Physics of CO2 electric discharge lasers

Bullis, R. H.; Fowler, Michael C.; Nighan, W. L.; Wiegand, W. J.

doi:10.2514/6.1971-64

Cited by 5 publications

(1 citation statement)

References 14 publications

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“…The neutral-gas temperature is determined by the power input to the discharge and is therefore a function of discharge impedance. The small-signal gain has been shown to be extremely sensitive to changes in the gas temperature [8]. Introduction of gases with large attachment or detachment rates modifies the positive-negative ion balance.…”

Section: Discussionmentioning

confidence: 99%

Influence of contaminants on the CO<inf>2</inf>electric-discharge laser

Bletzinger¹,

LaBorde²,

Bailey³

et al. 1975

IEEE J. Quantum Electron.

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In C02-N2-He electric-discharge lasers, small concentrations of impurities may be present in the original gases, or new species may be generated by the discharge. In order to determine the effects of such impurities, controlled amounts of possible contaminants were introduced into the amplifier of a C 0 2 probe-amplifier system. Smallsignal gain was reduced in all cases when CO, 02, NO, NzO, or NO2 molecules were added. It was found that less than 0.1 percent of NO2 or N 2 0 markedly reduces the laser gain and alters the discharge impedance. A discharge model which describes a three-component positivecolumn plasma (electrons, positive ions, and negative ions) yields results consistent with the observations. The influence of attachment and detachment rates on molecular gas discharge characteristics and stability are studied. T INTRODUCTIONHE C 0 2 dc discharge laser operates at high efficiency in the glow discharge mode with an optimum mixture of C 0 2 , N 2 , and He which depends on the total pressure, flow rate, current density, and discharge geometry [ I ] . The operating conditions for a given geometry of this weakly ionized plasma (n'/N= are determined by a self-consistent balance of charged-particle production and loss. The discharge properties are controlled by collisional kinetics, plasma chemistry, laser operation, and boundary conditions.In those papers dealing with mass-spectrometric measurements of C 0 2 laser discharges [2] -[ 6 ] the main emphasis has been on the rate of dissociation of C 0 2 into CO and O2 and how this dissociation is changed by operating conditions or gas additives. However, the possible effects on laser performance of the other minor species that are known to exist [7] have not been measured. Therefore, the purpose of the present study was to determine the influence of nitrogen oxides and other candidate dissociation products on the discharge properties and optical gain characteristics of a C 0 2 laser. EXPERIMENTCalibrated amounts of contaminant gases were added to an open-cycle flowing C 0 2 -N2 -He laser discharge. Discharge voltage and small-signal gain were monitored as functions of current. The discharges studied were at total pressures of 5 , Patterson Air Force Base, Ohio 45433. P. D. Tannen was with the Aerospace Research Laboratories, WrightPatterson Air Force Base, Ohio 45433. He is now with the Air Force Weapons Laboratory, Kirtland Air Force Base, N. Mex.10, and 15 torr. The amplifier-tube active length was approximately 57 cm between hollow Kovar electrodes in a watercooled Pyrex tube, with a 22-mm internal diameter (ID). The gas flow rates of C02-N2-He were in the ratio 5 : 10: 85, and the gas residence time in the discharge was approximately 20 ms.A frequency stable laser,' operating on the P20 line of the 10.6-1.1 transitions, was used to measure small-signal gain. The intensities of the reference and amplified beam were measured simultaneously using thermocouples with digital readouts. To compensate for any fluctuations in the probe oscillator output power, the...

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Section: Discussionmentioning

confidence: 99%

Influence of contaminants on the CO<inf>2</inf>electric-discharge laser

Bletzinger¹,

LaBorde²,

Bailey³

et al. 1975

IEEE J. Quantum Electron.

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Theory and Experiment of Electric Discharge CO, Convection Lasers

et al. 1972

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ThemeA THEORETICAL model has been developed for high flow rate molecular gas electric discharge lasers which considers the complete problem of coupling flow parameter variations with excitation and relaxation processes in the active region of a high-velocity laser system. Other studies 1 " 3 have investigated specific aspects of such systems, particularly at low flow rates where flow parameter variations are negligible, but none has considered the complete problem presented here. To validate the use of this model, numerical results of small signal gain for a coaxial system with premixed flows of CO 2 , N 2 , and He in a cylindrical discharge tube were generated and shown to agree favorably with experimental results obtained over a restricted (experimentally) range of flow rates. Theoretical results for the saturation intensity were generated also. With minor modifications the model is applicable to transverse geometries.

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