Design and analysis of 1.8K cold box of large scale superfluid helium refrigerator

As an important part of the CRAFT(Comprehensive Research Facility for Fusion Technology), a 250 W @ 1.8 K superfluid helium refrigerator was proposed to provide a 1.8 K cryogenic environment for the test of small and medium-sized high field superconducting magnets. The 1.8 K cold box, one of the core components of the 1.8 K superfluid helium refrigerator, mainly provided a vacuum insulation operation environment for cryogenic components such as heat exchangers, liquid helium tank, cold compressors and so on. In this paper, structure design of the 1.8 K cold box was presented. Then ANSYS Workbench software was used to simulate the stress and deformation of 1.8 K cold box container under normal and abnormal conditions. The results show that the design of cold box meets the maximum stress requirements. According to the seismic design code, the seismic response spectrum was obtained. Through the modal analysis and seismic spectrum analysis, the seismic response of the cold box container under each load was obtained, which shown the safety under the seismic load.