Comparison of ITS-90 realizations from 13 K to 273 K between LNE-CNAM and INRIM

Abstract

Since Key Comparison CCT-K2, only few comparisons as regards realizations of cryogenic fixed points have been carried out, either bilateral (three, of which one still pending) or multilateral (two trilateral). Since a forthcoming follow-up is unlikely, any bilateral comparison, apart from key comparisons, is most welcome to provide evidence of the continuing thermometric capabilities of the laboratories involved in the realization of the ITS-90.Not too long after the establishment in 2018 of the Joint Research Laboratory for Fluid Metrology “Evangelista Torricelli” between LNE-CNAM and INRIM, the two laboratories agreed to perform a bilateral comparison, involving all the cryogenic fixed points of the scale between 13.8033 K and 273.16 K – including the two hydrogen vapour-pressure temperatures – required to cover the full platinum resistance-thermometer range, as dealt with in Section 3.3.1 of the text underlying the ITS-90. The results are reported here and show a substantial agreement within the combined uncertainties.