WP 2: Dissemination of primary thermometry between 25 K and 303 K

INRiM (WP leader), CEM, CMI, CNAM, INTiBS, LNE, NPL, PTB, TIPC-CAS, TUBITAK, UL

The main aim of this work package is to demonstrate that in the range between 25 K and 303 K the redefined kelvin may be disseminated by capsule standard platinum resistance thermometers (cSPRTs) directly calibrated to thermodynamic temperature. The target uncertainty of the dissemination in this range spans between 0.25 mK at 25 K and 0.6 mK at 300 K by two primary thermometry methods (DCGT and AGT) which will be implemented by absolute and/or relative and measurement schemes.

Importantly, and for the first time ever, the low uncertainty claimed by primary methods will be tested by comparing the thermodynamic calibration results obtained by different experiments as a part of a dissemination trial to NMIs without primary thermometry capabilities. These NMIs will initially be responsible for the ITS-90 calibration of the cSPRTs and their delivery to primary experiments, with the calibration results remaining undisclosed not to bias the thermodynamic comparison. Finally, the emerging capabilities of two NMIs in primary acoustic thermometry (AGT) will be boosted by active collaboration with a more experienced partner. Two new AGT apparatus will be completed and used for the realization of the redefined kelvin over the temperature range between 234 K and 303 K, with the quality of these realizations verified by comparison to ITS-90 calibrations and also, directly, by the dissemination activities of Task 2.2.