Expanding market of 4KGM cryocooler.

There are several types of cryocoolers that generate cooling power at cryogenic temperatures. The Gifford-McMahon (GM) cryocooler is the most widely used cryocooler in industrial applications such as cryopumps for semiconductor manufacturing, MRI (Magnetic Resonance Imaging), etc., due to high reliability and ease of operation and handling. GM cryocoolers are closed-cycle regenerative refrigerators originally invented by Gifford and McMahon in 1959. The lowest temperature of commercial GM cryocoolers had been around 10K, primarily due to the very low specific heat capacity of conventionally-used regenerator material (Pb) below 10K. 10K cryocoolers functioned to reduce liquid helium boil-off in superconducting applications, particularly MRI. As MRI and other superconducting applications continued to develop commercially, liquid helium became scarcer and more expensive. This drove the need for cryocoolers to reliably achieve 4K temperatures to further reduce, and even eliminate, helium losses. Research and development activities began in the late 1980s and early 1990s, specifically focused on new regenerator materials and gas sealing technologies to address this need. The world's first 4KGM cryocooler was commercialized in 1996, which became an enabling technology for “zero boil-off” superconducting applications.

现有多种可在低温区间产生制冷量的低温制冷机（cryocooler）。其中，吉福德-麦克马洪（Gifford-McMahon，简称GM）低温制冷机是工业应用中应用最为广泛的低温制冷设备，其场景涵盖半导体制造用低温泵、磁共振成像（Magnetic Resonance Imaging，MRI）等，这得益于其极高的可靠性与简便的操作维护特性。GM低温制冷机属于闭式循环蓄冷式制冷机，最早由吉福德与麦克马洪于1959年发明。早期商用GM低温制冷机的最低制冷温度约为10K，这主要是由于传统蓄冷器材料铅（Pb）在10K以下的比热容极低。此类10K级低温制冷机主要用于降低超导应用中的液氦挥发量，尤以MRI场景为代表。随着MRI及其他超导应用的商业化推进，液氦资源日益稀缺且价格持续攀升，由此催生了对可稳定实现4K制冷温度的低温制冷机的需求，以进一步降低乃至完全消除氦气损耗。为此，研究人员于20世纪80年代末至90年代初启动相关研发工作，重点聚焦新型蓄冷器材料与气体密封技术。1996年，全球首台4K级GM低温制冷机实现商业化落地，该设备成为实现“零挥发”超导应用的使能技术。