Equilibrium chemical composition of the gases in a sealed high-pressure pulsed CO2laser

Abstract

The dynamics of changes in the chemical composition of the gas mixture in a pulsed high-pressure gasdischarge CO2 laser with photopreionization, a high current-pulse repetition rate, and transverse circulation of the gas around a closed loop was studied and the setting up of an equilibrium chemical composition was investigated. The use of a high repetition frequency for the current pulses facilitated the rapid establishment of an equilibrium chemical composition in the gas mixture (in about 10–15 min), in a relatively large volume (60 liters), without the mixture being strongly contaminated by desorbed gases. It was established that after this interval of time, following the initiation of a discharge in the gas, a dynamic equilibrium was set up between the dissociation of the CO2 molecules and the recombination of the dissociation products. It was shown that a steady-state degree of dissociation of the CO2 gas was a function of the electric-discharge parameters and of the initial composition of the gas mixture, and was independent of the pressure. Under typical laser discharge conditions, the steady-state degree of dissociation of the CO2 molecules was 20–30%. It was found that hydrogen could be used as a catalyst for oxidizing carbon monoxide. On the basis of these investigations, the use of reduced pressures of the gas mixture is recommended for practically important operating regimes of pulsed CO2 lasers which employ gas mixtures in chemical equilibrium.