terms of its fundamental constituents.</p> <p><strong>James Collins</strong></p> <p>Formerly known as the Biological Physics Prize, the Delbruck Prize includes $10,000, an allowance for travel to attend the meeting at which the prize is awarded, and a certificate citing the contributions made by the recipient or recipients. It is presented annually.</p> <p>“Max Delbruck was a world-class physicist whose work on bacteriophages helped to launch the molecular biology revolution,” says Collins. “To be associated with&nbsp;his name for our work in synthetic biology at the interface of biology and&nbsp;physics is a great honor."</p> <p>His many pioneering contributions at the physics-biology interface include applications of nonlinear dynamics and statistical physics to biological systems at multiple levels, ranging from human balance control to neurosensory function to cardiac dynamics to natural and synthetic gene networks.</p> <p>“He is an extraordinary physicist, besides being an outstanding engineer and biologist,” says his nominator, Gabor Balazsi, the Henry Laufer Associate Professor at Stony Brook University. “Collins has a unique ability to make fundamental discoveries by cross-disciplinary approaches.”</p> <p>“Collins' 2000 <em>Nature </em>paper (cited ~4000 times) marks the beginnings of synthetic biology, which is likely to have major impacts on biological physics by deciphering the function of natural gene regulatory networks,” wrote Laufer. “Collins’ radically innovative discoveries and path-blazing work are transforming biological physics, medicine, and the biomedical sciences in many ways that shape the future. His work clearly demonstrates how cutting-edge biological physics research can answer fundamental questions about life, and improve human lives.”</p> <p>Collins is the senior author of a recent study that uses CRISPR to create novel materials, such as gels, that can change their properties when they encounter specific DNA sequences. This could be used to respond to viral and bacterial outbreaks, monitor antibiotic resistance, and detect cancer. “The scientific possibilities get very exciting very quickly,” Collins said.</p> <p>Collins is a member of the Harvard-MIT Health Sciences and Technology faculty. He is also a core founding faculty member of the Wyss Institute for Biologically Inspired Engineering at Harvard University and an Institute Member of the Broad Institute of MIT and Harvard. Collins' honors include a Rhodes Scholarship, a MacArthur Fellowship, and an NIH Director's Pioneer Award. Collins is also an elected member of the National Academy of Sciences, the National Academy of&nbsp;Engineering, and the National Academy of Medicine.</p> American Physical Society honorees (left to right): Richard Milner and Pablo Jarillo-Herrero, professors of physics, and James Collins, professor of biological engineering.Physics, Biological engineering, Laboratory for Nuclear Science, School of Science, School of Engineering, Harvard-MIT Health Sciences and Technology, Broad Institute, Awards, honors and fellowships, CRISPR, Diagnostic devices, Graphene Enhanced nuclear energy online class aims to inform and inspire http://news.mit.edu/2019/enhanced-nuclear-energy-mooc-aims-to-inform-inspire-1024 Revamped version of MITx MOOC includes new modules on nuclear security, nuclear proliferation, and quantum engineering. Thu, 24 Oct 2019 14:30:01 -0400 Leda Zimmerman | Department of Nuclear Science and Engineering http://news.mit.edu/2019/enhanced-nuclear-energy-mooc-aims-to-inform-inspire-1024 <p>More than 3,000 users hailing from 137 countries signed up for the MIT Department of Nuclear Energy's debut massive open online course (MOOC), Nuclear Energy: Science, Systems and Society, which debuted last year on <em>MITx. </em>Now, after roaring success, the course will be <a href="https://www.edx.org/course/nuclear-energy-science-systems-and-society" target="_blank">offered again</a> in spring 2020, with key upgrades.</p> <p>“We had hoped there was an appetite in the general public for information about nuclear energy and technology,” says Jacopo Buongiorno, the TEPCO Professor of Nuclear Science and Engineering and one of the course instructors. “We were fully confirmed by this first offering.”</p> <p>Unfolding over nine weeks, the MOOC provides a primer on nuclear energy and radiation and the wide-ranging applications of nuclear technology in medicine, security, energy, and research. It aims not just to educate, but to capture the interest of a distance-learning audience not necessarily well acquainted with physics and mathematics.</p> <p>“The MOOC builds on a tradition in our department of a first-year seminar that exposes students to a broad overview of the field,” says another instructor, Anne White, professor and head, Department of Nuclear Science and Engineering. “We set ourselves the challenge of translating the experience of being MIT first-years, who jump into something they know nothing about, and come out with excitement for the foundations of the field and its frontiers.”</p> <p>Before setting out to tackle this problem, the creative team — which also includes Michael Short, the Class of ’42 Career Development Assistant Professor of Nuclear Science and Engineering, and John Parsons, senior lecturer in the Finance Group at MIT Sloan School of Management — carefully reviewed existing online nuclear science offerings.</p> <p>“When we looked at MOOCs out in the world, a lot of them are wonderful, but highly technical,” says White. “We had a different vision of what MIT could accomplish, and that was reaching a big audience of virtual first-years.”</p> <p>For last year’s launch, the MOOC was structured around three modules. The first, taught by Short, introduced nuclear science at the atomic level. “We focused on the basics — the nucleus and particles, and the technologies that naturally emerge out of the study of the discipline,” says Buongiorno. This included a close look at ionizing radiation and how to measure it, with an invitation for online users to build a simple Geiger counter to measure radiation in their own backyards.</p> <p>The second module, led by Buongiorno and Parsons, delved into how nuclear reactors function, what makes nuclear energy attractive, issues of safety and waste, and questions of nuclear power plant economics and policy.</p> <p>The third module, taught by White, discussed magnetic fusion energy research, with a look at pioneering work at MIT and elsewhere dealing with high-magnetic-field fusion. “We lay the foundation first for fission power, and see a lot of enthusiasm about decarbonizing the grid in the short term,” says White. “We then present fusion power and MIT’s SPARC experiment, which really captures students’ imagination with its potential as a future energy source.”</p> <p>Translating key elements of nuclear science and technology syllabi from the MIT classroom setting to prerecorded video segments, slides, and online assessments for the MOOC proved a significant effort for instructors.</p> <p>“Much of the material was drawn from classes we collectively taught, and it took nearly a year to develop this curriculum and make sure it was the right content, at the right level,” says Buongiorno. “It was a huge challenge to make this intelligible and attractive to a much broader audience than usual, people without a science background, or who might not be on the same page around energy.” It was, he adds, “more difficult than a typical class I teach.”</p> <p>The MOOC included opportunities for students to interact with each other and the instructors at key junctures, through the means of online write-in forums. Buongiorno and his colleagues had hoped to duplicate online the vibrant interactions of residential classrooms, and even offer office hours, but it proved infeasible. “Because of the geographic distribution of participants, it made no sense; half of the students would be excluded because the event would be taking place in the middle of the night.”</p> <p>The team, not content to rest on its laurels, is adding elements for the MOOC’s second run: R. Scott Kemp, the MIT Class of ’43 Associate Professor of Nuclear Science and Engineering, will teach a new module on nuclear security and nuclear proliferation, and Paola Cappellaro, the Esther and Harold E. Edgerton Associate Professor of Nuclear Science and Engineering, will offer a module on quantum engineering.</p> <p>In addition to this expansion, White envisions an eventual residential version of the course, where first-years could take the MOOC online and attend seminars on campus to receive MIT credit. “Our goal as a department is not just educating majors in nuclear science and engineering, but creating classes appealing to students outside the major,” she says. “It’s in the pipeline.”</p> <p>Given rising concern about climate change, and the emergence of new technologies in fission and fusion, the timing of this MOOC seems propitious to its founding team.</p> <p>“We’d like to have an impact with the course on the greater debate about the use of nuclear energy as part of the solution for climate change,” says Buongiorno. “The public in this debate needs science-based input and facts about different technologies, which is one of our major objectives.” Adds White, “We believe the course will appeal to folks working in government, policy, industry, as well as to those who are simply curious about what’s happening at the frontiers of our field.”</p> “We’d like to have an impact with the course on the greater debate about the use of nuclear energy as part of the solution for climate change,” says Professor Jacopo Buongiorno.Nuclear science and engineering, School of Engineering, Sloan School of Management, Classes and programs, Education, teaching, academics, Design, Energy, Environment, Nuclear power and reactors, EdX, Physics, Fusion, Massive open online courses (MOOCs), Climate change, MITx A new way to corrosion-proof thin atomic sheets http://news.mit.edu/2019/corrosion-proof-atomic-sheets-1004 Ultrathin coating could protect 2D materials from corrosion, enabling their use in optics and electronics. Fri, 04 Oct 2019 00:00:00 -0400 David L. Chandler | MIT News Office http://news.mit.edu/2019/corrosion-proof-atomic-sheets-1004 <p>A variety of two-dimensional materials that have promising properties for optical, electronic, or optoelectronic applications have been held back by the fact that they quickly degrade when exposed to oxygen and water vapor. The protective coatings developed thus far have proven to be expensive and toxic, and cannot be taken off.</p> <p>Now, a team of researchers at MIT and elsewhere has developed an ultrathin coating that is inexpensive, simple to apply, and can be removed by applying certain acids.</p> <p>The new coating could open up a wide variety of potential applications for these “fascinating” 2D materials, the researchers say. Their findings are reported this week in the journal <em>PNAS</em>, in a paper by MIT graduate student Cong Su; professors Ju Li, Jing Kong, Mircea Dinca, and Juejun Hu; and 13 others at MIT and in Australia, China, Denmark, Japan, and the U.K.</p> <p>Research on 2D materials, which form thin sheets just one or a few atoms thick, is “a very active field,” Li says. Because of their unusual electronic and optical properties, these materials have promising applications, such as highly sensitive light detectors. But many of them, including black phosphorus and a whole category of materials known as transition metal dichalcogenides (TMDs), corrode when exposed to humid air or to various chemicals. Many of them degrade significantly in just hours, precluding their usefulness for real-world applications.</p> <p>“It’s a key issue” for the development of such materials, Li says. “If you cannot stabilize them in air, their processability and usefulness is limited.” One reason silicon has become such a ubiquitous material for electronic devices, he says, is because it naturally forms a protective layer of silicon dioxide on its surface when exposed to air, preventing further degradation of the surface. But that’s more difficult with these atomically thin materials, whose total thickness could be even less than the silicon dioxide protective layer.</p> <p>There have been attempts to coat various 2D materials with a protective barrier, but so far they have had serious limitations. Most coatings are much thicker than the 2D materials themselves. Most are also very brittle, easily forming cracks that let through the corroding liquid or vapor, and many are also quite toxic, creating problems with handling and disposal.</p> <p>The new coating, based on a family of compounds known as linear alkylamines, improves on these drawbacks, the researchers say. The material can be applied in ultrathin layers, as little as 1 nanometer (a billionth of a meter) thick, and further heating of the material after application heals tiny cracks to form a contiguous barrier. The coating is not only impervious to a variety of liquids and solvents but also significantly blocks the penetration of oxygen. And, it can be removed later if needed by certain organic acids.</p> <p>“This is a unique approach” to protecting thin atomic sheets, Li says, that produces an extra layer just a single molecule thick, known as a monolayer, that provides remarkably durable protection. “This gives the material a factor of 100 longer lifetime,” he says, extending the processability and usability of some of these materials from a few hours up to months. And the coating compound is “very cheap and easy to apply,” he adds.</p> <p>In addition to theoretical modeling of the molecular behavior of these coatings, the team made a working photodetector from flakes of TMD material protected with the new coating, as a proof of concept. The coating material is hydrophobic, meaning that it strongly repels water, which otherwise would diffuse into the coating and dissolve away a naturally formed protective oxide layer within the coating, leading to rapid corrosion.</p> <p>The application of the coating is a very simple process, Su explains. The 2D material is simply placed into bath of liquid hexylamine, a form of the linear alkylamine, which builds up the protective coating after about 20 minutes, at a temperature of 130 degrees Celsius at normal pressure. Then, to produce a smooth, crack-free surface, the material is immersed for another 20 minutes in vapor of the same hexylamine.</p> <p>“You just put the wafer into this liquid chemical and let it be heated,” Su says. “Basically, that’s it.” The coating “is pretty stable, but it can be removed by certain very specific organic acids.”</p> <p>The use of such coatings could open up new areas of research on promising 2D materials, including the TMDs and black phosphorous, but potentially also silicene, stanine, and other related materials. Since black phosphorous is the most vulnerable and easily degraded of all these materials, that’s what the team used for their initial proof of concept.</p> <p>The new coating could provide a way of overcoming “the first hurdle to using these fascinating 2D materials,” Su says. “Practically speaking, you need to deal with the degradation during processing before you can use these for any applications,” and that step has now been accomplished, he says.</p> <p>The team included researchers in MIT’s departments of Nuclear Science and Engineering, Chemistry, Materials Science and Engineering, Electrical Engineering and Computer Science, and the Research Laboratory of Electronics, as well as others at the Australian National University, the University of Chinese Academy of Sciences, Aarhus University in Denmark, Oxford University, and Shinshu University in Japan. The work was supported by the Center for Excitonics and the Energy Frontier Research Center funded by the U.S. Department of Energy, and by the National Science Foundation, the Chinese Academy of Sciences, the Royal Society, the U.S. Army Research Office through the MIT Institute for Soldier Nanotechnologies, and Tohoku University.</p> This diagram shows an edge-on view of the molecular structure of the new coating material. The thin layered material being coated is shown in violet at bottom, and the ambient air is shown as the scattered molecules of oxygen and water at the top. The dark layer in between is the protective material, which allows some oxygen (red) through, forming an oxide layer below that provides added protection.Illustration courtesy of the researchers.Research, 2-D, Nuclear science and engineering, Materials Science and Engineering, DMSE, Nanoscience and nanotechnology, Physics, Electrical Engineering & Computer Science (eecs), Research Laboratory of Electronics, Department of Energy (DoE), National Science Foundation (NSF), School of Engineering, School of Science How to dismantle a nuclear bomb http://news.mit.edu/2019/verify-dismantle-nuclear-bombs-0927 MIT team successfully tests a new method for verification of weapons reduction. Mon, 30 Sep 2019 05:00:00 -0400 Peter Dizikes | MIT News Office http://news.mit.edu/2019/verify-dismantle-nuclear-bombs-0927 <p>How do weapons inspectors verify that a nuclear bomb has been dismantled? An unsettling answer is: They don’t, for the most part. When countries sign arms reduction pacts, they do not typically grant inspectors complete access to their nuclear technologies, for fear of giving away military secrets.</p> <p>Instead, past U.S.-Russia arms reduction treaties have called for the destruction of the delivery systems for nuclear warheads, such as missiles and planes, but not the warheads themselves. To comply with the START treaty, for example, the U.S. cut the wings off B-52 bombers and left them in the Arizona desert, where Russia could visually confirm the airplanes’ dismemberment.</p> <p>It’s a logical approach but not a perfect one. Stored nuclear warheads might not be deliverable in a war, but they could still be stolen, sold, or accidentally detonated, with disastrous consequences for human society.</p> <p>“There’s a real need to preempt these kinds of dangerous scenarios and go after these stockpiles,” says Areg Danagoulian, an MIT nuclear scientist. “And that really means a verified dismantlement of the weapons themselves.”</p> <p>Now MIT researchers led by Danagoulian have successfully tested a new high-tech method that could help inspectors verify the destruction of nuclear weapons. The method uses neutron beams to establish certain facts about the warheads in question — and, crucially, uses an isotopic filter that physically encrypts the information in the measured data.</p> <p>A paper detailing the experiments, “A physically cryptographic warhead verification system using neutron induced nuclear resonances,” is being published today in <em>Nature Communications</em>. The authors are Danagoulian, who is an&nbsp;assistant professor of nuclear science and engineering at MIT, and graduate student Ezra Engel. Danagoulian is the corresponding author.</p> <p><strong>High-stakes testing</strong></p> <p>The experiment builds on previous theoretical work, by Danagoulian and other members of his research group, who last year published two papers detailing computer simulations of the system. The testing took place at the Gaerttner Linear Accelerator (LINAC) Facility on the campus of Rensselaer Polytechnic Institute, using a 15-meter long section of the facility’s neutron-beam line.</p> <p>Nuclear warheads have a couple of characteristics that are central to the experiment. They tend to use particular isotopes of plutonium — varieties of the element that have different numbers of neutrons. And nuclear warheads have a distinctive spatial arrangement of materials.</p> <p>The experiments consisted of sending a horizontal neutron beam first through a proxy of the warhead, then through a an encrypting filter scrambling the information. The beam’s signal was then sent to a lithium glass detector, where a signature of the data, representing some of its key properties, was recorded. The MIT tests were performed using molybdenum and tungsten, two metals that share significant properties with plutonium and served as viable proxies for it.</p> <p>The test works, first of all, because the neutron beam can identify the isotope in question.</p> <p>“At the low energy range, the neutrons’ interactions are extremely isotope-specific,” Danagoulian says. “So you do a measurement where you have an isotopic tag, a signal which itself embeds information about the isotopes and the geometry. But you do an additional step which physically encrypts it.”</p> <p>That physical encryption of the neutron beam information alters some of the exact details, but still allows scientists to record a distinct signature of the object and then use it to perform object-to-object comparisons. This alteration means a country can submit to the test without divulging all the details about how its weapons are engineered.</p> <p>“This encrypting filter basically covers up the intrinsic properties of the actual classified object itself,” Danagoulian explains.</p> <p>It would also be possible just to send the neutron beam through the warhead, record that information, and then encrypt it on a computer system. But the process of physical encryption is more secure, Danagoulian notes: “You could, in principle, do it with computers, but computers are unreliable. They can be hacked, while the laws of physics are immutable.”</p> <p>The MIT tests also included checks to make sure that inspectors could not reverse-engineer the process and thus deduce the weapons information countries want to keep secret.</p> <p>To conduct a weapons inspection, then, a host country would present a warhead to weapons inspectors, who could run the neutron-beam test on the materials. If it passes muster, they could run the test on every other warhead intended for destruction as well, and make sure that the data signatures from those additional bombs match the signature of the original warhead.</p> <p>For this reason, a country could not, say, present one real nuclear warhead to be dismantled, but bamboozle inspectors with a series of identical-looking fake weapons. And while many additional protocols would have to be arranged to make the whole process function reliably, the new method plausibly balances both disclosure and secrecy for the parties involved.</p> <p><strong>The human element</strong></p> <p>Danagoulian believes putting the new method through the testing stage has been a significant step forward for his research team.</p> <p>“Simulations capture the physics, but they don’t capture system instabilities,” Danagoulian says. “Experiments capture the whole world.”</p> <p>In the future, he would like to build a smaller-scale version of the testing apparatus, one that would be just 5 meters long and could be mobile, for use at all weapons sites.</p> <p>“The purpose of our work is to create these concepts, validate them, prove that they work through simulations and experiments, and then have the National Laboratories to use them in their set of verification techniques,” Danagoulian says, referring to U.S. Department of Energy scientists.</p> <p>Karl van Bibber, a professor in the Department of Nuclear Engineering at the University of California at Berkeley, who has read the group’s papers, says “the work is promising and has taken a large step&nbsp;forward,” but adds that “there is yet a ways to go” for the project. More specifically, van Bibber notes, in the recent tests it was easier to detect fake weapons based on the isotopic characteristics of the materials rather than their spatial arrangements. He believes testing at the relevant U.S. National Laboratories — Los Alamos or Livermore — would help further assess the verification techniques on sophisticated missile designs.</p> <p>Overall, van Bibber adds, speaking of the researchers, “their persistence is paying off, and the treaty&nbsp;verification community has got to be paying attention.”</p> <p>Danagoulian also emphasizes the seriousness of nuclear weapons disarmament. A small cluster of several modern nuclear warheads, he notes, equals the destructive force of every armament fired in World War II, including the atomic bombs dropped on Hiroshima and Nagasaki. The U.S. and Russia possess about 13,000 nuclear weapons between them.</p> <p>“The concept of nuclear war is so big that it doesn’t [normally] fit in the human brain,” Danagoulian says. “It’s so terrifying, so horrible, that people shut it down.”</p> <p>In Danagoulian’s case, he also emphasizes that, in his case, becoming a parent greatly increased his sense that action is needed on this issue, and helped spur the current research project.</p> <p>“It put an urgency in my head,” Danagoulian says. “Can I use my knowledge and my skill and my training in physics to do something for society and for my children? This is the human aspect of the work.”</p> <p>The research was supported, in part, by a U.S. Department of Energy National Nuclear Security Administration Award.</p> Back, standing (left to right): William Koch, Jacob Bickus, David Stern*, Hin “Jimmy” Lee Front, seated (Left to right): Ruaridh Macdonald, Areg Danagoulian, Ethan Klein *David Stern is a student at Tufts who is working this summer in Areg’s Lab. Melanie Gonick, MITResearch, Nuclear science and engineering, School of Engineering, Nuclear security and policy, Security studies and military, Cryptography Four from MIT named American Physical Society Fellows for 2019 http://news.mit.edu/2019/four-from-mit-named-american-physical-society-fellows-0920 Matthew Evans, Joseph Formaggio, Markus Klute, and Anne White are named MIT’s newest APS fellows for their contributions to physics. Fri, 20 Sep 2019 14:00:01 -0400 Fernanda Ferreira | School of Science http://news.mit.edu/2019/four-from-mit-named-american-physical-society-fellows-0920 <p>Four members of the MIT community have been elected fellows of the <a href="https://www.aps.org/programs/honors/fellowships/index.cfm">American Physical Society</a> (APS) for 2019. The APS fellowship was created in 1921 for those in the physics community to recognize peers who have contributed to advances in physics through original research, innovative applications, teaching, and leadership.</p> <p><a href="https://web.mit.edu/physics/people/faculty/evans_matthew.html">Matthew Evans</a> is a professor of physics, a member of the MIT Kavli Institute of Astrophysics and Space Research, and a member of the MIT Laser Interferometer Gravitational-Wave Observatory (LIGO) research group. Evans was nominated by APS’ Division of Gravitational Physics for his “critical contributions to the development of advanced gravitational-wave detectors, as well as for developing techniques to enable further improvements in detector sensitivity, and for leading community efforts to design future large-scale ground-based detectors.”</p> <p><a href="https://web.mit.edu/physics/people/faculty/formaggio_joseph.html">Joseph A. Formaggio</a> is a professor of physics and a member of the Laboratory of Nuclear Science. Formaggio was nominated by APS’ Division of Nuclear Physics for his “leadership in the pursuit of neutrino masses determination, and for developing novel technologies to attack the problem of direct detection.”</p> <p><a href="https://web.mit.edu/physics/people/faculty/klute_markus.html">Markus Klute</a> is a professor of physics and member of the Laboratory of Nuclear Science. Klute was nominated by APS’ Division of Particles and Fields for his “work establishing the coupling of the Higgs boson to tau leptons, and for establishing the physics case for colliders beyond the Large Hadron Collider, including the High Luminosity LHC.”</p> <p><a href="http://web.mit.edu/nse/people/faculty/white.html">Anne White</a> is a professor and head of the Department of Nuclear Science and Engineering. Nominated by the APS’ Division of Plasma Physics, White was cited for her “outstanding contributions and leadership in understanding turbulent electron heat transport in magnetically confined fusion plasmas via diagnostic development, novel experimentation, and validation of nonlinear gyrokinetic codes.”