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    Team engineers nanoparticles using ion irradiation to advance clean energy and fuel conversion

    MIT researchers and colleagues have demonstrated a way to precisely control the size, composition, and other properties of nanoparticles key to the reactions involved in a variety of clean energy and environmental technologies. They did so by leveraging ion irradiation, a technique in which beams of charged particles bombard a material.

    They went on to show that nanoparticles created this way have superior performance over their conventionally made counterparts.

    “The materials we have worked on could advance several technologies, from fuel cells to generate CO2-free electricity to the production of clean hydrogen feedstocks for the chemical industry [through electrolysis cells],” says Bilge Yildiz, leader of the work and a professor in MIT’s departments of Nuclear Science and Engineering and Materials Science and Engineering.

    Critical catalyst

    Fuel and electrolysis cells both involve electrochemical reactions through three principal parts: two electrodes (a cathode and anode) separated by an electrolyte. The difference between the two cells is that the reactions involved run in reverse.

    The electrodes are coated with catalysts, or materials that make the reactions involved go faster. But a critical catalyst made of metal-oxide materials has been limited by challenges including low durability. “The metal catalyst particles coarsen at high temperatures, and you lose surface area and activity as a result,” says Yildiz, who is also affiliated with the Materials Research Laboratory and is an author of an open-access paper on the work published in the journal Energy & Environmental Science.

    Enter metal exsolution, which involves precipitating metal nanoparticles out of a host oxide onto the surface of the electrode. The particles embed themselves into the electrode, “and that anchoring makes them more stable,” says Yildiz. As a result, exsolution has “led to remarkable progress in clean energy conversion and energy-efficient computing devices,” the researchers write in their paper.

    However, controlling the precise properties of the resulting nanoparticles has been difficult. “We know that exsolution can give us stable and active nanoparticles, but the challenging part is really to control it. The novelty of this work is that we’ve found a tool — ion irradiation — that can give us that control,” says Jiayue Wang PhD ’22, first author of the paper. Wang, who conducted the work while earning his PhD in the MIT Department of Nuclear Science and Engineering, is now a postdoc at Stanford University.

    Sossina Haile ’86, PhD ’92, the Walter P. Murphy Professor of Materials Science and Engineering at Northwestern University, who was not involved in the current work, says:

    “Metallic nanoparticles serve as catalysts in a whole host of reactions, including the important reaction of splitting water to generate hydrogen for energy storage. In this work, Yildiz and colleagues have created an ingenious method for controlling the way that nanoparticles form.”

    Haile continues, “the community has shown that exsolution results in structurally stable nanoparticles, but the process is not easy to control, so one doesn’t necessarily get the optimal number and size of particles. Using ion irradiation, this group was able to precisely control the features of the nanoparticles, resulting in excellent catalytic activity for water splitting.”

    What they did

    The researchers found that aiming a beam of ions at the electrode while simultaneously exsolving metal nanoparticles onto the electrode’s surface allowed them to control several properties of the resulting nanoparticles.

    “Through ion-matter interactions, we have successfully engineered the size, composition, density, and location of the exsolved nanoparticles,” the team writes in Energy & Environmental Science.

    For example, they could make the particles much smaller — down to 2 billionths of a meter in diameter — than those made using conventional thermal exsolution methods alone. Further, they were able to change the composition of the nanoparticles by irradiating with specific elements. They demonstrated this with a beam of nickel ions that implanted nickel into the exsolved metal nanoparticle. As a result, they demonstrated a direct and convenient way to engineer the composition of exsolved nanoparticles.

    “We want to have multi-element nanoparticles, or alloys, because they usually have higher catalytic activity,” Yildiz says. “With our approach, the exsolution target does not have to be dependent on the substrate oxide itself.” Irradiation opens the door to many more compositions. “We can pretty much choose any oxide and any ion that we can irradiate with and exsolve that,” says Yildiz.

    The team also found that ion irradiation forms defects in the electrode itself. And these defects provide additional nucleation sites, or places for the exsolved nanoparticles to grow from, increasing the density of the resulting nanoparticles.

    Irradiation could also allow extreme spatial control over the nanoparticles. “Because you can focus the ion beam, you can imagine that you could ‘write’ with it to form specific nanostructures,” says Wang. “We did a preliminary demonstration [of that], but we believe it has potential to realize well-controlled micro- and nano-structures.”

    The team also showed that the nanoparticles they created with ion irradiation had superior catalytic activity over those created by conventional thermal exsolution alone.

    Additional MIT authors of the paper are Kevin B. Woller, a principal research scientist at the Plasma Science and Fusion Center (PSFC), home to the equipment used for ion irradiation; Abinash Kumar PhD ’22, who received his PhD from the Department of Materials Science and Engineering (DMSE) and is now at Oak Ridge National Laboratory; and James M. LeBeau, an associate professor in DMSE. Other authors are Zhan Zhang and Hua Zhou of Argonne National Laboratory, and Iradwikanari Waluyo and Adrian Hunt of Brookhaven National Laboratory.

    This work was funded by the OxEon Corp. and MIT’s PSFC. The research also used resources supported by the U.S. Department of Energy Office of Science, MIT’s Materials Research Laboratory, and MIT.nano. The work was performed, in part, at Harvard University through a network funded by the National Science Foundation. More

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    Dennis Whyte steps down as director of the Plasma Science and Fusion Center

    Dennis Whyte, who spearheaded the development of the world’s most powerful fusion electromagnet and grew the MIT Plasma Science and Fusion Center’s research volume by more than 50 percent, has announced he will be stepping down as the center’s director at the end of the year in order to devote his full attention to teaching, engaging in cutting-edge fusion research, and pursuing entrepreneurial activities at the PSFC.

