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Dive into the research topics where Naoki Kuramoto is active.

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Featured researches published by Naoki Kuramoto.


Metrologia | 2011

Counting the atoms in a 28Si crystal for a new kilogram definition

Birk Andreas; Yasushi Azuma; Guido Bartl; P. Becker; Horst Bettin; Michael Borys; Ingo Busch; P Fuchs; Kenichi Fujii; Hiroyuki Fujimoto; Ernest G. Kessler; Michael Krumrey; Ulrich Kuetgens; Naoki Kuramoto; Giovanni Mana; Enrico Massa; Shigeki Mizushima; Arnold Nicolaus; A. Picard; Axel Pramann; Olaf Rienitz; Detlef Schiel; S. Valkiers; Atsushi Waseda; S Zakel

This paper concerns an international research project aimed at determining the Avogadro constant by counting the atoms in an isotopically enriched silicon crystal. The counting procedure was based on the measurement of the molar volume and the volume of an atom in two 1 kg crystal spheres. The novelty was the use of isotope dilution mass spectrometry as a new and very accurate method for the determination of the molar mass of enriched silicon. Because of an unexpected metallic contamination of the sphere surfaces, the relative measurement uncertainty, 3 × 10−8 NA, is larger by a factor 1.5 than that targeted. The measured value of the Avogadro constant, NA = 6.022 140 82(18) × 1023 mol−1, is the most accurate input datum for the kilogram redefinition and differs by 16 × 10−8 NA from the CODATA 2006 adjusted value. This value is midway between the NIST and NPL watt-balance values.


Metrologia | 2015

Improved measurement results for the Avogadro constant using a 28Si-enriched crystal

Yasushi Azuma; Pauline Barat; Guido Bartl; Horst Bettin; Michael Borys; Ingo Busch; L Cibik; G D’Agostino; Kenichi Fujii; Hiroyuki Fujimoto; Akiharu Hioki; Michael Krumrey; Ulrich Kuetgens; Naoki Kuramoto; Giovanni Mana; Enrico Massa; R Meeß; Shigeki Mizushima; Tomohiro Narukawa; Arnold Nicolaus; Axel Pramann; Savelas A. Rabb; Olaf Rienitz; C Sasso; Michael Stock; Robert D. Vocke; Atsushi Waseda; S Wundrack; S Zakel

New results are reported from an ongoing international research effort to accurately determine the Avogadro constant by counting the atoms in an isotopically enriched silicon crystal. The surfaces of two 28Si-enriched spheres were decontaminated and reworked in order to produce an outer surface without metal contamination and improved sphericity. New measurements were then made on these two reconditioned spheres using improved methods and apparatuses. When combined with other recently refined parameter measurements, the Avogadro constant derived from these new results has a value of


conference on precision electromagnetic measurements | 2004

Present Status of the a Vogadro Constant Determination from Silicon Crystals with Natural Isotopic Composition

Kenichi Fujii; Atsushi Waseda; Naoki Kuramoto; Shigeki Mizushima; P. Becker; Horst Bettin; R. Arnold Nicolaus; Ulrich Kuetgens; S. Valkiers; Philip Taylor; Paul De Bièvre; Giovanni Mana; Enrico Massa; Richard J. Matyi; Ernest G. Kessler; M. Hanke

N_A = 6.022 140 76(12) \times 10^{23}


Metrologia | 2011

Surface layer determination for the Si spheres of the Avogadro project

Ingo Busch; Yasushi Azuma; Horst Bettin; Levent Cibik; P Fuchs; Kenichi Fujii; M. Krumrey; Ulrich Kuetgens; Naoki Kuramoto; S Mizushima

mol


Metrologia | 2011

Volume measurements of 28Si spheres using an interferometer with a flat etalon to determine the Avogadro constant

Naoki Kuramoto; Kenichi Fujii; K. Yamazawa

^{-1}


IEEE Transactions on Instrumentation and Measurement | 2003

Evaluation of the molar volume of silicon crystals for a determination of the Avogadro constant

