Current feeder system for the KSTAR device

The current feeder system consisting of superconducting (SC) bus-lines, SC bus-line interface terminal, and current leads is used as the current transmission system for the KSTAR SC coils. The current lead system consists of 11 pairs of vapor-cooled leads for the PF coils and a pair of leads for the TF coils. The PF coils are operated at full currents only during a portion of the entire time. The heat loads of current leads in idle mode, when it carries no current, depend quite strongly on the using material. We have measured the heat load and temperature profile when the overload current was charged in 200 A optimum brass lead. Also, the current feeder system requires a long bus-line that must supply a large amount of current from a current lead to SC coils. We have designed a SC bus-line with NbTi cable-in-conduit conductor (CICC) to reduce Joule heating loss. The CICC is cooled with forced-flow supercritical helium (SHe). The bus-line requires higher reliability and safety than those of the SC coils of the KSTAR. The KSTAR bus-line has been designed to have an independent vacuum space and consist of SHe return and 60 K thermal shield line for shielding. To connect the bus-line with a cryostat of the KSTAR and current lead box, we have developed a prototype SC bus-line interface terminal.