Influence of contaminants on the CO2electric-discharge laser

In CO2-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 CO2probe-amplifier system. Small-signal gain was reduced in all cases when CO, O2, NO, N2O, or NO2molecules were added. It was found that less than 0.1 percent of NO2or N2O markedly reduces the laser gain and alters the discharge impedance. A discharge model which describes a three-component positive-column 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.