21.09.2012
On 01 June 2012, the European research project "Developing a practical means of disseminating the new kilogram" (EMRP/SIB05) started with the participation of fourteen partners from thirteen countries.
The kilogram is the only one of the seven base units of the International System of Units (SI) which is still defined by a material measure – the international prototype of the kilogram. The international prototype of the kilogram has so far been kept in air and has also been used for official comparison measurements in air. In a future SI, the definition of the kilogram will relate to a fundamental constant . As the redefinition will be realised with the aid of different experiments under vacuum conditions such as, for example, the Avogadro experiment and the watt balance experiment, it is the objective of this project to develop practical methods and procedures to trace the secondary standards – which are used by the national metrology institutes in air – back to the primary mass standards in vacuum. Here, the uncertainty contributions which result from the different steps in the dissemination chain must be significantly smaller than the required relative uncertainty of the realization (2 · 10-8). In five working packages, the project will mainly be focused on the following points:
- Development and evaluation of suitable mass standards for maintenance and dissemination of the redefined kilogram
- Development and evaluation of methods and procedures for the transfer of mass standards between vacuum, air and selected inert gases
- Analysis of surface effects and dynamic processes on the surface of mass standards during the transition between vacuum, air and selected inert gases
- Evaluation of the mass stability of mass standards when different storage, cleaning and transport methods are used
- Analysis of the uncertainty contributions for the practical realisation of the redefinition (mise en pratique) and their propagation in the dissemination chain.
This program will be funded within the scope of the call "SI Broader Scope" of the European Metrology Research Programme" (EMRP). PTB is involved in all five working packages and makes – with the direction of a working package related to the transfer of mass standards between vacuum, air and selected inert gases – an essential contribution to this research project.
References:
[1] BIPM 
Link
Contact person:
Michael Borys, Dept 1.1, WG 1.11, e-mail: michael.borys@ptb.de