NIST vacuum-to-air mass calibration system as part of a Mise-en-Pratique for the new kilogram definition

The SI unit of mass, the kilogram, will be redefined in terms of the Planck constant, perhaps as soon as 2018. A methodology for the practical realization and dissemination of the new kilogram, or Mise-en-Pratique (MeP), is in progress within the Consultative Committee for Mass and Related Quantities (CCM). The new kilogram will be realized in a vacuum environment and will require transfer to air in order to maintain artifact mass metrology. NIST is developing a vacuum-to-air mass calibration system that uses magnetic suspension to directly compare a mass in vacuum to a mass in air or other gas. This method does not rely on empirical measurement of adsorption characteristics of water in order to correct for mass gain of a primary realization in air. This paper will discuss the realization of the new kilogram and propose a roadmap for dissemination using the NIST magnetic suspension calibration system.