The realisation of the vapour pressure of Helium-3 and Helium-4 according to the ITS-90

Project Description

Partners will independently realise the ITS-90 in the temperature range between 0,65 K and 4,2 K. By exchange of (RhFe and/or Ge) resistance thermometers, the result will be compared in order to access the agreement between the scale realisations.

Part of the work has already been carried out. This proposal is to allow other laboratories to participate and to give the project a EUROMET status.

Final Report 2007-03-19

The project started 15 March 1995. Measurements on the vapour pressure scales are completed and published by NMi-VSL and NIST. NPL has performed measurements with rhodium–iron resistance thermometers within the framework of CIPM Key Comparison CCT‑K1 (Rusby et al. “Final Report on CCT-K1: Realizations of the ITS-90, 0.65 K to 24.5561 K, using rhodium–iron resistance thermometers”, Metrologia 43 (2006) 03002).
PTB has performed measurements, the results of which are the basis for establishing a new ³He vapour-pressure scale from 0.65 K to 3.2 K and described in detail in two papers:

1. J. Engert, B. Fellmuth: ³He Vapour-Pressure Measurements at PTB. In: Temperature: Its Measurement and Control in Science and Industry, Vol. 7, D. C. Ripple et al. (ed.), Melville, NY, American Institute of Physics, 2003, pp. 113-118.
2. J. Engert, B Fellmuth, K. Jousten: A new ³He vapour-pressure based temperature scale from 0.65 K to 3.2 K consistent with the PLTS‑2000. In: Metrologia, 2007, 44, pp. 40-52.

The comparisons performed within the framework of this EUROMET Project corroborate the estimates for the uncertainty of the new scale being the final result. Since the experiments performed and the data obtained are described comprehensively in the papers listed above and the references cited therein, this completed form can serve as a short final report to be posted on the EUROMET homepage. Thus, the project is completed.