Influence of an electric field inhomogeneity and preionization on the spatial and temporal dynamics of the discharge and emission of radiation from an XeCl laser

Processes in the plasma of XeCl lasers utilizing He–Xe–HCl mixtures under conditions of an inhomogeneous electric field and preionization were analyzed theoretically taking into account an extended system of plasma-chemical reactions and various component compositions of the mixture. An experimental investigation was made of the influence of the halogen carrier concentration, the discharge circuit parameters, and the electrode profile on the radiation power distribution in the cross section of the output beam. It was found that if the electrodes had a large radius of curvature (weak inhomogeneity of the field), the discharge contracted either toward the axis or toward the edges of the electrodes, depending on the initial halogen carrier concentration. An ~ 5–10% inhomogeneity of the initial ionization (depending on the initial field inhomogeneity ) at the rate of Q≈10¹⁶ cm ^– 3 · s ^– 1 influenced the current distribution over the electrode cross section during a pump pulse. When the pump pulse duration was increased, localization of the discharge current density was observed at the edge of the electrodes. The radiation power from various parts of the laser beam was amplitude-modulated with a modulation depth of up to 15% (this increased with decreasing pressure and increasing voltage) and a period equal to twice the radiation transit time in the resonator. Practical recommendations are given for obtaining homogeneous discharge and radiation profiles.