Temperature measurement in high pressure cells using a rhodium +0.5% iron-chromel thermocouple pair

Abstract

Temperature measurement inside high pressure cells is most conveniently made with a thermocouple, since unless there is a large temperature difference between the thermocouple junction and the region of the pressure seal where the pressure gradient occurs, the ambient pressure-temperature calibration can be used. The authors have used a thermocouple pair of rhodium +0.5 at.% iron-chromel. This pair provides usable sensitivity down to liquid-helium temperatures (lowest sensitivity approximately 4 mu V K-1 at 15K) together with sufficient mechanical strength to withstand the handling necessary to pass the pair into the pressure cell. This has been incorporated in a beryllium-copper cell for use up to 1.5 GPa over the temperature range 4-400K.