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 7.3ยท10-8. Recent results on the volume determination for three 1 kg silicon spheres are shown.
- Keywords:
- volume standard, density standard, silicon sphere, Avogadro constant
- Download:
- PWC-2006-TC3-032u.pdf
- DOI:
- -
- Event details
- Event name:
- XVIII IMEKO World Congress
- Title:
Metrology for a Sustainable Development
- Place:
- Rio de Janeiro, BRAZIL
- Time:
- 17 September 2006 - 22 September 2006