INFLUENCE OF THERMAL CYCLING ON CRITICAL CURRENT OF SUPERCONDUCTING SILVER-SHEATHED HIGH-TC OXIDE WIRES

The influence of thermal cycling between room temperature and 77 K on the critical current of silver-sheathed YBaCuO and Bi(Pb)SrCaCuO superconducting composite wires and tapes was studied. The critical current was reduced by cycling when the strength of the oxide was low but not when it was high. The experimental and calculated results on the stress exerted on the oxide suggested that the reduction resulted from the tensile stress occurring on heating to room temperature, which caused fracture of the oxide when the oxide was weak.