Quench behavior of a no-insulation coil wound with stainless steel cladding REBCO tape at 4.2 K

A single pancake no-insulation (NI) coil was wound in a hermetic way with REBCO tape having a thin (1–2 μ m) cladding layer of stainless steel. With an electric heater embedded at the innermost turn of the coil, heater-induced quench tests were performed under a background field of 15 T in a bath of liquid helium at 4.2 K. Despite the large average contact surface resistance of 1.63 m Ω cm 2 , > 20 times larger than those of pure NI coils, ‘thermal recovery’ was observed at a coil current density ( J e ) below 700 A mm −2 mainly due to the local current sharing. The coil experienced nine consecutive ‘thermal runaway’ quenches at J e of 700–820 A mm −2 (power supply limit), yet no discernible coil degradation or damage was observed. The results demonstrated that the stainless steel cladding REBCO tape may be effective at reducing the charging delay of high field NI REBCO magnets without sacrificing the self-protecting feature.