We have designed and tested superconducting current leads using Bi ( 2223 ) oxide supercon ducting bulk material. Bi (2223) leads were supported by a glass fiber-reinforced plastic (GFRP) which was chosen in consideration of thermal conductivity and thermal expansion. The thermal conductivity of GFRP was one order of magnitude less than that of Bi (2223) bulk material. The difference of the thermal expansion between GFRP and Bi (2223) bulk material was less than 0.1% in the temperature range

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... m 293K to 20K. The critical current of the Bi (2223) leads did not change by the heat cycle from room temperature to 77K. The current lead was cooled by a two-stage Gifford-McMahon cycle refrigerator and operated in a conduction-cooled superconduct ing magnet successfully.