COOLDOWN PERFORMANCE OF AN INNER VERTICAL FIELD-COIL FOR THE LARGE HELICAL DEVICE

A single cooldown test of an Inner Vertical (IV) field coil for the La rge Helical Device (LHD) was started on February 1 of 1995, and the su perconducting transition of the coil pms confirmed on February 23. The coil is a forced-flow type using a cable-in-conduit (CIC) conductor a nd weighing about 16 tons. The total cooldown time was about 250 hours not including suspended time, Pressure drop characteristics were meas ured during the cooldown, and the same results were obtained as the RE D coil previously tested. The cooldown time could be reduced by indire ct cooling using stainless steel sleeves with cooling pipes The indire ct cooling is effective for the CIC conductor which has no subchannel because otherwise an adequate mass flow cannot de obtained due to a hi gh pressure drop in the high temperature region. The temperature distr ibution in the vertical direction was also examined during the indirec t cooling.