Kenichi Fujii; Atsushi Waseda; Naoki Kuramoto; Shigeki Mizushima; Mitsuru Tanaka; S. Valkiers; Philip Taylor; R. Kessel; Paul De Bièvre

. The X-ray crystal density method has thus achieved the target relative standard uncertainty of


conference on precision electromagnetic measurements | 2004

Volume determination of a silicon sphere using an improved interferometer with optical frequency tuning

Naoki Kuramoto; Kenichi Fujii

2.0 \times 10^{-8}


Metrologia | 2004

Accurate density measurements of reference liquids by a magnetic suspension balance

Naoki Kuramoto; Kenichi Fujii; Atsushi Waseda

necessary for the realization of the definition of the new kilogram.


Metrologia | 2011

Phase corrections in the optical interferometer for Si sphere volume measurements at NMIJ

Birk Andreas; Luca Ferroglio; Kenichi Fujii; Naoki Kuramoto; Giovanni Mana

The determination of the Avogadro constant from two selected silicon crystals is described. The density, molar mass, and lattice spacing of the two crystals were measured at NMU, PTB, IRMM, IMGC, and NIST. When all the data are combined, it leads to the Avogadro constant of 6.022 1353 (21) times 1023 mol-1 with a relative combined standard uncertainty of 3.4 times 10-7


IEEE Transactions on Instrumentation and Measurement | 2007

Density Determination of Silicon Spheres Using an Interferometer With Optical Frequency Tuning

Naoki Kuramoto; Kenichi Fujii; Yasushi Azuma; Shigeki Mizushima; Yasutake Toyoshima

For the accurate determination of the Avogadro constant, two 28Si spheres were produced, whose macroscopic density, in addition to other values, must be determined. To make a contribution to the new definition of the kilogram, a relative standard uncertainty of less than 2 ? 10?8 has to be achieved. Each silicon surface is covered by a surface layer (SL). Consequently, correction parameters for the SL are determined to be applied to the mass and volume determination of the enriched spheres. With the use of a large set of surface analysing techniques, the structure of the SL is investigated. An unexpected metallic contamination existing on the sphere surface enlarges the uncertainty contribution of the correction parameters above the originally targeted value of 1 ? 10?8. In the framework of this investigation this new obstacle is resolved in two ways. A new combination of analytical methods is applied to measure the SL mass mSL and the thickness dSL, including this new contamination, with an uncertainty of u(mSL) = 14.5??g and 14.4??g, respectively, and u(dSL) = 0.33?nm and 0.32?nm for the 28Si spheres AVO28-S5 and AVO28-S8, respectively.In the second part of the work, the chemical composition of these metallic contaminations is found to be Cu, Ni and Zn silicide compounds. For the removal of this contamination, a special procedure is developed, tested and applied to the spheres to produce the originally expected surface structure on the spheres. After the application of this new procedure the use of x-ray reflectometry directly at the spheres will be possible. It is expected to reduce the uncertainty contribution due to the SL down to 1 ? 10?8.

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Kenichi Fujii

National Institute of Advanced Industrial Science and Technology

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Yasushi Azuma

National Institute of Advanced Industrial Science and Technology

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Shigeki Mizushima

National Institute of Advanced Industrial Science and Technology

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Atsushi Waseda

National Institute of Advanced Industrial Science and Technology

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Lulu Zhang

National Institute of Advanced Industrial Science and Technology

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Akira Kurokawa

National Institute of Advanced Industrial Science and Technology

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Hiroyuki Fujimoto

National Institute of Advanced Industrial Science and Technology

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Hajime Inaba

National Institute of Advanced Industrial Science and Technology

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Kazuaki Fujita

National Institute of Advanced Industrial Science and Technology

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Akiharu Hioki

National Institute of Advanced Industrial Science and Technology

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