超导单光子探测器用1~2 K制冷机热力学优化

Thermodynamic optimization on the 1-2 K hybrid cryocooler used for cooling Superconducting Nanowire Single Photon Detectors

摘要:

对工作在1~2 K的超导纳米线单光子探测器(SNSPD)用多级脉冲管预冷焦耳－汤普逊(JT)的复合制冷机制冷性能进行了系统的热力学优化研究。阐述了该复合制冷机的结构设计和工作机理；基于热力循环分析提出了焓流模型，同时建立了适用于3 K以下温区的实际流体质量流量模型，并将二者结合，分析复合制冷机的性能；探讨了理想情况下净制冷量随末级预冷温度和上游压力的变化特性，应用所提出的模型通过离散参数拟合方法对二者进行优化。发现对于He-4和He-3工质，多级脉冲管末级最优预冷温度分别为11 K和8 K；以He-4为工质，该复合制冷机能在2.2 K的温度下提供85 mW以上的制冷量；以He-3为工质，能在1.0 K提供18.5 mW的制冷量，该性能能够满足SNSPD的实际应用需求。

Abstract:

The systematic thermodynamic optimization on the cooling performance of the hybrid cryocooler composed of multi-stage pulse tube and Joule-Thomson(JT) working at 1-2 K for cooling the Superconducting Nanowire Single Photon Detectors(SNSPD) is carried out. The structure design and working mechanism are described. An enthalpy flow model is proposed based on the thermodynamic cycle analysis, and a real fluid mass flow model for the temperature region below 3K is established. The two models are combined to analyze the hybrid cryocooler performance. The variations of the gross cooling capacity with the last stage precooling temperature and upstream pressure under ideal conditions are discussed and the proposed model is utilized to optimize the two variables by discrete parameter fitting method. For He-4 and He-3 working fluids, the optimal last stage precooling temperature of the multi-stage pulse tube is 11 K and 8 K, respectively. The results show that the hybrid cryocooler with He-4 as the working fluid can provide more than 85 mW cooling capacity at 2.2 K, and that with He-3 as the working fluid can provide 18.5 mW cooling capacity at 1.0 K. The performance of the hybrid cryocooler can meet the requirement of the practical applications of SNSPD.