This program is aimed at developing open-cycle jt coolers including the dewar for cooling new detector arrays that require a stable operating temperature below 80 k for application in missiles that require fast cooldown followed by extended run time with minimum weight. during phase i it was demonstrated that the requirements could be met for the smallest size unit, .32 in. (8.1 mm) long. cooldown from 70 deg c to 79 k was achieved in 4.0 s and run time was 12 m from 25 in.(3) (.41 l). this was made possible by a very small two-stage matrix-tube heat exchanger installed in a housing with 14 miniature feedthroughs and a pump-out tube. this proposal for phase ii extends the work by developing a unit for a larger array, one having 488 x 640 pixels. a two-stage matrix-tube heat exchanger is proposed that will extend the run time by improving the efficiency and by developing a new type of demand flow control mechanism that will minimize gas consumption and have less than 1 k temperature cycling. concepts for reducing the thermal mass that has to be cooled and improving the heat transfer will be developed. a major area of work will be material selection and processing studied that will assure dewar vacuum integrity for 10-year shelf life.
Keywords: heat exchangers jt crystat coolers detector arrays dewars joule thomson miniaturization heat transfer
