Metrology for Comparison of Displacements at the Picometer Level
| Autor: | Douglas A. Olson, Gregory E. Scace, Jay Hendircks, Gregory F. Strouse, Jack A. Stone, Jacob E. Ricker, Donavon Gerty, Patrick F. Egan |
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| Rok vydání: | 2014 |
| Předmět: |
business.industry
Chemistry Computer Science::Information Retrieval Mechanical Engineering Picometre Displacement (vector) Metrology symbols.namesake Interferometry Optics Mechanics of Materials Dimensional metrology Boltzmann constant symbols General Materials Science business Refractive index Fabry–Pérot interferometer |
| Zdroj: | Key Engineering Materials. 625:79-84 |
| ISSN: | 1662-9795 |
| Popis: | An apparatus capable of comparing displacements with picometer accuracy is currently being designed at NIST. In principle, we wish to compare one displacement in vacuum to a second, equal displacement in gas, in order to determine gas refractive index. If the gas is helium, the refractive index is expected to be amenable to high-accuracy ab initio calculations relating refractive index to gas density or to the ratio of pressure and temperature (P/T); the measured refractive index can then be used to infer (P/T) with an accuracy goal of about 1×10-6(relative standard uncertainty). If either the pressure or temperature is known, the refractive index measurement will allow us to determine the second quantity. Our goal is to achieve an uncertainty limited primarily by the uncertainty of the Boltzmann constant (before redefinition of SI units, which will give the Boltzmann constant a defined value). The technique is an optical analog of dielectric constant gas thermometry and can be used in a similar manner. The dimensional metrology is uniquely challenging, requiring picometer-level uncertainty in the comparison of the displacements. |
| Databáze: | OpenAIRE |
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