Construction and Operation of an Internal Coil Device with a High Temperature Superconductor

Abstract

We have constructed and operated an internal coil device with a high temperature superconductor. Three different types of Ag-sheathed Bi-2223 tapes are employed; i.e., a high critical current tape with a low silver ratio for the main HTS coil, a 0.3wt%Mn-doped one for the persistent current switch, and a 3at%Au-doped one for the coil-leads. Cold gas helium is provided by a GM refrigerator and supplied to the coil through a check valve, and the coil current is directly excited by the external power supply through removable electrodes. It took about 11 hours to cool the coil to 21 K from room temperature, and a nominal cable current of 118 A (overall coil current: 50 kA) was achieved. A decay time constant of the persistent current is a few tens of hours. Plasma experiments in a dipole configuration have been initiated.