Development of a self-initiated volume discharge in nonchain HF lasers

The dynamics of a self-initiated volume discharge (SIVD) is studied in SF₆ – C₂H₆ mixtures, which are used as the working media in nonchain HF lasers, employing discharge gaps of different geometry. The results of investigation are consistent with the previously made assumption that there exist mechanisms which limit the current density of a volume discharge in SF₆ and SF₆-based mixtures. SIVD simulations were performed taking into account the SF₆ dissociation by electron impact, the dissociative electron – ion recombination, the electron detachment from negative ions by electron impact, and the ion – ion recombination. The simulation results are in qualitative agreement with experimental results. The electron – ion recombination and the electron detachment from negative ions were found to cancel each other, to within the accuracy of estimates of the rate constants. The dissociation of SF₆ (and other components of the mixture) is most likely responsible for the limitation of the current density in the diffusive discharge channel and for the increase in discharge volume with increasing input energy.