Evaluation of the Neutral Xenon Laser for Infrared Measurement of Nitrous Oxide from Combustion Sources

摘要

The report evaluates the feasibility of using a simple gas-discharge xenon laser operating at a wavelength of 3.9 micrometers for direct measurements of N2O concentrations in combustion systems. The method relies on a near-coincidence between the laser line and the R4 line of the 2vl infrared absorption band of N2. A prototype pulsed xenon laser was constructed and used to measure this frequency difference, found to be 0.07 plus/minus 0.01 per cm corresponding to an effective absorption coefficient of 0.74 per atm per cm in atmospheric pressure air. The laser also operates at two other wavelengths which are suitable for reference absorption measurements. Computer simulations of atmospheric transmission through combustion gases have been used to estimate system performance for both extractive sampling and in-situ measurements using either dual beam or single beam absorption methods. A detection limit of less than 0.1 ppm in a 1 second averaging time should be feasible with minimal interference from other combustion gases.