Redefinition of the Kilogram

This project will conduct the research and development required to support the international efforts to prepare for a future redefinition of the unit of mass - the kilogram - the last remaining SI basic unit defined by an artifact.  We use magnetic levitation techniques combined with precision mass measurements  to provide a direct link between the future definition realized in vacuum and the current kilogram defined in ambient air. 

Experiments to redefine the Kilogram with an invariant of nature (such as the Watt balance or the Avogadro project) are performed in vacuum, while current realization of the mass unit and all associated methods of dissemination of the unit are done in air. Transfer of the unit to vacuum requires an unbroken traceability chain to the International Prototype Kilogram, as well as characterization of the stability of the artifacts and their surfaces during transfers from air to vacuum and vice versa. This requirement remains a major challenge and obstacle for further advances in redefining the unit of mass. This project will establish the first complete stable realization and dissemination system that directly ties the current air-based Kilogram definition to the vacuum-based alternative definition using stable artifacts with wear-resistant and chemical inertness characteristics that are maintained in controlled environments.