</p> Four MIT faculty have been named 2019 American Physics Society Fellows: (left to right) Matthew Evans, Joseph Formaggio, Markus Klute, and Anne White. Photos courtesy of the researchers (Bryce Vickmark for Anne White)Awards, honors and fellowships, Faculty, Physics, LIGO, Kavli Institute, Laboratory for Nuclear Science, Nuclear science and engineering, School of Science, School of Engineering 3Q: Scientists shave estimate of neutrino’s mass in half http://news.mit.edu/2019/katrin-neutrino-mass-half-0917 Joseph Formaggio explains the discovery that the ghostly particle must be no more than 1 electronvolt, half as massive as previously thought. Mon, 16 Sep 2019 23:59:59 -0400 Jennifer Chu | MIT News Office http://news.mit.edu/2019/katrin-neutrino-mass-half-0917 <p><em>An international team of scientists, including researchers at MIT, has come closer to pinning down the mass of the elusive neutrino. These ghost-like particles permeate the universe and yet are thought to be nearly massless, streaming by the millions through our bodies while leaving barely any physical trace. </em></p> <p><em>The researchers have determined that the mass of the neutrino should be no more than 1 electron volt. Scientists previously estimated the upper limit of the neutrino’s mass to be around 2 electron volts, so this new estimate shaves down the neutrino’s mass range by more than half. </em></p> <p><em>The new estimate was determined based on data taken by KATRIN, the Karlsruhe Tritium Neutrino Experiment, at the Karlsruhe Institute of Technology in Germany, and reported at the 2019 Conference on Astroparticle and Underground Physics last week. The experiment triggers tritium gas to decay, which in turn releases neutrinos, along with electrons. While the neutrinos&nbsp; are quick to dissipate, KATRIN’s sequence of magnets directs tritium’s electrons into the the heart of the experiment — a giant 200-ton spectrometer, where the electrons’ mass and energy can be measured, and from there, researchers can calculate the mass of the corresponding neutrinos.</em></p> <p><em>Joseph Formaggio, professor of physics at MIT, is a leading member of the KATRIN experimental group, and spoke with </em>MIT News<em> about the new estimate and the road ahead in the neutrino search.</em></p> <p><strong>Q:</strong> The neutrino, based on KATRIN’s findings, can’t be more massive than 1 electron volt. Put this context for us: How light is this, and how big a deal is it that the neutrino’s maximum mass could be half of what people previously thought?</p> <p><strong>A:</strong> Well, that’s somewhat of a difficult question, since people (myself included) don’t really have an intuitive sense of what the mass is of&nbsp;any&nbsp;particle, but let’s try. Consider something very small, like a virus. Each virus is made up of roughly 10 million&nbsp;proton<em>s</em>. Each proton weighs about 2,000 times more than each&nbsp;electron&nbsp;inside that virus. And what our results showed is that the neutrino has a mass less than 1/ 500,000 of a single electron!</p> <p>Let me put it another way. In each cubic centimeter of space around you, there are about 300 neutrinos zipping through. These are remnants of the early universe, just after the Big Bang. If you added up all the neutrinos residing inside the sun, you’d get about a kilogram or less. So, yeah, it’s small.</p> <p><strong>Q:</strong> What went into determining this new mass limit for the neutrino, and what was MIT’s role in the search?</p> <p><strong>A:</strong> This new mass limit comes from studying the radioactive decay of tritium, an isotope of hydrogen. When tritium decays, it produces a helium-3 ion, an electron, and an antineutrino. We actually never see the antineutrino, however; the electron carries information about the neutrino’s mass. By studying the energy distribution of the electrons ejected at the highest energies allowed, we can deduce the mass of the neutrino, thanks to Einstein’s equation, E=mc<sup>2</sup>.</p> <p>However, studying those high-energy electrons is very difficult. For one thing, all the information about the neutrino is embedded in a tiny fraction of the spectrum — less than 1 billionth of decays are of use for this measurement. So, we need a lot of tritium inventory. We also need to measure the energy of those electrons very, very precisely. This is why the KATRIN experiment is so tricky to build. Our very first measurement presented today is the culmination of almost two decades of hard work and planning.</p> <p>MIT joined the KATRIN experiment when I came to Boston in 2005. Our group helped develop the simulation tools to understand the response of our detector to high precision. More recently, we have been involved in developing tools to analyze the data collected by the experiment.</p> <p><strong>Q:</strong> Why does the mass of a neutrino matter, and what will it take to zero in on its exact mass?</p> <p><strong>A:</strong> The fact that neutrinos have any mass at all was a surprise to many physicists. Our earlier models predicted that the neutrino should have exactly zero mass, an assumption dispelled by the <a href="http://news.mit.edu/2015/3q-massive-impact-neutrino-research-1006">discovery</a> that neutrinos oscillate between different types. That means we do not really understand the mechanism responsible for neutrino masses, and it is likely to be very different than how other particles attain mass. Also, our universe is filled with primordial neutrinos from the Big Bang. Even a tiny mass has a significant impact on the structure and evolution of the universe because they are so aplenty.</p> <p>This measurement represents just the beginning of KATRIN’s measurement. With just about one month of data, we were able to improve previous experimental limits by a factor of two. Over the next few years, these limits will steadily improve, hopefully resulting in a positive signal (rather than just a limit). There are also a number of other direct neutrino mass experiments on the horizon that are also competing to reach greater sensitivity, and with it, discovery!</p> KATRIN’s spectrometer, shown here, precisely measures the energy of electrons emitted in the decay of tritium, which has helped scientists come closer to pinning down the mass of the ghost-like neutrino.Image: The KATRIN CollaborationAstrophysics, Physics, Research, School of Science, 3 Questions, Space, astronomy and planetary science, Neutrinos, Laboratory for Nuclear Science Department of Nuclear Science and Engineering spreads its wings http://news.mit.edu/2019/nuclear-science-and-engineering-spreads-its-wings-0913 New 22-ENG undergraduate degree provides expansive vision of nuclear studies and nuclear careers. Fri, 13 Sep 2019 12:40:01 -0400 Leda Zimmerman | Nuclear science and engineering http://news.mit.edu/2019/nuclear-science-and-engineering-spreads-its-wings-0913 <p>After a nearly five-year effort, fueled by the passionate persistence of faculty and students, the Department of Nuclear Science and Engineering (NSE) began offering a new degree this fall: 22-ENG, a program that offers the same fundamentals in the discipline as Course 22, but with considerably more flexibility in course selection. Institute faculty approved the new degree in April.</p> <p>“I’m very relieved,” says junior Colt Hermesch, who is in the naval ROTC program. “I discovered I really liked quantum physics late in my academic career, and by switching to the new degree, I can take what I’m interested in and still major in nuclear.”</p> <p>This is precisely the kind of response anticipated by Michael Short ’05, SM and PhD ’10, undergraduate chair of the department, and the Class of ’42 Associate Professor of Nuclear Science and Engineering. In 2014, the department tasked Short with reforming the undergraduate curriculum. He says that 22-ENG was motivated largely by mounting student demand for a path of study in nuclear science and engineering that doesn’t lead exclusively to traditional jobs in the nuclear industry.</p> <p>“Every year I’ve been advising, increasing numbers of students have expressed interest in focusing their nuclear studies on topics like materials, robotics, policy, or sustainability,” says Short. “These are hybrid fields, fields of the future, but in spite of this growing demand, until now we have had no mechanism in the department for helping them.”</p> <p>The new flex degree will allow students, once they have completed a cluster of required courses, to focus in such areas as nuclear medicine, clean energy technologies, policy, fusion, plasma science, nuclear computation, nuclear materials, and modeling/simulation. Working with their advisors, undergraduates will be able to map out a customized suite of classes in a nuclear-relevant discipline of their creation.</p> <p>Sophomore Analyce Hernandez is wasting no time in taking advantage of this new degree option. “I was so excited to hear about it, and rushed to lay out a course map with my adviser,” she says. Hernandez was worried about double majoring in Course 22 and physics because of the formidable class requirements. “With 22-ENG, I don’t have to choose one over the other.”</p> <p>Short says he has seen too many students forced to make comparably tough choices. Some, due to personal choices, depart from their true passion in nuclear science for other majors that offer opportunities which they believe can more easily secure them jobs at Google or Facebook. Others “were leaving our major because they can’t pursue subjects they become deeply invested in, often through lab work,” says Short. “People should not be penalized for having gigantic passions that don’t fit into one of our boxes.”</p> <p>He believes with its larger menu of topics, trimmed requirements, and connection to real-world applications of NSE, 22-ENG will both retain students who might be on the fence about majoring in NSE, and capture new candidates to the field.</p> <p><strong>Seeking alternatives</strong></p> <p>Junior Daniel Korsun personifies the kind of passionate student Short hopes to persuade to commit to NSE.</p> <p>“I became interested in NSE as a freshman, and quickly realized I wanted to pursue fusion, both for my education and as a career,” Korsun says. But it became clear to him that Course 22 would not allow him break out and explore fusion at the depth he desired. “The current degree is rigorous and demanding, which is great, but it primarily prepares students for traditional nuclear careers or doctorates in fission,” he says.</p> <p>In conversations with fellow undergrads, Korsun discovered that he was not alone in yearning for alternatives: “A lot of my friends were also interested in pursuing different subfields within NSE, such as materials science and sustainability, but the coursework just didn’t support them.”</p> <p>Last spring, Korsun decided to act. Working with NSE academic administrator Brandy Baker, Korsun developed suggestions for a flexible degree parallel to those offered by mechanical engineering and physics. “We laid out a reasonable course load, retaining the core requirements, but added choices for specialization,” says Korsun. “We sent the proposal off to Professor Short, and he loved the idea.”</p> <p>The flex degree idea resonated powerfully for Short because he had been pressing to create something like it for years. “When I started here as an undergraduate in 2001, I worked in Ron Ballinger’s nuclear materials lab, and I loved it — I knew immediately it was my calling,” he says. “But when I began looking for NSE classes that could help get me further into this research, there weren’t any.”</p> <p>Short’s solution was to major in both nuclear engineering and materials science. “It was intellectually stimulating, and miserable in terms of work/life balance,” he says. Others in his cohort who wanted a deep immersion in a subdiscipline of nuclear would rather change majors and minor in nuclear engineering. So when Short joined the NSE faculty in 2013, he sought opportunities to make the curriculum more welcoming to undergraduates.</p> <p>That moment arrived the next year, when he was charged with rethinking the undergraduate curriculum. “I said great, I’ve got stuff I’ve wanted to do for a decade,” says Short.</p> <p>Some of Short’s initiatives were implemented quickly. He found ways to bring hands-on learning to early classes, ensuring multiple modes of engagement to the fundamentals of NSE. The previous theory-first, applications-later curricular framework was viewed by the students and Short as “boring.” Short also sought to trim certain classes from Course 22 that he felt were not essential to mastering the central tenets of nuclear engineering. Eliminating what he calls “dangling ends in the curriculum” — advanced courses like waves and vibrations, and analog electronics — could make room for electives that offered students the chances for immersion in nuclear domains that link more directly to careers. Short had the outlines for the new flex degree.</p> <p>With the impetus of students like Korsun, and “after much collegial debate,” according to Short, the NSE faculty added 22-ENG to its curriculum.</p> <p><strong>In sync with institutional reforms</strong></p> <p>With its debut right around the corner, the new degree promises to position NSE at the vanguard of other large-scale changes at the Institute.</p> <p>For one, 22-ENG will feature a track for computation “to use the latest advances in computing to solve problems related to nuclear,” says Short. This focus area was suggested by Anantha P. Chandrakasan, dean of the School of Engineering, who wanted to create an explicit bridge not just to computer science, but to the new Schwarzman College of Computing.</p> <p>“We’ll be first at the front door, since we’ll launch our track before the new college even starts,” says Short. “When students come for computer science, they will know they can direct their studies toward nuclear.”</p> <p>Adds Dennis Whyte, Hitachi America Professor of Engineering and former head of nuclear science and engineering, “As MIT implements new opportunities for our undergraduates, such as the new college of computing, 22-ENG will serve to grow the evolving demands of our undergraduate student population for a multi-disciplinary education.”</p> <p>The new major explicitly sets out to span fields. It will, for instance, create a focus area in policy and economics, tying NSE more closely to the School of Humanities, Arts, and Social Sciences. “More than any other engineering discipline, nuclear is inseparable from the social sciences, because when you switch on a nuclear plant, everyone takes notice,” says Short. “Every step we take is ultra-scrutinized by ethicists and political scientists, as it should be.” Beyond the specialty track, Short sees “the social problems of nuclear as inseparable from the program as basic nuclear physics,” and will be working to integrate humanities and social sciences into some of the department’s core courses.</p> <p>Benchmarks for the success of NSE curriculum changes will emerge not just in the form of higher enrollment, Short anticipates, but in feedback from future employers of NSE students.</p> <p>“As we send out students with blended skillsets, capable of working in multidisciplinary ways, employers will say, ‘Wow, they’re sending us students both technically expert and well-rounded,’” says Short.</p> <p>This is the type of graduate, he notes, who could save the nuclear industry, which is sorely challenged economically. “Whether they select advanced reactors or fusion reactors, utilities, policy, or advocacy, our students could move the industry beyond the 1960s,” says Short. “They could give new meaning and substance to the department’s motto, ‘science, systems and society.’”</p> "Whether they select advanced reactors or fusion reactors, utilities, policy, or advocacy, our students could move the industry beyond the 1960s,” says MIT Professor Michael Short. “They could give new meaning and substance to the department’s motto, ‘science, systems and society.’”Photo: Gretchen ErtlNuclear science and engineering, School of Engineering, Classes and programs, Education, teaching, academics, Design, Energy, Environment, Nuclear power and reactors, Physics Physicists design an experiment to pin down the origin of the elements http://news.mit.edu/2019/experiment-oxygen-universe-0820 With help from next-generation particle accelerators, the approach may nail down the rate of oxygen production in the universe. Tue, 20 Aug 2019 00:00:00 -0400 Jennifer Chu | MIT News Office http://news.mit.edu/2019/experiment-oxygen-universe-0820 <p>Nearly all of the oxygen in our universe is forged in the bellies of massive stars like our sun. As these stars contract and burn, they set off thermonuclear reactions within their cores, where nuclei of carbon and helium can collide and fuse in a rare though essential nuclear reaction that generates much of the oxygen in the universe.</p> <p>The rate of this oxygen-generating reaction has been incredibly tricky to pin down. But if researchers can get a good enough estimate of what’s known as the “radiative capture reaction rate,” they can begin to work out the answers to fundamental questions, such as the ratio of carbon to oxygen in the universe. An accurate rate might also help them determine whether an exploding star will settle into the form of a black hole or a neutron star. &nbsp;</p> <p>Now physicists at MIT’s Laboratory for Nuclear Science (LNS) have come up with an experimental design that could help to nail down the rate of this oxygen-generating reaction. The approach requires a type of particle accelerator that is still under construction, in several locations around the world. Once up and running, such “multimegawatt” linear accelerators may provide just the right conditions to run the oxgen-generating reaction in reverse, as if turning back the clock of star formation.</p> <p>The researchers say such an “inverse reaction” should give them an estimate of the reaction rate that actually occurs in stars, with higher accuracy than has previously been achieved.</p> <p>“The job description of a physicist is to understand the world, and right now, we don’t quite understand where the oxygen in the universe comes from, and, how oxygen and carbon are made,” says Richard Milner, professor of physics at MIT. “If we’re right, this measurement will help us answer some of these important questions in nuclear physics regarding the origin of the elements.”</p> <p>Milner is a co-author of a paper appearing today in the journal <em>Physical Review C</em>, along with lead author and MIT-LNS postdoc Ivica Friščić and MIT Center for Theoretical Physics Senior Research Scientist T. William Donnelly.</p> <p><strong>A precipitous drop</strong></p> <p>The radiative capture reaction rate refers to the reaction between a carbon-12 nucleus and a helium nucleus, also known as an alpha particle, that takes place within a star. When these two nuclei collide, the carbon nucleus effectively “captures” the alpha particle, and in the process, is excited and radiates energy in the form of a photon. What’s left behind is an oxygen-16 nucleus, which ultimately decays to a stable form of oxygen that exists in our atmosphere.</p> <p>But the chances of this reaction occurring naturally in a star are incredibly slim, due to the fact that both an alpha particle and a carbon-12 nucleus are highly positively charged. If they do come in close contact, they are naturally inclined to repel, in what’s known as a Coulomb’s force. To fuse to form oxygen, the pair would have to collide at sufficiently high energies to overcome Coulomb’s force — a rare occurrence. Such an exceedingly low reaction rate would be impossible to detect at the energy levels that exist within stars.</p> <p>For the past five decades, scientists have attempted to simulate the radiative capture reaction rate, in small yet powerful particle accelerators. They do so by colliding beams of helium and carbon in hopes of fusing nuclei from both beams to produce oxygen. They have been able to measure such reactions and calculate the associated reaction rates. However, the energies at which such accelerators collide particles are far higher than what occurs in a star, so much so that the current estimates of the oxygen-generating reaction rate are difficult to extrapolate to what actually occurs within stars.</p> <p>“This reaction is rather well-known at higher energies, but it drops off precipitously as you go down in energy, toward the interesting astrophysical region,” Friščić says.</p> <p><strong>Time, in reverse</strong></p> <p>In the new study, the team decided to resurrect a previous notion, to produce the inverse of the oxygen-generating reaction. The aim, essentially, is to start from oxygen gas and split its nucleus into its starting ingredients: an alpha particle and a carbon-12 nucleus. The team reasoned that the probability of the reaction happening in reverse should be greater, and therefore more easily measured, than the same reaction run forward. The inverse reaction should also be possible at energies nearer to the energy range within actual stars.</p> <p>In order to split oxygen, they would need a high-intensity beam, with a super-high concentration of electrons. (The more electrons that bombard a cloud of oxygen atoms, the more chance there is that one electron among billions will have just the right energy and momentum to collide with and split an oxygen nucleus.)</p> <p>The idea originated with fellow MIT Research Scientist Genya Tsentalovich, who led a proposed experiment at the MIT-Bates South Hall electron storage ring in 2000.&nbsp; Although the experiment was never carried out at the Bates accelerator, which ceased operation in 2005, Donnelly and Milner felt the idea merited to be studed in detail. With the initiation of construction of next-generation linear accelerators in Germany and at Cornell University, having the capability to produce electron beams of high enough intensity, or current, to potentially trigger the inverse reaction, and the arrival of Friščić at MIT in 2016, the study got underway.</p> <p>“The possibility of these new, high-intensity electron machines, with tens of milliamps of current, reawakened our interest in this [inverse reaction] idea,” Milner says.</p> <p>The team proposed an experiment to produce the inverse reaction by shooting a beam of electrons at a cold, ultradense cloud of oxygen. If an electron successfully collided with and split an oxygen atom, it should scatter away with a certain amount of energy, which physicists have previously predicted. The researchers would isolate the collisions involving electrons within this given energy range, and from these, they would isolate the alpha particles produced in the aftermath.</p> <p>Alpha particles are produced when O-16 atoms split. The splitting of other oxygen isotopes can also result in alpha particles, but these would scatter away slightly faster — about 10 nanoseconds faster — than alpha particles produced from the splitting of O-16 atoms. So, the team reasoned they would isolate those alpha particles that were slightly slower, with a slightly shorter “time of flight.”</p> <p>The researchers could then calculate the rate of the inverse reaction, given how often slower alpha particles — and by proxy, the splitting of O-16 atoms — occurred. They then developed a model to relate the inverse reaction to the direct, forward reaction of oxygen production that naturally occurs in stars.</p> <p>“We’re essentially doing the time-reverse reaction,” Milner says. “If you measure that at the precision we’re talking about, you should be able to directly extract the reaction rate, by factors of &nbsp;up to 20 beyond what anybody has done in this region.”</p> <p>Currently, a multimegawatt linear accerator, MESA, is under construction in Germany. &nbsp;Friščić and Milner are collaborating with physicists there to design the experiment, in hopes that, once up and running, they can put their experiment into action to truly pin down the rate at which stars churn oxygen out into the universe.</p> <p>“If we’re right, and we make this measurement, it will allow us to answer how much carbon and oxygen is formed in stars, which is the largest uncertainty that we have in our understanding of how stars evolve,” Milner says.</p> <p>This research was carried out at MIT’s Laboratory for Nuclear Science and was supported, in part, by the U.S. Department of Energy Office of Nuclear Physics.</p> A new experiment designed by MIT physicists may help to pin down the rate at which huge, massive stars produce oxygen in the universe.Image: NASA/ESA/HubbleBlack holes, Center for Theoretical Physics, Laboratory for Nuclear Science, Nuclear science and engineering, Physics, Research, School of Science, Space, astronomy and planetary science Boosting computing power for the future of particle physics http://news.mit.edu/2019/boosting-computing-power-for-future-particle-physics-mit-lns-0819 Prototype machine-learning technology co-developed by MIT scientists speeds processing by up to 175 times over traditional methods. Mon, 19 Aug 2019 10:20:01 -0400 Laboratory for Nuclear Science http://news.mit.edu/2019/boosting-computing-power-for-future-particle-physics-mit-lns-0819 <p>A new machine learning technology tested by an international team of scientists including MIT Assistant Professor Philip Harris and postdoc Dylan Rankin, both of the Laboratory for Nuclear Science, can spot specific particle signatures among an ocean of Large Hadron Collider (LHC) data in the blink of an eye.</p> <p>Sophisticated and swift, <a href="https://arxiv.org/abs/1904.08986" target="_blank">the new system</a> provides a glimpse into the game-changing role machine learning will play in future discoveries in particle physics as data sets get bigger and more complex.</p> <p>The LHC creates some 40 million collisions every second. With such vast amounts of data to sift through, it takes powerful computers to identify those collisions that may be of interests to scientists, whether, perhaps, a hint of dark matter or a Higgs particle.</p> <p>Now, scientists at Fermilab, CERN, MIT, the University of Washington, and elsewhere have tested a machine-learning system that speeds processing by 30 to 175 times compared to existing methods.</p> <p>Such methods currently process less than one image per second. In contrast, the new machine-learning system can review up to 600 images per second. During its training period, the system learned to pick out one specific type of postcollision particle pattern.</p> <p>“The collision patterns we are identifying, top quarks, are one of the fundamental particles we probe at the Large Hadron Collider,” says Harris, who is a member of the MIT Department of Physics. “It’s very important we analyze as much data as possible. Every piece of data carries interesting information about how particles interact.”</p> <p>Those data will be pouring in as never before after the current LHC upgrades are complete; by 2026, the 17-mile particle accelerator is expected to produce 20 times as much data as it does currently. To make matters even more pressing, future images will also be taken at higher resolutions than they are now. In all, scientists and engineers estimate the LHC will need more than 10 times the computing power it currently has.</p> <p>“The challenge of future running,” says Harris, “becomes ever harder as our calculations become more accurate and we probe ever-more-precise effects.”&nbsp;&nbsp;</p> <p>Researchers on the project trained their new system to identify images of top quarks, the most massive type of elementary particle, some 180 times heavier than a proton. “With the machine-learning architectures available to us, we are able to get high-grade scientific-quality results, comparable to the best top-quark identification algorithms in the world,” Harris explains. “Implementing core algorithms at high speed gives us the flexibility to enhance LHC computing in the critical moments where it is most needed.”</p> Artificial intelligence interfaced with the Large Hadron Collider can lead to higher precision in data analysis, which can improve measurements of fundamental physics properties and potentially lead to new discoveries. Image: FermiLabLaboratory for Nuclear Science, Physics, School of Science, Machine learning, Computer science and technology, Artificial intelligence, Particles, Research Data-mining for dark matter http://news.mit.edu/2019/tracy-slatyer-professor-0816 Tracy Slatyer hunts through astrophysical data for clues to the invisible universe. Thu, 15 Aug 2019 23:59:59 -0400 Jennifer Chu | MIT News Office http://news.mit.edu/2019/tracy-slatyer-professor-0816 <p>When Tracy Slatyer faced a crisis of confidence early in her educational career, Stephen Hawking’s “A Brief History of Time” and a certain fictional janitor at MIT helped to bolster her resolve.</p> <p>Slatyer was 11 when her family moved from Canberra, Australia, to the island nation of Fiji. It was a three-year stay, as part of her father’s work for the South Pacific Forum, an intergovernmental organization.