Development of a space 100 mW@5 K closed loop JT cooler

•Cooling capacity of the 4.5 K JT cooler will decrease when the size of the JT orifice is larger than 35 μm.•JT element with multi-orifice is proposed to improve the cooling capacity of the JT loop.•Cooling capacity of 102.3 mW@5.02 K is achieved when the JT loop is driven by three stage oil-free compressors. A space 100 mW@4.5 K JT cooler is designed, manufactured and experimentally tested by our laboratory. The multi-orifice JT element is proposed to improve the performance of the JT loop. And compared to single orifice, the multi-orifice JT elements perform better. Cooling power of 100.3 mW@4.55 K is achieved when JT element is 4 * 20 μm orifice and supply pressure is 2.0 MPa in open loop experiment. In closed loop experiment, three oil-free linear compressors are used to drive the JT loop, and cooling capacity 102.3 mW at 5.02 K is achieved. This JT cooler will be the potential cryocooler for the future space detectors working at 4.5 K.