中文摘要：

给出了1．8K常压超流氦低温系统的工作原理。对HeⅡ腔的漏热进行了分析和计算，包括环氧隔热板、安全阀、支撑杆以及测量线与电流引线底座同HeI腔的导热，真空夹层之间的残余气体导热以及HeII腔内杜瓦与其外周冷屏的辐射换热。根据漏热值，对所需真空泵的抽速进行了计算，同时给出了预冷与节流相结合获取1．75K超流氦方案物理过程的温-熵图。

英文摘要：

The operating principle of a 1.8 K-atmospheric super fluid helium cryogenic system was giv- en. The heat leak of the He Ⅱ chamber were analyzed and calculated, which including the epoxy insulating board, safety valve, support bars, measurement leads and current leads heat conduction with He Ⅰ cham- ber, residual gas heat conduction in vacuum between the layers, radiation heat transfer between the dewar of He Ⅱ chamber and cold shield. According to the result of heat leak, vacuum pump speed was calculated, temperature-entropy diagram of the process of throttling process accompanied with pre-cooling were put for- ward.