REBCO High-Temperature-Superconductor Magnets

The breeder's field is set by REBCO coated-conductor magnets that produce a 16.84 T peak on the conductor and 8 T on axis.

Why REBCO

The breeder (Hyperion) is a compact spherical tokamak with major radius R0 near 1.2 m and aspect ratio A of 2.5. A small machine can only reach a useful confinement regime if it carries a high field on a thin center stack. That is a job for REBCO (rare-earth barium copper oxide) high-temperature superconductor, which sustains high critical current at high field where low-temperature niobium conductors fall off.

The design point is a 16.84 T peak field on the conductor and roughly 8 T on axis, supporting a plasma current of 9.66 MA. The gap between the two numbers is geometric: field falls roughly as 1/R from the center stack outward, so the conductor sees far more than the plasma does.

The engineering consequence

High field buys performance but sets the hardest structural problem in the machine. Electromagnetic loads scale with the square of field, so a 16.84 T coil set is dominated by how its structure holds the conductor in place. REBCO magnet feasibility, not plasma physics, is the pacing item for the breeder, and it is one of the named gates the FOAK build must clear.

What is settled and what is not

The conductor choice, field level, and current are frozen design values. The open engineering question is the coil structure and stress margin at full field, addressed across the magnet pages in this section. REBCO is commercially available as coated-conductor tape, but qualifying it to a fusion magnet's combined field, strain, and radiation environment is a supply and manufacturing program, not an off-the-shelf purchase.

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.