Improving the Measurement of the Diameter of Si Spheres

Nicolaus, R.A.; Geckeler, Ralf D.

doi:10.1109/tim.2007.890619

Cited by 26 publications

(13 citation statements)

References 11 publications

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“…For the target uncertainty the temperature of the sphere needs to be measured with an uncertainty of less than 1 mK. To reduce any effects of influencing the temperature of the sphere, thermocouple pairs measure the temperature difference between the sphere and a copper block inside the interferometer frame which acts as a reference body [5]. The temperature of this copper block is measured by common means, i.e.…”

Section: Experimental Setup Of the Spherical Fizeau Interferometermentioning

confidence: 99%

Volume determination of the Avogadro spheres of highly enriched²⁸Si with a spherical Fizeau interferometer

et al. 2011

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Within the scope of the efforts concerning the redefinition of the SI base unit "kg" the final results of the international research project aiming at the redetermination of the Avogadro constant are ready to be announced. Among other quantities the volume of two spheres which are made of a highly enriched 28 Si single crystal had to be determined. For this purpose a special Fizeau interferometer for the measurement of the spheres' diameters has been developed at PTB. This paper reports the final results of the volumes, the uncertainties and also the latest findings regarding systematic corrections including the effects of surface layers on the pure silicon core. The results are confirmed by density comparison measurements.

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Section: Experimental Setup Of the Spherical Fizeau Interferometermentioning

confidence: 99%

Volume determination of the Avogadro spheres of highly enriched²⁸Si with a spherical Fizeau interferometer

et al. 2011

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“…The volume is determined from the measurement values of 280 diameters distributed nearly uniformly all over the surface of the sphere. The relative Figures 20 and 21 show the spherical-etalon interferometer developed by the PTB [86]. The aperture of the interferometer objectives is 60 • , allowing 16 000 simultaneous diameter measurements.…”

Section: Optical Interferometers For Silicon Spheresmentioning

confidence: 99%

The Avogadro constant determination via enriched silicon-28

Becker

Friedrich

Fujii³

et al. 2009

Meas. Sci. Technol.

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This review describes the efforts of several national metrology institutes to replace the present definition of the kilogram by a new one based on the mass of a given number of 12C atoms. This requires the determination of the Avogadro constant with a relative uncertainty no greater than 2 × 10−8. Since in previous attempts the most significant limiting factor has been the measurement of the average molar mass of the natural silicon, an international collaboration has been set up to produce a 5 kg single crystal with an isotope enrichment over 99.985%. The technological steps enabling the production of this high-purity 28Si crystal are also reported.

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“…The interferometer frame is placed inside a vacuum chamber to eliminate any influences of the refraction index of air. Furthermore, temperature fluctuations are reduced to some mK per day by a thermostatic control of the temperature of the vacuum chamber and a weak thermal contact to the interferometer frame [12]. The components of the illuminating and imaging optics are aligned symmetrically on both sides of the vacuum chamber.…”

Section: The Sphere Interferometermentioning

confidence: 99%

Influence of the distribution of measuring points on the mean diameter determination of the Avogadro project's silicon spheres

Bartl¹,

Nicolaus²

2009

Meas. Sci. Technol.

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The members of the International Avogadro Project are aiming at the redetermination of Avogadro's constant with a relative uncertainty of less than 2×10−8 in order to be qualified for the redefinition of the kilogram. Therefore, among other quantities, the volume of a sphere made of a silicon single crystal has to be determined very precisely with a diameter uncertainty of 0.3 nm. A special Fizeau interferometer with spherical reference faces has been developed at PTB providing the required precision in absolute interferometry and a generous coverage of the surface of the sphere at the same time. Due to the intrinsic imbalanced distribution of measurement positions given by the setup, an equalization has to be performed without introducing a numerical error. In this paper an appropriate procedure using point distributions on a sphere is described and characterized with regard to the number of points involved.

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Improving the Measurement of the Diameter of Si Spheres

Cited by 26 publications

References 11 publications

Volume determination of the Avogadro spheres of highly enriched²⁸Si with a spherical Fizeau interferometer

Volume determination of the Avogadro spheres of highly enriched²⁸Si with a spherical Fizeau interferometer

The Avogadro constant determination via enriched silicon-28

Influence of the distribution of measuring points on the mean diameter determination of the Avogadro project's silicon spheres

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Improving the Measurement of the Diameter of Si Spheres

Cited by 26 publications

References 11 publications

Volume determination of the Avogadro spheres of highly enriched28Si with a spherical Fizeau interferometer

Volume determination of the Avogadro spheres of highly enriched28Si with a spherical Fizeau interferometer

The Avogadro constant determination via enriched silicon-28

Influence of the distribution of measuring points on the mean diameter determination of the Avogadro project's silicon spheres

Contact Info

Product

Resources

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Volume determination of the Avogadro spheres of highly enriched²⁸Si with a spherical Fizeau interferometer

Volume determination of the Avogadro spheres of highly enriched²⁸Si with a spherical Fizeau interferometer