Evaluation of equipment and procedures for the transfer and storage of mass standards in inert gas

This paper reports on work to improve mass stability when transferring platinum/iridium, stainless steel and silicon artefacts between air and vacuum using inert gas (argon) as a transfer/storage medium. Work is underway to redefine the kilogram in terms of a fundamental constant of nature and this will involve realizing a kilogram in vacuum. The development of an effective traceability link to this kilogram in vacuum is therefore essential for dissemination of the mass scale in the future. The work reported here investigates the effect of cycling artefacts between air and vacuum compared with cycling artefacts between argon and vacuum. Additionally, the effect of transferring artefacts between short-term storage in air compared with short term-storage in argon is investigated. The results presented demonstrate improved stability in the artefacts that are transferred between storage in argon and vacuum compared with those that are transferred between storage in air and vacuum.