Vibrational kinetics in CO electric discharge lasers: Modeling and experiments

Abstract

Numerous models have been developed to predict the performance of CO electric discharge lasers. Although many comparisons of predicted and observed laser power have been made, few comparisons exist at the more fundamental level of predicted and measured CO vibrational population distributions. Such comparisons provide a critical test of the vibrational kinetic mechanisms assumed in the models and may help explain discrepancies between predicted and measured laser output. In the present study, a model of CO laser vibrational kinetics is developed, and predicted vibrational distributions are compared with measurements. The experimental distributions were obtained at various flow locations in a transverse cw discharge in supersonic (M=3) flow. Good qualitative agreement is obtained in the comparisons, including the prediction of a total inversion at low discharge current densities. The major area of discrepancy is an observed loss in vibrational energy downstream of the discharge which is not predicted by the model. This discrepancy may be due to three-dimensional effects in the experiment which are not included in the model. Possible kinetic effects which may contribute to vibrational energy loss are also examined.