Compact photomultiplier housing with controlled cooling.

Description of a compact photomultiplier housing which can provide controlled cooling to the photomultiplier tube down to -90 C. The cooling is accomplished by flowing liquid nitrogen cooled helium gas through a series of coils which envelop the photocathode portion of the tube. The temperature is controlled by controlling the flow of the gas with a fine adjustable needle valve. The temperature is measured near the photocathode of the photomultiplier by a calibrated thermistor.