Tiny tokamaks

In 2015, one of the company’s consultants, physicist Dr Alan Costley, proposed that tokamaks small enough to fit onto the back of a truck might have significant advantages over big ones in producing energy gain. The conventional view is that tokamaks have to be huge to keep the plasma hot enough for long enough, but Costley argued that small tokamaks can operate at higher plasma densities, making them more efficient without needing to get larger.

The crucial innovation, according to the Tokamak team, is the powerful magnets used to generate the fields that confine the plasma. Most tokamaks use either conventional ‘supermagnets’ made from special metal alloys, or electromagnets made from coils of superconducting materials, which lose all electrical resistance when cooled and can therefore carry large currents. But Tokamak goes one better by using so-called high-temperature superconductors (HTSs) to create the magnetic fields in their machine. These materials, discovered in the 1980s, can superconduct at higher temperatures than ordinary superconductors and so can be relatively easily cooled using liquid nitrogen. Crucially, they can also carry bigger currents and so generate stronger magnetic fields. Kingham thinks that using HTSs for nuclear fusion magnets could be their ‘killer app’.

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