Fabrication of Bi-2223 HTS magnet with a superconducting switch

A test pancake magnet, equipped with persistent superconducting switch, was fabricated with Bi-2223/Ag-Mg tape. The magnet was operated in persistent mode at 20 and 77 K. For large operating currents that forces the magnet to operate in the flux flow range, the field decays is exponentially with time. A simple circuit model is used to compute field decay time constants. It was also found that Pb-Sn solder joints are unsuitable for persistent mode operation.