In the field of nuclear fusion some are going big with their pursuit of clean, inexhaustible energy, like those piecing together the seven-story building to house ITER, the world's largest tokamak reactor. Others, meanwhile, are working on more compact and affordable designs in an attempt to edge the technology forward. A new breakthrough from MIT scientists demonstrates how some of the biggest advances might just come from these projects that are smaller in stature, with the team revealing a record-setting superconductive magnet, the most powerful of its type in the world.

The development of the novel magnet was led by MIT scientists working on an experimental fusion reactor design first revealed back in 2015. Called ARC (affordable, robust, compact), the reactor is a doughnut-shaped tokamak, which like ITER seeks to recreate the conditions inside our Sun that sees hydrogen atoms fuse together under extreme heat and pressure to release massive amounts of clean energy. ARC, however, will be around half the size of ITER, with a radius of 3.3 m (10.8 ft).

Whether it is ITER, ARC or fusion reactors that twist and turn like the Wendelstein 7-X stellarator in Germany, the physics and overarching aim is largely the same. Hydrogen isotopes deuterium and tritium are introduced into the chamber and superheated to form a swirling plasma, which needs to then be suspended and prevented from veering into the walls, or anything solid. And to achieve this, magnets are key.

Whether it is the misaligned magnetic coils at work in the Wendelstein 7-X, or the neat, repeating sequence of magnetic coils seen in conventional tokamaks, all are designed to generate magnetic fields so intense that they can pin the plasma in place long enough for the fusion reactions to occur. But the scientists working on ARC have been pursuing a magnet technology with a key point of difference.

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