CO Electric Discharge Research Articles

Vibrational kinetics in CO electric discharge lasers: Modeling and experiments

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.

Acoustic waves and heating due to molecular energy transfer in an electric discharge CO laser

This paper summarizes analytical studies and the interpretation of experimental results for the compression and rarefaction waves generated in the cavity of a pulsed CO electric discharge laser. A one-dimensional analysis of acoustic waves is applied to a transversely excited laser. The influences of heating in the cathode fall, heat transfer to the cathode, flow through both the anode and cathode, and bulk heating of the plasma are included. The analysis is used to relate the bulk heating rate to observable features of the pressure and density waves. Data obtained from interferograms and reported elsewhere are used to infer the bulk heating rates in a pulsed CO laser. Results are presented for CO/Ar, CO/N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , and N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> plasmas. Comparison of the data with recent theoretical results for the heating due to electron/ neutral collisions and the anharmonic defect associated with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V-V</tex> energy transfer shows substantial differences at lower values of total energy deposition. The change of heating With <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E/N</tex> is in fairly good agreement with predicted values.

CO Electric Discharge Lasers

The history and status of CO electric discharge lasers are reviewed, and the directions of current research and development activity are discussed. (MHR)

1346. Acoustical wave effects on the beam quality of a high energy CO electric discharge laser: G L McAllister et al, Appl Opt, 14 (6), 1975, 1290–1296

1346. Acoustical wave effects on the beam quality of a high energy CO electric discharge laser: G L McAllister et al, Appl Opt, 14 (6), 1975, 1290–1296

Experimental investigation of a supersonic CO electric discharge laser

Experimental investigation of a supersonic CO electric discharge laser

Acoustical wave effects on the beam quality of a high energy CO electric discharge laser

A high efficiency CO, e(-)-beam sustained electric discharge laser has been operated at 500 J/pulse with near diffraction limited beam quality. The high Fresnel number cavity configuration employs a confocal unstable resonator with a geometric magnification of approximately 2.5. In spite of the high quantum efficiency of the CO laser, significant fractions of the pumping energy are absorbed in the gas as bulk heating giving rise to acoustic waves that refract portions of the light from the beam axis. The strength of the density waves have been measured using interferometric techniques and correlate well with the observed refraction of the laser light.

Observations of small-signal gain in high-pressure pulsed CO electric discharge laser

Measurements are reported of the magnitude and temporal behavior of small-signal gain in a pulsed high-pressure carbon monoxide electric discharge laser. These are compared with predictions derived from kinetic modeling calculations. Maximum gain of 4.5%/cm was measured on the 9P (10) and 8P (10) transitions. The measurements and calculations support the hypothesis that resonance absorption by overlapping transitions is the mechanism responsible for gain suppression on certain lines.