</p> <p>“Fiji was quite a way behind the U.S. and Australia in terms of gender equality, and for a girl to be interested in math and science carried noticeable social stigma,” Slatyer recalls. “I got bullied quite a lot.”</p> <p>She eventually sought guidance from the school counselor, who placed the blame for the bullying on the victim herself, saying that Slatyer wasn’t sufficiently “feminine.” Slatyer countered that the bullying seemed to be motivated by the fact that she was interested in and good at math, and she recalls the counselor’s unsympathetic advice: “Well, yes, honey, that’s a problem you can fix.”</p> <p>“I went home and thought about it, and decided that math and science were important to me,” Slatyer says. “I was going to keep doing my best to learn more, and if I got bullied, so be it.”</p> <p>She doubled down on her studies and spent a lot of time at the library; she also benefited from supportive parents, who gave her Hawking’s groundbreaking book on the origins of the universe and the nature of space and time.</p> <p>“It seemed like the language in which these ideas could most naturally be described was that of mathematics,” Slatyer says. “I knew I was pretty good at math. And learning that that talent was potentially something I could apply to understanding how the universe worked, and maybe how it began, was very exciting to me.”</p> <p>Around this same time, the movie “Good Will Hunting” came out in theaters. The story, of a townie custodian at MIT who is discovered as a gifted mathematician, had a motivating impact on Slatyer.</p> <p>“What my 13-year-old self took out of this was, MIT was a place where, if you were talented at math, people would see that as a good thing rather than something to be stigmatized, and make you welcome — even if you were a janitor or a little girl from Fiji,” Slatyer says. “It was my first real indication that such places might exist. Since then, MIT has been an important symbol to me, of valuing intellectual inquiry and being willing to accept anyone in the world.”</p> <p>This year, Slatyer received tenure at MIT and is now the Jerrold R. Zacharias Associate Professor of Physics and a member of the Center for Theoretical Physics and the Laboratory for Nuclear Science. She focuses on searching through telescope data for signals of mysterious phenomena such as dark matter, the invisible stuff that makes up more than 80 percent of the matter in the universe but has only been detected through its gravitational pull. In her teaching, she seeks to draw out and support a new and diverse crop of junior scientists.</p> <p>“If you want to understand how the universe works, you want the very best and brightest people,” Slatyer says. “It’s essential that theoretical physics becomes more inclusive and welcoming, both from a moral perspective and to get the best science done.”</p> <p><strong>Connectivity</strong></p> <p>Slatyer’s family eventually moved back to Canberra, where she dove eagerly into the city’s educational opportunities.</p> <p>After earning an undergraduate degree from the Australian National University, followed by a brief stint at the University of Melbourne, Slatyer was accepted to Harvard University as a physics graduate student. Her interests were slowly gravitating toward particle physics, but she was unsure about which direction to take. Then, two of her mentors put her in touch with a junior faculty member, Doug Finkbeiner, who was leading a project to mine astrophysical data for signals of new physics.</p> <p>At the time, much of the physics community was eagerly anticipating the start-up of the Large Hadron Collider and the release of data on particle interactions at high energies, which could potentially reveal physics beyond the Standard Model.</p> <p>In contrast, telescopes have long made public their own data on astrophysical phenomena. What if, instead of looking through these data for objects such as black holes and neutron stars that evolved over millions of years, one could comb through it for signals of more fundamental mysteries, such as hints of new elementary particles and even dark matter?</p> <p>The prospects were new and exciting, and Slatyer promptly took on the challenge.</p> <p><strong>“Chasing that feeling”</strong></p> <p>In 2008, the Fermi Gamma-Ray Space Telescope launched, giving astronomers a new view of the cosmos in the gamma-ray band of the electromagnetic spectrum, where high-energy astrophysical phenomena can be seen. Slatyer and Finkbeiner proposed that Fermi’s data might also reveal signals of dark matter, which could theoretically produce high-energy electrons when dark matter particles collide.</p> <p>In 2009, Fermi made its data available to the public, and Slatyer and Finkbeiner —together with Harvard postdoc Greg Dobler and collaborators at New York University — put their mining tools to work as soon as the data were released online.</p> <p>The group eventually constructed a map of the Milky Way galaxy, shining in gamma rays, and revealed a fuzzy, egg-like shape. Upon further analysis, led by Slatyer’s fellow PhD student Meng Su, this fuzzy “haze” coalesced into a figure-eight, or double-bubble structure, extending some 25,000 light-years above and below the disc of the Milky Way. Such a structure had never been observed before. The group named the mysterious structure the “Fermi bubbles,” after the telescope that originally observed it.</p> <p>“It was really special — we were the first people in the history of the world to be able to look at the sky in this way and understand that this structure was there,” Slatyer says. “That’s a really incredible feeling, and chasing that feeling is something that inspires and motivates me, and I think many scientists.”</p> <p><strong>Searching for the invisible</strong></p> <p>Today, Slatyer continues to sift through Fermi data for evidence of dark matter. The Fermi Bubbles’ distinctive shape makes it unlikely they are associated with dark matter; they are more likely to reveal a past eruption from the giant black hole at the Milky Way’s center, or outflows fueled by exploding stars. However, other signals are more promising.</p> <p>Around the center of the Milky Way, where dark matter is thought to concentrate, there is a glow of gamma rays. In 2013, Slatyer, her first PhD student Nicholas Rodd, and collaborators at Harvard University and Fermilab showed this glow had properties similar to what theorists would expect if dark matter particles were colliding and producing visible light. However, in 2015, Slatyer and collaborators at MIT and Princeton University challenged this interpretation with a new analysis, showing that the glow was more consistent with originating from a new population of spinning neutron stars called pulsars.</p> <p>But the case is not quite closed. Recently, Slatyer and MIT postdoc Rebecca Leane reanalyzed the same data, this time injecting a fake dark matter signal into the data, to see whether the techniques developed in 2015 could detect dark matter if it were there. But the signal was missed, suggesting that if there were other, actual signals of dark matter in the Fermi data, they could have been missed as well.</p> <p>Slatyer is now improving on data mining techniques to better detect dark matter in the Fermi data, along with other astrophysical open data. But she won’t be discouraged if her search comes up empty.</p> <p>“There’s no guarantee there is a dark matter signal,” Slatyer says. “But if you never look, you’ll never know. And in searching for dark matter signals in these datasets, you learn other things, like that our galaxy contains giant gamma-ray bubbles, and maybe a new population of pulsars, that no one ever knew about. If you look closely at the data, the universe will often tell you something new.”</p> Associate professor Tracy Slatyer focuses on searching through telescope data for signals of mysterious phenomena such as dark matter, the invisible stuff that makes up more than 80 percent of the matter in the universe but has only been detected through its gravitational pull. In her teaching, she seeks to draw out and support a new and diverse crop of junior scientists.Images: Bryce VickmarkAstronomy, Astrophysics, Data, Center for Theoretical Physics, Faculty, Laboratory for Nuclear Science, Physics, Research, School of Science, Diversity and inclusion Daniel Freedman wins Special Breakthrough Prize in Fundamental Physics http://news.mit.edu/2019/daniel-freedman-breakthrough-prize-physics-0806 MIT professor emeritus will share $3 million prize with Sergio Ferrara and Peter van Nieuwenhuizen for discovery of supergravity. Tue, 06 Aug 2019 10:00:41 -0400 MIT News Office http://news.mit.edu/2019/daniel-freedman-breakthrough-prize-physics-0806 <p>Daniel Z. Freedman, professor emeritus in MIT’s departments of Mathematics and Physics, has been awarded the Special Breakthrough Prize in Fundamental Physics. He shares the $3 million prize with two colleagues, Sergio Ferrara of CERN and Peter van Nieuwenhuizen of Stony Brook University, with whom he developed the theory of supergravity.</p> <p>The trio is honored for work that combines the principles of supersymmetry, which postulates that all fundamental particles have corresponding, unseen “partner” particles; and Einstein's theory of general relativity, which explains that gravity is the result of the curvature of space-time.</p> <p>When the theory of supersymmetry was developed in 1973, it solved some key problems in particle physics, such as unifying three forces of nature (electromagnetism, the weak nuclear force, and the strong nuclear force), but it left out a fourth force: gravity. Freedman, Ferrara, and van Nieuwenhuizen addressed this in 1976 with their theory of supergravity, in which the gravitons of general relativity acquire superpartners called gravitinos.</p> <p>Freedman’s collaboration with Ferrara and van Nieuwenhuizen began late in 1975 at École Normale Supérior in Paris, where he was visiting on a minisabbatical from Stony Brook, where he was a professor. Ferrara had also come to ENS, to work on a different project for a week. The challenge of constructing supergravity was in the air at that time, and Freedman told Ferrara that he was thinking about it. In their discussions, Ferrara suggested that progress could be made via an approach that Freedman had previously used in a related problem involving supersymmetric gauge theories.</p> <p>“That turned me in the right direction,” Freedman recalls. In short order, he formulated the first step in the construction of supergravity and proved its mathematical consistency. “I returned to Stony Brook convinced that I could quickly find the rest of the theory,” he says. However, “I soon realized that it was harder than I had expected.”</p> <p>At that point he asked van Nieuwenhuizen to join him on the project. “We worked very hard for several months until the theory came together. That was when our eureka moment occurred,” he says.</p> <p>“Dan’s work on supergravity has changed how scientists think about physics beyond the standard model, combining principles of supersymmetry and Einstein’s theory of general relativity,” says Michael Sipser, dean of the MIT School of Science and the Donner Professor of Mathematics. “His exemplary research is central to mathematical physics and has given us new pathways to explore in quantum field theory and superstring theory. On behalf of the School of Science, I congratulate Dan and his collaborators for this prestigious award.”</p> <p>Freedman joined the MIT faculty in 1980, first as professor of applied mathematics and later with a joint appointment in the Center for Theoretical Physics. He regularly taught an advanced graduate course on supersymmetry and supergravity. An unusual feature of the course was that each assigned problem set included suggestions of classical music to accompany students’ work.&nbsp;</p> <p>“I treasure my 36 years at MIT,” he says, noting that he&nbsp; worked with “outstanding” graduate students with “great resourcefulness as problem solvers.” Freedman fully retired from MIT in 2016.</p> <p>He is now a visiting professor at Stanford University and lives in Palo Alto, California, with his wife, Miriam, an attorney specializing in public education law.</p> <p>The son of small-business people, Freedman was the first in his family to attend college. He became interested in physics during his first year at Wesleyan University, when he enrolled in a special class that taught physics in parallel with the calculus necessary to understand its mathematical laws. It was a pivotal experience. “Learning that the laws of physics can exactly describe phenomena in nature — that totally turned me on,” he says.</p> <p>Freedman learned about winning the Breakthrough Prize upon returning from a morning boxing class, when his wife told him that a Stanford colleague, who was on the Selection Committee, had been trying to reach him. “When I returned the call, I was overwhelmed with the news,” he says.</p> <p>Freedman, who holds a BA from Wesleyan and an MS and PhD in physics from the University of Wisconsin, is a former Sloan Fellow and a two-time Guggenheim Fellow. The three collaborators received the Dirac Medal and Prize in 1993, and the Dannie Heineman Prize in Mathematical Physics in 2006. He is a fellow of the American Academy of Arts and Sciences.</p> <p>Founded by a group of Silicon Valley entrepreneurs, the Breakthrough Prizes recognize the world’s top scientists in life sciences, fundamental physics, and mathematics. The Special Breakthrough Prize in Fundamental Physics honors profound contributions to human knowledge in physics. Earlier honorees include Jocelyn Bell Burnell; the <a href="http://news.mit.edu/2016/ligo-researchers-awarded-special-breakthrough-prize-fundamental-physics-0504">LIGO research team</a>, including MIT Professor Emeritus Rainer Weiss; and Stephen Hawking. &nbsp;</p> Daniel FreedmanImage courtesy of Daniel FreedmanPhysics, School of Science, Faculty, Awards, honors and fellowships, Center for Theoretical Physics, Laboratory for Nuclear Science, Mathematics Seeking new physics, scientists borrow from social networks http://news.mit.edu/2019/new-physics-anomalous-particles-0726 Technique can spot anomalous particle smashups that may point to phenomena beyond the Standard Model. Thu, 25 Jul 2019 23:59:59 -0400 Jennifer Chu | MIT News Office http://news.mit.edu/2019/new-physics-anomalous-particles-0726 <p>When two protons collide, they release pyrotechnic jets of particles, the details of which can tell scientists something about the nature of physics and the fundamental forces that govern the universe.</p> <p>Enormous particle accelerators such as the Large Hadron Collider can generate billions of such collisions per minute by smashing together beams of protons at close to the speed of light. Scientists then search through measurements of these collisions in hopes of unearthing weird, unpredictable behavior beyond the established playbook of physics known as the Standard Model.</p> <p>Now MIT physicists have found a way to automate the search for strange and potentially new physics, with a technique that determines the degree of similarity between pairs of collision events. In this way, they can estimate the relationships among hundreds of thousands of collisions in a proton beam smashup, and create a geometric map of events according to their degree of similarity.</p> <p>The researchers say their new technique is the first to relate multitudes of particle collisions to each other, similar to a social network.</p> <p>“Maps of social networks are based on the degree of connectivity between people, and for example, how many neighbors you need before you get from one friend to another,” says Jesse Thaler, associate professor of physics at MIT. “It’s the same idea here.”</p> <p>Thaler says this social networking of particle collisions can give researchers a sense of the more connected, and therefore more typical, events that occur when protons collide. They can also quickly spot the dissimilar events, on the outskirts of a collision network, which they can further investigate for potentially new physics. He and his collaborators, graduate students Patrick Komiske and Eric Metodiev, carried out the research at the MIT Center for Theoretical Physics and the MIT Laboratory for Nuclear Science. They detail their new technique this week in the journal <em>Physical Review Letters</em>.</p> <p><strong>Seeing the data agnostically</strong></p> <p>Thaler’s group focuses, in part, on developing techniques to analyze open data from the LHC and other particle collider facilities in hopes of digging up interesting physics that others might have initially missed.</p> <p>“Having access to this public data has been wonderful,” Thaler says. “But it’s daunting to sift through this mountain of data to figure out what’s going on.”</p> <p>Physicists normally look through collider data for specific patterns or energies of collisions that they believe to be of interest based on theoretical predictions. Such was the case for the discovery of the Higgs boson, the elusive elementary particle that was predicted by the Standard Model. The particle’s properties were theoretically outlined in detail but had not been observed until 2012, when physicists, knowing approximately what to look for, found signatures of the Higgs boson hidden amid trillions of proton collisions.</p> <p>But what if particles exhibit behavior beyond what the Standard Model predicts, that physicists have no theory to anticipate?</p> <p>Thaler, Komiske, and Metodiev have landed on a novel way to sift through collider data without knowing ahead of time what to look for. Rather than consider a single collision event at a time, they looked for ways to compare multiple events with each other, with the idea that perhaps by determining which events are more typical and which are less so, they might pick out outliers with potentially interesting, unexpected behavior.</p> <p>“What we’re trying to do is to be agnostic about what we think is new physics or not,” says Metodiev.&nbsp; “We want to let the data speak for itself.”</p> <p><strong>Moving dirt</strong></p> <p>Particle collider data are jam-packed with billions of proton collisions, each of which comprises individual sprays of particles. The team realized these sprays are essentially point clouds — collections of dots, similar to the point clouds that represent scenes and objects in computer vision. Researchers in that field have developed an arsenal of techniques to compare point clouds, for example to enable robots to accurately identify objects and obstacles in their environment.</p> <p>Metodiev and Komiske utilized similar techniques to compare point clouds between pairs of collisions in particle collider data. In particular, they adapted an existing algorithm that is designed to calculate the optimal amount of energy, or “work” that is needed to transform one point cloud into another. The crux of the algorithm is based on an abstract idea known as the “earth’s mover’s distance.”</p> <p>“You can imagine deposits of energy as being dirt, and you’re the earth mover who has to move that dirt from one place to another,” Thaler explains. “The amount of sweat that you expend getting from one configuration to another is the notion of distance that we’re calculating.”</p> <p>In other words, the more energy it takes to rearrange one point cloud to resemble another, the farther apart they are in terms of their similarity. Applying this idea to particle collider data, the team was able to calculate the optimal energy it would take to transform a given point cloud into another, one pair at a time. For each pair, they assigned a number, based on the “distance,” or degree of similarity they calculated between the two. They then considered each point cloud as a single point and arranged these points in a social network of sorts.</p> <p><img alt="" src="/sites/mit.edu.newsoffice/files/images/particle-networking1.gif" style="width: 500px; height: 300px;" /></p> <p><em><span style="font-size:10px;">Three particle collision events, in the form of jets, obtained from the CMS Open Data, form a triangle to represent an abstract "space of events." The animation depicts how one jet can be optimally rearranged into another.</span></em></p> <p>The team has been able to construct a social network of 100,000 pairs of collision events, from open data provided by the LHC, using their technique. The researchers hope that by looking at collision datasets as networks, scientists may be able to quickly flag potentially interesting events at the edges of a given network.</p> <p>“We’d like to have an Instagram page for all the craziest events, or point clouds, recorded by the LHC on a given day,” says Komiske. “This technique is an ideal way to determine that image. Because you just find the thing that’s farthest away from everything else.”</p> <p>Typical collider datasets that are made publicly available normally include several million events, which have been preselected from an original chaos of billions of collisions that occurred at any given moment in a particle accelerator. Thaler says the team is working on ways to scale up their technique to construct larger networks, to potentially visualize the “shape,” or general relationships within an entire dataset of particle collisions.</p> <p>In the near future, he envisions testing the technique on historical data that physicists now know contain milestone discoveries, such as the first detection in 1995 of the top quark, the most massive of all known elementary particles.</p> <p>“The top quark is an object that gives rise to these funny, three-pronged sprays of radiation, which are very dissimilar from typical sprays of one or two prongs,” Thaler says. “If we could rediscover the top quark in this archival data, with this technique that doesn’t need to know what new physics it is looking for, it would be very exciting and could give us confidence in applying this to current datasets, to find more exotic objects.”</p> <p>This research was funded, in part, by the U.S. Department of Energy, the Simons Foundation, and the MIT Quest for Intelligence.</p> MIT physicists find a way to relate hundreds of thousands of particle collisions, similar to a social network.Image: Chelsea Turner, MITData, Center for Theoretical Physics, Laboratory for Nuclear Science, Physics, Research, School of Science, Department of Energy (DoE) A vision of nuclear energy buoyed by molten salt http://news.mit.edu/2019/vision-nuclear-energy-buoyed-molten-salt-0724 NSE graduate student Kieran Dolan tackles a critical technical challenge to fluoride-salt-cooled high-temperature nuclear reactors. Wed, 24 Jul 2019 14:00:01 -0400 Leda Zimmerman | Department of Nuclear Science and Engineering http://news.mit.edu/2019/vision-nuclear-energy-buoyed-molten-salt-0724 <p>Years before he set foot on the MIT campus, Kieran P. Dolan participated in studies conducted at MIT's Nuclear Reactor Laboratory (NRL). As an undergraduate student majoring in nuclear engineering at the University of Wisconsin at Madison, Dolan worked on components and sensors for MIT Reactor (MITR)-based experiments integral to designing fluoride-salt-cooled high-temperature nuclear reactors, known as FHRs.</p> <p>Today, as a second-year doctoral student in MIT's Department of Nuclear Science and Engineering, Dolan is a hands-on investigator at the NRL, deepening his research engagement with this type of next-generation reactor.</p> <p>"I've been interested in advanced reactors for a long time, so it's been really nice to stay with this project and learn from people working here on-site," says Dolan.&nbsp;</p> <p>This series of studies on FHRs is part of a multiyear collaboration among MIT, the University of Wisconsin at Madison, and the University of California at Berkeley, funded by an Integrated Research Project (IRP) Grant from the U.S. Department of Energy (DOE). The nuclear energy community sees great promise in the FHR concept because molten salt transfers heat very efficiently, enabling such advanced reactors to run at higher temperatures and with several unique safety features compared to the current fleet of water-cooled commercial reactors.<br /> &nbsp;<br /> "Molten salt reactors offer an approach to nuclear energy that is both economically viable and safe," says Dolan.</p> <p>For the purposes of the FHR project, the MITR reactor simulates the likely operating environment of a working advanced reactor, complete with high temperatures in the experimental capsules. The FHR concept Dolan has been testing envisions billiard-ball-sized composites of fuel particles suspended within a circulating flow of molten salt — a special blend of lithium fluoride and beryllium fluoride called flibe. This salt river constantly absorbs and distributes the heat produced by the fuel's fission reactions.&nbsp;<br /> &nbsp;<br /> But there is a formidable technical challenge to the salt coolants used in FHRs. "The salt reacts with the neutrons released during fission, and produces tritium," explains Dolan. "Tritium is one of hydrogen’s isotopes, which are notorious for permeating metal." Tritium is a potential hazard if it gets into water or air. "The worry is that tritium might escape as a gas through an FHR's heat exchanger or other metal components."</p> <p>There is a potential workaround to this problem: graphite, which can trap fission products and suck up tritium before it escapes the confines of a reactor. "While people have determined that graphite can absorb a significant quantity of hydrogen, no one knows with certainty where the tritium is going to end up in the reactor,” says Dolan. So, he is focusing his doctoral research on MITR experiments to determine how effectively graphite performs as a sponge for tritium — a critical element required to model tritium transport in the complete reactor system.&nbsp;&nbsp;</p> <p>"We want to predict where the tritium goes and find the best solution for containing it and extracting it safely, so we can achieve optimal performance in flibe-based reactors," he says.</p> <p>While it's early, Dolan has been analyzing the results of three MITR experiments subjecting various types of specialized graphite samples to neutron irradiation in the presence of molten salt. "Our measurements so far indicate a significant amount of tritium retention by graphite," he says. "We're in the right ballpark."</p> <p>Dolan never expected to be immersed in the electrochemistry of salts, but it quickly became central to his research portfolio. Enthused by math and physics during high school in Brookfield, Wisconsin, he swiftly oriented toward nuclear engineering in college. "I liked the idea of making useful devices, and I was especially interested in nuclear physics with practical applications, such as power plants and energy," he says.</p> <p>At UW Madison, he earned a spot in an engineering physics material research group engaged in the FHR project, and he assisted in purifying flibe coolants, designing and constructing probes for measuring salt's corrosive effect on reactor parts, and experimenting on the electrochemical properties of molten fluoride salts. Working with&nbsp;<a href="http://www.exeloncorp.com/companies/exelon-generation/Pages/default.aspx">Exelon Generation</a>&nbsp;as a reactor engineer after college convinced him he was more suited for research in next-generation projects than in the day-to-day maintenance and operation of a commercial nuclear plant.&nbsp;</p> <p>"I was interested in innovation and improving things," he says. "I liked being part of the FHR IRP, and while I didn't have a passion for electrochemistry, I knew it would be fun working on a solution that could advance a new type of reactor."</p> <p>Familiar with the goals of the FHR project, MIT facilities, and personnel, Dolan was able to jump rapidly into studies analyzing MITR's irradiated graphite samples. Under the supervision of&nbsp;<a href="http://nrl.mit.edu/people/lin-wen-hu">Lin-wen Hu</a>, his advisor and NRL research director, as well as MITR engineers&nbsp;<a href="http://nrl.mit.edu/people/david-carpenter">David Carpenter</a>&nbsp;and&nbsp;<a href="http://nrl.mit.edu/people/gordon-kohse">Gordon Kohse</a>, Dolan came up to speed in reactor protocol. He's found on-site participation in experiments thrilling.</p> <p>"Standing at the top of the reactor as it starts and the salt heats up, anticipating when the tritium comes out, manipulating the system to look at different areas, and then watching the measurements come in — being involved with that is really interesting in a hands-on way," he says.