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ABSOLUTE VOLUME MEASRUMENET OF SILICON SPHERES AT NMIJ

Naoki Kuramoto, Kenichi Fujii
  • Abstract:
    The method and devices for absolute volume measurements of 1 kg silicon spheres are described. An interferometer equipped with a direct optical frequency tuning system is used to measure the sphere volume, in which the optical frequency of a diode laser can be tuned continuously over a frequency range of 19 GHz. Accurate frequency changes in the laser produced by this system are used to measure the sphere diameters by phase-shifting interferometry. A total of seventy diameters, which are distributed near-uniformly over the surface of the sphere, are measured in vacuum. The volume of the sphere is determined by fitting the diameters to a series of spherical harmonics. The mass of the sphere is compared with that of the national prototype of the kilogram through a secondary 1 kg standard. The relative combined standard uncertainty in the density determined by direct measurements of the mass and volume is presently estimated to be 7.3·10-8. Recent results on the volume determination for three 1 kg silicon spheres are shown.
  • Keywords:
    volume standard, density standard, silicon sphere, Avogadro constant
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  • DOI:
    _unreg_wc-2006.TC3-032

Event details:

  • IMEKO TC:
  • Event name:
    XVIII IMEKO World Congress
  • Title:

    Metrology for a Sustainable Development

  • Place:
    Rio de Janeiro, BRAZIL
  • Time:
    17 September 2006 - 22 September 2006