V-I characteristics of pulsed CO2 laser discharges

The voltage-current dependence is investigated for pulsed self-sustained uniform-glow discharges by using commerical-grade mixtures of CO2, N2, and He at near-atmospheric pressures. For a given mixture, the discharge is found to stablize at a value of E/N which is independent of discharge current density, total pressure, and electrode spacing; E is the electric field and N is the number density of the gas. We interpret these observations as evidence that the glow condition is effectively controlled by attachment to CO2 and also to H2O, a gaseous impurity. Calculations of the E/N characteristic, based on a model which includes recombination and attachment losses, are in agreement with experimental results for all mixtures studied.