    “The reason I came to MIT as a faculty member in ’06 was because of the PSFC and the very special place it held and still holds in fusion,” says Whyte, the Hitachi America Professor of Engineering in the Department of Nuclear Science and Engineering. When he was appointed director of the PSFC in 2015, Whyte saw it as an opportunity to realize even more of the PSFC’s potential: “After 10 years I think we’ve seen that dream come to life. Research and entrepreneurship are stronger than ever.”

    Whyte’s passion has always been for fusion — the process by which light elements combine to form heavier ones, releasing massive amounts of energy. One hundred years ago fusion was solely the provenance of astronomers’ speculation; through the efforts of generations of scientists and engineers, fusion now holds the potential to offer humanity an entirely new source of clean, abundant energy — and Whyte has been at the forefront of that effort.

    “Fusion’s challenges require interdisciplinary work, so it’s always fresh, and you get these unexpected intersections that can have wild outcomes. As an inherently curious person, fusion is perfect for me.”

    Whyte’s enthusiasm is legendary, especially when it comes to teaching. The effects of that enthusiasm are easy to see: At the start of his tenure, only a handful of students chose to pursue plasma physics and fusion science. Since then, the number of students has ballooned, and this year nearly 100 students from six departments are working with 15 faculty members.

    Of the growth, Whyte says, “It’s not just that we have more students; it’s that they’re working on more diverse topics, and their passion to make fusion a reality is the best part of the PSFC. Seeing full seminars and classes is fundamentally why I’m here.”

    Even as he managed the directorship and pursued his own scholarly work, Whyte remained active in the classroom and continued advising students. Zach Hartwig, a former student who is now a PSFC researcher and MIT faculty member himself, recalled his first meeting with Whyte as an incoming PhD student: “I had to choose between several projects and advisors and meeting Dennis made my decision easy. He catapulted out of his chair and started sketching his vision for a new fusion diagnostic that many people thought was crazy. His passion and eagerness to tackle only the most difficult problems in the field was immediately tangible.”

    For the past 13 years Whyte has offered a fusion technology design class that has generated several key breakthroughs, including liquid immersion blankets essential for converting fusion energy to heat, inside launch radio frequency systems used to stabilize fusing plasmas, and high-temperature superconducting electromagnets that have opened the door to the possibility of fusion devices that are not only smaller, but also more powerful and efficient.

    In fact, the potential of these electromagnets was significant enough that Whyte, an MIT postdoc, and three of Whyte’s former students (Hartwig among them) spun out a private fusion company to fully realize the magnets’ capabilities. Commonwealth Fusion Systems (CFS) both launched and signed a cooperative research agreement with the PSFC in 2018, and the founders’ vision parlayed into significant external investment, allowing a coalition of CFS and PSFC researchers to refine and develop the electromagnets first conceived in Whyte’s class.

    Three years later, after a historic day of testing, the magnet produced a field strength of 20 tesla, making it the most powerful fusion superconducting electromagnet in the world. According to Whyte, “The success of the TFMC magnet is an encapsulation of everything PSFC. It would’ve been impossible for a single investigator, or a lone spin-out, but we brought together all these disciplines in a team that could execute innovatively and incredibly quickly. We shortened the timescale not just for this project, but for fusion as a whole.”

    CFS remains an important collaborator, accounting for approximately 20 percent of the PSFC’s current research portfolio. While Whyte has no financial stake in the company, he remains a principal investigator on CFS’s SPARC project, a proof-of-concept fusion device predicted to produce more energy than it consumes, ready in 2025. SPARC is the lead-up to ARC, CFS’s commercially scalable fusion power plant planned to arrive in the early 2030s.

    The collaboration between CFS and MIT followed a blueprint that had been piloted more than a decade prior, when the Italian energy company Eni S.p.A signed on as a founding member of the MIT Energy Initiative to develop low-carbon technologies. After many years of successfully working in tandem with MITEI to advance renewable energy research, in 2018 Eni made a significant investment in a young CFS to assist in realizing commercial fusion power, which in turn indirectly funded PSFC research; Eni also collaborated directly with the PSFC to create the Laboratory for Innovative Fusion Technologies, which remains active.

    Whyte believes that “thoughtful and meaningful collaboration with the energy industry can make a difference with research and climate change. Industry engagement is very relevant — it changed both of us. Now Eni has fusion in their portfolio.” The arrangement is a demonstration of how public-private collaborations can accelerate the progress of fusion science, and ultimately the arrival of fusion power.

    Whyte’s move to diversify collaborators, leverage the PSFC’s strength as a multidisciplinary hub, and expand research volume was essential to the center’s survival and growth. Early in his tenure, a shift in funding priorities necessitated the shutdown of Alcator C-Mod, the fusion research device in operation at the PSFC for 23 years — though not before C-Mod set the world record for plasma pressure on its last day of operation. Through this transition, Whyte and the members of his leadership team were able to keep the PSFC whole.

    One alumnus was a particular source of inspiration to Whyte during that time: “Reinier [Beeuwkes] said to me, ‘what you’re doing doesn’t just matter to students and MIT, it matters to the world.’ That was so meaningful, and his words really sustained me when I was feeling major doubt.” In 2022 Beeuwkes won the MIT Alumni Better World Service Award for his support of fusion and the PSFC. Since 2018, sponsored research at the PSFC has more than doubled, as have the number of personnel.

    Whyte’s determination to build and maintain a strong community is a prevailing feature of his leadership. Matt Fulton, who started at the PSFC in 1987 and is now director of operations, says of Whyte, “You want a leader like Dennis on your worst days. We were staring down disaster and he had a plan to hold the PSFC together, and somehow it worked. The research was important, but the people have always been more important to him. We’re so lucky to have him.”

    The Office of the Vice President for Research is launching a search for the PSFC’s next leader. Should the search extend beyond the end of the year, an interim director will be appointed.  

