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Doctoral graduate Yuan Shi wins 2020 Marshall N. Rosenbluth Outstanding Doctoral Thesis Award

Physicist Yuan Shi, who received his doctorate from the Princeton Program in Plasma Physics in 2018, has won the prestigious 2020 Marshall N. Rosenbluth Outstanding Doctoral Thesis Award presented by the American Physical Society (APS).  The award recognizes “exceptional young scientists who have performed original doctoral thesis research of outstanding scientific quality and achievement in the area of plasma physics.” 

The 2020 honor recognizes Shi’s thesis with the citation: “For elegantly describing three-wave coupling in plasma modified by oblique magnetic fields, identifying applications including plasma-based laser amplifiers, and adapting quantum field theory to describe plasma physics in the strong-field regime.”

Intense laser beams

The “three-wave coupling in plasma” includes the classic interaction of intense laser beams propagating in plasma, where the energy contained in one laser beam can be transferred to the other two beams. If the energy in a long laser pulse is captured by a short laser pulse, the laser intensity can be significantly amplified. The “strong-field regime” refers to the regime in which electromagnetic fields are so intense that relativistic-quantum effects must be considered, such as virtual pairs of particles and anti-particles that undergo constant creation and annihilation, modifying the plasma environment. 

Shi was advised in his thesis by Professors Nat Fisch and Hong Qin. Fisch is Professor of Astrophysical Sciences, Director of the Program in Plasma Physics at Princeton University, and Associate Director for Academic Affairs at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL). Qin is Principle Research Physicist at PPPL and Lecturer with the rank of Professor in the Program in Plasma Physics.

A rare combination

“Yuan is the kind of student who teaches his advisors new things,” Fisch said. “Yuan’s thesis is a rare combination of significant advances in fundamental theory and computation, with profound recognition of connections between seemingly far-flung topics. It is a textbook-quality thesis that advances our understanding of magnetized plasma implosions, plasma-based laser amplification, and numerical methods to describe strong-field QED plasmas.”

When asked what had led to his success, Shi said, “I am deeply indebted to my thesis advisors. As it turned out, in having two advisors, I benefited not just from the intersection of their research interests, but also from the union of their research interests and styles. If working with Hong was more about elegant theories and algorithms, then working with Nat was more about imaginative ideas. Together they enabled me to find synergies between quantum field theory and plasma physics, and thus to pursue a certain brand of research that would be hard to imagine as available in graduate programs anywhere else in the world.” 

New ideas and methods

Qin noted that “a contributing factor to Yuan’s success has been his ability to absorb the full range of scientific opportunities at Princeton,” said co-advisor Qin. “Outside the plasma program, Yuan took more than 10 courses offered at Princeton University, which allowed him to bring new ideas and methods into his plasma research. Thus, his thesis introduced lattice QED [Quantum Electrodynamics] as a simulation tool, which, while unheard of in plasma physics, is well known in nuclear physics. He then used these techniques to model, among other phenomena, intense lasers interacting with plasmas.”

Shi earned his undergraduate degree at the University of Hong Kong, where he majored in physics and mathematics and minored in chemistry. His Ph.D. thesis research was supported in part through research grants from the National Nuclear Security Agency (NNSA), the Air Force Office of Scientific Research (AFOSR), and the DOE Office of Science.

Shi is now a Lawrence Postdoctoral Fellow at the Lawrence Livermore National Laboratory (LLNL), where he and others are extending his thesis research in new directions. One direction is magnetized inertial confinement fusion (ICF), where external magnetic fields are imposed upon laser-driven plasma capsules with the hope of achieving higher fusion yield leading eventually to ignited plasma.

“The magnetic field may change laser-plasma interactions (LPI) and modify crossbeam laser energy transfer,” Shi said. “This process, which was in part addressed in my thesis, needs to be understood and mitigated in order to attain the desired drive symmetry in ICF.”

Integrating fusion and quantum science

Another activity set in motion by Shi’s thesis lies in the integration of fusion energy science with quantum information science, which has become a research priority in the field of plasma physics following the passage of the National Quantum Initiative Act by Congress. At Livermore, Shi recently showed how the classic three-wave coupling in plasma that his thesis explored could be simulated on a quantum computer. “Yuan’s thesis work on quantum plasmas actually anticipated the current interest in the field,” said Qin. “His development of algorithms for quantum computers that solve plasma problems is now a remarkable new direction of research.”

Added Fisch, “Yuan’s thesis was indeed a remarkable achievement. But the real impact of his thesis may lie in what Yuan is now doing in his even more exciting postdoctoral work. He is bringing his ideas on laser plasma interactions to inform on experiments in magnetized imploding plasma in the most extreme environments of high magnetic fields and pressures. And he is formulating new algorithms for quantum computers. As proud as we were to have Yuan as a student, we are even prouder to see him shine now in his dazzling new research accomplishments.”

Shi will receive the Rosenbluth award during the annual meeting of the APS Division of Plasma Physics that will be held online in November. The award is named for the pioneering physicist whose career included 13 years as a visiting research scientist at PPPL. Included in the award is $2,000, a certificate, and an invitation to present a talk to the conference.

Shi becomes the eighth graduate of the Program in Plasma Physics to receive the Rosenbluth honor since the APS first awarded it in 1986. Previous winners were: Carey Forest, 1992; Michael Beer, 1996; Mark Herrmann, 2000; Yang Ren, 2008; Jong-Kyu Park, 2010; Jonathan Squire, 2017; and Seth Davidovits, 2018. 

The Program in Plasma Physics is a graduate program within the Department of Astrophysical Sciences at Princeton University. Students are admitted directly to the program and are granted degrees through the Department of Astrophysical Sciences. The program is based at PPPL.

The award announcement appears on the APS website: https://www.aps.org/programs/honors/prizes/rosenbluth.cfm.

PPPL, on Princeton University's Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit energy.gov/science.

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Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.

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