Observation of a self-generated current to self-confine fusion plasmas
Peer-Reviewed PublicationIMAGE: . view more
CREDIT: SEOUL NATION UNIVERSITY
Nuclear fusion has drawn more attention in the era of carbon neutrality because of no carbon dioxide production during power generation and no generation of high-level radioactive wastes.
A tokamak, a torus-shaped nuclear fusion device, needs an electric current in the plasma to produce magnetic field around the torus for confining fusion plasmas. Plasma current is conventionally generated by electromagnetic induction.
However, for a steady-state fusion reactor, minimizing the inductive current is essential to extend the tokamak operating duration. Several non-inductive current drive schemes have been developed for steady-state operations such as radio-frequency waves and neutral beams. However, commercial reactors require minimal use of these external sources to maximize the fusion gain, Q, the ratio of the fusion power to the external power. Apart from these external current drives, a self-generated current, so-called bootstrap current, was predicted theoretically and demonstrated experimentally.
The research team led by Prof. Yong-Su Na in the Department of Nuclear Engineering at Seoul National University and Dr. Jaemin Seo at Princeton University have revealed that another type of self-generated current can exist in a tokamak which can not yet been explained by present theories. They discovered this in the experiments on the KSTAR tokamak in collaboration with Korea Institute of Fusion Energy, Princeton Plasma Physics Laboratory, and General Atomics.
While conducting an experiment on plasma turbulence, it was discovered by chance that an un-identified plasma current that could not be explained by existing theories and simulations occurred. As a result of the analysis, it was found that this comprises a significant amount up to 30% of the total plasma current, and appears when the turbulence was relatively low.
The discovery of a new plasma current generated by itself without magnetic induction shows a new possibility that the plasma confines by itself and continues the fusion reaction in long-pulse operations for a fusion reactor.
The new current source in this experiment was unusually observed only when the fuel was injected into the plasma and the exact cause is still unknown, so follow-up studies are planned to proceed actively in the future.
Prof. Yong-Su Na, the co-first author and corresponding author of the study, said, “This result was obtained from a unfamiliar experiment to the extent that the experiment proposal was not selected at KSTAR. If we had tried to look at it from a conventional point of view, we would not have found it. “We were able to discover new things by approaching with an open perspective rather than being confined to what we wanted to see or get.” Another co-first author, Dr. Seo Jae-min, said, “Big science such as the nuclear fusion research is being devoted to small steps that put an apple on the shoulders of giants. I hope that future scientists who can step forward together will be interested in and support the nuclear fusion research.”
Seoul National University
Once the physics mechanism is found, this new discovery is expected to significantly contribute to the long continuous operation of ITER and commercial reactors, which are exploring current drive ways that do not reoly on inductive current.
This work was supported by National R&D Program through the National
Research Foundation of Korea (NRF) funded by the Korean government
(Ministry of Science and ICT) (NRF-2021M1A7A4091135 and
2021M3F7A1084419). This work was also supported by the Ministry of
Science and ICT under the KFE R&D Program of “KSTAR Experimental
Collaboration and Fusion Plasma Research (KFE-EN2201-12)”.
JOURNAL
Nature Communications
ARTICLE TITLE
Observation of a new type of self-generated current in magnetized plasmas
Delgado-Aparicio appointed to national fusion advisory committee
IMAGE: PPPL PHYSICIST LUIS DELGADO-APARICIO view more
CREDIT: ELLE STARKMAN / PPPL OFFICE OF COMMUNICATIONS
Luis Delgado-Aparicio, a principal research physicist at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL), has been named a member of the Fusion Energy Sciences Advisory Committee (FESAC), which advises the director of the United States Office of Science on complex scientific and technical matters related to America’s fusion energy sciences research program.
Delgado-Aparicio will specifically provide advice about confining plasma, ultra-hot gas sometimes known as the fourth state of matter, within doughnut-shaped fusion facilities known as tokamaks. Scientists around the world use tokamaks and other devices to try to harness the fusion process that powers the sun and stars to create electricity with producing greenhouse gases and long-lived radioactive waste.
Delgado-Aparicio will also provide expert counsel about the movement of heat and particles within plasma, as well as magnetohydrodynamics, a set of physical laws that describe plasma’s behavior and is used to create computer simulations that help improve tokamak performance.
The committee meets approximately three times a year in Washington, D.C. His three-year term began in October 2022 and will extend until June 2025.
“I am extremely honored to join the FESAC committee,” Delgado-Aparicio said. “It’s a huge responsibility and a wonderful opportunity.”
In addition, in October Delgado-Aparicio was named the new head of PPPL’s Department of Advanced Projects, replacing PPPL physicist David Gates. The department oversees the Lab’s efforts to build a new type of twisty stellarator fusion facility that incorporates permanent magnets, similar to those used on refrigerator doors. The department also manages PPPL’s collaboration with stellarators around the world, including Germany’s Wendelstein 7-X and Japan’s Large Helical Device, as well as PPPL’s efforts to provide plasma sensors that rely on powerful light known as X-rays. Other divisions within Advanced Projects include Fusion System Studies and Next-Step Project Development.
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 https://energy.gov/science
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