Development of a two-dimensional dark fringe method to measure sphere diameters and an accurate determination of the Avogadro constant by using a 28Si crystal

2014 Fiscal Year Final Research Report

• Project/Area Number: 24360037
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Applied physics, general
• Research Institution: National Institute of Advanced Industrial Science and Technology
• Principal Investigator: KURAMOTO NAOKI 独立行政法人産業技術総合研究所, 計測標準研究部門, 主任研究員 (60356938)
• Co-Investigator(Kenkyū-buntansha): WASEDA Atsushi 産業技術総合研究所, 計測標準研究部門, 主任研究員 (20272172) ; AZUMA Yasushi 産業技術総合研究所, 計測標準研究部門, 主任研究員 (30356365) ; FUJIMOTO Hiroyuki 産業技術総合研究所, 計測標準研究部門, 主任研究員 (30357917) ; FUJII Kenichi 産業技術総合研究所, 計測標準研究部門, 首席研究員 (50357901)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: 基礎物理定数 / 標準 / アボガドロ定数 / 光周波数制御 / 超精密計測

Outline of Final Research Achievements

The kilogram is currently defined by the international prototype of the kilogram. To redefine the kilogram based on fundamental constants, a two-dimensional dark fringe method to measure diameters of 1 kg Si spheres has been developed and a 28Si-enriched crystal has been used to determine the Avogadro constant by the X-ray crystal density method. The volume and mass of two 1 kg 28Si spheres have been measured by using a laser interferometer and a vacuum balance, respectively. The surface of the spheres has been analyzed by a spectroscopic ellipsometer calibrated by X-ray reflectometry. The Avogadro constant has been determined with a relative uncertainty of 2.0E-8. This is the most accurate value directly determined experimentally to date, resulting in a strong trigger to conduct the redefinition of the kilogram based on the fundamental constants in 2018.

Free Research Field

応用物理学（基礎物理定数の超精密測定、レーザー干渉技術による幾何形状精密計測）