Fabrication and Characterization of 4-T/203 mm RT Bore 2G HTS Magnet With No-Insulation Method

We fabricated superconducting magnet using second-generation (2G) high-temperature superconducting wire by SuNAM. Magnetic field strength at the center is 4 T, and room temperature bore diameter is 203 mm. The magnet consists of 30 double pancake coils (DPCs) with the inner diameter of 245 mm and outer diameter of 297 mm. All double pancakes were wound by no-insulation method and performance were tested separately before assemble. Tested DPCs were resistively connected by HTS tape(splice joint), and assembled coil was conduction cooled by a two-stage Gifford-McMahon cryo-cooler to the operating temperature of 8 K. The size of magnet is 452 mm in height. Current, voltage, and field strength were measured as a function of time with various ramping up and down conditions and results were compared with the simulated behavior. The coil generates 4 T when operating current ramped to 205 A by 0.03 A/s without quench. Initial cool down time was 72 h and the measure field homogeneity in 10 mm DSV was 0.015% and 0.012% in radial axis and vertical axis, respectively. The results showed that no-insulation winding method is a possible option for making compact magnet coil with sufficient structural integrity, thermal and electrical stability at the same time. The magnet showed quench at field strength of 4.49 T when ramped with 0.2 A/s to 235 A. The magnet showed same performance after recovery from quench.