    “As MIT works to magnify its impact in the areas of climate and sustainability, Dennis has built the PSFC into an extraordinary resource for the Institute to draw upon,” says Maria T. Zuber, MIT’s vice president for research. “His leadership has positioned MIT on the leading edge of fusion research and the emerging commercial fusion industry, and while the nature of his contributions will change, … the value he brings to the MIT community will remain clear. As Dennis steps down as director, the PSFC is ascendant.”  More

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    Rafael Mariano Grossi speaks about nuclear power’s role at a critical moment in history

    On Sept. 22, Rafael Mariano Grossi, director general of the International Atomic Energy Agency (IAEA), delivered the 2023 David J. Rose Lecture in Nuclear Technology at MIT. This lecture series was started nearly 40 years ago in honor of the late Professor David Rose — a nuclear engineering professor and fusion technology pioneer. In addition to his scientific contributions, Rose was invested in the ethical issues associated with new technologies. His widow, Renate Rose, who spoke briefly before Grossi’s lecture, said that her husband adamantly called for the abolishment of nuclear weapons, insisting that all science should serve the common good and that every scientist should follow his or her conscience.

    In his prefatory remarks, MIT Vice Provost Richard Lester, a former PhD student of David Rose, said that even today, he still feels the influence of his thesis advisor, many decades after they’d worked together. Lester called it a “great honor” to introduce Grossi, noting that the director general was guiding the agency through an especially demanding time. “His presence with us is a reminder that the biggest challenges we face today are truly global challenges, and that international organizations like the IAEA have a central role to play in resolving them.”

    The title of Grossi’s talk was “The IAEA at the Crossroads of History,” and he made a strong case for this being a critical juncture, or “inflection point,” for nuclear power. He started his speech, however, with somewhat of an historical footnote, discussing a letter that Rose sent in 1977 to Sigvard Eklund, IAEA’s then-director general. Rose urged the IAEA to establish a coordinated worldwide program in controlled fusion research. It took a while for the idea to gain traction, but international collaboration in fusion formally began in 1985, eight years after Rose’s proposal. “I thought I would begin with this story, because it shows that cooperation between MIT and the IAEA goes back a long way,” Grossi said.

    2023 David J. Rose Lecture in Nuclear TechnologyVideo: MIT Department of Nuclear Science and Engineering

    Overall, he painted a mostly encouraging picture for the future of nuclear power, largely based on its potential to generate electricity or thermal energy without adding greenhouse gases to the atmosphere. In the face of rapidly-unfolding climate change, Grossi said, “low-carbon nuclear power is now seen as part of [the] solution by an increasing number of people. It’s getting harder to be an environmentalist in good faith who is against nuclear.”

    Public acceptance is growing throughout the world, he added. In Sweden, where people had long protested against radioactive waste transport, a poll now shows that more than 85 percent of the people approve of the nation’s high-level waste handling and disposal facilities. Even Finland’s Green Party has embraced nuclear power, Grossi said. “I don’t think we could imagine a pro-nuclear Green Party five years ago, let alone in 1970 or ’80.”

    Fifty-seven nuclear reactors are being constructed right now in 17 countries. One of the world’s newest facilities, the Barakah nuclear power plant in the United Arab Emirates, “was built on ground rich in oil and natural gas,” he said. In China, the world’s first pebble-bed high-temperature reactor has been operating for two years, offering potential advantages in safety, efficiency, and modularity. For countries that don’t have any nuclear plants, small modular reactors of this kind “offer the chance of a more gradual and affordable way to scale up nuclear power,” Grossi noted. The IAEA is working with countries like Ghana, Kenya, and Senegal to help them develop the safety and regulatory infrastructures that would be needed to build and responsibly operate modular nuclear reactors like this.

    Grossi also discussed a number of lesser-known projects the IAEA is engaged in that have little to do with power generation. Seventy percent of the people in Africa, for example, have no access to radiotherapy to fight cancer. To this end, the IAEA is now helping to provide radiotherapy services in Tanzania and other African countries. At the IAEA’s Marine Environmental Laboratories in Monaco, researchers are using isotopic tracing techniques to study the impact of microplastic pollution on the oceans. The Covid-19 pandemic illustrated the potentially devastating effects of zoonotic diseases that can infect humans with animal-borne viruses. To counteract this threat, the IAEA has sent hundreds of reverse transcription-polymerase chain reaction (RT-PCR) machines — capable of detecting specific genetic materials in pathogens — to more than 130 countries.

    Meanwhile, new risks have emerged from the war in Ukraine, where fighting has raged for a year-and-a-half near the six nuclear reactors in Zaporizhzhia — Europe’s largest nuclear power plant. Early in the conflict, the IAEA sent a team of experts to monitor the plant and to do everything possible to prevent a nuclear accident that would bring “even more misery to people who are already suffering so much,” Grossi said. A major accident, he added, would likely stall investments in nuclear power at a time when its future prospects were starting to brighten.

    At the end of his talk, Grossi returned to the subject of fusion, which he expects to become an important energy source, perhaps in the not-too-distant future. He was encouraged by the visit he’d just had to the MIT spinoff company, Commonwealth Fusion Systems. With regard to fusion, he said, “for the first time, all the pieces of the puzzle are there: the physics, the policy drivers, and the investment.” In fact, an agreement was signed on the day of his lecture, which made MIT’s Plasma Science and Fusion Center an IAEA collaboration center — the second such center in the United States.

    “When I think of all the new forms of collaboration happening today, I imagine Professor Rose would be delighted,” Grossi said. “It really is something to hold [his] letter and know how much progress has been made since 1977 in fusion. I look forward to our collaboration going forward.” More

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    Fast-tracking fusion energy’s arrival with AI and accessibility

    As the impacts of climate change continue to grow, so does interest in fusion’s potential as a clean energy source. While fusion reactions have been studied in laboratories since the 1930s, there are still many critical questions scientists must answer to make fusion power a reality, and time is of the essence. As part of their strategy to accelerate fusion energy’s arrival and reach carbon neutrality by 2050, the U.S. Department of Energy (DoE) has announced new funding for a project led by researchers at MIT’s Plasma Science and Fusion Center (PSFC) and four collaborating institutions.

