Adjustments to the ICVGT scale of INRIM

At the 8th Temperature Symposium the results have been presented for the Interpolating Constant Volume Gas thermometer at INRIM (then IMGC), featuring a cryogenic pressure transducer, with an expanded uncertainty of less then 1.5 mK. However, for its fixed points this scale still relied on a NPL calibration as carried by rhodium-iron thermometer 232324. After the clarification, in 2005, by the Consultative Committee on Thermometry (CCT) of the definition of the equilibrium hydrogen (e-H2) triple point this scale was due to be adjusted for the isotopic content in the e-H2 fixed point cell. Only when this thermometer was re-calibrated in 2010 at INRIM at the three fixed points of the ICVGT was this adjustment performed, being the isotopic composition of the hydrogen cell known. With the start of the Neon Project in 2005, it became clear that a second adjustment would soon be needed, once the CCT will have decided on the way to deal with the isotopic composition of neon. The paper presents the experimental data of 2010, discusses the stability of the thermometer, and the size of the correction at the hydrogen point and of the likely correction (and its uncertainty) to be applied to the neon point, the isotopic composition of this cell being known as well

Effect of the temperature scale on the difference between the triple point temperatures of pure 22Ne and 20 Ne

The construction of the ITS-90 gives rise to relatively small temperature differences depending on the specific interpolation equation (temperature range) used. Also the use of different thermometers gives rise to small temperature differences. These and the already published temperature differences between the ITS-90 and thermodynamic temperature lead to an additional small uncertainty in the difference between the triple point temperatures of pure 22Ne and 20Ne. Estimates are given for the various contributions

Final report on CCT-K2.5: NRC/NMIJ/INRIM comparison of capsule-type standard platinum resistance thermometers from 13.8 K to 273.16 K

A trilateral comparison of capsule-type standard platinum resistance thermometers is reported that links the NMIJ and INRIM realisations of the International Temperature Scale of 1990 to the results of the Consultative Committee for Thermometry Key Comparison 2 in the temperature range 13.8033 K to 273.16 K

Experimental Verification of Ideality of 22Ne in 20 Neon Mixtures at the Triple Point by Means of Certified Artificial Mixtures

The paper reports the results of an experimental verification of the assumption of ideality for mixtures of 22Ne in 20Ne by means of binary mixtures, artificially-produced and certified by weighing and whose full isotopic compositions were then measured at KRISS using a mass-spectrometer calibrated with these mixtures. Thermal measurements on the mixtures were performed at INRIM. The assessment of the validity of the ideality condition was critical to the conclusion of a comprehensive study on the effect of neon isotopic composition on the values of its triple point temperature. At KRISS three mixtures were prepared with 22Ne amount concentrations 22x = 62 088(20) 10^-6, 91 678(22) 10^-6 and 166 025(26) 10^-6 in 20Ne, respectively, the intermediate one being very close to the range of ‘natural’ compositions. The thermal measurements were performed in the same INRIM experimental apparatus of previous published studies, with an expanded uncertainty (k = 2) of 30 microK for a single sample and 50 microK for the comparison of sample pairs, using the same model of cryogenic metal sealed cell for each sample. The results, corrected for the measured, low, content of 21Ne and of relevant chemical impurities (H2 and N2) showed an agreement with a theoretical model for the binary mixture assuming ideal behaviour within 10 microK, with a standard uncertainty of uc = 50 microK. These results allowed to construct a ternary mixture model for the actual neon isotopic composition, including 21Ne, where the IUPAC recommended composition was used as the reference composition, and whose characteristics are discussed in the paper. This also allowed reassigning the T(tp,90) values to all samples