&nbsp;</p> <p>For the immediate future, "the main focus is getting data," says Dolan. But eventually "the data will predict what happens to tritium in different conditions, which should be the main driving force determining what to do in actual commercial FHR reactor designs."</p> <p>For Dolan, contributing to this next phase of advanced reactor development would prove the ideal next step following his doctoral work. This past summer, Dolan interned at&nbsp;<a href="https://kairospower.com/">Kairos Power</a>, a nuclear startup company formed by the UC Berkeley collaborators on two DOE-funded FHR IRPs. Kairos Power continues to develop FHR technology by leveraging major strategic investments that the DOE has made at universities and national laboratories, and has recently started collaborating with MIT.&nbsp;&nbsp;</p> <p>"I've built up a lot of experience in FHRs so far, and there's a lot of interest at MIT and beyond in reactors using molten salt concepts," he says. "I will be happy to apply what I've learned to help accelerate a new generation of safe and efficient reactors."</p> "I've been interested in advanced reactors for a long time, so it's been really nice to stay with this project and learn from people working here on site," says Kieran Dolan. Photo: Gretchen ErtlNuclear science and engineering, School of Engineering, Profile, Students, Nuclear power and reactors, Energy, graduate, Graduate, postdoctoral, Nuclear Reactor Lab, Renewable energy New faces in the School of Science faculty http://news.mit.edu/2019/four-new-faces-mit-school-science-faculty-0723 Departments of Biology, Brain and Cognitive Sciences, Chemistry, and Physics welcome new faculty members. Tue, 23 Jul 2019 16:00:01 -0400 School of Science http://news.mit.edu/2019/four-new-faces-mit-school-science-faculty-0723 <p>This fall, the School of Science will welcome seven new members joining the faculty in the departments of Biology, Brain and Cognitive Sciences, Chemistry, and Physics.</p> <p><a href="https://web.mit.edu/physics/people/faculty/engelhardt_netta.html">Netta Engelhardt</a> studies gravitational aspects of quantum gravity with an emphasis on string theory She looks into the thermodynamic behavior of black holes and the idea that singularities are always hidden behind event horizons. Engelhardt joins the Department of Physics as an assistant professor. Engelhardt’s BS is in physics and mathematics from Brandeis University, and she received her PhD in physics from the University of California at Santa Barbara. Previously, she was a member of the Princeton Gravity Initiative at Princeton University. Engelhardt is also affiliated with the MIT Center for Theoretical Physics and the Laboratory for Nuclear Science.</p> <p><a href="https://evlab.mit.edu/">Evelina Fedorenko</a> investigates how our brains process language. She has developed novel analytic approaches for functional magnetic resonance imaging (fMRI) and other brain imaging techniques to help answer the questions of how the language processing network functions and how it relates to other networks in the brain. She works with both neurotypical individuals and individuals with brain disorders. Fedorenko joins the Department of Brain and Cognitive Sciences as an assistant professor. She received her BA from Harvard University in linguistics and psychology and then completed her doctoral studies at MIT in 2007. After graduating from MIT, Fedorenko worked as a postdoc and then as a research scientist at the McGovern Institute for Brain Research. In 2014, she joined the faculty at Massachusetts General Hospital and Harvard Medical School, where she was an associate researcher and an assistant professor, respectively. She is also a member of the McGovern Institute.</p> <p><a href="https://web.mit.edu/physics/people/faculty/kara_erin.html">Erin Kara</a> researches black holes. She looks into their formation and how they grow and impact the environments around them, particularly with respect to event horizons. To do this, she employs X-ray spectral timing observations. Kara is welcomed by the Department of Physics as an assistant professor. Kara joins MIT from the University of Maryland and the NASA Goddard Space flight Center where she was a Hubble Postdoctoral Fellow and a Joint Space-Science Institute Fellow. She received her undergraduate degree from Barnard College in 2011, and an MPhil in astrophysics and PhD in astronomy from Cambridge University. She is also a member of the MIT Kavli Institute for Astrophysics and Space Research.</p> <p><a href="https://biology.mit.edu/profile/pulin-li/">Pulin Li</a> is a developmental and synthetic biologist. Her work aims to lead to methods that might allow the programming of cells that could produce tissues and cells in regenerative medicine. She and her lab group accomplish this by using bioengineering tools, making quantitative measurements of genetic circuits in natural systems and invoking mathematical modelling. Li is joining the MIT community as an assistant professor in the Department of Biology. Her bachelor’s degree was obtained at Peking University, and she completed a PhD in chemical biology at Harvard University. Prior to her appointment at MIT, she was a postdoc at Caltech. Li is also a member of the Whitehead Institute for Biomedical Research.</p> <p><a href="https://picower.mit.edu/morgan-sheng">Morgan Sheng</a> focuses on the structure, function, and turnover of synapses, the junctions that allow communication between brain cells. His discoveries have improved our understanding of the molecular basis of cognitive function and diseases of the nervous system, such as autism, Alzheimer’s disease, and dementia. Being both a physician and a scientist, he incorporates genetic as well as biological insights to aid the study and treatment of mental illnesses and neurodegenerative diseases. He rejoins the Department of Brain and Cognitive Sciences (BCS), returning as a professor of neuroscience, a position he also held from 2001 to 2008. At that time, he was a member of the Picower Institute for Learning and Memory, a joint appointee in the Department of Biology, and an investigator of the Howard Hughes Medical Institute. Sheng earned his PhD from Harvard University in 1990, completed a postdoc at the University of California at San Francisco in 1994, and finished his medical training with a residency in London in 1986. From 1994 to 2001, he researched molecular and cellular neuroscience at Massachusetts General Hospital and Harvard Medical School. From 2008 to 2019 he was vice president of neuroscience at Genentech, a leading biotech company. In addition to his faculty appointment in BCS, Sheng is core institute member and co-director of the Stanley Center for Psychiatric Research at the Broad Institute of MIT and Harvard, as well as an affiliate member of the McGovern Institute and the Picower Institute.</p> <p><a href="https://www.voslab.org/research">Seychelle Vos</a> studies genome organization and its effect on gene expression at the intersection of biochemistry and genetics. Vos uses X-ray crystallography, cryo-electron microscopy, and biophysical approaches to understand how transcription is physically coupled to the genome’s organization and structure. She joins the Department of Biology as an assistant professor after completing a postdoc at the Max Plank Institute for Biophysical Chemistry. Vos received her BS in genetics in 2008 from the University of Georgia and her PhD in molecular and cell biology in 2013 from the University of California at Berkeley.</p> <p><a href="https://chemistry.mit.edu/chemistry-news/xiao-wang-to-join-the-faculty/">Xiao Wang</a> is a chemist and molecular engineer working to improve our understanding of biology and human health. She focuses on brain function and dysfunction, producing and applying new chemical, biophysical, and genomic tools at the molecular level. Previously, she focused on RNA modifications and how they impact cellular function. Wang is joining MIT as an assistant professor in the Department of Chemistry. She was previously a postdoc of the Life Science Research Foundation at Stanford University. Wang received her BS in chemistry and molecular engineering from Peking University in 2010 and her PhD in chemistry from the University of Chicago in 2015. She is also a core member of the Broad Institute of MIT and Harvard.</p> New faculty of the MIT School of Science: (clockwise from top left) Netta Engelhardt, Evelina Fedorenko, Erin Kara, Pulin Li, Morgan Sheng, Seychelle Vos, and Xiao Wang.Brain and cognitive sciences, School of Science, McGovern Institute, Picower Institute, Biology, Broad Institute, Chemistry, Faculty, Physics, Laboratory for Nuclear Science, Whitehead Institute, Kavli Institute Portraits of mentoring excellence http://news.mit.edu/2019/mit-portraits-mentoring-excellence-0718 Committed to Caring honors professors Modiano, Kelly, and Li, and calls for nominations. Thu, 18 Jul 2019 11:50:01 -0400 Courtney Lesoon | Office of Graduate Education http://news.mit.edu/2019/mit-portraits-mentoring-excellence-0718 <p>What makes a great faculty mentor? Appreciative graduate students from across the Institute have thoughts — lots of them.</p> <p>In letters of nomination to the Committed to Caring (C2C) program over the past five years, students have lauded faculty who validate them, who encourage work-life balance, and who foster an inclusive work environment, among other caring actions. Professors&nbsp;Eytan Modiano, Erin Kelly, and Ju Li especially&nbsp;excel at&nbsp;advocating for students, sharing behind-the-scenes information, and demonstrating empathy.</p> <p>The pool of C2C honorees is still expanding, along with a growing catalog of supportive actions known as Mentoring Guideposts. A&nbsp;new selection round has just begun, and the C2C program&nbsp;invites&nbsp;all graduate students to&nbsp;<a href="https://oge.mit.edu/community/committed-to-caring-c2c/c2c-nomination-form/">nominate professors</a>&nbsp;for their outstanding mentorship by&nbsp;July 26.</p> <p><strong>Eytan Modiano: listening and advocating</strong></p> <p>Eytan Modiano is professor of aeronautics and astronautics and the associate director of the Laboratory for Information and Decision Systems (LIDS). His work addresses communication networks and protocols with application to satellite, wireless, and optical networks. The primary goal of his research is the design of network architectures that are cost-effective, scalable, and robust. His research group crosses disciplinary boundaries by combining techniques from network optimization;&nbsp;queueing theory; graph theory; network protocols and algorithms;&nbsp;machine learning; and physical layer communications.</p> <p>When students reach out to Modiano for advice, he makes time in his schedule to meet with them, usually the same day or the next. In doing so, students say that Modiano offers invaluable support and shows students that he prioritizes them.</p> <p>Modiano provides his students with channels to express their difficulties (a&nbsp;<a href="https://oge.mit.edu/community/committed-to-caring-c2c/mentoring-guideposts/">Mentoring Guidepost</a>&nbsp;identified by the C2C program). For example, he allots unstructured time during individual and group meetings for student feedback. “These weekly meetings are mainly focused on research,” Modiano says, “but I always make sure to leave time at the end to talk about anything else that is on a student's&nbsp;mind, such as concerns about their career plans, coursework, or anything else.”</p> <p>He also reaches out to student groups about how the department and lab could better serve them. As associate director of LIDS, Modiano has responded to such feedback in a number of ways, including working alongside the LIDS Social Committee to organize graduate student events. He has advocated for funding of MIT Graduate Women in Aerospace Engineering, and was a key proponent of the Exploring Aerospace Day, an event the group hosted for interested high school students.</p> <p>Modiano does not think in binary terms about success and failure: “No single event, or even a series of events, is likely to define a career.” Rather, a career should be seen as a path “with ups and downs and whose trajectory we try to shape.”</p> <p>Modiano advises,&nbsp;“If you persist, you are likely to find a path that you are happy with, and meet your goals.”</p> <p><strong>Erin Kelly: sustainably moving forward</strong></p> <p>In her students’ estimation, Erin Kelly, the Sloan Distinguished Professor of Work and Organization Studies, rises to the level of exceptional mentorship by channeling her expertise in work and organization studies to the benefit of her advisees.</p> <p>Kelly investigates the implications of workplace policies and management strategies for workers, firms, and families; previous research has examined scheduling and work-family supports, family leaves, harassment policies, and diversity initiatives. As part of the Work, Family, and Health Network, she has evaluated innovative approaches to work redesign with group-randomized trials in professional/technical and health care workforces. Her book with Phyllis Moen, "Overload: How Good Jobs Went Bad and What to Do About It," will be published by Princeton University Press in early 2020.&nbsp;</p> <p>In Kelly’s words, she tries to “promote working in ways that feel sane and sustainable.” She does not count how many hours her students spend on projects or pay attention to where they work or how quickly they respond to emails. Kelly says that she knows her students are committed to this effort long-term, and that everyone works differently.</p> <p>One student nominator noted that Kelly was extremely supportive of her decision to have a child during graduate school, offering her advice about how to balance work and home as well as how to transition back into school after maternity leave. The nominator notes, “Erin does not view the baby as an impediment to my professional career.”</p> <p>In addition to providing advice on course selection and dissertation planning, Kelly offers her students “informal” advising (a&nbsp;<a href="https://oge.mit.edu/community/committed-to-caring-c2c/mentoring-guideposts/">Mentoring Guidepost</a>) that goes beyond the usual academic parameters. Kelly “explained to me the importance of networking in finding an academic job,” another student says, “I’ve appreciated this informal mentoring, particularly because I am a woman trying to enter a male-dominated field; understanding how to succeed professionally is important, but is not always obvious.”</p> <p><strong>Ju Li: a proven mentor and friend</strong></p> <p>Ju Li is the Battelle Energy Alliance Professor of&nbsp;Nuclear Science and Engineering and professor of materials science and engineering at MIT. Li’s research focuses on mechanical properties of materials, and energy storage and conversion. His lab also studies the effects of radiation and aggressive environments on microstructure and materials properties.</p> <p>Li shows empathy for students’ experiences (a&nbsp;<a href="https://oge.mit.edu/community/committed-to-caring-c2c/mentoring-guideposts/">Mentoring Guidepost</a>&nbsp;identified by the C2C program). One student remarked that when they were not confident in their own abilities, Li was “extremely patient” and showed faith in their work. Li “lifted me up with his encouraging words and shared his own experiences and even struggles.”</p> <p>He concerns himself with both training academic researchers and also preparing students for life after MIT, whether their paths lead them to academic, industry, governmental, or entrepreneurial endeavors. Li’s attention to his students and their aims does not go unnoticed. One C2C nominator says that former group members often come back to visit and to seek advice from Li whenever possible, “and nobody regrets being a member of our group.”</p> <p>It is clear from their letters of nomination that Li’s students deeply admire his character and hold him up as a lifelong role model. In addition to his caring actions, they cite his humility and his treatment of students as “equals and true friends.”</p> <p>Just as Li’s students admire him, Li was inspired by his own graduate mentor, Sydney Yip, professor emeritus of nuclear science and engineering, and materials science and engineering at MIT. Li says that Yip taught everyone who encountered him to become better researchers and better people. In graduate school, Li says, “I benefited so much by watching how Sid managed his group, and how he interacted with the world … I felt lucky every day.”</p> <p><strong>More on Committed to Caring (C2C)</strong></p> <p>The Committed to Caring (C2C) program, an initiative of the Office of Graduate Education, honors faculty members from across the Institute for their outstanding support of graduate students. By sharing the stories of great mentors, like professors Modiano, Kelly, and Li, the C2C Program hopes to encourage exceptional mentorship at MIT.</p> <p>Selection criteria for the award include the scope and reach of advisor impact on the experience of graduate students, excellence in scholarship, and demonstrated commitment to diversity and inclusion.</p> <p>Nominations for the next round of honorees must be submitted by July 26. Selections will be announced in late September.</p> Left to right: MIT professors Eytan Modiano, Erin Kelly, and Ju Li.Photo: Joseph LeeAeronautics and Astronautics, Laboratory for Information and Decision Systems (LIDS), Nuclear science and engineering, School of Engineering, Sloan School of Management, Mentoring, Awards, honors and fellowships, Leadership, Faculty, Community, DMSE, Students, Graduate, postdoctoral New team to lead MIT Nuclear Reactor Laboratory http://news.mit.edu/2019/new-team-lead-mit-nuclear-reactor-laboratory-0715 Gordon Kohse, Jacopo Buongiorno, and Lance Snead will co-lead the laboratory; David Moncton will step down after 15 years of service. Mon, 15 Jul 2019 11:30:58 -0400 Office of the Vice President for Research http://news.mit.edu/2019/new-team-lead-mit-nuclear-reactor-laboratory-0715 <p>The Office of the Vice President for Research announced the appointment of a new leadership team for the Nuclear Reactor Laboratory (NRL). The team will consist of Gordon Kohse, managing director for operations; Jacopo Buongiorno, science and technology director and director for strategic R&amp;D partnerships; and Lance Snead, senior advisor for strategic partnerships and business development and leader of the NRL Irradiation Materials Sciences Group. The team will succeed David Moncton, who plans to return to his research after taking a department head sabbatical. Moncton has served as director of the NRL since 2004.</p> <p>The new leadership team will collectively oversee an updated organizational model for the NRL that will allow the laboratory to more closely align its operations with the scientific research agenda of the Department of Nuclear Science and Engineering and other MIT researchers. “I look forward to working with this thoughtful and experienced team as they implement their vision for a vibrant operation supporting the critical work of our research community,” says Maria Zuber, vice president for research.</p> <p>Kohse, a principal research scientist with the NRL and previously the deputy director of research and services, has worked with the NRL for over 40 years, ensuring the smooth operation of experiments at the laboratory. As managing director for operations, Kohse will oversee reactor operations, the newly created program management group, quality assurance, and the irradiation engineering group, and will work closely with Lance Snead on overseeing the Irradiation Materials Sciences Group. Kohse says, “I look forward to a new chapter in my work at the NRL. This is an exciting opportunity to build on the skills and dedication of the laboratory staff and to renew and strengthen cooperation with MIT faculty. My goal is to continue safe, reliable operation of the reactor, and to expand its capabilities in the service of expanding missions in nuclear research and education.”</p> <p>In his new NRL leadership role, Jacopo Buongiorno, the TEPCO Professor of Nuclear Science and Engineering, will oversee the NRL’s Centers for Irradiation Materials Science. These centers will focus on a variety of research questions ranging from new nuclear fuels, to in-core sensors, to nuclear materials degradation. All experimental research utilizing the MIT reactor will be coordinated through the Centers for Irradiation Materials Science. Ongoing and installed programs will be managed through the program management group.</p> <p>Buongiorno is also the director of the Center for Advanced Energy Systems (CANES), which is one of eight Low-Carbon-Energy Centers (LCEC) of the MIT Energy Initiative (MITEI); he is also the director of the recently completed <a href="http://news.mit.edu/2018/mitei-releases-report-future-nuclear-energy-0904">MIT study</a> on the Future of Nuclear Energy in a Carbon-Constrained World.&nbsp;</p> <p>Buongiorno and Snead, an MIT research scientist and former corporate fellow with Oak Ridge National Laboratory, will spearhead efforts to expand external collaborations with federal and industry sponsors and work with MIT’s faculty to identify ways the NRL can provide the needed experimental support for their research and education objectives. “Our vision is to grow the MIT reactor value to MIT’s own research community as well as position it at the center of the worldwide efforts to develop new nuclear technologies that contribute to energy security and decarbonization of the global economy,” says Buongiorno.&nbsp;</p> <p>This new leadership team will build on NRL’s accomplishments under the direction of David Moncton. Moncton was instrumental in the 20-year relicensing of the reactor, led the NRL in developing the research program which boasts the most productive and innovative program for in-core studies of structural materials, new fuel cladding composites, new generations of nuclear instrumentation based on ultrasonic sensors and fiber optics, and studies of the properties of liquid salt in a radiation environment for use as a coolant in a new generation of high-temperature reactors. The NRL has become a key partner of the Nuclear Science User Facilities (NSUF) sponsored by Idaho National Laboratory, and it has established a world-class reputation for its in-core irradiation program.</p> <p>Anne White, professor and head of the Department of Nuclear Science and Engineering, notes, “The unique capabilities of NRL together with the Centers for Irradiation Materials Science will create a new and exciting nexus for nuclear-related research and education at MIT, opening up opportunities not only for faculty in the nuclear science and engineering department (Course 22), but across the entire Institute.”</p> <p>The new leadership team will begin their tenure effective Aug. 1, 2019.&nbsp;&nbsp;</p> Left to right: Gordon Kohse, Jacopo Buongiorno, Lance SneadPhotos courtesy of the researchersNuclear Reactor Lab, Nuclear science and engineering, School of Engineering, Nuclear power and reactors, Faculty, Staff, Administration, Renewable energy Meet the 2019 tenured professors in the School of Science http://news.mit.edu/2019/new-tenured-professors-mit-school-science-0710 Eight faculty members are granted tenure in five science departments. Wed, 10 Jul 2019 11:20:01 -0400 School of Science http://news.mit.edu/2019/new-tenured-professors-mit-school-science-0710 <p>MIT granted tenure to eight School of Science faculty members in the departments of Biology; Chemistry; Earth, Atmospheric and Planetary Sciences; Mathematics; and Physics.</p> <p><a href="http://web.mit.edu/Physics/people/faculty/detmold_william.html">William Detmold</a>’s research within the area of theoretical particle and nuclear physics incorporates analytical methods, as well as the power of the world’s largest supercomputers, to understand the structure, dynamics, and interactions of particles like protons and to look for evidence of new physical laws at the sub-femtometer scale probed in experiments such as those at the Large Hadron Collider. He joined the Department of Physics in 2012 from the College of William and Mary, where he was an assistant professor. Prior to that, he was a research assistant professor at the University of Washington. He received his BS and PhD from the University of Adelaide in Australia in 1996 and 2002, respectively. Detmold is a researcher in the Center for Theoretical Physics in the Laboratory for Nuclear Science.<br /> <br /> <a href="http://math.mit.edu/~dyatlov/">Semyon Dyatlov</a> explores scattering theory, quantum chaos, and general relativity by employing microlocal analytical and dynamical system methods. He came to the Department of Mathematics as a research fellow in 2013 and became an assistant professor in 2015. He completed his doctorate in mathematics at the University of California at Berkeley in 2013 after receiving a BS in mathematics at Novosibirsk State University in Russia in 2008. Dyatlov spent time after finishing his PhD as a postdoc at the Mathematical Sciences Research Institute before moving to MIT.</p> <p><a href="https://biology.mit.edu/profile/mary-gehring/">Mary Gehring</a> studies plant epigenetics. By using a combination of genetic, genomic, and molecular biology, she explores how plants inherit and interpret information that is not encoded in their DNA to better understand plant growth and development. Her lab focuses primarily on <em>Arabidopsis thaliana</em>, a small flowering plant that is a model species for plant research. Gehring joined the Department of Biology in 2010 after performing postdoctoral research at the Fred Hutchinson Cancer Research Center. She received her BA in biology from Williams College in 1998 and her doctorate from the University of California at Berkeley in 2005. She is also a member of the Whitehead Institute for Biomedical Research.</p> <p><a href="https://eapsweb.mit.edu/people/davidmcg">David</a><a href="http://eapsweb.mit.edu/people/davidmcg"> McGee</a> performs research in the field of paleoclimate, merging information from stalagmites, lake deposits, and marine sediments with insights from models and theory to understand how precipitation patterns and atmospheric circulation varied in the past. He came to MIT in 2012, joining the Department of Earth, Atmospheric and Planetary Sciences after completing a NOAA Climate and Global Change Postdoctoral Fellowship at the University of Minnesota. Before that, he attended Carleton College for his BA in geology in 1993-97, Chatham College for an MA in teaching from 1999 to 2003, Tulane University for his MS from 2004 to 2006, and Columbia University for his PhD from 2006 to 2009. McGee is the director of the MIT Terrascope First-Year Learning Community, a role he has held for the past four years.</p> <p><a href="https://math.mit.edu/directory/profile.php?pid=1502">Ankur Moitra</a> works at the interface between theoretical computer science and machine learning by developing algorithms with provable guarantees and foundations for reasoning about their behavior. He joined the Department of Mathematics in 2013. Prior to that, he received his BS in electrical and computer engineering from Cornell University in 2007, and his MS and PhD in computer science from MIT in 2009 and 2011, respectively. He was a National Science Foundation postdoc at the Institute for Advanced Study until 2013. Moitra was a 2018 recipient of a School of Science Teaching Prize. He is also a principal investigator in the Computer Science and Artificial Intelligence Laboratory (CSAIL) and a core member of the Statistics and Data Science Center.</p> <p><a href="https://chemistry.mit.edu/profile/matthew-d-shoulders/">Matthew Shoulders</a> focuses on integrating biology and chemistry to understand how proteins function in the cellular setting, including proteins’ shape, quantity, and location within the body. This research area has important implications for genetic disorders and neurodegenerative diseases such as Alzheimer’s, diabetes, cancer, and viral infections. Shoulders’ lab works to elucidate, at the molecular level, how cells solve the protein-folding problem, and then uses that information to identify how diseases can develop and to provide insight into new targets for drug development. Shoulders joined the Department of Chemistry in 2012 after earning a BS in chemistry and minor in biochemistry from Virginia Tech in 2004 and a PhD in chemistry from the University of Wisconsin at Madison in 2009. He is also an associate member of the Broad Institute of MIT and Harvard, and a member of the MIT Center for Environmental Health Sciences.