    Cristina Rea, a research scientist and group leader at the PSFC, will serve as the primary investigator for the newly funded three-year collaboration to pilot the integration of fusion data into a system that can be read by AI-powered tools. The PSFC, together with scientists from the College of William and Mary, the University of Wisconsin at Madison, Auburn University, and the nonprofit HDF Group, plan to create a holistic fusion data platform, the elements of which could offer unprecedented access for researchers, especially underrepresented students. The project aims to encourage diverse participation in fusion and data science, both in academia and the workforce, through outreach programs led by the group’s co-investigators, of whom four out of five are women. 

    The DoE’s award, part of a $29 million funding package for seven projects across 19 institutions, will support the group’s efforts to distribute data produced by fusion devices like the PSFC’s Alcator C-Mod, a donut-shaped “tokamak” that utilized powerful magnets to control and confine fusion reactions. Alcator C-Mod operated from 1991 to 2016 and its data are still being studied, thanks in part to the PSFC’s commitment to the free exchange of knowledge.

    Currently, there are nearly 50 public experimental magnetic confinement-type fusion devices; however, both historical and current data from these devices can be difficult to access. Some fusion databases require signing user agreements, and not all data are catalogued and organized the same way. Moreover, it can be difficult to leverage machine learning, a class of AI tools, for data analysis and to enable scientific discovery without time-consuming data reorganization. The result is fewer scientists working on fusion, greater barriers to discovery, and a bottleneck in harnessing AI to accelerate progress.

    The project’s proposed data platform addresses technical barriers by being FAIR — Findable, Interoperable, Accessible, Reusable — and by adhering to UNESCO’s Open Science (OS) recommendations to improve the transparency and inclusivity of science; all of the researchers’ deliverables will adhere to FAIR and OS principles, as required by the DoE. The platform’s databases will be built using MDSplusML, an upgraded version of the MDSplus open-source software developed by PSFC researchers in the 1980s to catalogue the results of Alcator C-Mod’s experiments. Today, nearly 40 fusion research institutes use MDSplus to store and provide external access to their fusion data. The release of MDSplusML aims to continue that legacy of open collaboration.

    The researchers intend to address barriers to participation for women and disadvantaged groups not only by improving general access to fusion data, but also through a subsidized summer school that will focus on topics at the intersection of fusion and machine learning, which will be held at William and Mary for the next three years.

    Of the importance of their research, Rea says, “This project is about responding to the fusion community’s needs and setting ourselves up for success. Scientific advancements in fusion are enabled via multidisciplinary collaboration and cross-pollination, so accessibility is absolutely essential. I think we all understand now that diverse communities have more diverse ideas, and they allow faster problem-solving.”

    The collaboration’s work also aligns with vital areas of research identified in the International Atomic Energy Agency’s “AI for Fusion” Coordinated Research Project (CRP). Rea was selected as the technical coordinator for the IAEA’s CRP emphasizing community engagement and knowledge access to accelerate fusion research and development. In a letter of support written for the group’s proposed project, the IAEA stated that, “the work [the researchers] will carry out […] will be beneficial not only to our CRP but also to the international fusion community in large.”

    PSFC Director and Hitachi America Professor of Engineering Dennis Whyte adds, “I am thrilled to see PSFC and our collaborators be at the forefront of applying new AI tools while simultaneously encouraging and enabling extraction of critical data from our experiments.”

    “Having the opportunity to lead such an important project is extremely meaningful, and I feel a responsibility to show that women are leaders in STEM,” says Rea. “We have an incredible team, strongly motivated to improve our fusion ecosystem and to contribute to making fusion energy a reality.” More

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    Simple superconducting device could dramatically cut energy use in computing, other applications

    MIT scientists and their colleagues have created a simple superconducting device that could transfer current through electronic devices much more efficiently than is possible today. As a result, the new diode, a kind of switch, could dramatically cut the amount of energy used in high-power computing systems, a major problem that is estimated to become much worse. Even though it is in the early stages of development, the diode is more than twice as efficient as similar ones reported by others. It could even be integral to emerging quantum computing technologies.

    The work, which is reported in the July 13 online issue of Physical Review Letters, is also the subject of a news story in Physics Magazine.

    “This paper showcases that the superconducting diode is an entirely solved problem from an engineering perspective,” says Philip Moll, director of the Max Planck Institute for the Structure and Dynamics of Matter in Germany. Moll was not involved in the work. “The beauty of [this] work is that [Moodera and colleagues] obtained record efficiencies without even trying [and] their structures are far from optimized yet.”

    “Our engineering of a superconducting diode effect that is robust and can operate over a wide temperature range in simple systems can potentially open the door for novel technologies,” says Jagadeesh Moodera, leader of the current work and a senior research scientist in MIT’s Department of Physics. Moodera is also affiliated with the Materials Research Laboratory, the Francis Bitter Magnet Laboratory, and the Plasma Science and Fusion Center (PSFC).

    The nanoscopic rectangular diode — about 1,000 times thinner than the diameter of a human hair — is easily scalable. Millions could be produced on a single silicon wafer.

    Toward a superconducting switch

    Diodes, devices that allow current to travel easily in one direction but not in the reverse, are ubiquitous in computing systems. Modern semiconductor computer chips contain billions of diode-like devices known as transistors. However, these devices can get very hot due to electrical resistance, requiring vast amounts of energy to cool the high-power systems in the data centers behind myriad modern technologies, including cloud computing. According to a 2018 news feature in Nature, these systems could use nearly 20 percent of the world’s power in 10 years.

    As a result, work toward creating diodes made of superconductors has been a hot topic in condensed matter physics. That’s because superconductors transmit current with no resistance at all below a certain low temperature (the critical temperature), and are therefore much more efficient than their semiconducting cousins, which have noticeable energy loss in the form of heat.

