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Why are superconducting coils useful in tokamak designs?

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3D illustration of the interior reaction chamber of a tokamak fusion reactor, showing a large, cylindrical, metallic structure with curved walls and bright light panels. — fusion reactor A tokamak is a device used in nuclear-fusion research for magnetic confinement of plasma.

In tokamak fusion reactor designs, superconducting coils are primarily utilized to minimize power losses within the magnetic field coils.1

Because tokamaks require the generation of intense toroidal magnetic fields—often measuring several teslas—using traditional copper coils would result in significant energy dissipation due to electrical resistance. By employing superconducting materials, which exhibit a complete disappearance of electrical resistance when cooled below a specific transition temperature, engineers can maintain these powerful magnetic fields with significantly lower power consumption. This efficiency is critical for the practical operation of large-scale fusion devices, where the plasma must be confined within a vacuum chamber of substantial size.123