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Closed-cycle cryocoolers have become an important cooling tool for scientific research at low temperatures [1]. Among the family of regenerative cryocoolers, GM-type pulse tubes (PTC) in particular stand out because they have no moving mechanical parts at cryogenic temperatures. This characteristic makes them ideal candidates for cooling vibration-sensitive applications that also require extended service intervals. The working principle of PTCs relies on the cyclic pressure waves of Helium gas at relatively high pressure differences around 1 MPa. These pressure levels are commonly provided by dedicated Helium gas compressors, which represent the main unit of energy consumption in the cryo system with input powers ranging from 1 kW to above 10 kW.
Due to rapid developments in quantum technology there is a fast growing demand for low power, highly mobile and minimum maintenance cooling systems at 4 K for optical quantum components, e.g., single photon detectors, sensor arrays or single photon emitters and small superconductive electronic circuits. Here we present a combination of the smallest so far reported 4 K ‘PTC Susy’ [2] driven by an oil-free low power compressor technology ‘IGLU’ achieving cooling powers necessary for typical optical quantum components below 4.2 K. The IGLU compressor is based on a mechanism with hydraulically driven metal bellows, providing minimum maintenance and maximum mobility with a miniature footprint [3]. With an input power as low as 1 kW the compressor is air cooled and can be supplied by single phase power sockets. Here we report the performance of the SUSY PTC when operated with the IGLU compressor. This combination reaches the physical minimum temperature of 2.2 K at no load, and a cooling capacity of 240 mW at 4.2K, with the compressor operating at maximum speed at 1.3 kW input power. At 3 K the cooling capacity still reaches 80 mW, relevant in particular for cooling quantum optical components. The coefficient of performance reaches values of up to 185 mW/kW, which is among the highest currently reported values for small to medium power pulse tubes.
In summary, this closed-cycle cryocooler compressor combination provides a unique miniaturized, energy efficient and mobile cooling tool for applications at 4K and below.
[1] R. Güsten, et al., Nature 568 (2019) 357-359.
[2] B. Schmidt, M. Vorholzer, M. Dietrich, J. Falter, A. Schirmeisen, G. Thummes, "A small two-stage pulse tube cryocooler operating at liquid Helium temperatures with an input power of 1 kW", Cryogenics 88 (2017) 129
[3] J. Höhne, “High efficiency, low frequency linear compressor proposed for Gifford-McMahon and pulse tube cryocoolers“ AIP Conference Proceedings 1573, 1242 (2014)
