High-J/sub c/ silver-sheathed Bi-based superconducting wires

Abstract

Silver-sheathed BiPbSrCaCuO wires were fabricated using the powder-in-tube method. Critical current densities at 77.3 K were 4.7*10/sup 4/ A/cm/sup 2/ in a zero magnetic field, 3.1*10/sup 4/ A/cm at 0.1 T, and 1.1*10/sup 4/ A/cm/sup 2/ at 1 T. In liquid He, these wires can carry 1.03*10/sup 5/ A/cm/sup 2/ at 23 T. J/sub c/ and J/sub c/-B enhancements are due to grain-boundary improvements. Detailed investigation of J/sub c/-B characteristics in magnetic fields, especially increasing and decreasing fields, revealed that history effect behaviours caused by weak links disappeared with improvements of grain-boundary characteristics at both temperatures. It was observed that 1296 multifilamentary wires were capable of sustaining over 70% of J/sub co/ even after a strain of up to 0.66% repeated 10 times. Prototypes of coils and current leads were fabricated using 20-m-long wires. One coil showed critical currents of 54.2 A at 77.3 K and 367 A at 4.2 K. This coil generated a B/sub m/ of 142 G at 77.3 K and 876 G at 4.2 K. A prototype of a react & wind-processed coil was demonstrated using greater than 4-m-long multifilamentary wires, and it successfully produced enough magnetic field to rotate copper windings between steel cores.