Evaluation of superconducting current feeder system for the Large Helical Device (LHD)

A superconducting (SC) current feeder system for LHD has been operated since March of 1998. It consists of 9 SC bus-lines, 9 pairs of current leads and 3 current lead cryostats, SC bus-lines have a total length of 497 m, rated current of 32 kA and withstand voltage of 5 kV under 77 K helium gas condition. After 2 years operation of this system it was demonstrated that the SC current feeder system is reliable and useful. On the basis of these operational experiences, the authors have evaluated the performance, reliability and operation cost of the SC current feeder system in comparison with nonSC type current feeder system. They have concluded that the SC current feeder system with high current capacity is more suitable than other current feeder systems such as using a water-cooled busbar, especially for large-scale SC fusion experimental devices.