High-Tc Oxide Current Leads and Superconducting Magnet Using No Liquid Helium
We applied Bi-based oxide superconducting bulk for use as current leads in a cryocoolercooled superconducting magnet that does not use liquid helium. The bulk has a composition of (Bi + Pb):Sr:Ca:Cu = 2:2:2:3 and is utilized in the form of thin-walled sintered cylindrical tubes. The critical current and the critical current density of the bulk under a self-magnetic field at 77 K are 1100 A and 1200 A/cm2, respectively.
Within the cryocooler-cooled superconducting magnet unit, conductive cooling of a (Nb,Ti)3Sn coil is performed with a Gifford-McMahon type (G-M) cryocooler. The Bi-based oxide bulk is used for current leads. The magnet is capable of generating, at a current of 400 A, a steady magnetic field of 4 T in a room-temperature 38 mm diameter bore. Heat leakage at this time is less than 0.4 W. This marks the first successful application of high-Tc oxide superconducting bulk leads to such a magnet system.
KeywordsLiquid Helium Critical Current Density Stray Field Heat Leakage Coil Temperature
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