Enrico Massa

Learn More
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)
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)
he capability of operating a separate crystal x-ray interferometer over centimeter displacements has made it possible to observe minute strain fields of a bent crystal at the atomic scale resolution by means of phase-contrast x-ray topography. Measurement and predictive capabilities of lattice strain are key ingredients of a highly accurate measurement of(More)
The Avogadro constant links the atomic and the macroscopic properties of matter. Since the molar Planck constant is well known via the measurement of the Rydberg constant, it is also closely related to the Planck constant. In addition, its accurate determination is of paramount importance for a definition of the kilogram in terms of a fundamental constant.(More)
Optically heterodyned laser interferometry, as applied to measuring linear displacements, requires different optical frequencies to be encoded onto unique polarization states. To eliminate non-linear contributions to the interferometer signal, the frequency difference must be introduced after beam splitting and the interfering beams must be recombined via(More)
To base the kilogram definition on the atomic mass of the Si atom, the present relative uncertainty of the Si lattice parameter must lowered to 3 × 10. To achieve this goal, a new experimental apparatus capable of a centimetre measurement-baseline has been made at the INRIM. The comparison between the determinations of the lattice parameter of crystals MO*4(More)
High-accuracy dimensional measurements by laser interferometers require corrections because of diffraction, which makes the effective fringe-period different from the wavelength of a plane (or spherical) wave λ<sub>0</sub>. By using a combined X-ray and optical interferometer as a tool to investigate diffraction across a laser beam, we observed wavelength(More)