中文摘要：

提高液氦温区脉管制冷机的制冷量对于冷却超导磁体和氦液化具有重要意义。本文将已成功应用于单级脉管制冷机和4 K G-M制冷机模拟的回热器模拟软件REGEN用于液氦温区脉管制冷机二级回热器的模拟。计算结果显示,脉管制冷机在4.2 K的制冷量一定程度上随着二级质量流量的增加而增大。在此基础上,我们在实验中采用不同质量流量的压缩机对第二级进行驱动以对计算结果进行验证。实验结果与计算结果基本吻合。在用单台6.8 kW压缩机同时对第一级和第二级驱动时,制冷机在第一级和第二级分别有20 W@40 K和0 7 W@4.2 K的制冷量。改用双压缩机和双旋转阀分别驱动第一级和第二级（第一级：CP4000,第二级：CP6000）,在制冷机第一级和第二级分别获得20 W@47.5 K和1 1 W@4.2 K的制冷量,总输入电功率为11.7 kW。这是目前分离型二级脉管制冷机获得的最大制冷量。

英文摘要：

Improvement of cooling power of pulse tube cryocooler（PTC） working at 4.2 K is an important issue for superconductor magnet cooling and helium liquefaction.The National Institute of Standards and Technology（NIST） numerical model known as REGEN which was successfully used in the calculation of single-stage PTC and 4 K G-M cryocooler was applied to the simulation of the second stage regenerator.The calculation results showed that the higher the second stage mass flux,the higher the cooling power.The experiment with different mass flux of the second stage was implemented.Cooling power of 0.7 W at 4.2 K and 20 W at 40 K were achieved simultaneously with a single compressor.Two compressors together with two rotary valves were used to drive the two stages and the cryocooler can provide 1.1 W at 4.2 K and 20 W at 47.5 K respectively,which is the largest cooling power ever obtained in a separate 4 K PTC.The total actual input power was 11.7 kW.