</p> <p><a href="https://web.mit.edu/physics/people/faculty/slatyer_tracy.html">Tracy Slatyer</a> researches fundamental aspects of theoretical physics, answering questions about both visible and dark matter by searching for potential indications of new physics in astrophysical and cosmological data. She has developed and adapted novel techniques for data analysis, modeling, and calculations in quantum field theory; her work has also inspired a range of experimental investigations. The Department of Physics welcomed Slatyer in 2013 after she completed a three-year postdoctoral fellowship at the Institute for Advanced Study. She majored in theoretical physics as an undergraduate at the Australian National University, receiving a BS in 2005, and completed her PhD in physics at Harvard University in 2010. In 2017, Slatyer received the School of Science Prize in Graduate Teaching and was also named the first recipient of the school’s Future of Science Award. She is a member of the Center for Theoretical Physics in the Laboratory for Nuclear Science.</p> <p><a href="http://web.mit.edu/physics/people/faculty/williams_mike.html">Michael Williams</a> uses novel experimental methods to improve our knowledge of fundamental particles, including searching for new particles and forces, such as dark matter. He also works on advancing the usage of machine learning within the domain of particle physics research. He joined the Department of Physics in 2012. He previously attended Saint Vincent College as an undergraduate, where he double majored in mathematics and physics. Graduating in 2001, Williams then pursued a doctorate at Carnegie Mellon University, which he completed in 2007. From 2008 to 2012 he was a postdoc at Imperial College London. He is a member of the Laboratory for Nuclear Science.</p> Clockwise from top left: William Detmold, Semyon Dyatlov, Mary Gehring, David McGee, Ankur Moitra, Matthew Shoulders, Tracy Slatyer, and Michael Williams.Photos courtesy of the faculty.School of Science, Biology, Chemistry, EAPS, Mathematics, Physics, Laboratory for Nuclear Science, Computer Science and Artificial Intelligence Laboratory (CSAIL), Broad Institute, Center for Environmental Health Sciences (CEHS), Faculty, Awards, honors and fellowships, Whitehead Institute, Center for Theoretical Physics Benoit Forget named associate head of the Department of Nuclear Science and Engineering http://news.mit.edu/2019/benoit-forget-named-associate-head-nuclear-science-and-engineering-0709 Co-leader of the MIT Computational Reactor Physics Group will focus on expanding computational science and engineering activities. Tue, 09 Jul 2019 14:50:02 -0400 Department of Nuclear Science and Engineering http://news.mit.edu/2019/benoit-forget-named-associate-head-nuclear-science-and-engineering-0709 <p>Professor Anne White, head of the Department of Nuclear Science and Engineering (NSE), has announced the appointment of Professor&nbsp;<a href="http://web.mit.edu/nse/people/faculty/forget.html">Benoit Forget</a>&nbsp;as associate department head.</p> <p>The MIT Computational Reactor Physics Group — which Forget leads with Professor Kord Smith — focuses on developing new ways of streamlining the complex software needed to simulate the vast numbers of random interactions that take place inside a nuclear reactor core, in order to better understand how to develop new generations of improved reactor architectures.</p> <p>Forget earned a BS in chemical engineering and an MS in energy engineering at the École Polytechnique de Montréal. He completed his PhD in nuclear engineering at Georgia Tech in 2006, after which he spent a year and a half working at Idaho National Laboratory before accepting an appointment at MIT.</p> <p>As associate head, Professor Forget will focus on expanding computational science and engineering activities within NSE, including leading NSE engagement with the new MIT Stephen A. Schwarzman College of Computing. He currently serves as co-chair of the Working Group on College Infrastructure for the MIT Schwarzman College of Computing, which is charged with examining how to ensure that departments, labs, and centers have the information and resources they require to meet their computational needs, such as accessing and storing data.&nbsp;</p> <p>Forget replaces Professor Jacopo Buongiorno, who served as associate department head and led academic organization and oversight in NSE from 2015 through June 2019.</p> Professor Benoit Forget will focus on expanding computational science and engineering activities within NSE, including leading NSE engagement with the new MIT Schwarzman College of Computing.Photo: Bryce VickmarkNuclear science and engineering, School of Engineering, Faculty, MIT Schwarzman College of Computing, Administration Anne White named head of the Department of Nuclear Science and Engineering http://news.mit.edu/2019/anne-white-nuclear-science-engineering-0618 Fusion energy and turbulence modeling expert will succeed Dennis Whyte. Tue, 18 Jun 2019 13:30:00 -0400 School of Engineering http://news.mit.edu/2019/anne-white-nuclear-science-engineering-0618 <p>Anne White, associate professor of nuclear science and engineering and associate director of the Plasma Science and Fusion Center at MIT, has been named the new head of the Department of Nuclear Science and Engineering, effective July 1.</p> <p>“Professor White is a brilliant researcher who has had a tremendous impact on students at MIT,” says Anantha Chandrakasan, dean of the MIT School of Engineering and the Vannevar Bush Professor of Electrical Engineering and Computer Science. “As a tireless ambassador and advocate for the potential of nuclear fusion as an energy source, she inspires our students and our research community. I look forward to working with her on the school’s leadership team.”</p> <p>An international leader in assessing and refining the mathematical models used in fusion reactor design, White and the members of her research group develop diagnostic techniques that allow for simultaneous measurements of fluctuations in plasma density, and temperature in the core and edge of tokamak reactors, which are large toroidal devices in which plasmas reach temperatures higher 100 million degrees. She and her team hope to improve the understanding of how turbulence is suppressed and how the turbulent-transport of particles, energy, and momentum can be separated from one another — essential data in the development of fusion reactors.&nbsp;&nbsp;&nbsp;&nbsp;</p> <p>White has taught a variety of courses at MIT, including graduate plasma physics, undergraduate electronics, and an advanced graduate course on the principles of plasma diagnostics, which attracts students from across the Institute and other local universities. She also helped team-teach the first offering of a new undergraduate course, 22.061 (Fusion Energy). Recently, White and a team of faculty led the development of a new MOOC on <em>MITx</em> covering nuclear science and engineering, <a href="https://www.edx.org/course/nuclear-energy-science-systems-and-society">22.011x</a> (Nuclear Science: Energy, Systems and Society), which was jointly offered online and on campus in spring 2019 as the new first-year seminar in NSE.&nbsp;&nbsp;&nbsp;</p> <p>A past winner of the U.S. Department of Energy (DoE) Early Career Award, the American Physical Society Katherine E. Weimer Award, and the Fusion Power Associates Excellence in Fusion Engineering Award, White received a DoE ORISE Fusion Energy Science Fellowship, won the Marshall N. Rosenbluth Outstanding Doctoral Thesis Award, and was named a DoE Fusion Energy Postdoctoral Research Program Fellow and an APS Division of Plasma Physics distinguished lecturer. She is a member of the Division of Plasma Physics at the American Physical Society, and the American Nuclear Society. White is also a past recipient of the Junior Bose Award for Excellence in Teaching from the MIT School of Engineering and the PAI Outstanding Faculty Award, presented by the student chapter of the American Nuclear Society. She currently serves on the DoE Fusion Energy Sciences Advisory Committee and the advisory board for the Princeton Plasma Physics Laboratory.&nbsp;&nbsp;&nbsp;</p> <p>A member of the MIT faculty since 2009, White earned her BS in physics and applied mathematics at the University of Arizona in 2003, and her MS and PhD in physics at the University of California at Los Angeles, in 2004 and 2008.</p> <p>White succeeds Dennis Whyte, who has been department head since 2015 and will remain director of MIT’s Plasma Science and Fusion Center. “Under Dennis’s leadership, NSE has implemented a range of innovative strategies to accelerate growth and development in recruiting, education, and research,” Chandrakasan noted in his email to the nuclear science community. “He has been a remarkable and committed leader for the department.”</p> Anne WhiteImage: Bryce VickmarkSchool of Engineering, Nuclear science and engineering, Faculty, Plasma Science and Fusion Center, Fusion, Nuclear power and reactors, Administration The tenured engineers of 2019 http://news.mit.edu/2019/tenured-mit-engineers-0604 Seventeen appointments have been made in eight departments within the School of Engineering. Tue, 04 Jun 2019 10:30:01 -0400 School of Engineering http://news.mit.edu/2019/tenured-mit-engineers-0604 <p>The School of Engineering has announced that 17 members of its faculty have been granted tenure by MIT.</p> <p>“The tenured faculty in this year’s cohort are a true inspiration,” said Anantha Chandrakasan, dean of the School of Engineering. “They have shown exceptional dedication to research and teaching, and their innovative work has greatly advanced their fields.”</p> <p>This year’s newly tenured associate professors are:</p> <p><a href="https://dmse.mit.edu/people/antoine-allanore" target="_blank">Antoine Allanore</a>, in the Department of Materials Science and Engineering, develops more sustainable technologies and strategies for mining, metal extraction, and manufacturing, including novel methods of fertilizer production.</p> <p><a href="https://cee.mit.edu/people_individual/saurabh-amin/" target="_blank">Saurabh Amin</a>, in the Department of Civil and Environmental Engineering, focuses on the design and implementation of network inspection and control algorithms for improving the resilience of large-scale critical infrastructures, such as transportation systems and water and energy distribution networks, against cyber-physical security attacks and natural events.</p> <p><a href="https://web.mit.edu/nse/people/faculty/baglietto.html" target="_blank">Emilio Baglietto</a>, in the Department of Nuclear Science and Engineering, uses computational modeling to characterize and predict the underlying heat-transfer processes in nuclear reactors, including turbulence modeling, unsteady flow phenomena, multiphase flow, and boiling.</p> <p><a href="https://be.mit.edu/directory/paul-blainey" target="_blank">Paul Blainey</a>, the Karl Van Tassel (1925) Career Development Professor in the Department of Biological Engineering, integrates microfluidic, optical, and molecular tools for application in biology and medicine across a range of scales.</p> <p><a href="https://aeroastro.mit.edu/kerri-cahoy" target="_blank">Kerri Cahoy</a>, the Rockwell International Career Development Professor in the Department of Aeronautics and Astronautics, develops nanosatellites that demonstrate weather sensing using microwave radiometers and GPS radio occultation receivers, high data-rate laser communications with precision time transfer, and active optical imaging systems using MEMS deformable mirrors for exoplanet exploration applications.&nbsp;</p> <p><a href="https://dmse.mit.edu/people/juejun-jj-hu" target="_blank">Juejun Hu</a>, in the Department of Materials Science and Engineering, focuses on novel materials and devices to exploit interactions of light with matter, with applications in on-chip sensing and spectroscopy, flexible and polymer photonics, and optics for solar energy.</p> <p><a href="http://karaman.mit.edu/" target="_blank">Sertac Karaman</a>, the Class of 1948 Career Development Professor in the Department of Aeronautics and Astronautics, studies robotics, control theory, and the application of probability theory, stochastic processes, and optimization for cyber-physical systems such as driverless cars and drones.</p> <p><a href="http://lnsp.mit.edu/r-scott-kemp" target="_blank">R. Scott Kemp</a>, the Class of 1943 Career Development Professor in the Department of Nuclear Science and Engineering, combines physics, politics, and history to identify options for addressing nuclear weapons and energy. He investigates technical threats to nuclear-deterrence stability and the information theory of treaty verification; he is also developing technical tools for reconstructing the histories of secret nuclear-weapon programs.</p> <p><a href="https://www.eecs.mit.edu/people/faculty/aleksander-madry" target="_blank">Aleksander Mądry</a>, in the Department of Electrical Engineering and Computer Science, investigates topics ranging from developing new algorithms using continuous optimization, to combining theoretical and empirical insights, to building a more principled and thorough understanding of key machine learning tools. A major theme of his research is rethinking machine learning from the perspective of security and robustness.</p> <p><a href="https://dmse.mit.edu/people/frances-m-ross" target="_blank">Frances Ross</a>, the Ellen Swallow Richards Professor in the Department of Materials Science and Engineering, performs research on nanostructures using transmission electron microscopes that allow researchers to see, in real-time, how structures form and develop in response to changes in temperature, environment, and other variables. Understanding crystal growth at the nanoscale is helpful in creating precisely controlled materials for applications in microelectronics and energy conversion and storage.</p> <p><a href="http://people.csail.mit.edu/sanchez/" target="_blank">Daniel Sanchez</a>, in the Department of Electrical Engineering and Computer Science, works on computer architecture and computer systems, with an emphasis on large-scale multi-core processors, scalable and efficient memory hierarchies, architectures with quality-of-service guarantees, and scalable runtimes and schedulers.</p> <p><a href="http://meche.mit.edu/people/faculty/sapsis@MIT.EDU" target="_blank">Themistoklis Sapsis</a>, the Doherty Career Development Professor in the Department of Mechanical Engineering, develops analytical, computational, and data-driven methods for the probabilistic prediction and quantification of extreme events in high-dimensional nonlinear systems such as turbulent fluid flows and nonlinear mechanical systems.</p> <p><a href="https://aeroastro.mit.edu/julie-shah" target="_blank">Julie Shah</a>, the Boeing Career Development Professor in the Department of Aeronautics and Astronautics, develops innovative computational models and algorithms expanding the use of human cognitive models for artificial intelligence. Her research has produced novel forms of human-machine teaming in manufacturing assembly lines, healthcare applications, transportation, and defense.</p> <p><a href="https://cheme.mit.edu/profile/hadley-sikes/">Hadley Sikes</a>, the Esther and Harold E. Edgerton Career Development Professor in the Department of Chemical Engineering, employs biomolecular engineering and knowledge of reaction networks to detect epigenetic modifications that can guide cancer treatment, induce oxidant-specific perturbations in tumors for therapeutic benefit, and improve signaling reactions and assay formats used in medical diagnostics.</p> <p><a href="https://cheme.mit.edu/profile/william-a-tisdale/" target="_blank">William Tisdale</a>, the ARCO Career Development Professor in the Department of Chemical Engineering, works on energy transport in nanomaterials, nonlinear spectroscopy, and spectroscopic imaging to better understand and control the mechanisms by which excitons, free charges, heat, and reactive chemical species are converted to more useful forms of energy, and on leveraging this understanding to guide materials design and process optimization.</p> <p><a href="http://people.csail.mit.edu/virgi/" target="_blank">Virginia Vassilevska Williams</a>, the Steven and Renee Finn Career Development Professor in the Department of Electrical Engineering and Computer Science, applies combinatorial and graph theoretic tools to develop efficient algorithms for matrix multiplication, shortest paths, and a variety of other fundamental problems. Her recent research is centered on proving tight relationships between seemingly different computational problems. She is also interested in computational social choice issues, such as making elections computationally resistant to manipulation.</p> <p><a href="http://meche.mit.edu/people/faculty/awinter@mit.edu" target="_blank">Amos Winter</a>, the Tata Career Development Professor in the Department of Mechanical Engineering, focuses on connections between mechanical design theory and user-centered product design to create simple, elegant technological solutions for applications in medical devices, water purification, agriculture, automotive, and other technologies used in highly constrained environments.</p> The MIT School of Engineering newly tenured faculty are: (first row, left to right) Amos Winter, Kerri Cahoy, Antoine Allanore, R. Scott Kemp, Juejun Hu, Emilio Baglietto, Virginia Vassilevska Williams, Aleksander Mądry, and Julie Shah. (second row, left to right) William Tisdale, Paul Blainey, Themistoklis Sapsis, Frances Ross, Sertac Karaman, Hadley Sikes, Saurabh Amin, and Daniel Sanchez.School of Engineering, Materials Science and Engineering, Civil and environmental engineering, Biological engineering, Nuclear science and engineering, Aeronautical and astronautical engineering, Electrical engineering and computer science (EECS), Mechanical engineering, Chemical engineering, Awards, honors and fellowships, Faculty Ultra-Quantum Matter research gets $8 million boost http://news.mit.edu/2019/ultra-quantum-matter-uqm-research-given-8m-boost-0529 MIT’s Senthil Todadri and Xiao-Gang Wen will study highly entangled quantum matter in a collaboration supported by the Simons Foundation. Wed, 29 May 2019 14:40:01 -0400 Julia C. Keller | School of Science http://news.mit.edu/2019/ultra-quantum-matter-uqm-research-given-8m-boost-0529 <p>MIT professors Senthil Todadri and Xiao-Gang Wen are members of the newly established Simons Collaboration on Ultra-Quantum Matter. The effort, funded by the Simons Foundation, is an $8 million&nbsp;four-year award, renewable for three additional years, and will support theoretical physics research across 12 institutions, including MIT.</p> <p>The science of the collaboration is based on a series of recent developments in theoretical physics, revealing that even large macroscopic systems that consist of many atoms or electrons — matter — can behave in an essentially quantum way. Such ultra-quantum matter (UQM)&nbsp;allows for quantum phenomena beyond what can be realized by individual atoms or electrons, including distributed storage of quantum information, fractional quantum numbers, and perfect conducting boundary.&nbsp;</p> <p>While some examples of UQM have been experimentally established, many more have been theoretically proposed, ranging from highly entangled topological states to unconventional metals that behave like a complex soup. The Simons Collaboration on Ultra-Quantum Matter will classify possible forms of UQM, understand their physical properties, and provide the key ideas to enable new realizations of UQM in the lab.&nbsp;</p> <p><strong>Ultra dream team</strong></p> <p>In particular, the collaboration will draw upon lessons from recently discovered connections between topological states of matter and unconventional metals, and seeks to develop a new theoretical framework for those phases of ultra-quantum matter. Achieving these goals requires ideas and tools from multiple areas of theoretical physics, and accordingly the collaboration brings together experts in condensed matter physics, quantum field theory, quantum information, and atomic physics&nbsp;to forge a new interdisciplinary approach.<br /> &nbsp;<br /> Directed by Professor Ashvin Vishwanath at Harvard University, the collaboration comprises researchers at MIT, Harvard, Caltech, the Institute for Advanced Study, Stanford University, University of California at&nbsp;Santa Barbara, University of California at&nbsp;San Diego, University of Chicago, University of Colorado at Boulder, University of Innsbruck, University of Maryland, and University of Washington.&nbsp;&nbsp;<br /> &nbsp;<br /> “I am looking forward to scientific interactions with MIT theorists Senthil and Wen, who are key members of our Simons collaboration on Ultra-Quantum Matter, and hope this will further strengthen collaborations within the Cambridge area and beyond. Their research on highly entangled quantum materials is of fundamental significance, and may provide new directions for device applications, quantum computing, and high-temperature superconductors,” says collaboration director Ashvin Vishwanath of Harvard University.&nbsp;</p> <p>“They have also been mentors for several collaboration members,” says Vishwanath, who worked with Senthil as a Pappalardo Fellow in physics from 2001 to 2004.</p> <p>Senthil has played a leading role in the field of non-Fermi liquids, in the classification of strongly interacting topological insulators and related topological phases, and in the development of field theory dualities with diverse applications in condensed matter physics.</p> <p>Wen is one of the founders of the field of topological phases of matter, introducing the concept of topological order in 1989&nbsp;and opening up a new research direction in condensed matter physics. Wen’s research has often exposed mathematical structures that have not appeared before in condensed matter physics problems.</p> <p><strong>MIT-grown</strong></p> <p>Of the 17 faculty members who are participating in the collaboration, more than half, including Senthil, Wen, and Vishwanath, have MIT affiliations.&nbsp;</p> <p>Michael Hermele, the collaboration’s deputy director and an associate professor at the University of Colorado at Boulder, was a postdoc in the MIT Condensed Matter Theory group.&nbsp;</p> <p>Associate professors Xie Chen PhD ’12 and Michael Levin PhD ’06, at Caltech and the University of Chicago, respectively, earned their doctorates at MIT under Wen.&nbsp;</p> <p>Other principal investigators include alumni Subir Sachdev ’82, now chair of the Department of Physics at Harvard, and Leon Balents ’89, a physics professor at&nbsp;UC Santa Barbara's Kavli Institute for Theoretical Physics. John McGreevy, a string theorist who conducted research in the Center for Theoretical Physics (CTP), is now a professor of physics at UC San Diego. Dam Thanh Son and Andreas Karch, former CTP postdocs, are now with the University of Chicago and the University of Washington, respectively.&nbsp;</p> <p>The collaboration is part of the <a href="https://www.simonsfoundation.org/event/mps-conference-on-ultra-quantum-matter-ii/">Simons Collaborations in Mathematics and Physical Sciences</a> program, which aims to “stimulate progress on fundamental scientific questions of major importance in mathematics, theoretical physics and theoretical computer science.” The Simons Collaboration on Ultra-Quantum Matter is one of 12 such collaborative grants ranging across these fields.</p> <p>The first meeting of the newly established collaboration will take place Sept.&nbsp;12-13 in Cambridge, Massachusetts.</p> An artistic impression depicts ultra-quantum matter: from the cold topological matter (blue) to hot, strongly correlated metal (red).Image: Harald Ritsch/University of InnsbruckSchool of Science, Physics, Research, Quantum computing, Materials Science and Engineering, School of Engineering, Metals, Laboratory for Nuclear Science, Center for Theoretical Physics, Collaboration, Funding, Alumni/ae Plotting new paths to a nuclear “yes” http://news.mit.edu/2019/plotting-paths-nuclear-arms-control-mareena-robinson-snowden-0528 Nuclear science and engineering alumna Mareena Robinson Snowden PhD &#039;17 devises new solutions for problems of arms control and proliferation. Tue, 28 May 2019 15:30:00 -0400 Leda Zimmerman | Department of Nuclear Science and Engineering http://news.mit.edu/2019/plotting-paths-nuclear-arms-control-mareena-robinson-snowden-0528 <p>These are tough times for proponents of arms control and nuclear nonproliferation. Talks with North Korea seem to be at another impasse, and the United States and Russia are walking away from decades-old weapons agreements. But this state of affairs doesn’t seem to faze&nbsp;<a href="https://www.mareenarobinsonsnowden.com/" target="_blank">Mareena Robinson Snowden</a> PhD ’17 in nuclear science and engineering.</p> <p>“It’s exciting as a researcher to work on something that people are thinking about now, something with real-world implications,” says Snowden. A Stanton nuclear security fellow at the Carnegie Endowment for International Peace (CEIP), she is focused on bringing new ideas to the table on nuclear arms control.</p> <p>“I try to understand how policymakers and negotiators think, explore current nuclear challenges, and then try to evolve technical frameworks to meet the world as it is,” she says.</p> <p>Snowden’s work is part of a larger CEIP initiative, the “nuclear firewall” project. Through this effort, scholars hope “to distinguish between peaceful nuclear programs and those focused on weapons,” applying both technical and contextual analysis, explains Snowden. CEIP wants to help nations sidestep nuclear crises, and to stem the acquisition of nuclear weapons by non-nuclear states.</p> <p>Since joining Carnegie last summer, Snowden has been looking especially hard at the question of nuclear verification, a problem that is quite different today than in years past.</p> <p>With the United States and Russia — established nuclear states — verification frameworks permit reciprocal inspection of nuclear weapons systems. Under the 2015 Iran nuclear deal, an international agency goes on location to monitor progress on the accumulation of fissile nuclear materials used for bomb building.</p> <p>But North Korea presents a new, hybrid challenge for verification, according to Snowden. “The U.S. does not consider North Korea a peer nation like Russia, and reciprocal nuclear inspections are not on the table here,” she says. And given North Korea’s sprawling, highly developed, and very secretive nuclear system — from missiles and mobile launchers to warheads and enrichment plants — it seems implausible to establish a framework involving demands for the system’s complete dismantlement, and intrusive visits to ensure compliance with the framework.</p> <p>So what kind of plan might work for the kind of evolving, emerging nuclear challenge represented by North Korea?</p> <p>One concept, suggests Snowden, might require “the U.S. government and international community to prioritize what constitutes militarily significant activities within the larger program, and to ask for limits and demonstrations of compliance on just those activities.”</p> <p>Under “probabilistic verification,” negotiators pose the question, “What’s enough?” says Snowden. They zero in on a cluster of technically critical features whose elimination or destruction would prove sufficient for the purposes of reducing nuclear weapons capability.</p> <p>But it seems unlikely the current U.S. administration would embrace such a framework. “Today the expectation in the American mind, set by the current commander in chief, is to go big, go for an all-or-nothing deal,” she says. Successful agreements require lengthy negotiations between diplomats, says Snowden, noting it took 10 years to lay the groundwork for the 1987 Intermediate-Range Nuclear Forces pact between Soviet leader Mikhail Gorbachev and U.S. President Ronald Reagan. “One-and-done” — a single nuclear summit between two leaders — is unrealistic, believes Snowden.</p> <p><strong>Driven to succeed</strong></p> <p>It took just a single class on the history of nuclear non-proliferation to seize Snowden’s interest as a graduate student.</p> <p>“I had so many questions: ‘Why were there such tensions between countries? What policies deal with these weapons?’” she says. “There are technical questions at the heart of nuclear disagreements between nations, and for a technical person, this was a clear lane for me,” she says.