Realising the redefined kelvin

WP 1: Realisation and dissemination of the redefined kelvin above 1300 K

The aim of this work package is to prepare for the future dissemination of the redefined kelvin, above 1300 K, by radiation thermometry. This will be achieved by developing a number of high-temperature fixed points (HTFPs) to cover the whole temperature range above the freezing temperature of copper (the current highest fixed point of the international temperature scale). These new fixed points will complement the existing high-temperature fixed points filling the gaps and extending the temperature range to 3020 K. We aim to achieve target standard-uncertainties from 0.1 K to 0.4 K, which will allow the application of these points for the Mise en Pratique of the kelvin with a significantly improved uncertainties compared to the current scheme based on the ITS-90. Finally, practical dissemination routes will be tested to prove, for the first time, the ability of HTFPs with assigned temperatures to improve the traceability to the kelvin up to 3000 K.

Section of a high-performance HFTP

Realisation of HTFP cells for thermodynamic temperature assignment and dissemination

The aim is to develop and construct a series of reliable HTFP cells for two purposes:

  1. A collective determination of the thermodynamic temperature of their solid-liquid phase change
  2. Traceability tests towards NMIs and Industry

Four HTFPs have been identified as the best candidates for these purposes: Fe-C (1426 K), Pd-C (1765 K), Ru-C (2226 K) and WC-C (3020 K).

Characterisation of the thermal effects on the reproducibility of the cells

The aim is to assess the sensitivity of the cells constructed to thermal conditions during their implementation and the effect of changing these thermal conditions on the uncertainty of the determination of the temperature of their phase transition. The expected output of this work is to achieve a comprehensive analysis of the uncertainty components that will need to be considered when using such HTFPs for dissemination purposes.

Assignment of thermodynamic temperatures to the Fe-C, Pd-C, Ru-C and WC-C cells

The aim is to determine the thermodynamic temperature of a set of HTFP cells at the Fe-C, Pd-C and Ru-C eutectic phase transitions and WC-C peritectic phase transition. This is to provide HTFPs with known T to realise and disseminate T by indirect radiometry as described in the MeP-K-19. For this work several approaches will be for the assignment of thermodynamic temperatures to the phase transitions either by a direct radiometric measurement (radiance or irradiance methods) or by extrapolation or interpolation using HTFPs of known thermodynamic temperatures (i.e. Cu, Co-C, Pt-C, Re-C). The fact that different independent methods will be implemented will allow reducing the final uncertainty of the assigned thermodynamic temperatures.

Traceability trials towards industry and NMIs

The aim is to demonstrate the feasibility and the added value of a traceability scheme based on the developed HTFP cells. The dissemination trials proposed will benefit either industrial partners or national metrology institutes which don’t have the possibility of measuring thermodynamic temperature by radiometric methods. These trials will be the proof of concept for the Mise en Pratique for the definition of the kelvin at the highest temperatures and aims to show the ease of thermodynamic temperature dissemination through HTFPs.