    Until now, however, other approaches to the problem have involved much more complicated physics. “The effect we found is due [in part] to a ubiquitous property of superconductors that can be realized in a very simple, straightforward manner. It just stares you in the face,” says Moodera.

    Says Moll of the Max Planck Institute, “The work is an important counterpoint to the current fashion to associate superconducting diodes [with] exotic physics, such as finite-momentum pairing states. While in reality, a superconducting diode is a common and widespread phenomenon present in classical materials, as a result of certain broken symmetries.”

    A somewhat serendipitous discovery

    In 2020 Moodera and colleagues observed evidence of an exotic particle pair known as Majorana fermions. These particle pairs could lead to a new family of topological qubits, the building blocks of quantum computers. While pondering approaches to creating superconducting diodes, the team realized that the material platform they developed for the Majorana work might also be applied to the diode problem.

    They were right. Using that general platform, they developed different iterations of superconducting diodes, each more efficient than the last. The first, for example, consisted of a nanoscopically thin layer of vanadium, a superconductor, which was patterned into a structure common to electronics (the Hall bar). When they applied a tiny magnetic field comparable to the Earth’s magnetic field, they saw the diode effect — a giant polarity dependence for current flow.

    They then created another diode, this time layering a superconductor with a ferromagnet (a ferromagnetic insulator in their case), a material that produces its own tiny magnetic field. After applying a tiny magnetic field to magnetize the ferromagnet so that it produces its own field, they found an even bigger diode effect that was stable even after the original magnetic field was turned off.

    Ubiquitous properties

    The team went on to figure out what was happening.

    In addition to transmitting current with no resistance, superconductors also have other, less well-known but just as ubiquitous properties. For example, they don’t like magnetic fields getting inside. When exposed to a tiny magnetic field, superconductors produce an internal supercurrent that induces its own magnetic flux that cancels the external field, thereby maintaining their superconducting state. This phenomenon, known as the Meissner screening effect, can be thought of as akin to our bodies’ immune system releasing antibodies to fight the infection of bacteria and other pathogens. This works, however, only up to some limit. Similarly, superconductors cannot entirely keep out large magnetic fields.

    The diodes the team created make use of this universal Meissner screening effect. The tiny magnetic field they applied — either directly, or through the adjacent ferromagnetic layer — activates the material’s screening current mechanism for expelling the external magnetic field and maintaining superconductivity.

    The team also found that another key factor in optimizing these superconductor diodes is tiny differences between the two sides, or edges, of the diode devices. These differences “create some sort of asymmetry in the way the magnetic field enters the superconductor,” Moodera says.

    By engineering their own form of edges on diodes to optimize these differences — for example, one edge with sawtooth features, while the other edge not intentionally altered — the team found that they could increase the efficiency from 20 percent to more than 50 percent. This discovery opens the door for devices whose edges could be “tuned” for even higher efficiencies, Moodera says.

    In sum, the team discovered that the edge asymmetries within superconducting diodes, the ubiquitous Meissner screening effect found in all superconductors, and a third property of superconductors known as vortex pinning all came together to produce the diode effect.

    “It is fascinating to see how inconspicuous yet ubiquitous factors can create a significant effect in observing the diode effect,” says Yasen Hou, first author of the paper and a postdoc at the Francis Bitter Magnet Laboratory and the PSFC. “What’s more exciting is that [this work] provides a straightforward approach with huge potential to further improve the efficiency.”

    Christoph Strunk is a professor at the University of Regensburg in Germany. Says Strunk, who was not involved in the research, “the present work demonstrates that the supercurrent in simple superconducting strips can become nonreciprocal. Moreover, when combined with a ferromagnetic insulator, the diode effect can even be maintained in the absence of an external magnetic field. The rectification direction can be programmed by the remnant magnetization of the magnetic layer, which may have high potential for future applications. The work is important and appealing both from the basic research and from the applications point of view.”

    Teenage contributors

    Moodera noted that the two researchers who created the engineered edges did so while still in high school during a summer at Moodera’s lab. They are Ourania Glezakou-Elbert of Richland, Washington, who will be going to Princeton University this fall, and Amith Varambally of Vestavia Hills, Alabama, who will be entering Caltech.

    Says Varambally, “I didn’t know what to expect when I set foot in Boston last summer, and certainly never expected to [be] a coauthor in a Physical Review Letters paper.

    “Every day was exciting, whether I was reading dozens of papers to better understand the diode phenomena, or operating machinery to fabricate new diodes for study, or engaging in conversations with Ourania, Dr. Hou, and Dr. Moodera about our research.

    “I am profoundly grateful to Dr. Moodera and Dr. Hou for providing me with the opportunity to work on such a fascinating project, and to Ourania for being a great research partner and friend.”

    In addition to Moodera and Hou, corresponding authors of the paper are professors Patrick A. Lee of the MIT Department of Physics and Akashdeep Kamra of Autonomous University of Madrid. Other authors from MIT are Liang Fu and Margarita Davydova of the Department of Physics, and Hang Chi, Alessandro Lodesani, and Yingying Wu, all of the Francis Bitter Magnet Laboratory and the Plasma Science and Fusion Center. Chi is also affiliated with the U.S. Army CCDC Research Laboratory.

    Authors also include Fabrizio Nichele, Markus F. Ritter, and Daniel Z. Haxwell of IBM Research Europe; Stefan Ilićof Materials Physics Center (CFM-MPC); and F. Sebastian Bergeret of CFM-MPC and Donostia International Physics Center.

    This work was supported by the Air Force Office of Sponsored Research, the Office of Naval Research, the National Science Foundation, and the Army Research Office. Additional funders are the European Research Council, the European Union’s Horizon 2020 Research and Innovation Framework Programme, the Spanish Ministry of Science and Innovation, the A. v. Humboldt Foundation, and the Department of Energy’s Office of Basic Sciences. More

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    A welcome new pipeline for students invested in clean energy

    Akarsh Aurora aspired “to be around people who are actually making the global energy transition happen,” he says. Sam Packman sought to “align his theoretical and computational interests to a clean energy project” with tangible impacts. Lauryn Kortman says she “really liked the idea of an in-depth research experience focused on an amazing energy source.”

