Long-term stability of a cryogenic diode thermometer

Abstract

One of the most important qualities for a cryogenic thermometer is its ability to maintain its calibration upon thermal cycling. While it is most preferable to perform slow thermal cycling on cryogenic temperature sensors, it is not always practical to do so. Fast thermal cycling, or thermal shocking, induces stresses within the sensor that at best can cause shifts in calibration and at worst can cause catastrophic failure. From 1992 to present, ten Lake Shore Cryotronics model DT-470-SD cryogenic diodes have been used to aid the quality control testing of production devices. These diodes were randomly tested with production thermometers and subjected to thermal shock cycling between room temperature and 4.2 K during the production test cycle. This paper analyzes the data collected over the nine year period and reports the long-term stability of the ten diode thermometers at 305 K, 77.35 K, and 4.2 K after extensive thermal shocking. The data show that these devices exhibit long-term stability at each tested temperature to better than ±0.2 mK/thermal shock cycle. Individual diode thermometers exhibited a low temperature drift that could be in either the positive or negative direction, but the group as a whole averaged to a much lower drift overall drift.