Refrigeration Process to Realize a Multistage and Gas-Cooled Current Lead

Heat leak from the current lead is the major source of power loss for superconducting (SC) magnets, motors and generators, and short distance SC power transmission lines. Therefore, reducing the heat leak from the current lead can improve the economy of the SC system and allow the use of SC systems commercially. The Peltier current lead was proposed and developed at Chubu University to reduce the electrical power consumption of the refrigerator. The heat leakage of the Peltier current lead saves almost 40%, but the power requirement of the refrigerator is still high. In order to realize greater power savings, the multistage current lead (MCL) and the gas-cooled MCL are proposed. The heat leakage reduction of the gas-cooled MCL depends on the characteristics of the cryogen and its pressure and the realization of high cost of performance and a high-temperature refrigerator. Here, we show the calculation results of the high-pressure effect of cryogen and discuss the performance of nitrogen trifluoride as cryogen.