Volume Measurement of a 28Si-enriched Sphere to Realize the Kilogram Based on the Planck Constant at NMIJ

Abstract

The kilogram based on the new definition revised in 2019 will be realized at the National Metrology Institute of Japan (NMIJ) by using the x-ray crystal density method. For the realization, the volume of a 28Si-enriched sphere, named AVO28-S5c, was measured. The volume was determined from the diameter measurement in many directions by an optical interferometer. The determined volume was also used to evaluate the long-term stability of the volume by comparison to the volume determined in 2016. Detail of the analysis of the volume measurement is presented.