Cryostat engineering design and manufacturing of the EAST superconducting Tokamak

EAST cryostat is a large single walled vessel surrounding the entire basic machine consisting of central cylindrical section and two end enclosures, a flat base structure with external reinforcements and dome-shaped lid structure. The main function of EAST cryostat provides the thermal barrier between the ambient temperature testing hall and the supercritical helium cooled superconducting magnet with the base pressure of 5 × 10−4 Pa. The base structure has been connected with the main support which has eight equally spaced support legs anchored on the concrete base. It also provides feed through penetrations for all the connecting elements inside and outside the cryostat. The cryostat vessel was executed to satisfy the performance and operation requirements. The major loads applied to the cryostat are vacuum pressure, dead weight of vacuum vessel, PFC, thermal shield, and magnet which are total 360 tonnes, seismic events and electromagnetic forces originated by eddy currents. The structural analyses including buckling for the cryostat vessel under the plasma operation condition have been carried out using finite element code. Stress analysis results show that the maximum stress intensity was below the allowable value, and the cryostat had buckling safety factor of over 16. Based on the results, structural robustness of the cryostat vessel has been proved. The engineering design and fabrication has been completed. The paper will summarize the structural analyses, the design activities and give a short description of the fabrication of the cryostat component.