Aluminium fixed-point cells for thermodynamic temperature assignment

Abstract

In the frame of the EMPIR-funded joint research project 15SIB02 “Implementing the new kelvin – 2” (InK2) the determination of T-T90 over the temperature range between 430 K and 1358 K with a target uncertainty around the 10 mK level is under preparation in several NMIs, among which LNE-Cnam and CEM. The two laboratories have joined their efforts for the thermal characterisation of a set of three aluminium fixed-point pyrometric cells. The cells were constructed using the hybrid design based crucibles and the piston filling method both developed by LNE-Cnam over the past decade. To study the effect of the temperature gradients on the freezing temperatures of the cells, two three-zone furnaces were used for the implementations of the cells with different temperature distributions. Finally, a first determination of the thermodynamic temperature of the freezing plateau was determined by extrapolation from the thermodynamic temperature of the copper point of LNE-Cnam. The results of the characterisations and the temperature determination are presented.