Experimental study on vibration reduction of a cryogen-free dilution refrigerator system pre-cooled by a GM cryocooler

Abstract

In order to carry out vibration reduction work on a cryogen-free dilution refrigerator system pre-cooled by a GM cryocooler, this paper first introduces the method of vibration measurement, particularly presenting the results and verification of displacement measurement obtained through acceleration integration. Subsequently, based on the construction of our dilution refrigerator, the paper reports experimental evidence of the direct impact of vibration on temperature and provides an effective vibration reduction scheme for the system. The study finds that vibrations transmitted through the path of “low-temperature part of GM- copper braid − support structure − various cold plates” have the most significant impact, hence making good internal soft connections is key. The influence of vibrations from the room-temperature part of GM can be mitigated to some extent by suspending the cold head, either by a separate frame or using the dilution refrigerator’s own frame. The use of a structure composed of air springs and honeycomb rubber in the suspension system has proven to be effective. Our final experimental results have demonstrated that with adequate vibration damping, the impact of vibrations from the GM on temperature can be essentially eliminated, allowing the dilution refrigerator to achieve a temperature level close to that when pre-cooled by a PT. The research in this paper has certain reference value for the construction and vibration mitigation of ultra-low temperature refrigeration systems.