Closed cycle operation of CO2 E-beam ionized discharges

Experimental investigations of the closed cycle operation of ultra-high vacuum CO2-N2-He laser discharges with external electron beam preionization are reported. Differences between closed-cycle and sealed-off gas laser systems are discussed, noting the similarity in achieving changes in plasma-chemical reaction rates. Ion- and excited-state reactions dominate the discharge volume while neutral reactions are only significant in the rest of the flow in the gas system considered. The CO2-N2-He discharge comprises over 200 reactions, with the CO2 dissociation the most important, while nitrogen oxides were the worst contaminant. The laser discharge was monitored for CO to measure the dissociation reaction rates for a 1:2:3 CO2:N2:He ratio. The contaminant concentrations were less than 20 ppm because of the vacuum system, while oxygen addition to the mixture caused large increases in the N2O contaminant levels.