Reproducibility of the Realization of the Kilogram Based on the Planck Constant by the XRCD method at NMIJ

The new definition of the kilogram based on the Planck constant was implemented on May 20 2019. Based on the new definition, the kilogram will be realized at the National Metrology Institute of Japan (NMIJ) by the X-ray crystal density method using a
²⁸
Si-enriched sphere. An international comparison of the realizations of the new definition is presently ongoing, where the volume measurement of a
²⁸
Si-enriched sphere and the sphere surface characterization required for the realization were performed by NMIJ. Details of the measurements and the uncertainty evaluation for the realization are described.