Conduction-cooled Bi-2212-Ag solenoid magnet system with 50-mm RT bore (III): Test results

摘要

High-field high-temperature superconductor (HTS) conduction-cooled magnet system is considered to be the most promising system for superconducting magnets of the next generation. In order to demonstrate the feasibility, we have been developing a Bi-2212/Ag magnet system that consists of five solenoid coils fabricated with ROtation-Symmetric Arranged Tape-in-tube wire (ROSATwire). ROSATwire shows less field anisotropy on the transport current property than conventional tape conductors; therefore ROSATwire is ideal for solenoid magnets that generate high and precise uniform magnetic field. We succeeded in the fabrication of a 3.5 km long ROSATwire, and the critical current was achieved up to 500 A at 4.2 K, 10 T. Several coils were fabricated. We tested the inner two coils in the conduction cooling system. The maximum current of dc operation test was 120 A (2.17 T). However, the maximum current of ac operation test (repeat high-sweep-rate operation test) was 160 A (2.89 T) with sweep rate of 1 A/s (0.0181 T/s). This property, the maximum current of ac operation being larger than the one of dc operation, is considered to be characteristic of HTS magnets. The operation test results and the thermal stability are also reported.