Theoretical physicist Don Spong has been recognized by Fusion Power Associates (FPA) with the 2021 Distinguished Career Award.
Don is a member of the Plasma Theory and Modeling Group in the Fusion Energy Division at Oak Ridge National Laboratory (ORNL).
FPA acknowledged Spong’s “significant and life-long research on the physics of energetic ions and runaway electrons in tokamak plasmas, as well as for seminal contributions to transport optimization of stellarator configurations. He is especially recognized for the variety of his research topics and impressive record of collaborations with other fusion groups throughout the world,” the announcement said.
“This is an unexpected award and I’m very honored to receive it,” Spong said.
The ORNL scientist is sharing the honors with Sandia National Laboratories’ Stephen Slutze.
Spong’s other accolades include the 2020 Distinguished Researcher UT-Battelle Award. You can learn more about his field of research in this ORNL video.
Never-ending curiosity
Spong first arrived at ORNL for a summer internship in 1972 as he was wrapping up his second year in graduate school at the University of Michigan. “My advisor thought it would be good for me to come to ORNL because the lab had just built the first major new tokamak facility in the U.S. at that time, and they were working also on the ELMO Bumpy Torus device,” he said.
The experience sparked his interest in runaway electron problems that later led to his doctoral thesis. Once he graduated, he considered positions in several places, ultimately deciding to stay at ORNL, where he has been a core contributor in plasma physics for more than 40 years.
For the past two decades, Spong has dedicated a large portion of his time to understanding energetic particle physics and the interaction of particles with fusion devices. These interactions, facilitated by resonances between plasma waves and the orbits of either energetic ions or electrons, can put a high heat load on a fusion reactor wall, or cause enhanced transport; such phenomena can threaten the sustainability of the ignited fusion state or, in the worst case, damage the plasma-facing materials.
Taming instabilities
Plasma heating, either by external sources or from fusion reaction by-products, creates hot ion populations with energies 50 to 200 times the background thermal plasma energy. These high energy particles can drive instability in the plasma through resonances, which can put a high-heat load on the device or even cause enhanced transport.
“We use the power of supercomputers such as Summit to model energetic particle behavior, so we can try to understand the nature of the resonant interactions, in order to avoid or possibly mitigate them,” Spong explained.
“It’s possible to create detailed, complete models with all the necessary kinetic effects, but they tend to take a lot of time to run. What I’ve worked on a lot since the 1990s is the development of reduced models that can be run on more commodity-grade computers. These can be more readily used for comparison with experimental data and factored into long time scale integrated simulations,” he explained. Such models are also valuable for discharge optimization in the tokamak and shape optimization in the stellarator, which relies on 3D shaping to suppress instabilities.
Spong is a collaborator in Princeton University’s Simons “Finding Optimum Magnetic Fields with Hidden Symmetries project” which focuses on stellarator design and physics and an advisor to Type One Energy which seeks commercially viable stellarator designs. He has also been a visiting professor at Japan’s primary stellarator laboratory, the National Institute for Fusion Science.
“At ORNL we have a strong interest in developing all aspects of fusion systems, and plasma instability is one of the most crucial areas that scientists need to understand to conquer the challenge of carbon-free sustainable fusion energy. A primary initial motivation of the ITER project was to test the sustainability of fusion-grade plasmas against instabilities driven by energetic fusion-produced alpha particles. This area of physics had to be tested “at scale” and could not be adequately checked in existing experiments. It’s all about assessing the right conditions we would need to achieve a fusion reactor,” Spong added.
Spong will be honored at FPA’s 32nd annual meeting, which is scheduled to take place on December 15-16 in Washington, D.C.
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