    These three MIT students found what they wanted in the Fusion Undergraduate Scholars (FUSars) program launched by the MIT Plasma Science and Fusion Center (PSFC) to make meaningful fusion energy research accessible to undergraduates. Aurora, Kortman, and Packman are members of a cohort of 10 for the program’s inaugural run, which began spring semester 2023.

    FUSars operates like a high-wattage UROP (MIT’s Undergraduate Research Opportunities Program). The program requires a student commitment of 10 to 12 hours weekly on a research project during the course of an academic year, as well as participation in a for-credit seminar providing professional development, communication, and wellness support. Through this class and with the mentorship of graduate students, postdocs, and research scientist advisors, students craft a publication-ready journal submission summarizing their research. Scholars who complete the entire year and submit a manuscript for review will receive double the ordinary UROP stipend — a payment that can reach $9,000.

    “The opportunity just jumped out at me,” says Packman. “It was an offer I couldn’t refuse,” adds Aurora.

    Building a workforce

    “I kept hearing from students wanting to get into fusion, but they were very frustrated because there just wasn’t a pipeline for them to work at the PSFC,” says Michael Short, Class of ’42 Associate Professor of Nuclear Science and Engineering and associate director of the PSFC. The PSFC bustles with research projects run by scientists and postdocs. But since the PSFC isn’t a university department with educational obligations, it does not have the regular machinery in place to integrate undergraduate researchers.

    This poses a problem not just for students but for the field of fusion energy, which holds the prospect of unlimited, carbon-free electricity. There are promising advances afoot: MIT and one of its partners, Commonwealth Fusion Systems, are developing a prototype for a compact commercial fusion energy reactor. The start of a fusion energy industry will require a steady infusion of skilled talent.

    “We have to think about the workforce needs of fusion in the future and how to train that workforce,” says Rachel Shulman, who runs the FUSars program and co-instructs the FUSars class with Short. “Energy education needs to be thinking right now about what’s coming after solar, and that’s fusion.”

    Short, who earned his bachelor’s, master’s, and doctoral degrees at MIT, was himself the beneficiary of the Undergraduate Research Opportunity Program (UROP) at the PSFC. As a faculty member, he has become deeply engaged in building transformative research experiences for undergraduates. With FUSars, he hopes to give students a springboard into the field — with an eye to developing a diverse, highly trained, and zealous employee pool for a future fusion industry.

    Taking a deep dive

    Although these are early days for this initial group of FUSars, there is already a shared sense of purpose and enthusiasm. Chosen from 32 applicants in a whirlwind selection process — the program first convened in early February after crafting the experience over Independent Activities Period — the students arrived with detailed research proposals and personal goals.

    Aurora, a first-year majoring in mechanical engineering and artificial intelligence, became fixed on fusion while still in high school. Today he is investigating methods for increasing the availability, known as capacity factor, of fusion reactors. “This is key to the commercialization of fusion energy,” he says.

    Packman, a first-year planning on a math and physics double major, is developing approaches to help simplify the computations involved in designing the complex geometries of solenoid induction heaters in fusion reactors. “This project is more immersive than my last UROP, and requires more time, but I know what I’m doing here and how this fits into the broader goals of fusion science,” he says. “It’s cool that our project is going to lead to a tool that will actually be used.”

    To accommodate the demands of their research projects, Shulman and Short discouraged students from taking on large academic loads.

    Kortman, a junior majoring in materials science and engineering with a concentration in mechanical engineering, was eager to make room in her schedule for her project, which concerns the effects of radiation damage on superconducting magnets. A shorter research experience with the PSFC during the pandemic fired her determination to delve deeper and invest more time in fusion.

    “It is very appealing and motivating to join people who have been working on this problem for decades, just as breakthroughs are coming through,” she says. “What I’m doing feels like it might be directly applicable to the development of an actual fusion reactor.”

    Camaraderie and support

    In the FUSar program, students aim to seize a sizeable stake in a multipronged research enterprise. “Here, if you have any hypotheses, you really get to pursue those because at the end of the day, the paper you write is yours,” says Aurora. “You can take ownership of what sort of discovery you’re making.”

    Enabling students to make the most of their research experiences requires abundant support — and not just for the students. “We have a whole separate set of programming on mentoring the mentors, where we go over topics with postdocs like how to teach someone to write a research paper, rather than write it for them, and how to help a student through difficulties,” Shulman says.

    The weekly student seminar, taught primarily by Short and Shulman, covers pragmatic matters essential to becoming a successful researcher — topics not always addressed directly or in the kind of detail that makes a difference. Topics include how to collaborate with lab mates, deal with a supervisor, find material in the MIT libraries, produce effective and persuasive research abstracts, and take time for self-care.

    Kortman believes camaraderie will help the cohort through an intense year. “This is a tight-knit community that will be great for keeping us all motivated when we run into research issues,” she says. “Meeting weekly to see what other students are able to accomplish will encourage me in my own project.”

    The seminar offerings have already attracted five additional participants outside the FUSars cohort. Adria Peterkin, a second-year graduate student in nuclear science and engineering, is sitting in to solidify her skills in scientific writing.

    “I wanted a structured class to help me get good at abstracts and communicating with different audiences,” says Peterkin, who is investigating radiation’s impact on the molten salt used in fusion and advanced nuclear reactors. “There’s a lot of assumed knowledge coming in as a PhD student, and a program like FUSars is really useful to help level out that playing field, regardless of your background.”

    Fusion research for all

    Short would like FUSars to cast a wide net, capturing the interest of MIT undergraduates no matter their backgrounds or financial means. One way he hopes to achieve this end is with the support of private donors, who make possible premium stipends for fusion scholars.

