Researchers design simpler magnets for winding setups that could lead to steady-state melting operation

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Physicists Caoxiang Zhu, left, and Nicola Lonigro with computer-generated images of magnets used to confine plasma in fusion facilities called stellarators. Credit: Kiran Sudarsanan / PPPL Communications Office

Harnessing the power that makes the sun and stars shine could be aided by powerful magnets with straighter shapes than before. Researchers linked to the Princeton Plasma Physics Laboratory (PPPL) of the United States Department of Energy (DOE) have found a way to create such magnets for fusion facilities called stellarators.

These setups have complex twisted magnetic coils, compared to straight top-down coils in more widely used tokamak setups, and can produce fusion reactions without the risk of disturbances that tokamaks face. This advantage makes Stellarators a candidate to serve as a model for a next-generation fusion pilot plant.

Now, by adding relatively straight sections to the stellarator’s coils, researchers could both reduce manufacturing cost and make it easier to install openings that would allow technicians to repair the inside of the device. Both innovations could aid in the development of a stellar power plant, replicating fusion on Earth for a virtually inexhaustible supply of energy to generate electricity without producing greenhouse gases or long-lived radioactive waste.

“In the future, people will need to replace stellarator components as they wear out, which requires large openings between the magnet coils,” said physicist Caoxiang Zhu, author of the paper reporting the results in nuclear fusion who completed the research while on staff at PPPL. He is now on the staff of the University of Science and Technology of China. “But it’s hard to have large apertures in stellarators because electromagnetic coils zigzag and zag and are really complex.” But using a mathematical technique known as “spline representation,” Zhu and the other collaborators were able to design magnets with straighter sections than before while creating magnetic fields that can confine plasma. These straight sections could provide good locations for windows.

Invented by astrophysicist Lyman Spitzer, the first director of PPPL, stellarators are fusion facility concepts that use high-powered magnets to create intertwining magnetic fields that confine plasma, the hot gas composed of electrons and bare atomic nuclei. Stellarators have advantages over tokamaks, doughnut-shaped devices that are currently the world’s most popular fusion plant concept, but their incredibly complicated magnets have made design and construction difficult.

Zhu and the researchers added spline capability to Zhu’s FOCUS computer code. To test the concept, the team designed magnets that could fit the Helically Symmetric eXperiment (HSX) experiment, a stellarator at the University of Wisconsin-Madison.

The updated code showed that the researchers could create magnets that were straighter than before while preserving their strength and precision. “In principle, you can still make straighter coils, but the trade-off is that their magnetic fields might not confine the plasma as well as those produced by more sinuous coils,” said Nicola Lonigro, a student at DOE’s Science Undergraduate Laboratory. Internship (SULI program) at the time of research, senior author of the article, and now a Ph.D. candidate at the University of York in Great Britain. “But our research has shown that you can create a simpler coil with straighter sections that gives the same shape and magnetic field strength as conventional coils.”

Creating simpler magnets could aid in the development of a stellarator fusion power plant. “In the long term, this work is a contribution to the larger effort to make Stellarators commercially viable,” Lonigro said.


Breakthrough brings fusion energy device closer to realization


More information:
Nicola Lonigro et al, Stellarator coil design using cubic splines for better access from the outer side, nuclear fusion (2021). DOI: 10.1088/1741-4326/ac2ff3

Provided by Princeton Plasma Physics Laboratory

Quote: Researchers design simpler magnets for winding installations that could lead to steady-state fusion operation (2022, April 28) Retrieved April 28, 2022 from https://phys.org/news/2022-04-simpler -magnets-twisty-facilities-stationary.html

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