Rogelio Rosas M.S. Graduate Student Mechanical Engineering Room: 1337 ERB Hometown: Los Angeles, CA Thesis: Modeling a Superfluid Pulse Tube Refrigerator

Motivation Infrared and x-ray astrophysics missions have a need to cool below 1 Kelvin in order to use instruments such as transition edge sensor (TES) bolometers, microwave kinetic inductance detectors (MKIDs), and microcalorimeters Refrigerators with non-moveable parts are essential in low- gravity environments because of reliability and durability Continuous cooling provides for longer available time to record data

System and Component Modeling A detailed numerical model of the heat exchangers and pulse tubes will be developed The final model will be inserted into the system level model and used to complete the design of hardware The model will be used to determine required pump pressure ratio and volume, the size and effectiveness of the recuperative, cold end, and warm end heat exchangers, the pulse tube size, and the orifice size

Future Work Once system model has been optimized the equipment will then be assembled to test a complete unit Testing will include running the refrigerator with various cycle times and with 3 He- 4 He mixtures with different 3 He concentrations Maps of performance (cooling power vs cold end and warm end temperatures) for different operating conditions will be generated The data will be an analyzed and the system model will be refined using the experimental performance data