</p> <p>Her thesis investigated whether natural radiation signals generated inside of plutonium-based warheads could be using to monitor them in a future arms control agreement.</p> <p>Conducting this research wasn’t always smooth sailing. But Snowden found guidance and support from two key advisors. “<a href="http://web.mit.edu/nse/people/research/lanza.html" target="_blank">Richard Lanza</a>&nbsp;(a senior research scientist), a titan in the field of radiation detection, spent so much time brainstorming with me, and discussing my data and analysis,” she says. “And with&nbsp;<a href="http://web.mit.edu/nse/people/faculty/yip.html" target="_blank">Sidney Yip</a> [emeritus professor of nuclear science and engineering], it went beyond technical mentorship to personal mentorship: He talked about how difficult the PhD process is, and gave me the encouragement to get through it.”</p> <p>Snowden felt strongly driven to get through her graduate studies, which she describes as “an extended period of uncertainty.” She was the first black woman to receive a PhD from MIT’s nuclear science and engineering program. “I understood I existed in a unique space, and this was a complete motivator for me,” she says. “There was no license to lie down and give up, because who knows when the next person of color, particularly another black woman, will come in behind me.”</p> <p><strong>Dual missions</strong></p> <p>Snowden seeks to advance both the community she represents and her ideas in the arms control domain — sometimes simultaneously. In “Responsible Disruption,” a paper she recently published on the website N Square, she argues for greater inclusion of women and other marginalized voices in nuclear security debates.</p> <p>“For a long time, gender was not considered a valid part of nuclear security discussions, but it’s now becoming a vibrant conversation,” she says. “There are biological impacts related to the ionizing radiation of nuclear weapons that affect women differently, as well as gendered impacts associated with crisis and conflict during and following war.” She also notes that the impacts of most conflicts fall hardest on those pushed to the margins, whether along class, racial, or gender lines. So it is imperative, Snowden says, that “we have different voices at the table, especially when some are starting to entertain the premise of limited nuclear war.”</p> <p>She sees popular culture as a way to lure interest to arms policy discussions, and to her field more generally. Just as the film and book "Hidden Figures" drew attention to black women in computer science, making the discipline more accessible, she believes that creative storytellers could “dig into the history of the nuclear security space and tell that story in a new way that really connects with people, especially with underrepresented communities,” says Snowden. “We need to reframe who this space belongs to.”</p> <p>While Snowden might someday delve into such storytelling, she is at full throttle at Carnegie, currently preparing a paper on the necessary evolution of verification.</p> <p>“I discovered I really love research, so I would like to find a full-time position continuing this work,” she says. “There is a lot of instability now between countries with a history of conflict, which worries me, but I hope I will be able to provide valuable suggestions that will make a useful impact on real-world conversations about nuclear security, and navigate to a future that’s more stable.”</p> “I try to understand how policy makers and negotiators think, explore current nuclear challenges, and then try to evolve technical frameworks to meet the world as it is,” says Mareena Robinson Snowden PhD '17.Photo: Leslie JeanNuclear science and engineering, School of Engineering, Policy, Alumni/ae, Diversity and inclusion, STEM education, Nuclear security and policy, Government, Women in STEM 3Q: Yet-Ming Chiang on reopening the case of cold fusion http://news.mit.edu/2019/3q-yet-ming-chiang-reopening-the-case-of-cold-fusion-0527 The materials science and engineering professor is part of a multi-institution effort to investigate the possibility of cold fusion in a scientifically rigorous way. Mon, 27 May 2019 11:00:00 -0400 Rachel Kemper | Department of Materials Science and Engineering http://news.mit.edu/2019/3q-yet-ming-chiang-reopening-the-case-of-cold-fusion-0527 <p><em>Researchers at MIT have collaborated with a team of scientists from the University of British Columbia, the University of Maryland, Lawrence Berkeley National Laboratory, and Google to conduct a multiyear investigation into cold fusion, a type of benign nuclear reaction hypothesized to occur in benchtop apparatus at room temperature.</em></p> <p><em>In 1989, benchtop experiments were reported that raised hopes that cold fusion had been achieved. If true, this form of fusion could potentially be a source of limitless, carbon-free energy. However, researchers were unable to reproduce the results, and serious questions arose about the validity of the work. The topic laid largely dormant for 30 years. (In contrast, research in “hot” fusion has persisted, including the&nbsp;<a href="http://news.mit.edu/2018/mit-newly-formed-company-launch-novel-approach-fusion-power-0309">SPARC collaboration</a>, which aims to commercialize fusion technology.)</em></p> <p><em>Yet-Ming Chiang, the Kyocera Professor in MIT’s Department of Materials Science and Engineering, is part of the Google-sponsored team now revisiting the possibility of cold fusion through scientifically rigorous, peer-reviewed research. </em><em>A progress report published today in </em>Nature <em>publicly describes the group’s collaboration for the first time.</em></p> <p><em>The group, which included about 30 graduate students, postdocs, and staff scientists from across the collaborating institutions, has not yet found any evidence of the phenomenon, but they did find important new insights into metal-hydrogen interactions that could affect low-energy nuclear reactions. The team remains excited about investigating this area and hopes their ongoing journey will inspire others in the scientific community to contribute data to this intriguing field.</em></p> <p><strong>Q:</strong>&nbsp;How did you get involved with a project that many would not consider?</p> <p><strong>A:</strong>&nbsp;Matt Trevithick SB ’92, SM ’94, senior program manager at Google Research, approached me in spring of 2015 and he did so pretty gingerly, kind of poking around the edges at first, and then he popped the question, “What do you think of cold fusion?” And my answer to him was that I didn’t have an opinion one way or the other on the scientific merits,&nbsp;because in 1989, when the cold fusion story broke, I was working all-out on high-temperature superconductivity, which had broken in 1986-87. We were furiously doing research in my lab on that topic, and also had started a company with MIT collaborators. So the cold fusion story came and went, and I was peripherally aware of it.</p> <p>Then Matt asked if this was something I might be interested in. Google recruited the collaborators on this team not by telling us what they wanted done, but by asking us what we would find interesting to do. We wrote proposals that were internally reviewed.&nbsp;What was interesting to me is the idea that electrochemistry, and especially solid-state electrochemistry,&nbsp;is a very powerful driving force that can create unusual states of matter.&nbsp;We’ve applied that idea to high energy batteries and electrochemical actuators previously, and this was another field in which electrochemical manipulation of matter could be interesting.</p> <p>This project was carried out in stealth. We didn’t want the fact that Google was funding research in this area to become a distraction. For the first couple of years, we didn’t even tell other members of our group the real reason behind the hydrogen storage experiments going on in the lab!&nbsp;</p> <p>Ariel Jackson, a postdoc, had a major role in developing the original proposal. Later on, Daniel Rettenwander and Jesse Benck joined as postdocs, and David Young SB ’12, SM ’18 joined as a graduate student. Together, we pursued the idea of using different types of electrolytes, liquid, polymer, and ceramic, as the medium by which to electrochemically pump hydrogen into palladium metal in order to achieve as highly loaded a state as possible. We also developed techniques to&nbsp;measure loading dynamically more precisely and more accurately than had been done before.&nbsp;To date we’ve been able to reach a H:Pd ratio of 0.96, where the theoretical maximum is 1, measured to an uncertainty of + or – 0.02.&nbsp;These results have just been published in&nbsp;<a href="https://pubs.acs.org/doi/10.1021/acs.chemmater.9b01243" target="_blank"><em>Chemistry of Materials</em></a>, and one measure of the care we went to in this work is the fact that the supplemental information section of the paper is 50 pages long.</p> <p><strong>Q:</strong>&nbsp;What have you learned, and why did the group choose to publish now?&nbsp;</p> <p><strong>A:</strong>&nbsp;The <em>Nature</em> publication makes clear that to date we have not discovered compelling evidence for cold fusion. Our objective was to be scrupulously objective, and I think we have managed to avoid any form of “<a href="https://en.wikipedia.org/wiki/Confirmation_bias">confirmation bias</a>.” However, we’ve also learned that the high deuterium concentrations hypothesized to be necessary for cold fusion to occur are much more difficult to attain than we would have expected.&nbsp;And, there have been a number of other discoveries that have come about as a result of the group’s work that are applicable in other scientific areas.</p> <p>Google’s intent from the beginning was to fund a multi-institutional collaborative effort that would work quietly but intensively, then publish its findings&nbsp;in peer-reviewed journals. Now is the right time to disclose that this project exists, to tell people what we have found and not found. We are not finished – in many ways this is just the beginning – and we want others to join the&nbsp;effort to look into the materials science, electrochemistry, and physics surrounding this topic.</p> <p><strong>Q:</strong>&nbsp;What’s next at MIT?</p> <p><strong>A:</strong>&nbsp;The project at MIT goes on, and we are looking to add to the team. What we’ve learned over the past three years has suggested new ways to use electrochemistry and materials science to create highly loaded metal hydrides: palladium for sure, but also other metals. We believe that we have found certain knobs that could allow us to create phase states that have not been accessible before.&nbsp;If we can controllably produce these, they will be very interesting target materials for other experiments within the broader program looking at, for example, neutron yields from deuterium-deuterium fusion in a plasma discharge device at Lawrence Berkeley National Lab.&nbsp;</p> Yet-Ming Chiang, Kyocera Professor, Department of Materials Science and EngineeringPhoto: Tim PumphreyResearch, 3 Questions, Fusion, Nuclear science and engineering, Alternative energy, Renewable energy, Energy, Nuclear power and reactors, Physics, School of Engineering, DMSE, Materials Science and Engineering For one graduate student, MIT&#039;s nuclear reactor is like a &quot;second home&quot; http://news.mit.edu/2019/mit-nuclear-reactor-lab-agata-wisniowska-0523 On the cusp of graduation, health sciences and technology doctoral candidate Agata Wiśniowska &#039;11 sustains her decade-plus connection to the MIT Nuclear Reactor Lab. Thu, 23 May 2019 15:20:01 -0400 Leda Zimmerman | Nuclear Reactor Lab http://news.mit.edu/2019/mit-nuclear-reactor-lab-agata-wisniowska-0523 <p>Starting in 2008, as she pursued dual undergraduate degrees in physics, and nuclear science and engineering (NSE), and then a doctorate in health sciences and technology, there has been one constant in Agata Wiśniowska's life: work at MIT's Nuclear Research Laboratory (NRL).</p> <p>"I've always enjoyed it," says Wiśniowska '11. "The atmosphere at the lab is so nice — it's been comfortable and welcoming, like a refuge."</p> <p>During her notably venturesome academic journey, Wiśniowska has made the NRL an informal home base. It has served variously as her gateway to the world of nuclear science, a testing ground for technical competence, and a domain for practicing management skills. It has also functioned as a launchpad.</p> <p>"At the lab, I gained my first supervisory experience," Wiśniowska says. "I learned to deal with different types of people, handle different situations that might arise, and confidently make decisions."</p> <p>Wiśniowska's connection to the lab began the winter of her freshman year. Newly arrived to MIT from an international baccalaureate program in Poland where she had focused on physics, she was intent, she says, on "choosing as a major something I didn't already know a lot about." After sampling courses, she found nuclear science and engineering (NSE) particularly intriguing. At a departmental open house, she saw an advertisement encouraging students to train as MIT reactor operators.</p> <p>"Since I was considering nuclear engineering, and I like to learn in depth from basic principles, it made sense to work at the plant and see how it operated from the inside out," she says. "I thought if I wanted to become a nuclear engineer, this would be really helpful."</p> <p>In addition to an income, the reactor operator job provided unexpected benefits. "Imagine coming from a different country, with English as a second language, and receiving a manual for studying this complex system," says Wiśniowska. "I didn't understand many of the words, so I kept bugging my supervisor to explain by drawing things." While trying to master the technical demands of her job, Wiśniowska made progress in her efforts to become fluent in English.</p> <p>She also received the deep immersion she sought in nuclear science and engineering. She participated in studies conducted by a range of investigators using the reactor. And several of her NSE classes centered on studies taking place at the reactor, including one involving modeling tritium radiation as it dissipated through the layers of experimental capsule of molten salt coolant.&nbsp;</p> <p>"I could talk directly to experimenters and gain unique insights while sitting at the console as an operator," she says. "It was fun to be able to work on something very relevant to the reactor lab while also satisfying course work."</p> <p>Wiśniowska found the NRL life so rewarding that in her sophomore year, she decided to expand her role and train to become a shift supervisor. She vividly recalls some of her experiences early on in this new position.&nbsp;</p> <p>"My first reactor scram [automatic shutdown] was definitely memorable," she says. "I could hear the intercom announcement that the reactor power was decreasing, realized we had just scrammed, and knew that as supervisor, I'd have to work with the operator to figure out what to do next."</p> <p>It turned out that this was no emergency, but a run-of-the-mill power dip. For Wiśniowska it was a formative moment in a long learning process. "I had this sense of uncertainty, but realized I could handle it, and later, dealing with these issues became second nature."&nbsp;&nbsp;</p> <p><strong>A new direction</strong></p> <p>By the time she reached senior year, though, Wiśniowska began to push at the constraints of her NSE studies. She had become interested in chemistry and biology, and took enough classes to minor in both fields. Medical school seemed like a possibility. For her undergraduate thesis, Wiśniowska found a way to combine her interests, researching proton irradiation therapy for liver cancer patients at Massachusetts General Hospital.&nbsp;</p> <p>During her thesis work, she learned that the NRL had decades earlier contributed to medical studies, providing neutrons to irradiate patients with brain tumors using a technique called boron neutron capture therapy.&nbsp;</p> <p>"I became interested in medical applications of nuclear science, but because there was no NSE program that focused on this area to the degree I hoped for, I ended up changing programs," says Wiśniowska. "While sticking with NSE would have been easier, I needed a new challenge, even if it pushed me out of my comfort zone."</p> <p>Wiśniowska landed at the Harvard-MIT Program in Health Sciences and Technology (HST). A rigorous course of study, combining medical training at Boston's teaching hospitals with research, HST "felt like a beacon of possibilities," says Wiśniowska.&nbsp;</p> <p>After doing rotations in different specialties, Wiśniowska knew she wasn't cut out to be a doctor. But she spotted a research area that simultaneously satisfied her desire to stretch herself intellectually and to improve human health: studying the brain using novel imaging techniques.</p> <p>In the lab of Alan Jasanoff, an MIT professor of biological engineering, brain and cognitive sciences, and nuclear science and engineering, Wiśniowska has been able to draw on her expertise in a range of fields to develop methods for observing mechanistic molecular events in the brain.</p> <p>"The research is cutting edge," she says. "We're trying to understand the elusive concept of consciousness from the molecular standpoint, getting at the question by looking at signaling molecules in the living brain."</p> <p>For her doctoral work, Wiśniowska helped devise an organic sensor — a small protein — that when prompted by its small molecule target in the brain activates receptors on the smooth muscle cells lining blood vessels. This in turn triggers the cells to elongate and increase blood flow to the area, a process called vasodilation. The local increase in blood flow, indicative of detection of the target molecule, can be captured in real-time by molecular functional magnetic resonance imaging (fMRI).&nbsp;</p> <p>"This sensor, by tapping into the contrast naturally available in blood vessels, removes the need for metal-based contrast agents normally used in molecular fMRI and allows us to image mechanistically informative molecular events in the brain with an unprecedented degree of sensitivity," says Wiśniowska. It is work that may give scientists a close up view of how neurotransmitters work to inhibit or stimulate regions in the brain.&nbsp;</p> <p>"For the first time we may really come to understand the underlying processes of the brain, because we are developing tools that can look at the molecular aspects of signaling," she says. "The first application will involve mapping functions and determining normal brain activity, but downstream, it may be possible to diagnose people based on patterns of signaling molecules."</p> <p><strong>Ready to launch</strong></p> <p>Although pleased by the fruits of her doctoral labor, Wiśniowska decided to shift gears again. "I have contributed my bit to research, but I'd like to focus now on bringing tools like this to market." She will soon be joining the life sciences division of a consulting company, helping to evaluate and boost new biologics and medical devices.&nbsp;</p> <p>"It will be exciting to get a sense of the business end of drug discovery, where I hope to leverage my research and insights to help companies make an impact on a range of different conditions," she says.</p> <p>But even today, as she closes out her academic life at MIT and prepares for the next phase, Wiśniowska is sticking with her regular Sunday double shift (16 hours) at the NRL. "I have found it helpful staying at my desk there, with my tea mug and food supplies, rather than going back to my apartment," she says. "People at the lab motivate me to keep working on my thesis, and I’m more productive."</p> <p>She also credits the NRL for helping her land her consulting job. "My work as a reactor operator is a great conversation starter in interviews," she says. "But more important, the NRL gave me my first real work experience, showing me that my decisions can have real weight, and how to take responsibility."</p> <p>For the immediate future, Wiśniowska plans to stay connected. "I will continue to work as a temp and keep my license active," she says. "It's like my second home.</p> Agata Wiśniowska credits the MIT Nuclear Reactor Lab for helping her land a consulting job. "The NRL gave me my first real work experience, showing me that my decisions can have real weight, and how to take responsibility."Photo: Gretchen ErtlProfile, Students, Graduate, postdoctoral, Alumni/ae, Physics, Harvard-MIT Health Sciences and Technology, Biological engineering, Brain and cognitive sciences, Nuclear power and reactors, School of Science, School of Engineering, Nuclear science and engineering Steering fusion’s “D-turn” http://news.mit.edu/2019/steering-d-turn-nuclear-fusion-0517 Research scientist Alessandro Marinoni shows that reversing traditional plasma shaping provides greater stability for fusion reactions. Fri, 17 May 2019 16:10:01 -0400 Paul Rivenberg | Plasma Science and Fusion Center http://news.mit.edu/2019/steering-d-turn-nuclear-fusion-0517 <p>Trying to duplicate the power of the sun for energy production on earth has challenged fusion researchers for decades. One path to endless carbon-free energy has focused on heating and confining plasma fuel in tokamaks, which use magnetic fields to keep the turbulent plasma circulating within a doughnut-shaped vacuum chamber and away from the walls. Fusion researchers have favored contouring these tokamak plasmas into a triangular or D shape, with the curvature of the D stretching away from the center of the doughnut, which allows plasma to withstand the intense pressures inside the device better than a circular shape.</p> <p>Led by research scientists&nbsp;<a href="http://www.psfc.mit.edu/people/scientific-staff/alessandro-marinoni">Alessandro Marinoni</a> of MIT's Plasma Science and Fusion Center (PSFC) and Max Austin, of the University of Texas at Austin, researchers at the&nbsp;<a class="external" href="https://science.energy.gov/fes/facilities/user-facilities/diii-d/" target="_blank">DIII-D National Fusion Facility</a>&nbsp;have discovered promising evidence that reversing the conventional shape of the plasma in the tokamak chamber can create a more stable environment for fusion to occur, even under high pressure. The&nbsp;<a class="external" href="https://aip.scitation.org/doi/10.1063/1.5091802" target="_blank">results were recently published</a>&nbsp;in&nbsp;<em>Physical Review Letters and Physics of Plasmas</em>.</p> <p>Marinoni first experimented with the “reverse-D” shape, also known as “negative triangularity,” while pursuing his PhD on the TCV tokamak at Ecole Polytechnique Fédérale de Lausanne, Switzerland. The TCV team was able to show that negative triangularity helps to reduce plasma turbulence, thus increasing confinement, a key to sustaining fusion reactions.</p> <p>“Unfortunately, at that time, TCV was not equipped to operate at high plasma pressures with the ion temperature being close to that of electrons,” notes Marinoni, “so we couldn’t investigate regimes that are directly relevant to fusion plasma conditions.”</p> <p>Growing up outside Milan, Marinoni developed an interest in fusion through an early passion for astrophysical phenomena, hooked in preschool by the compelling mysteries of black holes.</p> <p>“It was fascinating because black holes can trap light. At that time I was just a little kid. As such, I couldn’t figure out why the light could be trapped by the gravitational force exerted by black holes, given that on Earth nothing like that ever happens.”</p> <p>As he matured he joined a local amateur astronomy club, but eventually decided black holes would be a hobby, not his vocation.</p> <p>“My job would be to try producing energy through nuclear fission or fusion; that’s the reason why I enrolled in the nuclear engineering program in the Polytechnic University of Milan.”</p> <p>After studies in Italy and Switzerland, Marinoni seized the opportunity to join the PSFC’s collaboration with the DIII-D tokamak in San Diego, under the direction of MIT professor of physics&nbsp;<a href="https://www.psfc.mit.edu/people/faculty/miklos-porkolab">Miklos Porkolab</a>. As a postdoc, he used MIT’s phase contrast imaging diagnostic to measure plasma density fluctuations in DIII-D, later continuing work there as a PSFC research scientist.</p> <p>Max Austin, after reading the negative triangularity results from TCV, decided to explore the possibility of running similar experiments on the DIII-D tokamak to confirm the stabilizing effect of negative triangularity. For the experimental proposal, Austin teamed up with Marinoni and together they designed and carried out the experiments.</p> <p>"The DIII-D research team was working against decades-old assumptions,” says Marinoni. “It was generally believed that plasmas at negative triangularity could not hold high enough plasma pressures to be relevant for energy production, because of macroscopic scale&nbsp;Magneto-Hydro-Dynamics&nbsp;(MHD) instabilities that would arise and destroy the plasma.&nbsp;MHD is&nbsp;a theory that governs the macro-stability of electrically conducting fluids such as plasmas.&nbsp;We wanted to show that under the right conditions the reverse-D shape could sustain MHD stable plasmas at high enough pressures to be suitable for a fusion power plant, in some respects even better than a D-shape."</p> <p>While D-shaped plasmas are the standard configuration, they have their own challenges. They are affected by high levels of turbulence, which hinders them from achieving the high pressure levels necessary for economic fusion. Researchers have solved this problem by creating a narrow layer near the plasma boundary where turbulence is suppressed by large flow shear, thus allowing inner regions to attain higher pressure. In the process, however, a steep pressure gradient develops in the outer plasma layers, making the plasma susceptible to instabilities called edge localized modes that, if sufficiently powerful, would expel a substantial fraction of the built-up plasma energy, thus damaging the tokamak chamber walls.</p> <p>DIII-D was designed for the challenges of creating D-shaped plasmas. Marinoni praises the DIII-D control group for “working hard to figure out a way to run this unusual reverse-D shape plasma.”</p> <p>The effort paid off. DIII-D researchers were able to show that even at higher pressures, the reverse-D shape is as effective at reducing turbulence in the plasma core as it was in the low-pressure TCV environment. Despite previous assumptions, DIII-D demonstrated that plasmas at reversed triangularity can sustain pressure levels suitable for a tokamak-based fusion power plant; additionally, they can do so without the need to create a steep pressure gradient near the edge that would lead to machine-damaging edge localized modes.</p> <p>Marinoni and colleagues are planning future experiments to further demonstrate the potential of this approach in an even more fusion-power relevant magnetic topology, based on a “diverted”&nbsp; tokamak concept. He has tried to interest other international tokamaks in experimenting with the reverse configuration.</p> <p>“Because of hardware issues, only a few tokamaks can create negative triangularity plasmas; tokamaks like DIII-D, that are not designed to produce plasmas at negative triangularity, need a significant effort to produce this plasma shape. Nonetheless, it is important to engage the fusion community worldwide to more fully establish the data base on the benefits of this shape.”</p> <p>Marinoni looks forward to where the research will take the DIII-D team. He looks back to his introduction to tokamak, which has become the focus of his research.</p> <p>“When I first learned about tokamaks I thought, ‘Oh, cool! It’s important to develop a new source of energy that is carbon free!’ That is how I ended up in fusion.”</p> <p>This research is sponsored by the U.S. Department of Energy Office of Science's Fusion Energy Sciences, using their DIII-D National Fusion Facility.