The 4K Joule-Thomson (JT) cryocooler is a key cryogenic component for future astronomy missions such as ATHENA and LiteBIRD. It was originally developed for SMILES (2009) and upgraded for ASTRO-H/SXS (2016) and SPICA. The 20K two-stage Stirling cryocooler developed for AKARI (2006) was also upgraded and used as a precooler. The operational life is a critical factor in planning long-term missions. An engineering model of the 4K-JT cryocooler was built for continuous operation to verify its lifetime. Testing was done from 2010 to 2019 and successful three-year operation was demonstrated with an extended operation; this was beyond the design specification. This paper describes the overall history of the lifetime test of the 4K-JT cryocooler and an evaluation of the end-of-life cooling performance and performance changes during long-term operation.

4K焦耳-汤姆森（JT）低温冷却器是诸如ATHENA和LiteBIRD等未来天文学任务的关键低温组件。它最初是为SMILES（2009）开发的，并为ASTRO-H / SXS（2016）和SPICA进行了升级。为AKARI（2006）开发的20K两级斯特林低温冷却器也进行了升级并用作预冷器。使用寿命是计划长期任务的关键因素。建立了4K-JT低温冷却器的工程模型以实现连续运行，以验证其使用寿命。从2010年到2019年进行了测试，并通过扩展操作证明了成功的三年运行；这超出了设计规范。本文介绍了4K-JT低温冷却器的寿命测试的总体历史，并评估了使用寿命终止后的冷却性能和长期运行期间的性能变化。