Powerful Magnets Being Researched as a Solution for Delivering Fusion Energy

Permanent magnets akin to those used on refrigerators could speed the development of fusion energy – the same energy produced by the sun and stars.

In principle, such magnets can greatly simplify the design and production of twisty fusion facilities called stellarators, according to scientists at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) and the Max Planck Institute for Plasma Physics in Greifswald, Germany. PPPL founder Lyman Spitzer Jr. invented the stellarator in the early 1950s.

Most stellarators use a set of complex twisted coils that spiral like stripes on a candy cane to produce magnetic fields that shape and control the plasma that fuels fusion reactions. Refrigerator-like permanent magnets could produce the hard part of these essential fields, the researchers say, allowing simple, non-twisted coils to produce the remaining part in place of the complex coils.

Twisted coils most expensive

“The twisted coils are the most expensive and complicated part of the stellarator and have to be manufactured to very great precision in a very complicated form,” said physicist Per Helander, head of the Stellarator Theory Division at Max Planck and lead author of a paper describing the research (link is external) in Physical Review Letters (PRL). “We are trying to ease the requirement on the coils by using permanent magnets.”

Simplifying stellarators, which run without the risk of damaging disruptions that more widely used tokamak fusion devices face, can hold great appeal. “I am extremely excited about the use of permanent magnets to shape the plasma in stellarators,” said Steve Cowley, PPPL director and a coauthor of the paper. “It leads to much simpler engineering design.”

Fusion, the power that drives the sun and stars, combines light elements in the form of plasma — the hot, charged state of matter composed of free electrons and atomic nuclei — that generates massive amounts of energy. Scientists around the world are using tokamaks, stellarators, and other facilities in the effort to create and control fusion on Earth for a virtually inexhaustible supply of safe and clean power to generate electricity.

The novel idea for permanent magnets is an offshoot of a science fair project that Jonathan Zarnstorff, the son of PPPL Chief Scientist Michael Zarnstorff, a coauthor of the paper, put together in junior high school. Jonathan wanted to build a rail gun, a device that usually uses high-voltage current to generate a magnetic field that can fire a projectile. But the high-voltage current would be dangerous to use in a classroom.