Comparison of the copper blackbody fixed-point cavities between NIS and LNE-Cnam

This paper describes the results of a bilateral comparison at the copper blackbody fixed point (1084.62 °C), one of the defining fixed points of the International Temperature Scale of 1990 in the high-temperature range. The 'National Institute of Standards—Egypt (NIS)' and the 'Laboratoire Commun de Métrologie-–France (LNE-Cnam)' undertook such a comparison using an NIS linear pyrometer 'LP4' as a circulating radiation thermometer between the two laboratories. The main objective of this work was to compare the realizations of the copper blackbody fixed point for radiation thermometers and establish the level of agreement between the two laboratories in the high-temperature range. The comparison measurements revealed a slightly lower temperature of the NIS copper point than that of the LNE-Cnam copper point by about 0.08 °C. This difference is not significant with regard to the uncertainty and the stability of the pyrometer estimated as 0.15 °C. A second comparison was made a few months later by comparing simultaneously the two copper points at the LNE-Cnam premises. This comparison allowed determining a temperature difference of 0.045 ± 0.030 °C between the two cells, with the temperature of the LNE-Cnam cell being higher than that of NIS. (paper)