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Implementing the new kelvin 2


‚ÄčNovel Primary Thermometry

The aim of this work package is to establish novel primary thermometry approaches, based upon measurement of electromagnetic radiation, to measure T and T-T90. A variety of methods will be developed, optimised and tested. To this end, extensive measurements campaigns will be performed to identify and minimise systematic uncertainties. The thermometric methods of interest are:

  • Doppler Broadening Thermometry from the Hg triple point (234 K) to In freezing point (430 K)
  • Double Wavelength Thermometry from Sn freezing point (505 K) to the Re-C eutectic melting point (2747 K)
  • Radiation Thermometry Traceable to Synchrotron Radiation from the Cu freezing point (1358 K) to the Re-C eutectic melting point (2747 K) 

Upgrade and optimization of DBT spectrometers

Hitherto, Doppler broadening thermometry has been mostly developed and used at the temperature of the triple point of water (TPW), for the aims of spectroscopic determination of the Boltzmann constant, and for some preliminary primary thermometry investigations. The aim of this task is to develop, optimize and test Doppler broadening thermometry from the Hg triple point to the In freezing point, in order to demonstrate its potential and its limitations at high temperatures.


Isothermal cell for Doppler-broadening thermometry 

Novel radiometric approaches for primary thermometry

This task aims to develop and evaluate primary thermometric methods, different from classical filter radiometry, (but still based on radiometric principles) that potentially allow the measurement of thermodynamic temperatures in a broad temperature range but are independent from the cryogenic radiometer as primary detector.  This will be achieved either by realizing experimentally (for the first time) the double wavelength technique, which allows one to determine two blackbody temperatures from a relative spectral radiance measurement at suitable wavelengths or by realizing radiometric traceability to another primary radiometric source (in this case) synchrotron radiation whose physics is entirely different from that of a blackbody.


Synchrotron radiation source 

Measurements (
T-T90) with the several experimental approaches.

The aim of this task is to use the novel thermometric approaches for reliable determinations of T-T90 in a wide range of temperatures, from the mercury triple point (234 K) to the Re-C (2747 K).  For each of the methods, a complete uncertainty budget will be constructed.

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