Design and characteristic measurements of current lead for 3MJ SMES

The design of a superconducting coil and cryostat for 3MJ class SMES was completed in 2002. Before assembling the full system, some important parts were fabricated in order to find out whether their operating properties were fit for our 3MJ SMES or not. The assembling process will be performed in 2003. The 3MJ SMES will be operated at 1000 amps in the cryogenic environment of 4.2 K. So, it is essential to minimize the heat load from room temperature and to optimize its ohmic heating. A bundle of brass sheets with optimized length/area ratio was used for the metal part of the current lead and it is connected to HTS current lead in series. Two GM cryocooler sinks out the heat load and also the ohmic heating of the current lead which is located in vacuum chamber of the cryostat. Cold head of the cryocooler which is extended to the HTS lead with layered OFHC sheets keeps the temperature under the critical temperature of the HTS lead. We performed some experiments to examine the thermal and electrical properties of the current lead. In this paper, the fabrication process and test results of the current lead will be introduced in detail.