Grain-aligned YBCO superconducting current leads for conduction-cooled applications

Grain-aligned YBCO superconductors have been developed for use in a conduction-cooled, cryogen-free superconducting magnet application. A magnetic alignment technique has been used to orient the c-axis of the YBCO grains. Current leads 0.3*1.4*6.4 cm were fabricated and thermally connected between the first and second stage of a Gifford-McMahon cryocooler. The heat conduction down the leads was determined from a load map of the cryocooler. With operating temperatures of 40 K on the first stage and 10 K on the second stage, the measured heat leak was 0.15 W/lead. The YBCO current leads were used to power a conduction-cooled Nb/sub 3/Sn magnet at 10 K to 250 A. Test results for the YBCO leads are reported.>