Thermal cycling apparatus to test germanium thermometer stabilities

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Abstract
Apparatus has been developed for thermal cycling germanium thermometers from ambient temperatures to 20.280 K and evaluating their reproducibility at the lower temperature. Gaseous and liquid helium are drawn from a storage Dewar into refrigerators loosely attached to a shielded and insulated enclosure initially at room temperature. Cooling the enclosure requires 5 h; heating it up to room temperature afterwards, 7 h. The existing apparatus accommodates 30 germanium thermometers and a reference standard platinum resistance thermometer. Because digital voltmeters can be used effectively, most of the data collection is automated and statistical analysis of the data is performed in minutes. Experiments have demonstrated that the standard deviation of 11 series of measurements (no thermal cycling) is the equivalent of 0.04 mK for an average thermometer at 20.280 K. The apparatus is being employed to determine the stability of the 30 thermometers during a 100‐cycle test.
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