Abstract
Stability under a large number of thermal cycles between 300°K and 4.2°K is an essential requirement for Josephson and other superconductive thin film devices. An apparatus is described here using the exchange gas principle to subject such devices to repeated thermal cycles automatically. Through a careful design, liquid helium loss per cycle is kept to a very minimum of 0.6 litres without samples and 1.5 litres with a load of 10, 1″ diameter 20 mls thick, silicon wafers. Samples can be cycled between any two temperatures in the range of 300°K and 4.5°K by simple front panel settings. The cooling and warming rates are adjustable over a wide range. Built in safety features, an important consideration, allow the system to be operated continuously unattended, except for the refilling of the dewar, over a period of days and weeks. © 1978.