Measurements of critical currents in a sintered ring of YBa 2Cu 3O 7 with magnetically induced transport currents

Abstract

We attempted to measure electromagnetically transport critical currents in a ceramic ring of YBa 2Cu 3O 7 made by usual sintering technique from YBa 2Cu 3O 7 powder through a dry process, by observing saturations of currents to shield an inner region of the ring from pulse fields of a solenoid which was cooled down together with the specimen by a G-M cryo-cooler in the temperature range from its critical temperature to 30 K. The estimated values exceed 10 000 A/cm 2 at 77 K. The oscilloscope traces of the output of the search coil in the center of the ring indicate a possibility that the shielding currents consist of two components having different superconducting characteristics. The degradation of the critical currents with increasing sintering time was observed and the growth of the grains was also observed by SEM at each sintered state.