MEASURING PRESSURE AND VACUUM WITH LIGHT: A NEW PHOTONIC, QUANTUM-BASED, PRESSURE STANDARD |
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| Jay H. Hendricks, Jacob E. Ricker, Jack A. Stone, Patrick F. Egan, Gregory E. Scace, Gregory F. Strouse, Douglas A. Olson, Donavon Gerty |
- Abstract:
- The future of pressure and vacuum measurement will rely on lasers and Fabry–Pérot optical cavities, and will be based on fundamental physics of light interacting with a gas. Light interacts with matter such that light travels at a slower speed and has shorter wavelength in gas than it does in vacuum. A photonic-based pressure standard represents a disruptive change in the way of realizing and disseminating the SI unit of pressure, the pascal. The underlying metrology behind the advance is the ultra-accurate determination of the refractive index of a gas by picometer optical interferometry, and when value for molar refractive index is calculated from ab-initio quantum chemistry calculations it provides a quantum-based primary pressure standard. The aim of the project is a new technique that will improve accuracy and enable the complete replacement of all mercury-based pressure standards. The National Institute of Standards and Technology (NIST) has now built a working prototype of a fixed length optical cavity (FLOC) with impressive preliminary results. NIST is also developing an even more accurate variable length optical cavity (VLOC) that will make simultaneous ultra-precise measurements of vacuum and gas cavity optical lengths. This paper covers the current status and early prototype results of the photonic-based pressure standard. The early results from the FLOC have exceeded first experimental expectations in that the photonic-based standard is fast, sensitive, accurate, and wide range. Early results demonstrate a pressure resolution of 0.1 mPa (7.5 × 10-7 Torr), outperforming the NIST ultrasonic interferometer manometer by 35X. The lowest pressure measured is 10X more sensitive (1 mPa vs. 10 mPa). Accuracy of the photonic based pressure standard varies between 0.02 parts in 100 (%) at medium vacuum (1 kPa) to 35 mPa/kPa (35 parts in 106) at atmospheric pressure (~100 kPa), with repeatability of 5 mPa/kPa (5 parts in 106) or better, indicating that the standard, once fully developed, will effectively replace mercury manometers for the barometric pressure range, providing improved functionality without the associated hazards of mercury.
- Keywords:
- photonic, pressure, metrology, refractive index, primary standard
- Download:
- IMEKO-WC-2015-TC16-333.pdf
- DOI:
- -
- Event details
- Event name:
- XXI IMEKO World Congress
- Title:
Measurement in Research and Industry
- Place:
- Prague, CZECH REPUBLIC
- Time:
- 30 August 2015 - 04 September 2015