Modeling, development, and experimental validation of a Joule–Thompson superfluid refrigerator using a pulse tube cryocooler

Abstract

An economical method of refrigeration to temperatures near 1K is introduced in this work. Unlike traditional methods, our refrigeration system does not rely on the use of a helium bath; helium enters a Dewar at room temperature and pre-cools, condenses, and sub-cools to temperatures slightly lower than the normal boiling point of helium during its heat exchange with various components that are connected to a Cryomech pulse tube cryocooler (PT-410). A fixed Joule–Thompson restriction valve is used to create a large pressure difference between the incoming high-pressure helium line and the vacuum pumped space of the 1K pot causing the helium temperature to drop to its corresponding saturation condition in the pot upon an isenthalpic expansion across the valve. This is a comprehensive report on the performance of a Joule–Thompson superfluid refrigerator; we will discuss our model, techniques in the experimental setup, and present our data for this type refrigerator. This refrigerator reached an ultimate low temperature of 1.39K with no applied heat load and provided 150mW of cooling power at 1.65K.