Design and testing of current leads made from AgAu sheathed Bi-2223 superconducting wires

Abstract A pair of current leads consisting of spirally assembled AgAu sheathed Bi-2223 superconducting wires was fabricated. The heat leak into liquid helium (LHe) was measured in a vapour cooler under a self-cooling condition. The heat cycle of the fabricated superconducting current lead had no influence on the characteristics of both superconducting and joint parts. The measured heat leaks were 0.06 W per lead at 0A and 0.13 W per lead at 1000 A; these are about one-tenth those of conventional copper lead. About half of the heat leak at 1000 A involved resistive heat load caused by the joint resistance of the terminal connected to the short lead for short-circuit use when immersed in LHe.