Over-current quench test and self-protecting behavior of a 7 T/78 mm multi-width no-insulation REBCO magnet at 4.2 K

Abstract This paper presents the over-current quench test and post-quench operation results of a 7 T 78 mm winding diameter multi-width (MW), no-insulation (NI) magnet in a bath of liquid helium at 4.2 K. The MW-NI magnet consists of 13 double-pancake (DP) coils wound with GdBCO tapes having five different widths ranging from 4.1–8.1 mm. After the magnet reached 7.3 T at 253 A, the magnet current was further increased purposely until the magnet quenched at 312 A, corresponding to a current density of 895 A mm −2 for the central DP coils of the narrowest 4.1 mm tape. The NI DP coils showed a fast magnetically coupled quench propagation from the quenched DP to the rest of the ‘healthy’ DP coils. The stored magnetic energy of 25.4 kJ was completely dissipated in 0.3 s with an average dissipation power rate of 85 kW. The post-quench magnet, operated sequentially in baths of liquid nitrogen a…