PPPL physicists aim to unlock mysteries of fusion with Early Career Research awards

PPPL June 21, 2018

(Photo by Elle Starkman/PPPL Office of Communications )
Physicists Sam Lazerson, left, and Nate Ferraro.

Physicists Dr. Nate Ferraro and Dr. Sam Lazerson of the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have each won 2018 Early Career Research Program awards sponsored by the DOE Office of Science. The two five-year awards will fund PPPL research that could lead to development of the best designs for doughnut-shaped tokamaks and twisty stellarators — the main magnetic-bottles employed worldwide in the effort to produce virtually inexhaustible fusion power on Earth using the reactions that drive the sun and stars.

Ferraro and Lazerson are the first double PPPL winners in the same year since the Office of Science began the current award in 2010, and the sixth and seventh PPPL winners during that nine-year period. The honor, designed to fund exceptional young researchers in disciplines supported by the DOE Office of Science, went to 84 university and DOE national laboratory scientists this year, including 30 from DOE laboratories. National laboratory winners will receive at least $500,000 per year for salaries for themselves and research associates and for research costs.

“Supporting talented researchers early in their career is key to building and maintaining a skilled and effective scientific workforce for the nation. By investing in the next generation of scientific researchers, we are supporting lifelong discovery science to fuel the nation’s innovation system,” said Secretary of Energy Rick Perry. “We are proud of the accomplishments these young scientists have already made, and look forward to following their achievements in years to come.”

Fusion merges light elements in the form of plasma — the hot, charged state of matter composed of atomic nuclei and electrons — to produce vast amounts of energy. Tokamaks have long been the most widely used fusion magnetic configuration, with stellarators now gathering renewed interest. Both devices confine the plasma in strong magnetic fields and heat it to temperatures many times hotter than the core of the sun to cause the nuclei to fuse and release their energy, producing what has been called “a star in a jar.”

Ferraro and Lazerson currently work thousands of miles apart. Ferraro, a theoretical physicist in Princeton, New Jersey, has developed a flagship computer code for simulating disruptions that halt fusion reactions. Lazerson is lead U.S. collaborator on experiments on the Wendelstein 7-X (W7-X) stellarator in Greifswald, Germany, the largest and most advanced stellarator in the world. The award-winning programs and backgrounds of the two PPPL scientists are below:

Nate Ferraro

Ferraro focuses his research on ways to minimize disruptions that can slow or halt fusion reactions. He will use the M3D-C1 code to model a method for lessening or eliminating instabilities called edge localized modes (ELMs), which can damage a tokamak’s walls. The complex task calls first for determining precisely how perturbing the plasma with special magnetic coils — a common method for suppressing ELMs called “Resonant Magnetic Perturbations” (RMP) — changes the shape of the plasma from a symmetric, or 2D, doughnut to fully non-symmetric or three-dimensional (3D).

Ferraro will then combine the best models of perturbed 3D plasma geometry with models that simulate the loss of heat and particles from plasmas in 3D magnetic fields. The combined model will determine the chief mechanism behind the losses when Ferraro applies it to a database of experiments performed on tokamaks that used RMPs. The results could provide a predictive model for designing and optimizing future tokamaks to operate without ELMs – essentially providing a blueprint for improved future fusion devices.

Ferraro joined PPPL in 2015 after earning a doctorate from the Princeton Department of Astrophysical Sciences in 2008 and bachelor’s and master’s degrees from Dartmouth College. He worked at General Atomics with support from the Oak Ridge Institute for Science and Education Postdoctoral Fellowship from 2008 to 2011, and was a staff scientist at General Atomics from 2011 to 2015. General Atomics operates the DIII-D National Fusion Facility, a tokamak funded by the DOE in San Diego. “I’m excited to start working on this challenging and important problem,” Ferraro said, “and I’ll do my best to make the most of this opportunity.”

Physicist Stephen Jardin, who coordinates research on macroscopic equilibrium and stability in the Theory Department at PPPL, praised Ferraro for his research. “Nate has distinguished himself by first developing the flagship M3D-C1 code and then applying it to model the complex interplay between 3D magnetic perturbations and the plasma edge,” Jardin said. “His award will lead to even more advanced models for better understanding and controlling ELMs in existing and proposed experiments.”

Sam Lazerson

Lazerson will explore the confinement in stellarators of energetic particles that will be essential to maintaining fusion reactions in what is called a self-heated or “burning plasma.” Fusion reactions produce these fast-moving particles, which must be confined long enough to impart their energy to the slower-moving plasma particles. The process creates heat that maintains the reactions and gives rise to the term “burning plasma.”

On W7-X, Lazerson will study energetic particles from neutral beam and radio frequency heating systems, which mimic the fusion reaction particles. He will simulate and then validate models of the energetic particles by comparing them with experimental results, and will use the validated models to optimize the shape of stellarator magnetic fields to improve the high energy confinement. Successful demonstration of such an optimization could enable development of disruption-free, steady-state fusion-powered electric plants based on the stellarator design.

Lazerson earned his doctorate from the University of Alaska in 2010 after receiving a bachelor of science in engineering physics from Embry-Riddle Aeronautical University in Daytona Beach, Florida. He joined PPPL in 2010 and has served a year-long tour of duty at W7-X in addition to his current long-term assignment in Greifswald. “This award allows us to conduct research into processes that are fundamental to achieving burning plasma in future power plants,” Lazerson said. “Now we can begin to explore how shaping stellarator fields can improve the performance of future reactors.”

David Gates, who heads the stellarator physics divison at PPPL, said: “Sam is one of the most organized and energetic young scientists that I have had the pleasure to mentor. This Early Career Award will help put the topic of fast particle physics in stellarators on a very firm scientific footing.”