Closed cycle cryocoolers that can reach liquid helium temperatures (4.5 K could have important applications. The proposed effort covers the experimental demonstration of a four-stage cryocooler based on the orifice pulse-tube cycle. The design is based on a thermodynamic model of the cryocooler cycle developed in the Phase I effort. An advanced regenerator concept, based on perforated plates is required for the low temperature stages of the cryocooler. An overall COP of 5000 watt/watt is predicted for the cryocooler, assuming ideal compressor operation. The proposed machine should have high reliability since it has no moving parts or orifice restrictions in the cryogenic section. The absence of moving parts also means that the vibration and magnetic signatures are small. This is critical for applications that involve sensitive magnetic moment detectors, such as the SQUID Magnetometer.
