A closed-cycle mechanical refrigeration system has been adapted to cool photomultipliers automatically. Temperature is adjustable between +5° and −55°C and is stable to within ±0.3°C. An important feature of the design is the flexible connection to the cold box which allows extensive freedom of motion; this freedom is particularly important in astronomy where the cold box is mounted on the end of a telescope. Liquid Freon refrigerants have been used to cool photomultipliers for rocket flights. A brief description of two methods is given.
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