Test results of superconducting AC magnets for magnetic refrigeration experiment

Magnetic refrigeration can be achieved by cycling the magnetic field while leaving the magnetic material and the magnet stationary to avoid the large electromagnetic force problem. Two superconducting magnets were used to test this approach. First we reconfigured a force-cooled cable-in-conduit magnet to operate with liquid rather than supercritical helium. Limited by the available power supply voltage, the fastest charging rate achieved was 10 s to 5 T. A second low loss magnet was acquired for operation to 7 T with a 6-s duty cycle. This is a bath-cooled magnet with potted sub-coils. The conductor is a 20-strand Rutherford-type cable with Ebanol insulation on each strand. This magnet quenched prematurely at 6.4 T. It was charge rate sensitive and the fastest charging rate achieved was 10 s to 5.8 T