Hyperion Toroidal-Field Coils
The toroidal-field coils produce the field that circles the torus, confining the plasma at 8 T on axis and 16.84 T peak.
Field around the ring
The toroidal-field coils, or TF coils, are the D-shaped magnets that wrap around the plasma the short way to produce a field that runs the long way around the torus. This toroidal field is the backbone of tokamak confinement: it stops charged particles from drifting straight out and, combined with the plasma current, gives the twisted field lines that hold the plasma.
Field values
- 8 T on the plasma axis, the field the confinement is designed around.
- 16.84 T peak on the conductor itself, on the inboard leg where the coils crowd toward the machine axis.
- Wound from REBCO high-temperature superconductor.
The inboard problem
Because Hyperion is spherical, the inboard legs of the TF coils must pass through the very tight center stack. That is where the field peaks and where the conductor is most stressed, both magnetically and mechanically. The gap between the 8 T on-axis figure and the 16.84 T peak is exactly the price of the compact geometry: field falls off with radius, so the conductor near the axis sees far more than the plasma does.
In the model
The TF coils are selectable as a set and, for signed-in users, individually. A field callout attaches the on-axis and peak values to the geometry, so you can see where on the D-shape the peak occurs. The cutaway shows the inboard legs bundled in the center stack and the outboard legs sweeping around the vessel.
Loads and structure
TF coils try to spring toward each other and toward the machine axis under their own field, so they need heavy support structure. See the magnet support structure, and the REBCO magnet model for the conductor.