Thermal structure optimization of a supercondcuting cavity vertical test cryostat

Abstract

The cryostat for superconducting cavity vertical tests (SCVT) studied in this paper has the following two characteristics. One is that there is an uninsulated part of the inner vessel, which is exposed to the environment, to heat the outflow gas to prevent frost formation, and another is that there is a vapor cooled screen in direct contact with the inner vessel forming a thermal intercept. Based on the above characteristics, a heat leakage model for the SCVT cryostat was established in the case where the evaporation gas is involved. The effects of the thermal intercept position, height of the uninsulated part of the inner vessel and liquid level height on the heat leakage and gas outlet temperature of the cryostat were studied. The results showed that the thermal intercept position at 0.34 times the height of the insulation part of the inner vessel has the minimum required power, and at 0.388 times the height has the minimum heat leakage. The optimal thermal intercept position considering required power and heat leakage is located at 0.376 times the height of the insulated part. As the height of the uninsulated part changes from 0.1 m to 0.6 m, the gas outlet temperature rises from 71.83 K to 290 K. Although the heat leakage increases greatly with the height of the uninsulated part rises, it is mainly used to heat the outflow gas, which has less influence on the liquid helium evaporation. With a liquid level height from 1.8 m to 2.4 m, the gas outlet temperature has decreased by 29.6 K, and the heat leakage increases by 1.69%. The heat leakage and gas outlet temperature is not sensitive to the liquid level height.