High-Jc silver-sheathed Bi-based superconducting wires

Silver-sheathed BiPbSrCaCuO wires were fabricated using the powder-in-tube method. Critical current densities at 77.3 K were 4.7×10⁴ A/cm² in a zero magnetic field, 3.1×10⁴ A/cm at 0.1 T, and 1.1×10⁴ A/cm² at 1 T. In liquid He, these wires can carry 1.03×10⁵ A/cm² at 23 T. J_c and J _c-B enhancements are due to grain-boundary improvements. Detailed investigation of J_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_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_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