Experimental apparatus for critical current measurement above 5 K using Bi-based oxide current leads

Experimental apparatus for the measurement of temperature dependence of critical current within a strong magnetic field has been developed. Samples, which are tested by the four probe method are cooled by a Gifford-McMahon (GM) type cryocooler to the lowest temperature of 5 K. The sample holder has a diameter of 70 mm and a height of 70 mm. Transport currents, up to 150 A, are supplied to two samples through Bi-based oxide superconducting current leads. An external magnetic field of up to 15 T, which is applied to the samples perpendicular to the sample axis, is generated by a water cooled single Bitter magnet with a room temperature bore of 82 mm. As a performance test, the critical current properties of a silver clad Bi-based oxide tape have been measured at 5.5 K, 30 K and 50 K within a magnetic field up to 15 T. This experiment has demonstrated the validity of this experimental apparatus.