CORC^® wires allowing bending to 20 mm radius with 97.5% retention in critical current and having an engineering current density of 530 A mm⁻² at 20 T

Abstract

Low-inductance, high-field insert solenoid magnets and 20 T dipole magnets for particle accelerators require flexible cables, wound from high-temperature superconductors (HTS) such as RE-Ba2Cu3O7-δ (REBCO) coated conductors, that allow bending to a 20 mm radius without significant degradation in performance. They require an operating current of at least 5 kA and a high engineering current density (Je) exceeding 500 A/mm2 at 20 T. HTS cable technologies that target such demanding magnet applications so far haven’t been able to meet the combination of these requirements.
Here we present the development of the next generation of Conductor on Round Core (CORC®) wires that improves their bending flexibility by factor of more than 2 compared to previous generation CORC® wires. CORC® wires now allow for a bending radius of 20 mm with only 2 – 3 % performance degradation. They allow bending to a radius of 15 mm with a performance retention of 83.5 %. The performance of 30-tape CORC® wires wound from 2 mm wide REBCO tapes from SuperPower Inc, SuperOx and Shanghai Superconductor Technologies was measured at magnetic fields up to 12 T. The overall performance at high magnetic fields of the next generation of CORC® wires improved by a factor of 1.5 – 1.8, depending on the REBCO tape manufacturer. CORC® wires wound from production REBCO tapes achieved a new record Je of 751 A/mm2 at a current of 8.3 kA at 12 T, and a Je of 530 A/mm2 at a current of 5.8 kA when extrapolated to 20 T.