An Adiabatic Calorimeter for the Realization of the ITS-90 in the Cryogenic Range at the LNE-CNAM

Abstract

The LNE-CNAM, in cooperation with the IPN, has recently developed a new cryogen-free adiabatic calorimeter, to realize the International Temperature Scale of 1990 (ITS-90) in the temperature range between 6 K and 84 K. The new calorimeter, cooled by a closed-cycle Gifford-McMahon refrigerator, is equipped with three thermal shields and two separate vacuum chambers, to minimize the effect of parasitic heat fluxes. The inner adiabatic chamber can accommodate either a multi-compartment cell--containing the triple points of hydrogen, neon, oxygen, and argon, to realize the ITS-90 between 14 K and 84 K--or a comparison block for thermometers, the calibration of rhodium-iron (RhFe) thermometers between 6 K and 24 K. The use of a cryogen-free system and a fully computer-controlled measurement chain allow long lasting experiments and good thermal control, resulting in a substantial reduction of the measurement uncertainties. The new adiabatic calorimeter has been successfully tested at the LNE-CNAM. The overall standard uncertainties in the realization of the ITS-90 have been reduced from 2.08 mK to 0.37 mK at the hydrogen triple point, from 1.40 mK to 0.30 mK at the triple point of neon, and are maintained below 0.26 mK at the triple points of oxygen and argon. In the temperature range between 6 K and 24 K, calibrations of rhodium-iron resistance thermometers have been carried out with a standard uncertainty of the order of 0.80 mK

New adiabatic calorimeter for realization the triple point of water in metallic-sealed cell at NIS-Egypt

“…In order to estimate the quality of the improved adiabatic calorimeter, a characterization study is carried out as in references [4,7,8]. There are three main thermal factors of the study describing the thermal behaviour…”

“…The heat capacity of the compartement has a static thermal behaviour while its values did not change by varing the optimum conditions, which was determined by measuring the amount of heat energy required to increase the temperature of the compartment by a known amount [8,9]. The energy supplied to the cell was determined from the electrical power applied to the heater around the cell:…”

“…The thermal resistance between the compartement and the shield has a static thermal behaviour, which was determined as in references [4,8,9] by monitoring both the temperature drifts of the cell and the shield after a sudden change in the temperature of the shield.…”

Improvements in the realization of the triple point of water in metallic sealed cells at LNE-Cnam

“…In order to estimate the measurement accuracy of the adiabatic calorimeter, a characterization similar to that presented in [7] was realized, measuring the heat capacity C C of the cell and the thermal resistance R S between the cell and the adiabatic shield, at temperatures close to the TPW.…”

An adiabatic calorimeter for calibrating capsule type thermometers (CSPRTs) in the range 54 K to 273 K

“…NIS has made use of the experience of the LNE-CNAM [2][3][4][5] to build the calorimeter that would work with the existed facilities.…”