Effect of Flexible Thermal Connections on Temperature Oscillation in the Low-Temperature Range of GM Cryocooler

Copper flexible connecting structures are commonly used as flexible thermal transfer components at low temperatures. Gifford-McMahon (GM) cryocoolers are widely applied in cryogenic applications due to their wide temperature range coverage and ease of operation. However, the periodic motion of the displacer in a GM cryocooler generates a significant temperature oscillation below 20 K, approximately 300 mK, which is challenging to meet precise measurement requirements. The copper flexible connection has an attenuating effect on temperature oscillations due to the thermal conductivity and interfacial thermal resistance of the flexible connection. Therefore, the theoretical analysis and experiments were conducted to investigate the effect of copper flexible connection on temperature oscillation in the low-temperature range (4−20 K) of GM cryocoolers. Firstly, a COMSOL simulation model was established based on the one-dimensional heat transfer equation to investigate the major factors that reduce temperature oscillations; Secondly, the temperature fluctuations of the secondary cold head of GM chillers in the temperature range of 4−20 K were measured; Finally, the influence of the key parameters of the copper connection on temperature oscillations was experimentally verified on this basis. A base data is provided for the application of the thermal resistance method to suppress the temperature oscillation of the cold head in the lower temperature range.