Preliminary design of the CIT cryostat

For the Compact Ignition Tokamak (CIT) to achieve its performance goals, the toroidal-field (TF) and poloidal-field (PF) coil systems must operate in a cryogenic temperature regime. The cryostat has been designed to provide and maintain this environment. The preliminary design activity is in addressing the design issues and interfaces necessary to provide a cryogenic vessel that will (1) maintain a maximum temperature differential of 8°C between the outer vessel wall and the ambient test cell conditions; (2) operate in a pressure range of +5 psig to -2 psig; (3) accommodate numerous penetrations, including cooling, diagnostic, and gravity support items; and (4) maintain a maximum leak rate of gaseous nitrogen at 1 L/s at 1 atm. Conceptually, the cryostat consists of thermal insulation sandwiched between an inner primary stainless steel pressure vessel and a thin outer stainless steel wall. Design activities have concentrated on determining the size and shape of the primary vessel wall and selecting the best candidate thermal insulation materials for future irradiation testing. The configuration development of the cryostat used to maintain the cryogenic temperature environment for the CIT is described