    “Many of our students are economically disadvantaged, on financial aid or supporting family back home, and need work that pays more than $15 an hour,” he says. This generous stipend may be critical, he says, to “flipping students from something else to fusion.”

    Although this first FUSars class is composed of science and engineering students, Short envisions a cohort eventually drawn from the broad spectrum of MIT disciplines. “Fusion is not a nuclear-focused discipline anymore — it’s no longer just plasma physics and radiation,” he says. “We’re trying to make a power plant now, and it’s an all hands-on-deck kind of thing, involving policy and economics and other subjects.”

    Although many are just getting started on their academic journeys, FUSar students believe this year will give them a strong push toward potential energy careers. “Fusion is the future of the energy transition and how we’re going to defeat climate change,” says Aurora. “I joined the program for a deep dive into the field, to help me decide whether I should invest the rest of my life to it.” More

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    Panel addresses technologies needed for a net-zero future

    Five speakers at a recent public panel discussion hosted by the MIT Energy Initiative (MITEI) and introduced by Deputy Director for Science and Technology Robert Stoner tackled one of the thorniest, yet most critical, questions facing the world today: How can we achieve the ambitious goals set by governments around the globe, including the United States, to reach net zero emissions of greenhouse gases by mid-century?

    While the challenges are great, the panelists agreed, there is reason for optimism that these technological challenges can be solved. More uncertain, some suggested, are the social, economic, and political hurdles to bringing about the needed innovations.

    The speakers addressed areas where new or improved technologies or systems are needed if these ambitious goals are to be achieved. Anne White, aassociate provost and associate vice president for research administration and a professor of nuclear science and engineering at MIT, moderated the panel discussion. She said that achieving the ambitious net-zero goal “has to be accomplished by filling some gaps, and going after some opportunities.” In addressing some of these needs, she said the five topics chosen for the panel discussion were “places where MIT has significant expertise, and progress is already ongoing.”

    First of these was the heating and cooling of buildings. Christoph Reinhart, a professor of architecture and director of the Building Technology Program, said that currently about 1 percent of existing buildings are being retrofitted each year for energy efficiency and conversion from fossil-fuel heating systems to efficient electric ones — but that is not nearly enough to meet the 2050 net-zero target. “It’s an enormous task,” he said. To meet the goals, he said, would require increasing the retrofitting rate to 5 percent per year, and to require all new construction to be carbon neutral as well.

    Reinhart then showed a series of examples of how such conversions could take place using existing solar and heat pump technology, and depending on the configuration, how they could provide a payback to the homeowner within 10 years or less. However, without strong policy incentives the initial cost outlay for such a system, on the order of $50,000, is likely to put conversions out of reach of many people. Still, a recent survey found that 30 percent of homeowners polled said they would accept installation at current costs. While there is government money available for incentives for others, “we have to be very clever on how we spend all this money … and make sure that everybody is basically benefiting.”

    William Green, a professor of chemical engineering, spoke about the daunting challenge of bringing aviation to net zero. “More and more people like to travel,” he said, but that travel comes with carbon emissions that affect the climate, as well as air pollution that affects human health. The economic costs associated with these emissions, he said, are estimated at $860 per ton of jet fuel used — which is very close to the cost of the fuel itself. So the price paid by the airlines, and ultimately by the passengers, “is only about half of the true cost to society, and the other half is being borne by all of us, by the fact that it’s affecting the climate and it’s causing medical problems for people.”

    Eliminating those emissions is a major challenge, he said. Virtually all jet fuel today is fossil fuel, but airlines are starting to incorporate some biomass-based fuel, derived mostly from food waste. But even these fuels are not carbon-neutral, he said. “They actually have pretty significant carbon intensity.”

    But there are possible alternatives, he said, mostly based on using hydrogen produced by clean electricity, and making fuels out of that hydrogen by reacting it, for example, with carbon dioxide. This could indeed produce a carbon-neutral fuel that existing aircraft could use, but the process is costly, requiring a great deal of hydrogen, and ways of concentrating carbon dioxide. Other viable options also exist, but all would add significant expense, at least with present technology. “It’s going to cost a lot more for the passengers on the plane,” Green said, “But the society will benefit from that.”

    Increased electrification of heating and transportation in order to avoid the use of fossil fuels will place major demands on the existing electric grid systems, which have to perform a constant delicate balancing of production with demand. Anuradha Annaswamy, a senior research scientist in MIT’s mechanical engineering department, said “the electric grid is an engineering marvel.” In the United States it consists of 300,000 miles of transmission lines capable of carrying 470,000 megawatts of power.

    But with a projected doubling of energy from renewable sources entering the grid by 2030, and with a push to electrify everything possible — from transportation to buildings to industry — the load is not only increasing, but the patterns of both energy use and production are changing. Annaswamy said that “with all these new assets and decision-makers entering the picture, the question is how you can use a more sophisticated information layer that coordinates how all these assets are either consuming or producing or storing energy, and have that information layer coexist with the physical layer to make and deliver electricity in all these ways. It’s really not a simple problem.”

    But there are ways of addressing these complexities. “Certainly, emerging technologies in power electronics and control and communication can be leveraged,” she said. But she added that “This is not just a technology problem, really, it is something that requires technologists, economists, and policymakers to all come together.”

    As for industrial processes, Bilge Yildiz, a professor of nuclear science and engineering and materials science and engineering, said that “the synthesis of industrial chemicals and materials constitutes about 33 percent of global CO2 emissions at present, and so our goal is to decarbonize this difficult sector.” About half of all these industrial emissions come from the production of just four materials: steel, cement, ammonia, and ethylene, so there is a major focus of research on ways to reduce their emissions.

    Most of the processes to make these materials have changed little for more than a century, she said, and they are mostly heat-based processes that involve burning a lot of fossil fuel. But the heat can instead be provided from renewable electricity, which can also be used to drive electrochemical reactions in some cases as a substitute for the thermal reactions. Already, there are processes for making cement and steel that produce only about half the present carbon dioxide (CO2) emissions.

