Cooling Performance and Thermal Characteristics of No-Insulation GdBCO Magnet Cooled by a Mixed Cryogen Cooling System

This paper reports the cooling performance and thermal characteristics of a GdBCO magnet cooled by a mixed cryogen cooling system employing a mixture of solid nitrogen and a small amount of liquid neon. The test magnet, composed of four sets of no-insulation (NI) GdBCO double-pancake racetrack coils, was designed to have enhanced magnet stability. During cooldown to the operating temperature of 26 K, the temperature difference within the magnet was less than ∼0.5 K, an indication that the cooling performance was excellent due to the presence of solid nitrogen coupled with a large heat capacity. In repetitive heating tests at 26 K, the peak temperatures of the magnet when cooled by the mixed cryogen were much lower than when cooled by solid nitrogen alone. This was because liquid neon in the mixed cryogen serves as an effective heat exchanger and enhances the heat transfer between the magnet and the solid nitrogen. During charge testing, the magnet could successfully generate the target center field of 2 T at the operating current of 130 A. The test results demonstrated the feasibility of the NI GdBCO magnet in a mixed cryogen cooling system for the development of reliable next-generation portable superconducting applications.