HIGH-JC SILVER-SHEATHED BI-BASED SUPERCONDUCTING WIRES

Silver-sheathed BiPbSrCaCuO wires were fabricated through the powder-in-tube method. Jc-B properties, microstructures and Jc-strain properties were evaluated. Prototypes of coils and current leads were made and tested successfully. Critical current densities at 77.3 K were 4.7 x 10(4) A/cm2 in a zero magnetic field, 3.1 x 10(4) A/cm2 at 0.1 Tesla and 1.1 x 10(4) A/cm2 at 1 Tesla. In liquid He, 4.2 K, these wires can carry 1.03 x 10(5) A/cm2 at 23 Tesla. Jc and Jc-B enhancements are due to grain boundary improvements. Detailed investigation of Jc-B characteristics in magnetic fields, especially increasing and decreasing fields, revealed that history effect behaviors caused by weak links disappeared with improvements of grain boundary characteristics at both temperatures. 1296 multifilamentary wires were shown to sustain over 70 % of Jco even after a strain of up to 0.66 % repeated 10 times. These results show future possibilities of flexible cables and react & wind-processed magnets. 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 B(m) of 142 Gauss at 77.3 K and 876 Gauss at 4.2 K. Critical current properties were investigated with back-up fields of up to 990 Gauss at 77.3 K and 3.7 Tesla at 4.2 K. A prototype of react & wind-processed coil was demonstrated using over 4 m long multifilamentary wires, and successfully produced enough magnetic field to rotate copper windings between steel cores. 50 cm long current leads were made and tested at 77.3 K and proved to carry 242 A, showing overall current density of 2000 A/cm2 including silver-sheath.