Magnet Stress Limits at Full Field

At 16.84 T the coil structure, not the plasma, is the governing constraint; magnet stress is a named FOAK gate.

Where the load comes from

Electromagnetic body forces on a current-carrying conductor in a magnetic field scale with the product of current density and field, and the stored magnetic energy scales with the square of field. At a 16.84 T peak, the coil set carries loads that must be reacted by structure without letting the REBCO tape exceed its strain limit. This is the single hardest engineering problem in the breeder.

Two distinct limits

The magnet must satisfy two independent limits at once. The structural limit is set by the steel case and support that carry hoop and centering loads. The conductor limit is set by strain in the REBCO layer, which degrades critical current well before the metal yields. A design can be structurally sound and still fail the conductor limit, so both are tracked separately.

Honest status

Magnet feasibility at full field is one of the breeder's named gates. The design point is fixed, but demonstrating the coil structure holds the conductor within strain at 16.84 T is work the FOAK build must complete. We state this plainly: the field level is aggressive by design, and the stress margin is the reason the magnet program, not the plasma, paces the schedule.

Related pages break the problem into hoop stress and radial support, coil-case preload, quench protection, and radiation-driven property changes over life.

This page documents a design and simulation study, not a built machine. Construction begins Q2 2027; first-of-a-kind first tritium is targeted near 2030. Figures are computed, reproducible targets, not measurements.