SELF-FIELD AC LOSSES AND CRITICAL CURRENTS IN MULTITUBE AG-BI-2223 CONDUCTORS

The purpose pf this work was to investigate the influence of different technological treatments of silver sheathed Bi-2223 tapes on the crit ical current density and the AC transport losses. The tapes were produ ced using the 'tube-in-tube' technique, by including a silver rod in t he centre of the superconducting powder during packing of the silver t ube. The aim of the process is to increase the silver to superconducto r surface area and thus also the alignment at the centre of the conduc tor ceramic core. AC transport losses were measured by means of an ele ctrical method using sinusoidally varying currents in the frequency ra nge 30-180 Hz. in this range the power losses are hysteretic. The meas ured variation in losses from those predicted by a critical state mode l is attributed to the complex geometry of superconducting regions exi sting in these tapes.