    The production of ammonia, which is widely used in fertilizer and other bulk chemicals, accounts for more greenhouse gas emissions than any other industrial source. The present thermochemical process could be replaced by an electrochemical process, she said. Similarly, the production of ethylene, as a feedstock for plastics and other materials, is the second-highest emissions producer, with three tons of carbon dioxide released for every ton of ethylene produced. Again, an electrochemical alternative method exists, but needs to be improved to be cost competitive.

    As the world moves toward electrification of industrial processes to eliminate fossil fuels, the need for emissions-free sources of electricity will continue to increase. One very promising potential addition to the range of carbon-free generation sources is fusion, a field in which MIT is a leader in developing a particularly promising technology that takes advantage of the unique properties of high-temperature superconducting (HTS) materials.

    Dennis Whyte, the director of MIT’s Plasma Science and Fusion Center, pointed out that despite global efforts to reduce CO2 emissions, “we use exactly the same percentage of carbon-based products to generate energy as 10 years ago, or 20 years ago.” To make a real difference in global emissions, “we need to make really massive amounts of carbon-free energy.”

    Fusion, the process that powers the sun, is a particularly promising pathway, because the fuel, derived from water, is virtually inexhaustible. By using recently developed HTS material to generate the powerful magnetic fields needed to produce a sustained fusion reaction, the MIT-led project, which led to a spinoff company called Commonwealth Fusion Systems, was able to radically reduce the required size of a fusion reactor, Whyte explained. Using this approach, the company, in collaboration with MIT, expects to have a fusion system that produces net energy by the middle of this decade, and be ready to build a commercial plant to produce power for the grid early in the next. Meanwhile, at least 25 other private companies are also attempting to commercialize fusion technology. “I think we can take some credit for helping to spawn what is essentially now a new industry in the United States,” Whyte said.

    Fusion offers the potential, along with existing solar and wind technologies, to provide the emissions-free power the world needs, Whyte says, but that’s only half the problem, the other part being how to get that power to where it’s needed, when it’s needed. “How do we adapt these new energy sources to be as compatible as possible with everything that we have already in terms of energy delivery?”

    Part of the way to find answers to that, he suggested, is more collaborative work on these issues that cut across disciplines, as well as more of the kinds of cross-cutting conversations and interactions that took place in this panel discussion. More

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    A new mathematical “blueprint” is accelerating fusion device development

    Developing commercial fusion energy requires scientists to understand sustained processes that have never before existed on Earth. But with so many unknowns, how do we make sure we’re designing a device that can successfully harness fusion power?

    We can fill gaps in our understanding using computational tools like algorithms and data simulations to knit together experimental data and theory, which allows us to optimize fusion device designs before they’re built, saving much time and resources.

    Currently, classical supercomputers are used to run simulations of plasma physics and fusion energy scenarios, but to address the many design and operating challenges that still remain, more powerful computers are a necessity, and of great interest to plasma researchers and physicists.

    Quantum computers’ exponentially faster computing speeds have offered plasma and fusion scientists the tantalizing possibility of vastly accelerated fusion device development. Quantum computers could reconcile a fusion device’s many design parameters — for example, vessel shape, magnet spacing, and component placement — at a greater level of detail, while also completing the tasks faster. However, upgrading to a quantum computer is no simple task.

    In a paper, “Dyson maps and unitary evolution for Maxwell equations in tensor dielectric media,” recently published in Physics Review A, Abhay K. Ram, a research scientist at the MIT Plasma Science and Fusion Center (PSFC), and his co-authors Efstratios Koukoutsis, Kyriakos Hizanidis, and George Vahala present a framework that would facilitate the use of quantum computers to study electromagnetic waves in plasma and its manipulation in magnetic confinement fusion devices.

    Quantum computers excel at simulating quantum physics phenomena, but many topics in plasma physics are predicated on the classical physics model. A plasma (which is the “dielectric media” referenced in the paper’s title) consists of many particles — electrons and ions — the collective behaviors of which are effectively described using classic statistical physics. In contrast, quantum effects that influence atomic and subatomic scales are averaged out in classical plasma physics.  

    Furthermore, the descriptive limitations of quantum mechanics aren’t suited to plasma. In a fusion device, plasmas are heated and manipulated using electromagnetic waves, which are one of the most important and ubiquitous occurrences in the universe. The behaviors of electromagnetic waves, including how waves are formed and interact with their surroundings, are described by Maxwell’s equations — a foundational component of classical plasma physics, and of general physics as well. The standard form of Maxwell’s equations is not expressed in “quantum terms,” however, so implementing the equations on a quantum computer is like fitting a square peg in a round hole: it doesn’t work.

    Consequently, for plasma physicists to take advantage of quantum computing’s power for solving problems, classical physics must be translated into the language of quantum mechanics. The researchers tackled this translational challenge, and in their paper, they reveal that a Dyson map can bridge the translational divide between classical physics and quantum mechanics. Maps are mathematical functions that demonstrate how to take an input from one kind of space and transform it to an output that is meaningful in a different kind of space. In the case of Maxwell’s equations, a Dyson map allows classical electromagnetic waves to be studied in the space utilized by quantum computers. In essence, it reconfigures the square peg so it will fit into the round hole without compromising any physics.

    The work also gives a blueprint of a quantum circuit encoded with equations expressed in quantum bits (“qubits”) rather than classical bits so the equations may be used on quantum computers. Most importantly, these blueprints can be coded and tested on classical computers.

    “For years we have been studying wave phenomena in plasma physics and fusion energy science using classical techniques. Quantum computing and quantum information science is challenging us to step out of our comfort zone, thereby ensuring that I have not ‘become comfortably numb,’” says Ram, quoting a Pink Floyd song.

    The paper’s Dyson map and circuits have put quantum computing power within reach, fast-tracking an improved understanding of plasmas and electromagnetic waves, and putting us that much closer to the ideal fusion device design.    More