Operation of Wax-Impregnated GdBCO Layer-Wound Coil Using Cryocoolers

RE-Ba-Cu-O (REBCO) high-temperature superconducting conductors have the advantage of high critical current density in a magnetic field above 10 T as well as tolerance to high tensile stress. REBCO high-temperature superconducting coils are expected to be applied to superconducting magnets using cryocoolers. While epoxy-resin-impregnated superconducting coils are considered to be appropriate for superconducting magnets using cryocoolers because the impregnation provides sufficient thermal conductivity, the degradation of epoxy-resin-impregnated REBCO coils due to extremely low nominal cleavage strength is a serious problem. This problem is negligible for wax (paraffin)-impregnated REBCO coils. A wax-impregnated GdBCO layer-wound coil using cryocoolers was successfully operated at a current between $-$ 300 and 300 A.