Experimental Research on the Influence of Low Temperature Cycle on the Stability of Standard Platinum Cobalt Resistance Thermometer

There are three commonly used resistance thermometers at low temperature,especially below 24.556 1 K(neon triple point),mainly including platinum resistance thermometers,rhodium-iron resistance thermometers and platinumcobalt resistance thermometers.The latter platinum-cobalt resistance thermometers,are similar to rhodium-iron resistance thermometers in sensitivity and stability below 20K,can be used as a standard for accurate temperature measurement,drawing more and more attention from the cryogenic community.We study the low-temperature performance of the developed standard platinum-cobalt resistance thermometers with a platinum-shell structure.This article mainly focuses on the experimental study of cryogenic cycle on the standard platinum-cobalt resistance thermometers.This article only introduces the short-term stability after the low temperature cycle,including the test process of standard platinum-cobalt resistance thermometers,the calibration of the water triple point and the device for liquid nitrogen temperature cycle.We have completed temperature cycle assessment of 4 standard platinum-cobalt resistance thermometers from liquid nitrogen temperature to room temperature.After 20 temperature cycles,the stability of thermometers were tested at the triple point of water,and the results showed that the optimal stability was 0.3 mK.