Progress Towards the Determination of the Relationship of Triple-Point Temperature versus Isotopic Composition of Neon

Following the finalization of the work performed to establish the triple-point temperature versus isotopic composition relationship for protium (Metrologia 42 , 171 (2005)) adopted into the ITS-90 definition by the International Committee for Weights and Measures (CIPM) in 2005, and a preliminary exploration of the variability in the triple-point temperature of neon gas samples arising from differences in isotopic composition (Anal. Chem. 77 , 5076 (2005)), this article reports further progress toward the determination of a similar comprehensive relationship for neon, to be included in a future revision of the Technical Annexe to the ‘ mise en pratique ’ of the kelvin. This progress article mainly concerns a set of gas samples used for the neon triple-point measurements during CCT-K2, and subsequently, others for which the isotopic compositions were recently measured. Recent high accuracy measurements of the corresponding thermal data are now available for many of these samples, but not yet for all of them.