SUPERCONDUCTING CURRENT FEEDER SYSTEM FOR THE LARGE HELICAL DEVICE

A flexible superconducting (SC) busline was developed as a current fee der system for the fusion experimental device, LHD. An aluminum stabil ized NbTi/Cu compacted strand cable was developed to satisfy the fully stabilized requirements ata rated current of 31.3 kA. A pair of SC ca bles was electrically insulated and installed in a cryogenic transfer line. Measured breakdown voltage in the 77 K helium gas is 8.33 kV. Ni ne sets of SC current feeders with 45-65 m lengths are installed for L HD. The total heat loads into 80 and 4.2 K levels are estimated to be 2.12 and 1.02 kW, respectively. The SC current feeder system is design ed to maintain its rated capacities for 30 minutes, whenever the coola nts supplied to the current feeder system are accidentally stopped.