This grant funds R&D toward a portable cryogenic cooler for radiation detectors. The cooler would weigh less than 10 kg complete with a one week supply of cryogen, be self regulating in cryogen consumption to provide rapid cool down or response to transient demands while maintaining minimum consumption during steady state operation, require no electrical power, and have no critical moving parts which could pose reliability or maintenance problems. The liquid carbon dioxide used for the expansion cycle can provide an operating temperature below minus 75 Celsius and should have an essentially infinite shelf life. The R&D will be focussed on achieving good temperature stability and on minimizing microphonic noise in the associated high resolution Si X-Ray Detector.
