Giovanni Mana

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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 Si-enriched spheres were decontaminated and reworked in order to produce an outer surface without metal contamination and improved sphericity. New(More)
Laser interferometry, as applied in cutting-edge length and displacement metrology, requires detailed analysis of systematic effects due to diffraction, which may affect the measurement uncertainty. When the measurements aim at subnanometer accuracy levels, it is possible that the description of interferometer operation by paraxial and scalar approximations(More)
In displacement measurements by two-beam interferometers, the wavefront curvature of a laser beam causes a systematic increase of the fringe period. This increase depends on beam collimation: It is null for a plane wave and proportional to the squared divergence of the beam. With interfering beams not perfectly recombined, an additional fringe-period error(More)
B. Andreas, Y. Azuma, G. Bartl, P. Becker, H. Bettin, M. Borys, I. Busch, M. Gray, P. Fuchs, K. Fujii, H. Fujimoto, E. Kessler, M. Krumrey, U. Kuetgens, N. Kuramoto, G. Mana, P. Manson, E. Massa, S. Mizushima, A. Nicolaus, A. Picard, A. Pramann, O. Rienitz, D. Schiel, S. Valkiers, and A. Waseda PTB – Physikalisch-Technische Bundesanstalt, Bundesallee 100,(More)
The application of lasers in high-precision measurements and the demand for accuracy make the plane-wave model of laser beams unsatisfactory. Measurements of the variance of the transverse components of the photon impulse are essential for wavelength determination. Accuracy evaluation of the relevant calculations is thus an integral part of the assessment(More)
The latest determination of the Avogadro constant, carried out by counting the atoms in a pure silicon crystal highly enriched in Si, reached the target 2  10 relative uncertainty required for the redefinition of the kilogram based on the Planck constant. The knowledge of the isotopic composition of the enriched silicon material is central; it is measured(More)