Abstract
An investigation is made of the characteristics of the formation of a self-controlled volume discharge for pumping CO2 lasers, i.e., self-sustained volume discharge (SSVD), which involves the preliminary filling of a discharge gap by an electron flux from an auxiliary discharge plasma. It is determined that this method is suitable for large interelectrode gaps, that distortion of the electric field in the gap by the space charge of the electron flux plays an important role in the formation of the discharge, that the electrodes could be profiled dynamically during propagation of an electron flux through the discharge gap, and a SSVD could form in systems with a strongly inhomogeneous field. High-power SSVD-based CO2 laser systems are created and investigated. Another type of self-controlled volume discharge without preionization, i.e., a self-initiated volume discharge (SIVD), in nonchain HF lasers with SF6–C2H6 mixtures is also investigated. It is established that, after the primary local electrical breakdown of the discharge gap, the SIVD spreads along the gap in directions perpendicular to that of the electric field by means of the successive formation of overlapping diffuse channels under a discharge voltage close to its quasi-steady-state value. As new channels appear, the current that flows through the channels formed earlier decreases. The volume occupied by the SIVD increases when the energy deposited in the plasma increases, and, when the discharge volume is confined by a dielectric surface, the discharge voltage increases simultaneously when the current increases. The possible mechanisms that explain the observed phenomena, namely the dissociation and electron attachment of SF6 molecules, are examined. A simple analytical model is developed that makes it possible to describe these mechanisms at a qualitative level. High-power SIVD-based HF(DF) lasers are developed and tested.
