Development of high temperature superconducting current feeders for a large-scale superconducting experimental fusion system

The National Institute for Fusion Science (NIFS), in collaboration with universities and laboratories in Japan, the Forschungszentrum Karlsruhe (FZK) and the Max-Planck Institut fur Plasma Physik (IPP) in Germany, is planning to develop high temperature superconducting (HTS) current feeders for large-scale superconducting coils. Two programs are being progressed: one is a current feedthrough for superfluid helium (He II) cooled superconducting coils; the other is current leads for experimental fusion system. The paper describes the present status of the two programs, including joint experiments of a 20 kA Bi-2223 current lead developed by FZK and development of a prototype YBCO bulk current feedthrough for He II cooled superconducting coils. In addition, the test results of Bi-2212 tubes fabricated by diffusion process, applicable to HTS current leads, are described Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8/.