Three scientists behind an intriguing system for cooling plasma have won the Kaul Foundation Prize for Excellence in Plasma Physics Research and Technology Development. Eric Emdee, Robert Goldston and Jacob Schwartz of the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) conceptualized and streamlined the cooling device, called a lithium vapor box. 

“Handling the exhaust heat flux in a future fusion reactor is an enormous challenge — the lithium vapor box concept is one of the most promising and innovative solutions. This project is also a testament to the varied work we do here at PPPL, as it involved both the development of novel, real-world devices and extensive computer modeling,” said PPPL Director Steve Cowley, who announced the award during his Dec. 7 State of the Lab address reviewing major developments at PPPL over the past year. The Kaul Foundation Prize includes an award of $7,500 for each winner.

Plasma — the fourth state of matter found in the sun and stars — could one day be used to generate electricity on Earth. One of the challenges, however, is protecting the inner walls of the fusion device from the plasma within.

The lithium vapor box attempts to solve this problem by directing the outer edge of the plasma through a volume containing the metal vapor. As the vapor ionizes and radiates within the chamber, the heat from the plasma would typically dissipate before it reaches the reactor wall. The researchers believe the properties of lithium might make it ideal because it could cool the plasma edge while minimizing impurities in the plasma core.

Eric Emdee

In high school, Emdee was introduced to humankind’s most famous equation: e=mc². He learned that if you turned every atom in a single dollar bill into pure energy, it would be roughly equal to the energy released by an atomic bomb. He said this concept helped him realize how important fusion energy could be to the world, and he wanted to be a part of making it happen.

While completing his undergraduate degree in physics at the University of California, Davis, Emdee worked as a research intern at the Aerospace Corporation, where he designed an experiment for testing micro-capacitors for defects. He also analyzed data and ran simulations for the Large Underground Xenon (LUX) dark matter detection experiment. His honors thesis detailing the work received the highest honor bestowed by the university.

He went on to complete his doctoral degree in astrophysics at Princeton University under Goldston, which is how Emdee first got involved in the lithium vapor box project. Emdee’s contributions involved modeling the concept and matching simulations to experimental results. He has authored five papers detailing the work and presented at many conferences.

“I'm still doing a lot of work on this as a part of my postdoctoral work, so it’s very encouraging to know there is excitement around the Lab about this project. It motivates me to keep going,” Emdee said.
 

Robert J. Goldston

Were it not for an epiphany on a mountaintop, Goldston might never have become a physicist. He started at Harvard University in the social relations program, aiming to be a psychologist. But standing on a mountaintop in Vermont and looking at the smoke rising from a nearby town, he realized the real pleasure of being human was turning energy into beauty. If humankind could generate energy from fusion, he thought, without all of the issues associated with other sources of energy, we could bring a lot of beauty to the world. He decided to switch his major to physics.

Goldston started his career in fusion by studying neutral beam heating at Princeton University and PPPL. Still a doctoral student at the time, Goldston was thrilled when he got the chance to discuss his findings at his first American Physical Society meeting. In fact, Goldston was so exhilarated after giving his talk that he had to run around the block to work off some of the energy. Goldston wasn’t the only one excited by the presentation: This work became the first experimental basis for the Tokamak Fusion Test Reactor (TFTR).

Goldston also developed the first version of the Monte Carlo simulation code that is now the standard used worldwide for simulating neutral beam heating. He helped to discover the first fast-ion instability in a tokamak, a little burst in the magnetic field that looks like an X-ray of fish on an oscilloscope screen, and he developed a highly accurate scaling relation predicting the confinement of energy in the next generation of large tokamaks. 

From 1997 to 2009, Goldston served as PPPL’s director. During this time, PPPL brought NSTX online, demonstrated the effects of lithium on fusion plasmas, decommissioned the TFTR facility and started the U.S. down the road to seriously considering the use of stellarators. When he stepped down, he decided to continue studying fusion energy, now researching the outer edge of plasmas and how it interacts with the innermost surfaces of a tokamak. He has authored more than 220 papers and conference proceedings, co-authored the textbook “Introduction to Plasma Physics” and won multiple awards, including the American Physical Society Prize in 1988, the 2014 Leading Global Thinker award from Foreign Policy magazine for his work on arms control and the 2015 Nuclear Fusion Award. 

“It is a great pleasure to be awarded the Kaul Foundation Prize along with Eric and Jacob,” said Goldston. “It is an important recognition of the problem of heat exhaust as the next frontier (pun intended) for making fusion practical and of the need for innovative approaches like the lithium vapor box.”
 

Jacob Schwartz

As a physics major at the University of California, Los Angeles, Schwartz knew he wanted to work on technology to combat climate change, but he wasn’t quite sure how to pursue his goal. An older student suggested Schwartz apply to the summer internship program at PPPL. The internship clarified his path: He could help develop technology for fusion power plants. 

Schwartz worked on the lithium vapor box for his doctoral thesis, also under Goldston, designing an experiment that looked at the behavior of lithium as it evaporated and condensed in a vacuum.

The Dutch Institute for Fundamental Energy Research recently ran a trial for a successor device, and the results are promising, supporting the idea that lithium vapor could be used to dissipate the heat of a plasma beam and, one day, a fusion plant’s divertor.

After completing his doctoral degree and postdoctoral work at Princeton, Schwartz returned to PPPL as a staff researcher in January 2022. He hopes to build tools to design, evaluate and optimize stellarators.

Schwartz noted that the work was truly a team effort, specifically calling out Goldston and the contributions of the technicians at PPPL. “I relied heavily on technicians to help us build and design these devices,” he said. “They taught me so much.”

Schwartz added that he hopes the research is carried forward on NSTX-U, the primary fusion experiment at PPPL. “I think it’s a really interesting concept and could lead to smaller and better fusion power plants.”