Performance Test for a Rectifier-type Flux Pump Cooled by a Refrigerator

A half-wave rectifier-type flux pump cooled by a refrigerator has been built and its performance tested. The flux pump is composed of four elements as follows: a transformer, two thermal superconducting switches and a load coil (NbTi superconducting magnet). The transformer consists of an iron core, a primary winding with copper wire and a secondary winding with a NbTi/Cu-30wt% Ni superconductor. The primary winding and iron core of the transformer are cooled at the 1st stage of a 4K two-stage Gifford-McMahon (G-M) refrigerator. The load coil, superconducting switch and secondary winding are cooled by the 2nd stage of the G-M refrigerator. The load coil was cooled from room temperature to 3.8K in about 4h, indicating that the structure of the flux pump has no effect on G-M refrigerator cooling performance. The flux pump was operated at a speed of 1/7 [cycle/s]. The load coil current attained 57.7A in about 90min. Persistent mode operation has also been achieved.