Multistage, High Capacity 35 Kelvin Cryogenic Cooling

The cryogenic refrigeration requirements for many space-based infrared (IR) sensor systems are best met with a multistage cryocooler to simultaneously provide cooling at two distinct temperature levels. The requirement to cool a focal plane array to some very low operating temperature while simultaneously cooling the optical bench to some higher, though still cryogenic temperature is a typical example of a system need optimally met by a multistage cryocooler. A comparative study was performed during Phase I in which the thermodynamic performance of various two-stage cryocooler configurations were compared. Also considered were mechanical design complexity, reliability, and operational flexibility. The conclusion of the study was that the best balance of thermodynamic performance, ease of construction, and compatibility with long life is achieved with a Stirling/Pulse Tube "hybrid" approach. In Phase II, the models will be correlated and the hypotheses tested through development of feasibility demonstrator focusing on the expander. Extensive optimization and characterization experiments will provide a database for model correlation and a strong experimental basis for the subsequent build of flight-qualified Stirling/Pulse Tube cryocoolers during the Commercialization Phase.