Toroidal Field Magnet

The toroidal-field magnet produces the dominant field that confines the plasma the long way around the torus, peaking at 16.84 T on the conductor.

The confining field

The toroidal field (TF) is the primary magnetic field of a tokamak: it runs the long way around the torus and, combined with the field from the plasma current, gives field lines their helical twist. Hyperion's TF system is built from REBCO high-temperature superconductor and reaches a peak field of 16.84 T on the conductor, delivering roughly 8 T on the plasma axis.

Geometry in a spherical tokamak

Each TF coil is a loop whose inboard leg runs through the center stack and whose outboard leg arcs around the plasma. Because the inboard legs are crowded onto a slender center post, the field is far stronger there than at the plasma, which is why 16.84 T on the conductor yields about 8 T on axis. The coils are pulled toward the machine axis by centering forces that the center stack must react.

Field strength and machine size

Field strength trades directly against machine size: high TF is what lets Hyperion confine an 85.0 MW plasma at R0 1.2 m. The TF magnet therefore sets the compactness of the whole design, and its conductor, structure, and cooling are among the pacing engineering items. Its behavior under neutron irradiation near the center post is an open materials question tracked through the design phase.

• Dominant confining field, the long way around the torus
• 16.84 T peak on conductor, ~8 T on plasma axis
• REBCO conductor; centering forces reacted by the center stack

This page describes a design and simulation study, not a built machine. Construction begins Q2 2027; first-of-a-kind first tritium is targeted near 2030.