Two significant honors for plasma physics research have been awarded to scientists at the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) by the Division of Plasma Physics of the Association of Asia Pacific Physical Societies (AAPPS-DPP). Choongseok (CS) Chang, an emeritus senior scientist at the Lab, was selected as the 2026 winner of the Subrahmanyan Chandrasekhar Prize of Plasma Physics. Seong-Moo Yang, a staff research physicist, was awarded the Young Researcher Award for magnetic fusion plasma physics.
The awards will be presented at the 10th Asia-Pacific Conference on Plasma Physics, which will be held in Busan, South Korea, from Oct. 11-16.
A lifetime of work on fusion's hardest problems
According to AAPPS, the Chandrasekhar Prize of Plasma Physics honors "outstanding contributions to experimental and/or theoretical research in fundamental plasma physics plasma applications in all fields of physics." It is named after Subrahmanyan Chandrasekhar who won the Nobel Prize in physics in 1983 for his work on the structure and evolution of stars. Chang will receive a medal, a cash prize and a certificate.
"Winning the Chandrasekhar Prize gives me a kind of satisfactory feeling for my lifetime devotion to plasma physics," Chang said. "We always hope that our work will be recognizably beneficial to the advancement of science."
The citation for the award calls out Chang's work on neoclassical transport theory, which describes how heat and particles move through the plasma inside a fusion system. In the early 1980s, Chang derived a formula for ion heat conduction that now bears his name: the Chang-Hinton formula. Researchers around the world still use it as a standard baseline when they compare measured or simulated ion heat transport against theory.
The award was also given for Chang's research on the impact of heat and particles escaping the plasma to the exhaust system on doughnut-shaped fusion systems known as tokamaks, including ITER: an experimental fusion facility now under assembly in southern France. Earlier predictions for ITER suggested the heat would be squeezed into a channel too narrow for the plates of the exhaust system, known as the divertor, to handle, which would require difficult operational maneuvering. Chang determined the heat and particles will be spread out on a larger area of the divertor than initially thought, due to the inherently stronger plasma turbulence. This discovery suggests ITER could safely handle the heat exhaust, with some experiments confirming the basic physics behind Chang's predictions.
"I hope the ultimate impact of my theories and the resulting simple formulas will be in their use as benchmarking tools, for fast analysis of existing experiments, for the design of next-generation magnetic fusion systems and for predicting their performance based on a fundamental understanding of the physics behind them," Chang said.
Turning magnetic imperfections into tools
The AAPPS-DPP Young Researcher Award recognizes scientists younger than 40 years old who have made significant contributions to plasma physics. This year, the division chose six winners from 22 nominees. Yang was one of two honored in magnetic fusion plasma physics. He will receive a plate, a cash prize and a certificate at the conference on Oct. 12.
The division cited Yang "for his outstanding experimental contributions to magnetic-fusion plasma physics, particularly in understanding and controlling three-dimensional magnetic-field effects, plasma transport and instabilities in tokamak plasmas."
Every tokamak has small imperfections in its magnetic field that can disrupt the plasma. These are known as error fields. Yang developed a way to measure error fields and even use them to improve the plasma, instead of causing problems. In 2024, Yang led a team that showed that carefully adjusted error fieldss can stabilize the core and the edge of the plasma at the same time. Yang won first place at the 2023 Research SLAM at PPPL, where he presented on this topic. He traveled to Washington, D.C., for the National Research SLAM in 2024.
"I am pleased to see the work I have pursued recognized, and the award gives me renewed motivation to explore new questions. It is particularly rewarding to see methods we developed being used by other researchers in their own work," Yang said. "These achievements were made possible by PPPL's support, the expertise of my colleagues and close collaboration with the KSTAR team and our other research partners. I am grateful to the colleagues and mentors who helped develop these ideas and make the experiments possible. Through these collaborations, I hope to continue translating new physical understanding into practical benefits for fusion devices."
