Defect Tolerant High-Temperature Superconducting Cable for the Central Solenoid of Compact Fusion Reactor

The future compact fusion reactors, will feature very high, >16 tesla, magnetic fields, which can be only created by magnet coils wound with the second generation (2G) superconducting wire. The 2G wires are currently manufactured with a thin (1-2 μm) YBCO layer deposited on a ~100 μm thick metal substrate. The substrate makes up a considerable portion of the cross-section, thus reducing the engineering current density. It also prevents effective inter-filament current sharing, and the wide tape geometry is responsible for high magnetization loss. We report on the recent progress in the development of a new type of high-temperature superconducting cable architecture for the central solenoid of a high-field fusion reactor. The new architecture combines two recent innovations: (i) Reduction of AC loss by bundling narrow, 1-2 mm, exfoliated YBCO filaments into a cable, (ii) continuous winding and parallel slicing technologies, which eliminate labor-intensive and expensive handling of narrow filaments, critical for the central solenoid, which operates under pulsed load.