REBCO High-Temperature Superconducting Magnets
REBCO high-temperature superconductor lets a compact tokamak reach very high magnetic field. Kronos MetroVolt runs a 24.42 T peak-field graded winding pack.
- Material
- Rare-earth barium copper oxide (REBCO) HTS tape
- On-axis field
- B₀ = 6.37 T
- Peak conductor field
- 24.42 T at R_c = 1.50 m (B_peak/B₀ ≈ 3.8)
- Strain margin
- 0.252% peak vs 0.40% limit (1.59×, at the 24.6 T Mode-C-era stress basis)
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 = 6.37 T and a peak conductor field of 24.42 T on the inboard leg at Rc = 1.50 m — exactly the demonstrated single-coil field, at a peak-to-axis ratio of about 3.8 (the ratified Mode-D basis, 24 July 2026). The graded, demountable winding pack runs at 0.252% peak strain against a 0.40% irreversible limit — a 1.59× margin, carried at the 24.6 T Mode-C-era stress basis that bounds the operating point.
For context on where 24.42 T sits relative to demonstrated hardware, and how the strain clamp defends it, see the magnet-system deep-dive.