</p> Cross sections of pressure profiles are shown in two different tokamak plasma configurations (the center of the tokamak doughnut is to the left of these). The discharges have high pressure in the core (yellow) that decreases to low pressure (blue) at the edge. Researchers achieved substantial high-pressure operation of reverse-D plasmas at the DIII-D National Fusion Facility.Image: Alessandro Marinoni/MIT PSFCPlasma Science and Fusion Center, School of Science, School of Engineering, Fusion, Energy, Physics, Collaboration, Research, Nuclear science and engineering Manipulating atoms one at a time with an electron beam http://news.mit.edu/2019/manipulate-atoms-graphene-quantum-0517 New method could be useful for building quantum sensors and computers. Fri, 17 May 2019 14:23:59 -0400 David L. Chandler | MIT News Office http://news.mit.edu/2019/manipulate-atoms-graphene-quantum-0517 <p>The ultimate degree of control for engineering would be the ability to create and manipulate materials at the most basic level, fabricating devices atom by atom with precise control.</p> <p>Now, scientists at MIT, the University of Vienna, and several other institutions have taken a step in that direction, developing a method that can reposition atoms with a highly focused electron beam and control their exact location and bonding orientation. The finding could ultimately lead to new ways of making quantum computing devices or sensors, and usher in a new age of “atomic engineering,” they say.</p> <p>The advance is described today in the journal <em>Science Advances</em>, in a paper by MIT professor of nuclear science and engineering Ju Li, graduate student Cong Su, Professor Toma Susi of the University of Vienna, and 13 others at MIT, the University of Vienna, Oak Ridge National Laboratory, and in China, Ecuador, and Denmark.</p> <p>“We’re using a lot of the tools of nanotechnology,” explains Li, who holds a joint appointment in materials science and engineering. But in the new research, those tools are being used to control processes that are yet an order of magnitude smaller. “The goal is to control one to a few hundred atoms, to control their positions, control their charge state, and control their electronic and nuclear spin states,” he says.</p> <p>While others have previously manipulated the positions of individual atoms, even creating a neat circle of atoms on a surface, that process involved picking up individual atoms on the needle-like tip of a scanning tunneling microscope and then dropping them in position, a relatively slow mechanical process. The new process manipulates atoms using a relativistic electron beam in a scanning transmission electron microscope (STEM), so it can be fully electronically controlled by magnetic lenses and requires no mechanical moving parts. That makes the process potentially much faster, and thus could lead to practical applications.</p> <p>Using electronic controls and artificial intelligence, “we think we can eventually manipulate atoms at microsecond timescales,” Li says. “That’s many orders of magnitude faster than we can manipulate them now with mechanical probes. Also, it should be possible to have many electron beams working simultaneously on the same piece of material.”</p> <p>“This is an exciting new paradigm for atom manipulation,” Susi says.</p> <p>Computer chips are typically made by “doping” a silicon crystal with other atoms needed to confer specific electrical properties, thus creating “defects’ in the material — regions that do not preserve the perfectly orderly crystalline structure of the silicon. But that process is scattershot, Li explains, so there’s no way of controlling with atomic precision where those dopant atoms go. The new system allows for exact positioning, he says.</p> <p>The same electron beam can be used for knocking an atom both out of one position and into another, and then “reading” the new position to verify that the atom ended up where it was meant to, Li says. While the positioning is essentially determined by probabilities and is not 100 percent accurate, the ability to determine the actual position makes it possible to select out only those that ended up in the right configuration.</p> <p><strong>Atomic soccer</strong></p> <p>The power of the very narrowly focused electron beam, about as wide as an atom, knocks an atom out of its position, and by selecting the exact angle of the beam, the researchers can determine where it is most likely to end up. “We want to use the beam to knock out atoms and essentially to play atomic soccer,” dribbling the atoms across the graphene field to their intended “goal” position, he says.</p> <p>“Like soccer, it’s not deterministic, but you can control the probabilities,” he says. “Like soccer, you’re always trying to move toward the goal.”</p> <p>In the team’s experiments, they primarily used phosphorus atoms, a commonly used dopant, in a sheet of graphene, a two-dimensional sheet of carbon atoms arranged in a honeycomb pattern. The phosphorus atoms end up substituting for carbon atoms in parts of that pattern, thus altering the material’s electronic, optical, and other properties in ways that can be predicted if the positions of those atoms are known.</p> <p>Ultimately, the goal is to move multiple atoms in complex ways. “We hope to use the electron beam to basically move these dopants, so we could make a pyramid, or some defect complex, where we can state precisely where each atom sits,” Li says.</p> <p>This is the first time electronically distinct dopant atoms have been manipulated in graphene. “Although we’ve worked with silicon impurities before, phosphorus is both potentially more interesting for its electrical and magnetic properties, but as we’ve now discovered, also behaves in surprisingly different ways. Each element may hold new surprises and possibilities,” Susi adds.</p> <p>The system requires precise control of the beam angle and energy. “Sometimes we have unwanted outcomes if we’re not careful,” he says. For example, sometimes a carbon atom that was intended to stay in position “just leaves,” and sometimes the phosphorus atom gets locked into position in the lattice, and “then no matter how we change the beam angle, we cannot affect its position. We have to find another ball.”</p> <p><strong>Theoretical framework</strong></p> <p>In addition to detailed experimental testing and observation of the effects of different angles and positions of the beams and graphene, the team also devised a theoretical basis to predict the effects, called primary knock-on space formalism, that tracks the momentum of the “soccer ball.” “We did these experiments and also gave a theoretical framework on how to control this process,” Li says.</p> <p>The cascade of effects that results from the initial beam takes place over multiple time scales, Li says, which made the observations and analysis tricky to carry out. The actual initial collision of the relativistic electron (moving at about 45 percent of the speed of light) with an atom takes place on a scale of <a href="http://news.mit.edu/2012/explained-femtoseconds-and-attoseconds">zeptoseconds</a> — trillionths of a billionth of a second — but the resulting movement and collisions of atoms in the lattice unfolds over time scales of picoseconds or longer — billions of times longer.</p> <p>Dopant atoms such as phosphorus have a nonzero nuclear spin, which is a key property needed for quantum-based devices because that spin state is easily affected by elements of its environment such as magnetic fields. So the ability to place these atoms precisely, in terms of both position and bonding, could be a key step toward developing quantum information processing or sensing devices, Li says.</p> <p>“This is an important advance in the field,” says Alex Zettl, a professor of physics at the University of California at Berkeley, who was not involved in this research. “Impurity atoms and defects in a crystal lattice are at the heart of the electronics industry. As solid-state devices get smaller, down to the nanometer size scale, it becomes increasingly important to know precisely where a single impurity atom or defect is located, and what are its atomic surroundings. An extremely challenging goal is having a scalable method to controllably manipulate or place individual atoms in desired locations, as well as predicting accurately what effect that placement will have on device performance.”</p> <p>Zettl says that these researchers “have made a significant advance toward this goal. They use a moderate energy focused electron beam to coax a desirable rearrangement of atoms, and observe in real-time, at the atomic scale, what they are doing. An elegant theoretical treatise, with impressive predictive power, complements the experiments.”</p> <p>Besides the leading MIT team, the international collaboration included researchers from the University of Vienna, the University of Chinese Academy of Sciences, Aarhus University in Denmark, National Polytechnical School in Ecuador, Oak Ridge National Laboratory, and Sichuan University in China. The work was supported by the National Science Foundation, the U.S. Army Research Office through MIT’s Institute for Soldier Nanotechnologies, the Austrian Science Fund, the European Research Council, the Danish Council for Independent Research, the Chinese Academy of Sciences, and the U.S. Department of Energy.</p> This diagram illustrates the controlled switching of positions of a phosphorus atom within a layer of graphite by using an electron beam, as was demonstrated by the research team.Courtesy of the researchersResearch, Nuclear science and engineering, Carbon, Graphene, School of Engineering, Materials Science and Engineering, DMSE, National Science Foundation (NSF), Department of Energy (DoE) School of Engineering first quarter 2019 awards http://news.mit.edu/2019/school-of-engineering-first-quarter-awards-0503 Faculty members recognized for excellence via a diverse array of honors, grants, and prizes over the last quarter. Fri, 03 May 2019 15:30:01 -0400 School of Engineering http://news.mit.edu/2019/school-of-engineering-first-quarter-awards-0503 <p>Members of the MIT engineering faculty receive many&nbsp;awards in recognition of their scholarship, service, and overall excellence. Every quarter, the School of Engineering publicly recognizes&nbsp;their achievements by highlighting the&nbsp;honors, prizes, and medals won by faculty working in our academic departments, labs, and centers.</p> <p>Regina Barzilay, of the Department of Electrical Engineering and Computer Science, was named among the “<a href="http://analytics.dkv.global/data/pdf/AI-for-DD-Q4/Top-100-AI-Leaders.pdf">Top 100 AI Leaders in Drug Discovery and Advanced Healthcare</a>” by Deep Knowledge Analytics on Feb. 1.</p> <p>Sir Tim Berners-Lee, of the Department of Electrical Engineering and Computer Science, was named <a href="https://www.ft.com/content/9d3205a8-15af-11e9-a168-d45595ad076d">Person of the Year</a> by the <em>Financial Times</em> on Mar. 14.</p> <p>Ed Boyden, of the Department of Biological Engineering and the MIT Media Lab, was awarded the <a href="https://www.amacad.org/news/rumford-prize-optogenetics">Rumford Prize</a> on Jan. 30.</p> <p>Emery N. Brown, of the Department of Brain and Cognitive Sciences and the Institute for Medical and Engineering Science, was awarded an <a href="https://news.usc.edu/154221/usc-2019-honorary-degree-recipients-commencement/">honorary degree</a> from the University of Southern California on April 9.</p> <p>Areg Danagoulian, of the Department of Nuclear Science and Engineering, was named to the <a href="https://www.energy.gov/nnsa/articles/nnsa-grants-50-million-university-consortia-supporting-nonproliferation-research-and">Consortium of Monitoring, Technology, and Verification</a> by the Department of Energy’s National Nuclear Security Administration on Jan. 17.</p> <p>Luca Daniel, of the Department of Electrical Engineering and Computer Science, was awarded a <a href="https://www.eecs.mit.edu/news-events/announcements/three-eecs-professors-receive-faculty-research-innovation-fellowships">Thornton Family Faculty Research Innovation Fellowship</a> on Feb. 8.</p> <p>Constantinos Daskalakis, of the Department of Electrical Engineering and Computer Science, was awarded a <a href="https://www.eecs.mit.edu/news-events/announcements/three-eecs-professors-receive-faculty-research-innovation-fellowships">Frank Quick Faculty Research Innovation Fellowship</a> on Feb. 8.</p> <p>Srini Devadas, of the Department of Electrical Engineering and Computer Science, won the <a href="https://alumni.iitm.ac.in/daa/list.php">Distinguished Alumnus Award</a> by the Indian Institute of Technology, Madras on Feb. 1.</p> <p>Carmen Guerra-Garcia, of the Department of Aeronautics and Astronautics, was named an <a href="https://www.aiaa.org/">AIAA Senior Member</a> on April 5.</p> <p>Thomas Heldt, of the Department of Electrical Engineering and Computer Science and the Institute for Medical Engineering and Science, was named <a href="https://www.embs.org/about-embs/awards-recognition/distinguished-lecturers-program/distinguished-lecturers/">Distinguished Lecturer</a> by the IEEE Engineering in Medicine and Biology Society on Dec. 20, 2018.</p> <p>Tommi Jaakola, of the Department of Electrical Engineering and Computer Science, was named among “<a href="http://analytics.dkv.global/data/pdf/AI-for-DD-Q4/Top-100-AI-Leaders.pdf">Top 100 AI Leaders in Drug Discovery and Advanced Healthcare</a>” by Deep Knowledge Analytics on Feb. 1.</p> <p>Manolis Kellis, of the Department of Electrical Engineering and Computer Science, was named among “<a href="http://analytics.dkv.global/data/pdf/AI-for-DD-Q4/Top-100-AI-Leaders.pdf">Top 100 AI Leaders in Drug Discovery and Advanced Healthcare</a>” by Deep Knowledge Analytics on Feb. 1.</p> <p>Sangbae Kim, of the Department of Mechanical Engineering, was named a <a href="https://dssg.ida.org/">Defense Science Study Group</a> member on Mar. 20.</p> <p>Angela Koehler, of the Department of Biological Engineering, won the Junior Bose Award for Teaching Excellence on Mar. 11.</p> <p>Jing Kong, of the Department of Electrical Engineering and Computer Science, was awarded a <a href="https://www.eecs.mit.edu/news-events/announcements/three-eecs-professors-receive-faculty-research-innovation-fellowships">Thornton Family Faculty Research Innovation Fellowship</a> on Feb. 8.</p> <p>Luqiao Liu, of the Department of Electrical Engineering and Computer Science, was received a <a href="https://www.wpafb.af.mil/news/article-display/article/1645955/afosr-awards-grants-to-31-scientists-and-engineers-through-its-young-investigat/">Young Investigator Research Program</a> grant from the U.S. Air Force Office of Scientific Research on Sept. 26, 2018.</p> <p>Gareth McKinley, of the Department of Mechanical Engineering, was elected to the <a href="https://www.nae.edu/204087/Professor-Gareth-H-McKinley">National Academy of Engineering</a> on Feb. 2.</p> <p>Muriel Médard, of the Department of Electrical Engineering and Computer Science, was named a fellow by the <a href="https://academyofinventors.org/press-releases/">National Academy of Inventors</a> on Dec. 11, 2018.</p> <p>Stefanie Mueller, of the Department of Electrical Engineering and Computer Science, won an <a href="https://www.nsf.gov/funding/pgm_summ.jsp?pims_id=503214">NSF CAREER award</a> on Feb. 22.</p> <p>Julia Ortony, of the Department of Materials Science and Engineering, was awarded a Professor Amar G. Bose Research Grant on Feb. 14.</p> <p>Ellen Roche, of the Department of Mechanical Engineering and the Institute of Medical Engineering and Science, won an <a href="https://www.nsf.gov/funding/pgm_summ.jsp?pims_id=503214">NSF CAREER award</a> on Feb. 20.</p> <p>Christopher Schuh, of the Department of Materials Science and Engineering, was elected to the <a href="https://www.nae.edu/204087/Professor-Gareth-H-McKinley">National Academy of Engineering</a> on Feb. 7.</p> <p>Suvrit Sra, of the Department of Electrical Engineering and Computer Science, won an <a href="https://www.nsf.gov/funding/pgm_summ.jsp?pims_id=503214">NSF CAREER award</a> on Mar. 11.</p> <p>Leia Stirling, of the Department of Aeronautics and Astronautics, was named an <a href="https://www.aaas.org/programs/center-public-engagement-science-and-technology/2019-2020-leshner-leadership-institute">Alan I. Leshner Leadership Institute fellow</a> on Feb. 11.</p> <p>Peter Szolovits, of the Department of Electrical Engineering and Computer Science, was named among “<a href="http://analytics.dkv.global/data/pdf/AI-for-DD-Q4/Top-100-AI-Leaders.pdf">Top 100 AI Leaders in Drug Discovery and Advanced Healthcare</a>” by Deep Knowledge Analytics on Feb. 1.</p> Photo: Lillie Paquette / MIT School of Engineeringawards, Awards, honors and fellowships, Biological engineering, Aeronautical and astronautical engineering, Chemical engineering, Electrical Engineering & Computer Science (eecs), Mechanical engineering, Civil and environmental engineering, DMSE, Nuclear science and engineering, IDSS, Institute for Medical Engineering and Science (IMES) Harry Tuller wins Egleston Medal for his electroceramics work http://news.mit.edu/2019/mit-harry-tuller-wins-egleston-medal-for-electroceramics-work-0503 Pioneering materials science and engineering research enables better catalytic converters, miniature explosives detectors, and thin-film microbalances. Fri, 03 May 2019 13:10:01 -0400 Denis Paiste | Materials Research Laboratory http://news.mit.edu/2019/mit-harry-tuller-wins-egleston-medal-for-electroceramics-work-0503 <p>What do catalytic converters, miniature explosives detectors, and scales for weighing nanoscale quantities have in common? These technologies are all enabled by MIT Professor&nbsp;<a dir="ltr" href="https://dmse.mit.edu/people/harry-l-tuller" rel="noopener" target="_blank">Harry L. Tuller</a>’s pioneering research on electroceramics, which are complex materials that exhibit a distinctive variety of electrical, optical, magnetic, ionic, and electronic properties.</p> <p>In more than 40 years on the MIT Department of Materials Science and Engineering faculty, Tuller also has mentored many graduate students and postdocs, edited a specialized ceramics journal, and co-founded Boston MicroSystems, based on applications of his breakthrough method for micromachining silicon&nbsp;carbide. His work most often focuses on materials that can operate at high temperatures — for example, in fuel cells and auto exhaust manifolds.</p> <p>This spring, Tuller, 74, will receive for his accomplishments the&nbsp;<a dir="ltr" href="http://myceaa.org/ceaa-awards/egleston-medal/" rel="noopener" target="_blank">Thomas Egleston Medal</a> from his alma mater, Columbia University, where he earned both undergraduate and graduate degrees in electrical engineering and a doctorate in solid-state science and engineering.</p> <p>“I am truly happy to hear that Prof. Tuller will be honored with the Egleston Medal,” says&nbsp;<a dir="ltr" href="https://mse.kaist.ac.kr/index.php?mid=mse_pro_abc&amp;char=K" rel="noopener" target="_blank">Il-Doo Kim</a>, professor of materials science and engineering at the Korea Advanced Institute of Science and Technology (KAIST) in the Republic of Korea. Kim worked at MIT as a postdoc in Tuller’s&nbsp;<a dir="ltr" href="http://electroceramics.mit.edu/" rel="noopener" target="_blank">Crystal Physics and Electroceramics Laboratory</a>&nbsp;from 2003 to 2005, and he continues to collaborate with Tuller on research.</p> <p>“As the editor-in-chief of the&nbsp;<a dir="ltr" href="https://link.springer.com/journal/10832" rel="noopener" target="_blank"><em>Journal of Electroceramics</em></a>&nbsp;(since 1997) and a world-leading scientist, Prof. Tuller has accomplished a vast number of fascinating high-impact works that contributed significantly to the fields of electroceramics and solid state ionics; that is, defects, electronic structure, and transport of metal oxides and their integration into sensors and fuel cells,” Kim adds. Tuller served as president of the International Society of Solid State Ionics from 2015 to 2017.</p> <p><strong>Faculty mentor</strong></p> <p>MIT Professor Bilge Yildiz, who teaches in both the departments of&nbsp;Nuclear Science and Engineering&nbsp;and&nbsp;Materials Science and Engineering, says she is grateful to Tuller for mentoring her through her own tenure track at MIT, and for their continued collaboration. “Professor Tuller is the giant, the most significant figure in the advancement of electroceramics that are enablers to many important technologies, including energy conversion and storage, communications, electronics, and sensing. Because his work is so fundamental and based on physical principles, his contributions cross-cut and advance all of these wide-ranging applications,” Yildiz notes. Yildiz, Tuller, and three international collaborators won the International Union of Materials Research Societies <a dir="ltr" href="http://web.mit.edu/nse/news/2012/somiya-award.html" rel="noopener" target="_blank">Somiya Award</a>&nbsp;in 2012 for their work on designing ionic and mixed conducting ceramics for fuel cells.</p> <p><a dir="ltr" href="https://materials.technion.ac.il/members/avner-rothschild/" rel="noopener" target="_blank">Avner Rothschild</a>, now a professor of Electrochemical Materials and Devices in the Department of Materials Science and Engineering at the Technion – Israel Institute of Technology in Haifa, Israel, served as a postdoc under Tuller from 2003 to 2006. “I will always remember the years I spent with Harry Tuller as the most exciting time in my professional career,” Rothschild says.</p> <p>“Many technologies rely on our ability to tailor the electronic and ionic conductivities in ceramic materials, so-called electroceramic materials. For instance, the combustion process in our cars is controlled by oxygen sensors made of zirconium oxide (ZrO<sub>2</sub>), and toxic exhaust gases such as carbon monoxide (CO) and nitric oxide (NO) are converted to benign gases such as carbon dioxide (CO<sub>2</sub>), nitrogen (N<sub>2</sub>) and oxygen (O<sub>2</sub>) in the catalytic converter that is made of cerium oxide (CeO<sub>2</sub>),” Rothschild notes.</p> <p><strong>Enabling nanoionics</strong></p> <p>Tuller pioneered the defect chemistry and ionic transport in cerium oxide, an important material in catalytic converters, gas sensors, and fuel cells, while still a graduate student at Columbia University, Rothschild points out. “His doctoral work in Columbia University laid the foundation for understanding how doping — that is, substituting a tiny fraction of one of the constituent elements in an ionic compound with another element — modifies its electrical properties and opens up the way to create new functional materials with tailored electronic and ionic conductivities,” Rothschild says. “For two generations, Harry Tuller has been and continues to be the main authority in the field of defect chemistry and ionic and electronic transport in solid-state ionic materials and devices. His research encompasses a vast variety of materials, devices, and phenomena, making landmark contributions in many different areas within this field. For example, he pioneered the defect chemistry and ionic transport in nanocrystalline materials, paving the road to a new area of research called nanoionics.”</p> <p>Tuller’s work is known for its creativity, scientific depth, and analytical precision, Rothschild says. Tuller has published more than 480 articles, co-edited 15 books, and been awarded 34 patents. The Thomas Egleston Medal for Distinguished Engineering Achievement, awarded annually since 1939, is named for a key founder of the Columbia College School of Mines, which grew into today’s Fu Foundation School of Engineering and Applied Science at Columbia University. Tuller will receive the award in New York City on May 30.</p> <p><strong>Micromachining silicon carbide</strong></p> <p>Among his many accomplishments, Tuller says the most exciting was the research developing a micromachining process for diamond-like silicon carbide and shepherding it from lab bench to startup firm Boston MicroSystems through that firm’s acquisition by Pall Corp. in 2013. “This was kind of a fantastic opportunity to start from very fundamental questions in the laboratory, formulate ideas for patents, which were then developed at MIT, and demonstrate that yes, these concepts can be translated into technological innovations, and that they are practical,” Tuller explains.</p> <p>Tuller’s research in this area was motivated by some fundamental limits of important high-tech materials such as silicon, commonly used for computer chips because of its ability, in the form of p-n junctions, to switch between states that block or transmit electrical signals (insulating and conductive states); and quartz, used for wristwatches because of its ability to expand or contract in response to an electrical signal (piezoelectric response) and be driven to resonate. Neither material could stand up to the high-temperature environments for which Tuller sought to develop similar applications, such as specialized micro-electro-mechanical devices (MEMS). Such MEMS devices tell a car’s airbag when to turn on, for example, but MEMS have been developed for a wide range of applications, from gyroscopes in airplanes to laboratories on a chip.</p> <p>Silicon loses its semiconducting ability at about 150 degrees Celsius (about 300 degrees Fahrenheit) and it loses its mechanical strength at about 400 C (about 750 F), Tuller explains. At about 400-500 C, quartz undergoes a destructive transformation in its crystal structure that causes it to shatter. “We discovered a class of very high-temperature piezoelectric materials, that we’ve been refining over a period of years, and now we can replicate at 1,000 degrees Celsius the same level of performance that you can achieve at room temperature,” Tuller says.</p> <p>“The problem with something which is diamond-like is that it is resistant to nearly every kind of chemical that you could imagine,” Tuller says. “So if you attempt to apply a similar chemical etching route as used in silicon to remove material on an atomic scale, it becomes nearly impossible.” Tuller, and then-MIT graduate student Richard F. Mlcak ScD '94 developed a process to micromachine silicon carbide, which is much closer to diamond than to silicon in its ability to withstand high temperatures and retain its semiconducting properties. “So now, suddenly we could essentially replicate everything people could do in silicon in silicon carbide,” Tuller explains.</p> <p>“And it turns out coincidentally, bringing those two different fields together, that there is a very similar compound to silicon carbide in terms of its crystal structure and lattice parameter and properties, called gallium nitride, which happens to be piezoelectric. So actually, we’re able to do something which was quite unique, and that is to apply thin layers of gallium nitride to silicon carbide, and thereby cause those MEMS structures to vibrate in a similar way as the quartz crystal monitor, except on a very tiny scale. So now we’re able to make these piezoelectric resonators, working at 10 megahertz, on structures just hundreds of microns in dimensions. We combined those two technologies to form arrays of these sensors and, under support from Homeland Security Agency and NASA, we developed a series of devices which could detect explosives and toxic chemicals,” he says. Remarkably, the new MEMS-based sensor, which occupies a chip just a few millimeters in size (about one-eighth inch) can replace large benchtop devices like mass spectrometers that cost about $50,000 each. It became the basis for Boston Microsystems, a pioneer in MEMS designed for harsh environments, and high-sensitivity sensors for use in explosives detection and industrial monitoring.</p> <p><strong>Making connections</strong></p> <p>The ups and downs of that process enriched his interactions with students, Tuller says. “Something I like about being at MIT is that we’re interested in the connection between fundamental issues and engineering applications. And, I think, to be a good educator at a place like MIT, you have to be able to make those connections, and it’s hard to make those connections unless you’ve had actual experience in the field.”</p> <p>Taking a new process from laboratory to market means having to deal not just with technical issues, but also with economic issues, Tuller says. “Can you do this in a cost-effective manner? Are there customers who are going to be interested in your product? Can it be manufactured at scale? So suddenly, you have to address all these practical issues and, I think, having gone through that process, which sometimes is very painful, I come back in the laboratory, and I think that I can now do a much better job of making those connections for the students,” Tuller says. “And I think that’s one of the things that attracts a lot of students to MIT. It’s not just theory and science, but they know that there are people here who have that excitement about science translated into practice.” In April 2018, Tuller received the&nbsp;<a dir="ltr" href="http://news.mit.edu/2018/celebrating-great-mentorship-for-graduate-students-0424" rel="noopener" target="_blank">Committed to Caring Award</a>&nbsp;at MIT, for which he was nominated by several of his own students.