RE-Ba-Cu-O bulk superconductors fabricated by melt-process have the distinctive feature of a high critical current density of 77K in strong magnetic fields, and consequently are expected to be used for next-generation current leads. We have made proto-type of RE-Ba-Cu-O bulk current leads and investigated the transport properties, the heat leak, the thermal cycle toughness and the mechanical properties. This paper presents the structure of the bulk current leads and the test results obtained so far.
High temperature superconductors (HTS) have been successfully applied to current leads. Low thermal conductivity and high critical current density (Jc) are the characteristics desired for such applications. We have developed Y-Ba-Cu-O current leads for MAGLEV. The mechanical properties of Y-Ba-Cu-O bulk superconductors are improved by epoxy resin impregnation. In order to reduce the stress caused by the relative displacement between the inner vessel and the radiation shielding plate of superconducting magnet, flexible copper cables were connected in series with a Y-Ba-Cu-O current lead. We were able to feed a current up to 1000 A at 77 K, and then we measured V-I characteristics. The present results show that the bulk Y-Ba-Cu-O can be applied to the current leads for MAGLEV.