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Progress on accurate measurement of the Planck constant:Watt balance and counting atoms

Chinese Physics B 2015年第1期24卷 95-108页

作者：李世松张钟华赵伟李正坤黄松岭 Department of Electrical Engineering Tsinghua University National Institute of Metrology

The Planck constant h is one of the most significant constants in quantum physics. Recently, the precision measurement of the value of h has been a hot issue due to its important role for the establishment of both a new SI and a revised fundamental physical constant system. Up to date, two approaches, the watt balance and counting atoms, have been employed to determine the Planck constant at a level of several parts in 108. In this paper, the principle and progress on precision measurement of the Planck constant using watt balance and counting atoms at national metrology institutes are reviewed. Further improvement in determining the Planck constant and possible developments of a revised physical constant system in future are discussed.

关键词： Planck constant watt balance silicon sphere avogadro constant

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维普期刊数据库

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Uncertainty reevaluation in determining the volume of a silicon sphere by spherical harmonics in an avogadro project

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Chinese Physics B 2011年第9期20卷 152-158页

作者：张继涛吴学健李岩 State Key Laboratory of Precision Measurement Technology & Instruments Department of Precision Instruments and MechanologyTsinghua University

To determine the avogadro constant with a target relative uncertainty of 2 x 10-s, the uncertainty component of the silicon sphere＇s volume introduced by the spherical harmonics method, which is usually used in determining the sphere＇s volume, is reevaluated. By means of representing the shape of the silicon sphere by an ellipsoid with Gaussian white noise in its diameters, the uncertainty of the current mapping methods based on the spherical harmonics theory can be estimated theoretically. It is evidenced that the uncertainty component attributed to the current mapping method is underestimated. To eliminate this effect as much as possible, the number of mapping points should be increased to more than before. Moreover, a new mapping method is proposed to accomplish the equal-area mapping with large number points on the silicon sphere.

关键词： metrology avogadro constant silicon sphere spherical harmonics

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维普期刊数据库

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Mixed polarization in determining the film thickness of a silicon sphere by spectroscopic ellipsometry

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Chinese Physics B 2012年第1期21卷 147-152页

作者： Zhang Ji-Tao Wu Xue-Jian Li Yan State Key Laboratory of Precision Measurement Technology&Instruments Department of Precision Instruments and MechanologyTsinghua UniversityBeijing 100084China

The effect of a spherical shape on the measurement result of spectroscopic ellipsometry （SE） is analyzed, and a method to eliminate this effect is proposed. Based on the simulation result of the SE measurement on a silicon sphere by ray tracking, we find that the sphere makes the parallel incident beam of the SE be divergent after reflection, and the measurement error of the SE caused by this phenomenon is explained by the mixed polarization theory. By settling an aperture in front of the detector of the SE, we can almost eliminate the error. For the silicon sphere with a diameter of 94 mm used in the avogadro project, the thickness error of the oxide layer caused by the spherical shape can be reduced from 0.73 nm to 0.04 nm by using the proposed method. The principle of the method and the results of the experimental verification are presented.

关键词： spectroscopic ellipsometry silicon sphere avogadro constant metrology

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维普期刊数据库

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阿伏加德罗常数测定与摩尔复现

阿伏加德罗常数测定与摩尔复现

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2007年全国质谱学会无机质谱、同位素质谱、质谱仪器和教育学专业委员会学术交流会

作者：易洪逯海中国计量科学研究院

阿伏加德罗常数是一个基本物理常数,它是一摩尔物质所包含的实物粒子个数。阿伏加德罗常数在数值上与0.012 kg 基态碳-12的原子数目相等,因此,测定了阿伏加德罗常数即复现了摩尔。测定阿伏加德罗常数就是要准确确定一定质量物质所包含... 详细信息

阿伏加德罗常数是一个基本物理常数,它是一摩尔物质所包含的实物粒子个数。阿伏加德罗常数在数值上与0.012 kg 基态碳-12的原子数目相等,因此,测定了阿伏加德罗常数即复现了摩尔。测定阿伏加德罗常数就是要准确确定一定质量物质所包含的原子个数,这是一个极富挑战性的课题, 也是实现用原子质量重新定义千克的有效途径。阿伏加德罗常数是联系宏观世界与微观世界的桥

关键词： avogadro constant Mole silicon crystal atomic weight lattice constant

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