Electrical characterization of high temperature superconductors as a function of temperature

Abstract

The critical currents of silver sheathed multifilamentary Bi 2Sr 2Ca2 Cu3010 (BSCCO- 2223/Ag) tapes at temperatures ranging from 77 K to 110 K were measured using a typical four-terminal technique for two different BSCCO-2223/Ag tapes manufactured by Vacuumschmelze (VAC). The critical currents for the two VAC samples were measured as a function of magnetic field strength. The critical current of each sample was well described by the generalized Kim model. The critical current was also measured as a function of angle of the magnetic field with respect to the plane of the tapes, in all cases perpendicular to the transport current flow. Both samples displayed a high sensitivity to the magnetic field orientation with the largest critical currents measured when the magnetic field was in-plane with the broad face of the tapes. The current ramp rate effect on the critical current was investigated and showed no significant effect on the critical current measurements for ramp speeds between 6 A/min and 120 A/min. The energy dissipation or AC losses as a function of peak AC magnetic field, magnetic field sweep frequency, and transport current for a VAC sample and a sample manufactured by IGC - Advanced Superconductors (IGC) were measured at 77 K. The losses were measured using a pick up coil with a lock-in amplifier to measure the magnetization of the superconducting samples. The AC losses of both samples displayed complete electromagnetic coupling of the superconducting filaments at magnetic sweep frequencies of approximately 0.1 Hz. These results are consistent with results measured at magnetic field sweep frequencies of 60 Hz.