Operational status of the superconducting system for LHD

Large Helical Device (LHD) is a heliotron-type experimental fusion device which has the capability of confining current-less and steady-state plasma. The primary feature on the engineering aspect of LHD is using superconducting (SC) coils for magnetic confinement: two pool boiling helical coils (111, 112) and three pairs of forced-flow poloidal coils (IV, IS, OV). These coils are connected to the power supplies by SC bus-lines. Five plasma experimental campaigns have been performed successfully in,four years from 1998. The fifth operation cycle started in August 2001 and finished in March 2002. We have succeeded to obtain high plasma parameters such as 10 keV. of electron temperature, 5 keV of ion temperature and beta value of 3.2%. The operational histories of the SC coils, the SC bus-lines and the cryogenic system have been demonstrating high reliability of the large scale SC system. The operational status and the results of device engineering experiments are summarized.