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Proceedings Paper

Optical Interference Measurements For Equation-Of-State Measurements In High Pressure Gases
Author(s): D. H. Liebenberg
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Paper Abstract

A simple interferometer was built to fit inside a 0.64-cm bore high-pressure cylinder. One end of the cylinder was sealed with a sapphire optical window having a clear aperture of the unsupported area of a Bridgman seal. As the gas density in the cell is increased, successive interferences from a He-Ne laser are detected with a simple photo diode. From a calculated value of the refractive index at the He-Ne wavelength and a measurement of pressure against a calibrated pressure gage at a known temperature, the order shift with pressure is determined. On the basis of an assumption that the Clausius-Mossotti relation is constant, we calculate dP/dP and make comparisons with the equation of state. Measurements and comparisons for nitrogen up to 200 bar are presented and shown to agree well with the derivative values, dp/dP, obtained from the National Bureau of Standards equation of state. One order of interference represents a density change of p = 1.36x 10-4 gm/cm3 for N2 gas at 1 bar. In addition to the usefulness in equation of state studies with gases, the method permits calibration of phase-sensitive optical instruments and may be useful for the assessment of laser target gas loading.

Paper Details

Date Published: 13 November 1980
PDF: 4 pages
Proc. SPIE 0190, Los Alamos Conference on Optics 1979, (13 November 1980); doi: 10.1117/12.957793
Show Author Affiliations
D. H. Liebenberg, Los Alamos Scientific Laboratory (United States)

Published in SPIE Proceedings Vol. 0190:
Los Alamos Conference on Optics 1979
Donald H. Liebenberg, Editor(s)

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