Matthieu Thomas (LNE)

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20 mai 11:30 » 12:30 — Bibliothèque PCT - F3.04

New kilogram definition in the revised SI

The seven base units of the SI (Systeme International d’unites) will be defined on May 20, 2019 by reference to fixed and exact values of defining constants following after 30 years of progress in quantum physics. In particular, the kilogram will be defined from the Planck constant h, allowing weaknesses of the previous artefact definition to be lift up. The new kilogram will be based on electrical standards that are traceable to quantum effects like the Josephson and the quantum Hall effects.

The presentation will begin by a general introduction to metrology together with a presentation of the SI. Then, the primary methods to realize macroscopic mass within the new definition will be described : LNE (Laboratoire national de metrologie et d’essais) has developed such a balance (Kibble balance) in order to realise the unit of mass at the kilogram level. This balance has contributed to the latest adjustment of the h value, and will be used to realize the mass unit in France : its design choices, results and future development will be described.

Even if the redefinition of the kilogram on the basis of the Planck constant represents a real paradigm shift, this will definitely not result in any change for the end user. Nevertheless, in the future, the mass unit can be realized at any mass value from the Planck constant. Hence, I will show what possible ways can be followed in the future for realize mass unit at different scales.





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