Brits and Yanks join forces to make fusion magnets cool again

How cool? About -250°C

UK nuclear fusion outfit Tokamak Energy is teaming up with General Atomics in the US to work on high temperature superconducting magnets for fusion reactors and other potential industry applications.

The company, based near Oxford, recently announced a breakthrough in magnet systems for containing the high temperature fusion plasma, and now says it has signed a memorandum of understanding with California-based General Atomics to work together on the technology.

According to the pair, Tokamak Energy is bringing to the table its expertise in these high temperature superconducting magnets, while General Atomics has the manufacturing capabilities to produce large-scale magnet systems.

In 2015, General Atomics established a Magnet Technologies Center (MTC) to build the central modules for the International Thermonuclear Experimental Reactor (ITER) project, currently being slowly assembled in southern France and expected to be complete in 2025.

Tokamak Energy managing director Warrick Matthews said his company has been developing high temperature superconducting magnets for over a decade, and working with General Atomics promises to make these available for other markets besides cutting-edge fusion reaction experiments.

"The integration of these complementary capabilities promises to accelerate the development and production of HTS technologies in additional fields, such as aviation, naval, space and medical applications," he claimed in a statement.

Nuclear fusion is based on the same basic physics that happens inside stars, whereby lighter elements fuse together to form heavier ones, releasing energy in the process. High temperatures are required in order to drive the nuclei close enough together for fusion to happen, and at these temperatures the fuel becomes a plasma that needs containing in order to sustain the process, and this is where the magnets come in.

All of this is highly complex and extremely difficult to get right, of course, which led to the old joke that nuclear fusion power generation is 30 years away and always will be.

General Atomics, for example, established its first fusion research and development programs in the 1950s and claims to have upwards of five decades of experience operating tokamaks – the donut-shaped reaction chamber used to contain the super-hot plasma, from which Tokamak Energy gets its name.

And the reason for all this effort? One kilogram of fusion fuel releases the same amount of energy as burning around 10 million kilograms of coal, according to Tokamak Energy, but without the carbon dioxide emissions. If it can be made to work, the benefits are obvious as fusion power stations would deliver clean energy for towns and cities as well as industry.

But readers shouldn't be misled about the "high temperature" part of Tokamak Energy's high temperature superconducting magnets. These still need to be cooled to around -250°C (-418°F) to operate, and so they are only high temperature in comparison with most other superconducting materials, which operate close to absolute zero (-273°C or -460°F). This difference still makes them over five times more energy efficient, according to the company.

The technology centers round multi-layered tapes of material, mostly made of conductive metals but with the crucial addition of an internal coating of rare earth barium copper oxide (REBCO) superconducting material. The tapes are typically 12mm wide and less than 0.1 mm thick, and wound into coils to make superconducting magnets.

Earlier this month, Tokamak Energy welcomed Warren East, former CEO of Rolls-Royce and before that chip designer Arm, to its board as Non-Executive Director.

Last month, the company announced that its magnet technology was being shipped to the Gamma Irradiation Facility (GIF) at the US Department of Energy's Sandia Laboratories, Albuquerque, to be tested against the kind of gamma radiation it will be exposed to as part of an operating fusion reactor. ®

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