CCT Task Group on Future Thermodynamic Temperature Traceability (CCT-TG-CTh-TTT)

Terms of reference

1. Current traceability ITS-90/PLTS-2000, T-T₉₀ – just a statement meeting current and near future needs. In particular there is a need for improved T-T₉₀ measurements above 400 K.
2. The impact of the kelvin redefinition: facilitating traceability to thermodynamic temperature, T, from NMIs. This concerns the traditional traceability route from an NMI to the user, but with T instead of the defined scale. Summarise what work has been done towards this aim, e.g. the achievements of recent European projects and elsewhere. Include highlights of work needed in the next half decade, with a focus on new approaches to traceability to thermodynamic temperature. This could lead to a recommendation from CCT. It is suggested that the areas to examine be split into three broad temperature areas, with ‘high’ being possibly above the Ag point (or Al point) and ‘low’ being below 25 K (or possibly below ambient).

• High temperatures
• Low temperatures
• Intermediate temperatures

3. Self-calibrating thermometers – what does traceability mean and how to demonstrate it. Look at both and elucidate what traceability and the role of the NMI is, in this context, in assuring traceability and reliable operation. These generally work by incorporated fixed points, so, for example, assuring fixed point purity may be an issue.
4. Practical primary thermometry – what does traceability mean and how to demonstrate it. Examine both and elucidate what traceability and role of NMI is, in this context, in assuring traceability and reliable operation. For example, if JNT ever becomes usable, is traceability via quantum voltage standards? Or photonic thermometry by optical frequency standards?