KSTAR vacuum vessel thermal shield analysis

The KSTAR Vacuum vessel thermal shield is composed of multilayer insulation (MLI), cryopanel and supports. One of the major design parameters for the design of thermal shield cryopanel and supports is the eddy current induced during plasma disruption. The eddy current creates joule heating as well as electromagnetic (EM) loads combining with magnetic fields. Since the cryopanel should be maintained at a cryogenic temperature lower than 80 K, even a small amount of joule heating may play an important role in increasing the cyropanel temperature. Also the EM loads are very critical mechanical forces for the design of structure of the thermal shield, especially for the supports. Joule heating and EM loads on the vacuum vessel thermal shield during plasma disruption were calculated to provide the design requirement of the thermal shield. Based on the joule heating and EM loads, the structural and thermal stress analyses were performed for the assessment of the structural robustness of the vacuum vessel thermal shield. It was found that the effect of joule heating on the thermal shield design is minimal, but the EM loads are important for the design of cryopanel as well as supports. The optimal number and size of supports were determined.