Influence of ultraviolet preionization on the characteristics of an electric discharge HgBr laser

Abstract

Investigations were made of the dependences of the output energy of an HgBr laser on the delay time between an ultraviolet preionization pulse and the main discharge pulse, obtained for different HgBr2 concentrations and energies stored in the ultraviolet preionization source. The drop in the laser output energy on increase in the delay was found to be associated with the process of the dissociative attachment of electrons to the HgBr2 molecules. The rate of this process was found to be (2.6 ± 0.5) × 10− 12 cm3/s. Measurements of the density ne of the preionizing electrons by the charge collection method showed their principal source to be the HgBr2 vapor. An increase in the concentration of the HgBr2 vapor from 4 × 1016 to 1.3 × 1017 cm− 3 led to an exponential reduction in the electron density in the discharge gap of the investigated HgBr laser from 1010 to 1016 cm− 3 due to the absorption of the ionizing radiation by the layer of HgBr2 vapor. For HgBr2 concentrations of greater than 1017 cm−3, the observed fall in the laser output energy was due to a reduction in ne to a value close to the threshold for a volume discharge. Possible ways of increasing the discharge gap of an HgBr laser with ultraviolet preionization were analyzed.