The Spherical Tokamak (HYPERION)

The breeder is a spherical tokamak because that geometry buys the most plasma pressure per tesla — the key to a compact, economical neutron source.

A spherical tokamak squeezes the hole in the doughnut almost shut, running at low aspect ratio (A = 2.5). That geometry naturally supports strong elongation (κ = 2.0) and high beta, so it holds more plasma pressure for a given magnetic field than a conventional tokamak.

HYPERION runs 9.86 MA of plasma current in an 1.2 m major radius machine, with a peak field of 16.84 T and negative triangularity (δ = -0.30) to tame the plasma edge. Its product is not electricity but neutrons and tritium — the fuel and the driver for the burner economy.