Ryan Snodgrass

Millikelvin refrigerators are enabling tools for many fields of modern science, including quantum information processing. They are typically precooled to 4 K by low-frequency pulse-tube refrigerators, which perform a thermodynamic cycle based on compressing and expanding helium gas. Although the efficiency of these refrigerators is known to be poor, only the loss mechanisms that occur near the cold end have been sufficiently studied and characterized.

Measurement of oscillating mass flows is typically required for the study of cryocoolers and cryocooler compressors. Although many measurement techniques are used in the cryocooler literature, detailed comparisons are lacking, so it can be challenging for experimentalists to decide which method(s) may be most appropriate for them.

Pulse tube refrigerators are a critical enabling technology for many disciplines that require low temperatures. These refrigerators dominate the total power consumption of most modern cryostats, including those that reach millikelvin temperatures using additional cooling stages. In state-of-the-art commercial pulse tube refrigerators, the acoustic coupling between the driving compressor and the refrigerator is fixed and optimized for operation at base temperature.