A self consistent model for the discharge kinetics in a high-repetition-rate copper-vapor laser

A Self Consistent computer model has been developed to simulate the discharge kinetics and lasing characteristics of a copper-vapor laser (CVL) for typical operating conditions. Using a detailed rate-equation analysis, the model calculates the spatiotemporal evolution of the population densities of 11 atomic and ionic copper levels, four neon levels, and includes 70 collisional and radiative processes, in addition to radial particle transport. The long-term evolution of the plasma is taken into account by integrating the set of coupled rate equations describing the discharge and electrical circuit through multiple excitation-afterglow cycles. A time-dependent two-electron group model, based on a bi-Maxwellian electron energy distribution function, has been used to evaluate the energy partitioning between the copper vapor and the neon-buffer gas. The behavior of the plasma in the cooler end regions of the discharge tube near the electrodes, where the plasma kinetics are dominated by the buffer gas, has also been modeled. Results from the model have been compared to experimental data for a narrow-bore (ϕ = 1.8 cm) CVL operating under optimum conditions. Close agreement is obtained between the results from the model and experimental data when comparing electrical 1-V characteristics of the discharge tube and circuit, and spatiotemporal evolution of the population densities of the laser levels and other excited Cu I and Ne I states, and lasing characteristics. During the period of lasing action, the populations of the laser levels are perturbed by 10–20 percent due to stimulated emission. During the excitation phase, a significant population resides in the Cu I quadruplet states and in the Cu+metastable ion level. Depletion of electrons in the high-energy tail (∊ > 16.7 eV) of the electron energy distribution function is found to occur during the excitation phase, resulting in weak excitation of the neon-buffer gas in the central zone containing the Cu-Ne mixture. For the neon plasma in the end zones near the electrodes, the population densities of the neon excited states and ions are typically two orders of magnitude higher than in the central zone.