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| Avogadro Constant Determination and Kilogram Redefinition |
| LUO Zhi-yong,WANG Jin-tao,LIU Xiang,LI Zhan-hong |
| National Institute of Metrology, Beijing 100029, China |
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Abstract When the kilogram is redefined in terms of the fixed numerical value of the Planck constant h, the X-ray crystal density (XRCD) method, among others, is used for realizing the redefined kilogram. The XRCD method has been used for the determination of the Avogadro constant NA by counting the number of atoms in a 28Si-enriched crystal, contributing to a substantial reduction of uncertainty in the values of NA and h to 2×10-8. This method can be therefore used reversely for the mass determination of a 1 kg sphere prepared from the crystal. The key technologies of lattice constant, isotope, concentration of silicon, diameter of silicon sphere and surface oxide layer are described. The definition of atomic counting method and the method of its value reproduction are introduced. The method will be an important reference for the quality value reproduction of China after the reform of the international system of units.
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Received: 05 September 2017
Published: 12 April 2018
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Corresponding Authors:
Zhiyong Luo
E-mail: luozhy@nim.ac.cn
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2018, Vol. 39 
