Realization of both the Triple Points of 20Ne and 22Ne in a Multicell

In an effort to further reduce the uncertainties in the triple point temperatures of 20Ne and 22Ne, already established in previous publications, at INRIM a cell for each of the two high purity isotopes was mounted on the same copper block and their triple points were realized subsequently one after the other, allowing a reduction of the total experimental uncertainty on their temperature difference due to a full correlation of some of the uncertainty components arising from this type of realization. The two meltings remain perfectly distinct and do not interfere with each other, being the temperature difference 0.147 K while the melting ranges are below 0.2 mK. The main difference with respect to single measurements (mounting a single cell at a time), lies in the adiabatic conditions during measurement, which are hardly reproducible when mounting a single cell at a time, leading to one of the dominant uncertainty contributions, 15 μK (single). In the present work, the uncertainty component due to the adiabatic conditions is reduced by using a measurement in sequence (mounting the two cells at a time), 1 μK. Thus, an improved reliability in the experimental realization is obtained as reflected in the experimental contributions to the uncertainty budget.