Thermal behavior of a solid nitrogen impregnated high-temperature superconducting pancake test coil under transient heating

This paper presents experimental and analytical results on a solid nitrogen impregnated high-temperature superconducting (HTS) test coil under transient heating. The test coil is a 1-layer, 10-turn single-pancake wound with Bi2223/Ag composite tape, 9-mm wide and 0.5-mm thick, with an average winding diameter of 105 mm. The solid nitrogen impregnating the 0.38-mm turn-to-turn radial gaps in the winding enhances the winding's overall heat capacity significantly in the operating temperature range 30-40 K and thereby limits the test coil's temperature rise when it is subjected to overcurrent pulses. The presence of solid nitrogen within the winding improves stability against fault-mode overcurrent pulses for HTS magnets used in electric power devices.