Thermal and Mechanical Analysis of a U-Neck Vacuum Barrier

A vacuum barrier is necessary in the superconducting tokamak, to separate the high reliability main cryostat from the vacuum environments of other systems, like the cryogenic system, which is easier to leak due to the numerous openings for the control and safety valves. Because the vacuum barrier must have a separate plate between the two vacuum environments, all the cryogenic pipelines have to get through the plate with proper sealing, so there is a direct connection from the cryogenic pipeline to the outer duct, that is exposed to the atmosphere and at room temperature. Therefore, the heat load through the vacuum barrier to the cryogenic system must be carefully dealt with. Meanwhile, the vacuum barrier may face a pressure difference between the two sides in some cases, like a leakage accident, so the vacuum barrier should withstand this situation. This paper describes the thermal and mechanical analysis of a U-neck vacuum barrier, which is good at reducting the heat load to the cryogenic system, and is capable to resist the pressure from one side.