Fabrication of 1 kA class oxide superconducting transformer cooled by cryocooler for AC transport measurement

An AC current source of 1000 A class for AC transport measurements was designed and fabricated with using an oxide superconducting current transformer. Two cryocoolers were installed for cooling the transformer and a sample holder separately. A parallel conductor composed of six tapes was wound for a secondary winding and a transposition was performed to make the current distribution uniform in the parallel conductor. Temperatures of the transformer and the sample holder were controlled in the range of 35-50 and 25-77 K, respectively. The peak current in the secondary winding was over 1000 A in the frequency range of 1-75 Hz, when the primary peak current was 14 A.