Development of Termination Methods for 2G HTS Tape Cable Conductors

Two types of mechanical contact joint termination methods for a 2G YBCO cable have been developed. Each YBCO tape of a cable is connected to a BSCCO tape while the other ends of BSCCO tapes are bundled together and soldered inside a copper tube. Another termination method uses only YBCO tapes. It has been confirmed that both joint termination methods are very useful for 2G HTS cables. Mechanical contact joint resistances between YBCO-BSCCO tapes and YBCO-YBCO tapes have been measured under various contact pressures and contact surface conditions at 77 K. Joint resistance distribution among the tapes in the cable have been also evaluated for both termination methods. These contact joint methods can be used for a demountable joint. Joint resistance is greatly reduced with increasing applied pressure especially for YBCO-YBCO joints. However, in the case of a YBCO-BSCCO joint, the BSCCO tapes may degrade at high pressure. The contact pressure should be optimized to obtain low joint resistance.