Performance test of a refrigerator cooled magnet fabricated using Bi-2212 multilayer superconducting tapes

A stacked pancake coil was fabricated by Ag-alloy sheathed Bi-2212 multilayer tapes and tested using a refrigerator. The magnet consisted of ten double pancakes wound with 100 m class tapes. The I/sub c/ values of the tapes varied from 80 A to 150 A at 4.2 K and 10 T because of the scattering of the thickness in the superconducting layers. The magnet carried a critical current of 57 A at 12 K and generated B/sub max/ of 1.4 T in a 60 mm bore. At 12 K, the magnet could operate with an operating current of 45 A which corresponded to about 80% of I/sub c/. Thermal runaway was not observed even with a ramp rate of 10 T/min.