Robert J. Schroeder

Effect of high pressure on the optical detection of gas by index-of-refraction methods

An optical method for the detection of gas in high-pressure flow streams has been developed. One can detect gas by measuring the variation in intensity of reflected, p-polarized light at a sapphire-flow stream interface over a range of angles including the Brewster and critical angles for gas. The effects of high pressure and gas identity have been determined for this gas detection method. Pressure ranges to 20,000 psi of helium, nitrogen, argon, and methane along with a gas mixture were used in these experiments. Excellent agreement is obtained in the pressure- and gas-dependent shifts in critical angle between experimental observations and predictions based on literature values of gas densities and molar refractivities. Significant gas nonidealities are discussed in terms of the correspondence principle.