</p> <p><strong>Electronic nose</strong></p> <p>Former students and postdocs in Tuller’s group have gone on to positions at top universities and research institutes in Austria, Finland, France, Germany, India, Israel, Japan, Korea, and Switzerland. Former Tuller doctoral student Woochul Jung PhD '10, participated in the development of an “<a dir="ltr" href="http://news.mit.edu/2007/mits-electronic-nose-could-detect-hazards" rel="noopener" target="_blank">electronic nose</a>” in Tuller’s lab and is now an associate professor of Materials Science and Engineering at KAIST. "Professor Tuller is an excellent mentor who always encourages people around him with endless passion and intellectual curiosity,” Jung says. “Above all, he showed me the life of a scientist who enjoys the journey of asking questions and logically finding answers, which has been the most important teaching in my academic career so far."</p> <p>Tuller is collaborating with his former postdoc Il-Doo Kim at KAIST on extending the “electronic nose” technology to health monitoring. “Here you would just have someone breathe into your device and it would electronically tell you that this person likely has a particular disease: diabetes, or malaria, or even certain kinds of cancer,” Tuller says.</p> <p>Tuller is now probing how to use color differences as a measurement tool for monitoring defect creation/annihilation and the efficiency of fuel cell electrodes. “A particular material that we’re very much interested in now as a fuel cell electrode is praseodymium cerium oxide. And it turns out, this material under normal conditions is quite a deep red. But as we reduce the oxygen content of the gas phase, it becomes less and less intense red until it becomes transparent. And it turns out over that fairly wide range of gas composition, the intensity of that red can be correlated with the defects, the number of defects, in this material which control its properties,” Tuller says. By monitoring the rate of change in color following a step change in gas composition, one can also characterize the efficiency of the fuel cell electrode and its longer-term degradation.</p> <p>In 2018, the U.S. Department of Energy renewed funding for the Chemomechanics of Far-From-Equilibrium Interfaces (COFFEI) research project, which was its fourth three-year award. The COFFEI program, a collaboration with five other MIT colleagues, couples chemical and mechanical behavior of electroceramic oxides. Tuller also actively participated in MIT-Skoltech&nbsp;<a dir="ltr" href="https://cees-www.mit.edu/" rel="noopener" target="_blank">Center for Electrochemical Energy Storage</a>.</p> <p><strong>Exploiting defects</strong></p> <p>Defects in an electroceramic material lead to nearly all of its interesting functional properties, whether electronic, optical, or magnetic. In energy storage and conversion systems such as batteries and fuel cells, it is the migration of ions that confers on them their electrical properties. “For lithium batteries, it’s lithium ions. For fuel cell materials, it’s usually oxygen or hydrogen ions — protons — that are mobile, and all of those defects are within the crystal lattice,” Tuller explains. “That’s what allows them to actually transport matter, while the electronic properties also depend on the creation of defects in the structure.”<br /> <br /> “So being able to identify, monitor and predict how the defect concentrations will depend on the composition of the material, impurities, microstructure, temperature, atmosphere are all critical in being able to predict and optimize the properties of those materials,” he says. “And that’s something that we spent a lot of time trying to formalize, develop methods to improve characterization and also to model the connection between the defects and the properties of interest in specific applications.”&nbsp;The pico-level microbalances that Tuller developed can detect quantities as tiny as trillionths of a gram.</p> <p>That quest for structure and order in materials carries over into Tuller’s personal hobbies, which include classic sports cars, gardening, and photography. He has been a car buff since his college days, and last fall Tuller began restoring a 1972 Jaguar XKE, which he calls one of the most beautiful vehicles ever built. With his research frequently taking him to Japan, Tuller has developed an interest in Japanese gardens. His photography focuses on scenery or architecture. “It’s about form and function, that is what engineering is all about. The same thing as with gardening, the form and the function. There’s something to that,” he says.</p> <p>Tuller and his wife, Sonia, live in Wellesley, Massachusetts. They have two adult daughters, who also live in greater Boston with their spouses, and three grandchildren.</p> <p>Tuller has served on the MIT faculty, since 1975, after completing his doctorate at Columbia and a postdoc at the&nbsp;<a dir="ltr" href="https://www.technion.ac.il/en/technion-israel-institute-of-technology/" rel="noopener" target="_blank">Technion – Israel Institute of Technology</a>. “I’ve loved being at MIT all these years; it’s actually my first permanent job. The thing I love about MIT is what a stimulating environment it is; but at times I have to limit myself, because it easily becomes overstimulating,” Tuller says.</p> MIT Professor Harry Tuller will receive the Thomas Egleston Medal on May 30 from Columbia University, to recognize his pioneering research on electroceramic materials.Photo: Denis Paiste/MIT Materials Research LaboratoryMaterials Research Laboratory, Nanoscience and nanotechnology, Awards, honors and fellowships, Faculty, Materials Science and Engineering, Nuclear science and engineering, DMSE, School of Engineering Breakthrough in boiling http://news.mit.edu/2019/mit-boiling-simulations-optimizing-heat-transfer-nuclear-reactors-0422 High-fidelity simulations by MIT nuclear researchers point the way to optimizing heat transfer in current and next-generation reactors. Mon, 22 Apr 2019 13:55:00 -0400 Leda Zimmerman | Department of Nuclear Science and Engineering http://news.mit.edu/2019/mit-boiling-simulations-optimizing-heat-transfer-nuclear-reactors-0422 <p>Engineers must manage a maelstrom in the core of operating nuclear reactors. Nuclear reactions deposit an extraordinary amount of heat in the fuel rods, setting off a frenzy of boiling, bubbling, and evaporation in surrounding fluid. From this churning flow, operators harness the removal of heat.</p> <p>In search of greater efficiencies in nuclear systems, scientists have long sought to characterize and predict the physics underlying these processes of heat transfer, with only modest success.</p> <p>But now&nbsp;a research team led by <a href="http://web.mit.edu/nse/people/faculty/baglietto.html" target="_blank">Emilio Baglietto</a>, an associate professor of nuclear science and engineering at MIT, has made a significant breakthrough in detailing these physical phenomena. Their approach utilizes a modeling technology called computational fluid dynamics (CFD). Baglietto has developed new CFD tools that capture the fundamental physics of boiling, making it possible to track rapidly evolving heat transfer phenomena at the microscale in a range of different reactors, and for different operating conditions.</p> <p>“Our research opens up the prospect of advancing the efficiency of current nuclear power systems and designing better fuel for future reactor systems,” says Baglietto.</p> <p>The group, which includes Etienne Demarly, a doctoral candidate in nuclear science and engineering, and Ravikishore Kommajosyula, a doctoral candidate in mechanical engineering and computation, describes its work in the March 11&nbsp;issue of&nbsp;<em>Applied Physics Letters</em>.</p> <p>Baglietto, who arrived at MIT in 2011, is thermal hydraulics lead for the Consortium for Advanced Simulation of Lightwater Reactors (CASL), an initiative begun in 2010 to design predictive modeling tools to improve current and next generation reactors, and to ensure the economic viability of nuclear energy as an electricity source.</p> <p>Central to Baglietto’s CASL work has been the issue of critical heat flux (CHF), which “represents one of the grand challenges for the heat transfer community,” he says. CHF describes a condition of boiling where there is a sudden loss of contact between the bubbling liquid, and the heating element, which in the case of the nuclear industry is the nuclear fuel rod. This instability can emerge suddenly, in response&nbsp;to changes in power levels, for example. As boiling reaches a crisis, a vaporous film covers the fuel surface, which then gives way to dry spots that quickly reach very high temperatures.</p> <p>“You want bubbles forming and departing from the surface, and water evaporating, in order to take away heat,” explains Baglietto. “If it becomes impossible to remove the heat, it is possible for the metal cladding to fail.”</p> <p>Nuclear regulators have established power settings in the commercial reactor fleet whose upper limits are well beneath levels that might trigger CHF. This has meant running reactors below their potential energy output.</p> <p>“We want to allow as much boiling as possible without reaching CHF,” says Baglietto. “If we could know how far we are at all times from CHF, we could operate just on the other side, and improve the performance of reactors.”</p> <p>Achieving this, says Baglietto, requires better modeling of the processes leading to CHF. “Previous models were based on clever guesses, because it was impossible to see what was actually going on at the surface where boiling took place, and because models didn’t take into account all the physics driving CHF,” says Baglietto.</p> <p>So he set out to create a comprehensive, high-fidelity representation of boiling heat transfer processes up to the point of CHF. This meant creating physically accurate models of the movement of bubbles, boiling, and condensation taking place at what engineers call "the wall"&nbsp;— the cladding of four meter-tall, one centimeter-wide nuclear fuel rods, which are packed by&nbsp;the tens of thousands in a typical nuclear reactor core&nbsp;and surrounded by hot fluid.</p> <p>While some of Baglietto’s computational models took advantage of existing knowledge of the complex fuel assembly heat transfer processes inside reactors, he also sought new experimental data to validate his models. He enlisted the help of department colleagues Matteo Bucci, the Norman C. Rasmussen Assistant Professor of Nuclear Science and Engineering, and Jacopo Buongiorno, the TEPCO Professor and associate department head for nuclear science and engineering.</p> <p>Using electrically simulated heaters with surrogate fuel assemblies and transparent walls, MIT researchers were able to observe the fine details in the evolution of boiling to CHF.</p> <p>“You’d go from a situation where nice little bubbles removed a lot of heat, and new water re-flooded the surface, keeping things cold, to an instant later when suddenly there was no more space for bubbles and dry spots would form and grow,” says Baglietto.</p> <p>One fundamental corroboration emerged from these experiments. Baglietto’s initial models, contrary to conventional thinking, had suggested that during boiling, evaporation is not the exclusive form of heat removal. Simulation data showed that bubbles sliding, jostling and departing from the surface removed even more heat than evaporation, and experiments validated the findings of the models.</p> <p>“Baglietto’s work represents a landmark in the evolution of predictive capabilities for boiling systems, enabling us to model behaviors at a much more fundamental level than ever possible before,” says W. David Pointer, group leader of advanced reactor engineering at the Oak Ridge National Laboratory, who was not involved in the research. “This research will allow us to develop significantly more aggressive designs that better optimize the power produced by fuel without compromising on safety, and it will have an immediate impact on performance in the current fleet as well as on next-generation reactor design.”</p> <p>Baglietto’s research will also quickly improve the process for developing nuclear fuels. Instead of spending many months and millions of dollars on experiments, says Pointer, “We can shortcut those long sequences of tests by providing accurate, reliable models.”</p> <p>In coming years, Baglietto’s comprehensive approach may help deliver fuel cladding that is more resistant to fouling and impurities, more accident tolerant, and that encourages higher wettability, making surfaces more conducive to contact with water and less likely to form dry spots.&nbsp;</p> <p>Even small improvements in nuclear energy output can make a big difference,&nbsp;Baglietto says.</p> <p>“If fuel performs five percent better in an existing reactor, that means five percent more energy output, which can mean burning less gas and coal,” he says. “I hope to see our work very soon in U.S. reactors, because if we can produce more nuclear energy cheaply, reactors will remain competitive against other fuels, and make a greater impact on CO<sub>2</sub> emissions."</p> <p>The research was supported by the Department of Energy’s Consortium for Advanced Simulation of Light Water Reactors.</p> This frontal-view illustration shows the microscale mechanisms in the flow boiling framework. Each circle represents the footprint of a bubble on the heated surface, which is subdivided in a microlayer and dry area regions.Illustration courtesy of Emilio BagliettoSchool of Engineering, Nuclear science and engineering, Mechanical engineering, Energy, Nuclear power and reactors, Research, Alternative energy, Renewable energy Engineers develop concept for hybrid heavy-duty trucks http://news.mit.edu/2019/electric-hybrid-heavy-duty-trucks-0409 Long-haul trucks with electric motors combined with gas-alcohol engines could slash pollution levels and greenhouse gases. Tue, 09 Apr 2019 00:00:00 -0400 David L. Chandler | MIT News Office http://news.mit.edu/2019/electric-hybrid-heavy-duty-trucks-0409 <p>Heavy-duty trucks, such as the 18-wheelers that transport many of the world’s goods from farm or factory to market, are virtually all powered by diesel engines. They account for a significant portion of worldwide greenhouse gas emissions, but little has been done so far to curb their climate-change-inducing exhaust.</p> <p>Now, researchers at MIT have devised a new way of powering these trucks that could drastically curb pollution, increase efficiency, and reduce or even eliminate their net greenhouse gas emissions.</p> <p>The concept involves using a plug-in hybrid engine system, in which the truck would be primarily powered by batteries, but with a spark ignition engine (instead of a diesel engine). That engine, which would allow the trucks to conveniently travel the same distances as today’s conventional diesel trucks, would be a flex-fuel model that could run on pure gasoline, pure alcohol, or blends of these fuels.</p> <p>While the ultimate goal would be to power trucks entirely with batteries, the researchers say, this flex-fuel hybrid option could provide a way for such trucks to gain early entry into the marketplace by overcoming concerns about limited range, cost, or the need for excessive battery weight to achieve longer range.</p> <p>The new concept was developed by MIT Energy Initiative and Plasma Fusion and Science Center research scientist Daniel Cohn and principal research engineer Leslie Bromberg, who are presenting it at the annual SAE International conference on April 11.</p> <p>“We’ve been working for a number of years on ways to make engines for cars and trucks cleaner and more efficient, and we’ve been particularly interested in what you can do with spark ignition [as opposed to the compresson ignition used in diesels], because it’s intrinsically much cleaner,” Cohn says. Compared to a diesel engine vehicle, a gasoline-powered vehicle produces only a tenth as much nitrogen oxide (NOx) pollution, a major component of air pollution.</p> <p>In addition, by using a flex-fuel configuration that allows it to run on gasoline, ethanol, methanol, or blends of these, such engines have the potential to emit far less greenhouse gas than pure gasoline engines do, and the incremental cost for the fuel flexibility is very small, Cohn and Bromberg say. If run on pure methanol or ethanol derived from renewable sources such as agricultural waste or municipal trash, the net greenhouse gas emissions could even be zero. “It’s a way of making use of a low-greenhouse-gas fuel” when it’s available, “but always having the option of running it with gasoline” to ensure maximum flexibility, Cohn says.</p> <p>While Tesla Motors has announced it will be producing an all-electric heavy-duty truck, Cohn says, “we think that’s going to be very challenging, because of the cost and weight of the batteries” needed to provide sufficient range. To meet the expected driving range of conventional diesel trucks, Cohn and Bromberg estimate, would require somewhere between 10 and 15 tons of batteries “That’s a significant fraction of the payload” such a truck could otherwise carry, Cohn says.</p> <p>To get around that, “we think that the way to enable the use of electricity in these vehicles is with a plug-in hybrid,” he says. The engine they propose for such a hybrid is a version of one the two researchers have been working on for years, developing a highly efficient, flexible-fuel gasoline engine that would weigh far less, be more fuel-efficient, and produce a tenth as much air pollution as the best of today’s diesel-powered vehicles.</p> <p>Cohn and Bromberg did a detailed analysis of both the engineering and the economics of what would be needed to develop such an engine to meet the needs of existing truck operators. In order to match the efficiency of diesels, a mix of alcohol with the gasoline, or even pure alcohol, can be used, and this can be processed using renewable energy sources, they found. Detailed computer modeling of a whole range of desired engine characteristics, combined with screening of the results using an artificial intelligence system, yielded clear indications of the most promising pathways and showed that such substitutions are indeed practically and financially feasible.</p> <p>In both the present diesel and the proposed flex-fuel vehicles, the emissions are measured at the tailpipe, after a variety of emissions-control systems have done their work in both cases, so the comparison is a realistic measure of real-world emissions. The combination of a hybrid drive and flex-fuel engine is “a way to enable the introduction of electric drive into the heavy truck sector, by making it possible to meet range and cost requirements, and doing it in a way that’s clean,” Cohn says.</p> <p>Bromberg says that gasoline engines have become much more efficient and clean over the years, and the relative cost of diesel fuel has gone up, so that the cost advantages that led to the near-universal adoption of diesels for heavy trucking no longer prevail. “Over time, gas engines have become more and more efficient, and they have an inherent advantage in producing less air pollution,” he says. And by using the engine in a hybrid system, it can always operate at its optimum speed, maximizing its efficiency.</p> <p>Methane is an extremely potent greenhouse gas, so if it can be diverted to produce a useful fuel by converting it to methanol through a simple chemical process, “that’s one of the most attractive ways to make a clean fuel,” Bromberg says. “I think the alcohol fuels overall have a lot of promise.”</p> <p>Already, he points out, California has plans for new regulations on truck emissions that&nbsp;are very difficult to meet with diesel engine vehicles. “We think there’s a significant rationale for trucking companies to go to gasoline or flexible fuel,” Cohn says. “The engines are cheaper, exhaust treatment systems are cheaper, and it’s a way to ensure that they can meet the expected regulations. And combining that with electric propulsion in a hybrid system, given an ever-cleaner electric grid, can further reduce emissions and pollution from the trucking sector.”</p> <p>Pure electric propulsion for trucks is the ultimate goal, but today’s batteries don’t make that a realistic option yet, Cohn says: “Batteries are great, but let’s be realistic about what they can provide.”</p> <p>And the combination they propose can address two major challenges at once, they say. “We don’t know which is going to be stronger, the desire to reduce greenhouse gases, or the desire to reduce air pollution.” In the U.S., climate change may be the bigger push, while in India and China air pollution may be more urgent, but “this technology has value for both challenges,” Cohn says.</p> <p>The research was supported by the MIT Arthur Samberg Energy Innovation Fund.</p> Heavy trucks such as these 18-wheelers contribute a significant fraction of the world’s greenhouse gas emissions. MIT researchers say these emissions could be drastically reduced by using flex-fuel plug-in hybrid powertrains instead of diesel engines.MIT Energy Initiative, Research, Energy, Oil and gas, School of Engineering, Plasma Science and Fusion Center, Nuclear science and engineering, Transportation, Automobiles, Emissions, Climate change, Global Warming, Pollution, Environment, Sustainability, Batteries Getting to the bottom of the “boiling crisis” http://news.mit.edu/2019/boiling-crisis-nuclear-design-0405 New understanding of heat transfer in boiling water could lead to efficiency improvements in power plants. Thu, 04 Apr 2019 23:59:59 -0400 David L. Chandler | MIT News Office http://news.mit.edu/2019/boiling-crisis-nuclear-design-0405 <p>The simple act of boiling water is one of humankind’s oldest inventions, and still central to many of today’s technologies, from coffee makers to nuclear power plants. Yet this seemingly simple process has complexities that have long defied full understanding.</p> <p>Now, researchers at MIT have found a way to analyze one of the thorniest problems facing heat exchangers and other technologies in which boiling water plays a central role: how to predict, and prevent, a dangerous and potentially catastrophic event called a boiling crisis. This is the point when so many bubbles form on a hot surface that they coalesce into a continuous sheet of vapor that blocks any further heat transfer from the surface to the water.</p> <p>Such events can cause weakening or melting, so nuclear plants are designed to operate at levels far below those that could trigger a boiling crisis. This new understanding might allow such plants to operate safely at higher output levels by reducing the needed operating margins.</p> <p>The new results are presented today in the journal <em>Physical Review Letters</em> in a paper by assistant professor of nuclear engineering Matteo Bucci and graduate students Limiao Zhang and Jee Hyun Seong.</p> <p>“It’s a very complex phenomenon,” Bucci says, and although it has been “studied for over a century, it’s still very controversial.” Even in the 21st century, he says, “we talk about an energy revolution, a computer revolution, nanoscale transistors, all kinds of great things. Yet, still in this century, and maybe even in the next century, these are all limited by heat transfer.”</p> <p>As computer chips get smaller and more powerful, for example, some high-performance processors may require liquid cooling to dissipate heat that can be too intense for ordinary cooling fans. (Some supercomputers, and even some high-end gaming PCs, already use pumped water to cool their chips). Likewise, the power plants that produce most of the world’s electricity, whether they be fossil fuel, solar, or nuclear plants, mainly produce power by generating steam to turn turbines.</p> <p>In a nuclear plant, water is heated by the fuel rods, which heat up through nuclear reactions. The spread of heat through the metal surfaces to the water is responsible for transferring energy from the fuel to the generating turbine, but it also is key to preventing the fuel from overheating and potentially leading to a meltdown. In the case of a boiling crisis, the formation of a layer of vapor separating the liquid from the metal can prevent the heat from being transferred, and can lead to rapid overheating.</p> <p>Because of that risk, regulations require nuclear plants to operate at heat fluxes that are no more than 75 percent of the level known as the critical heat flux (CHF), which is the level when a boiling crisis could be triggered that could damage critical components. But since the theoretical foundations of the CHF are poorly understood, those levels are estimated very conservatively. It’s possible that those plants could be operated at higher heat levels, thus producing more power from the same nuclear fuel, if the phenomenon is understood with greater certainty, Bucci says.</p> <p>A better understanding of boiling and the CHF is “such a difficult problem because it is very nonlinear,” and small changes in materials or surface textures can have large effects, he says. But now, thanks to better instruments able to capture details of the process in lab experiments, “we have been able to actually measure and chart the phenomenon with the required spatial and temporal resolution” to be able to understand how a boiling crisis gets started in the first place.</p> <p>It turns out the phenomenon is closely related to the flow of traffic in a city, or to the way an outbreak of disease spreads through a population. Essentially, it’s an issue of the way things clump together.</p> <p>When the number of cars in a city reaches a certain threshold, there is a greater</p> <p>likelihood that they will bunch up in certain places and cause a traffic jam. And, when carriers of disease enter crowded places like airports or auditoriums, the chances of triggering an epidemic are increased. The researchers found that the population of bubbles on a heated surface follows a similar pattern; above a certain bubble density, the likelihood goes up that bubbles will crowd together, merge, and form an insulating layer on that surface.</p> <p>“The boiling crisis is essentially the result of an accumulation of bubbles that merge and coalesce with each other, which leads to failure of the surface,” he says.</p> <p>Because of the similarities, Bucci says, “we can take inspiration, take the same approach to model boiling as is used to model traffic jams,” and those models have already been well-explored. Now, based on both experiments and mathematical analysis, Bucci and his co-authors have been able to quantify the phenomenon and arrive at better ways to pin down when the onset of such bubble mergers will take place. “We showed that using this paradigm, we can predict when the boiling crisis will occur,” based on the patterns and density of bubbles that are forming.</p> <p>The nanoscale texture of the surface plays an important role, the analysis shows, and that’s one of several factors that might be used to make adjustments that could raise the CHF, and thus potentially lead to more reliable heat transfer, whether for power plants, liquid cooling for advanced computer chips, or many other processes where heat transfer is a crucial factor.</p> <p>“We can use this information not only to predict the boiling crisis, but also to explore solutions, by changing the boiling surface, to minimize the interaction between bubbles,” Bucci says. “We’re using this understanding to improve the surface, so we can control and avoid the ‘bubble jam.’”</p> <p>If this research enables changes that could allow for safe operation of nuclear plants at higher heat fluxes — that is, the rate at which they dissipate heat — than currently allowed, the impact could be significant. “If you can show that by manipulating the surface, you can increase the critical heat flux by 10 to 20 percent, then you increase the power produced by the same amount, on a global scale, by making better use of the fuel and resources that are already there,” Bucci says.</p> Image shows the rate of heat transfer from a metal surface, with red the highest and blue the lowest. The large blue areas show the beginning of a boiling crisis.Courtesy of the researchersSchool of Engineering, Nuclear science and engineering, Nuclear power and reactors, Energy, Research, Heat