REBCO High-Temperature Superconducting Magnets
REBCO high-temperature superconductor lets a compact tokamak reach very high magnetic field. Kronos MetroVolt runs a 24.6 T peak-field graded winding pack.
- Material
- Rare-earth barium copper oxide (REBCO) HTS tape
- On-axis field
- B₀ = 6.0 T
- Peak conductor field
- 24.6 T at R_c = 1.40 m (B_peak/B₀ = 5)
- Strain margin
- 0.252% peak vs 0.40% limit (1.59×)
REBCO (rare-earth barium copper oxide) is a high-temperature superconductor manufactured as a coated tape. Its ability to carry current at very high magnetic field — far beyond conventional low-temperature superconductors like Nb₃Sn — is what makes a compact high-field tokamak possible. Fusion power density scales steeply with magnetic field, so a stronger magnet lets a smaller machine reach the same performance.
The Kronos MetroVolt magnet system produces an on-axis field of B₀ = 6.0 T and a peak conductor field of 24.6 T on the inboard leg at Rc = 1.40 m — a peak-to-axis ratio of 5. The graded, demountable winding pack runs at 0.252% peak strain against a 0.40% irreversible limit, a 1.59× margin at the operating point.
For context on where 24.6 T sits relative to demonstrated hardware, and how the strain clamp defends it, see the magnet-system deep-dive.