Much of our work may be viewed as preparation for a possible redefinition of the kilogram, which may occur as early as 2011. We continue to lead the tasks involving mass metrology within the framework of the International Avogadro Coordination (IAC) project. This work has recently been complemented by our participation in the iMERA-Plus project of EURAMET. Experience gained in the Avogadro work is directly relevant to the development of the mise en pratique for a new kilogram definition. Our future work in this area will be in close coordination with the new Task Groups of the CCM Working Group on Mass Standards (CCM-WGM). Both Task Groups held their first organizational meetings in April 2008. Other pertinent work this year includes provision of sorption artefacts to interested laboratories working on watt balances and the IAC, and installation of a glove box that will form part of a system to transfer mass standards maintained under an inert atmosphere.
We have continued to perform calibrations of 1 kg prototypes and other mass standards. However, routine quality checks of these measurements revealed unexpected changes to our working standards. The issuing of certificates has therefore been suspended until the recent history of our working standards was re-established.
At the request of the NPL, we have compared the so-called “BIPM method” for cleaning/washing 1 kg prototypes with a method developed by the NPL based on ultraviolet light and ozone. The NPL cleaning apparatus was transported to the BIPM for this study. The results are still being evaluated, but should provide useful information for the Task Groups mentioned above.
An automated weight exchanger has been installed for our 100 g balance and is being instrumented. When completed, the new facility will increase our efficiency in providing internal calibrations in the range 100 g to 5 g, for ourselves and other scientific sections.
Two notable publications this year have been the new CIPM-2007 formula for the density of moist air and the report of a supplementary comparison with the LNE to validate our internal pressure calibrations.
Three of our staff of five persons have devoted between 60 % and 100 % of their time to the watt balance experiment.
Summary
