Development of a 4 K two-stage commercial cooler assisted J-T with off-the-shelf mini compressor

Abstract The helium compressor system for a miniaturized 4 K J-T cooler has been developed by using a set of commercial compressors. The considered cooler is intended to provide 10 mW of cooling capacity for a superconducting nanowire single photon detector (SNSPD) or for other quantum information devices. The cooler structure consists of an auxiliary 2-stage GM cooler to precool the helium stream and operate the radiation shields; three recuperators; an expansion orifice; and an evaporator. Two commercial miniaturized compressors, originally intended for R134a, have been repurposed for helium. Additionally, a custom oil removal system has been developed to provide a helium flow free of oil mist and other contaminants that may clog the expansion orifice. A model of the thermodynamic cycle was used to obtain the optimal coldhead temperatures. Subsequently, a numerical simulation of the recuperators has been employed to evaluate the required pressures and mass flow rate from the compressor. Lastly, the compressors and the oil removal system have been tested for similar operating conditions.