Fabrication and Characterization of 3-T/102-mm RT Bore Magnet Using 2nd Generation (2G) HTS Wire With Conducting Cooling Method

A conduction-cooled high-temperature superconducting magnet using 2nd generation HTS wire, which has a room-temperature bore 102 mm in diameter, has been developed and tested up to 3 T with the operating temperature of 20 K. The magnet consists of 22 double pancake coils (DPCs) with an inner diameter of 140 mm and outer diameter of 182 mm. Twenty-two double pancake coils were tested separately at 77 K for checking the IV-curve. Selected DPCs were resistively connected by HTS tape (Splice joint), and an assembled magnet coil with the size of 182.5 mm diameter and 242 mm in height was conduction cooled by a two-stage Gifford-McMahon cryo-cooler to 20 K. Current, voltage, and field strength were measured as a function of time with various ramping up and down conditions. The resulting performance data of the assembled magnet agreed well with the expectation from FEM simulation. The aimed field homogeneity of 0.1% in 10 mm diameter sphere volume was proved when operating current was 141.6 A at 20 K with central magnetic field intensity of 2.9975 T by hall sensor. The magnetic flux density at center showed nonlinear dependence with ramping current within the range of 0.05 A/sec ~0.15 A/sec because of charging delay. However, saturated magnetic flux density showed the same value of 2.9975 T regardless of ramping rate.