Design of port structure between vacuum vessel and cryostat in JT-60SA

Abstract

Port structure in the JT-60SA is designed to access vacuum vessel inside for vacuum exhausts, plasma heating systems and diagnostics etc. from cryostat outside. The port consists of a rectangular pipe, bellows and additional materials such as electrical insulations and connection parts for onsite assembly. The vacuum space as the thermal insulation for superconducting coils is penetrated by the port as the vacuum interfaces between the vacuum vessel and the cryostat so that port structure is required to be structurally integrated against plasma and baking operations and accidental events. This structure must be installed in narrow space, and electrical insulation is functionally designed to avoid the unexpected large eddy current loop. This paper reports the design of port connection structure for the assembly. Port connection parts “Port Extension” and “adjustable plate” are introduced to absorb vertical of 10 mm, toroidal of 8 mm, and port axial of 10 mm error due to the manufacturing and assembly. The bellows are expected to absorb relative displacement of 39 mm only between the vacuum vessel and the cryostat during the operation. The structure is confirmed to withstand the load conditions because stress is estimated to be lower than allowable level by FEM analysis.