Advanced studies on powerful wide-aperture nonchain HF(DF) lasers with a self-sustained volume discharge to initiate chemical reaction

摘要

This paper reports on the physics of a self-sustained volume discharge without preionization, self-initiated volume discharge (SIVD), in working mixtures of nonchain HF(DF) lasers. Dynamics of SIVD in discharge gaps of different geometry is thoroughly described. The mechanisms of restricting current density in a diffuse channel in electric discharges in SF_6 and SF_6 based mixtures determining the possibility of the existence of SIVD were suggested and analyzed using simple models. It is shown that the most probable mechanisms are the electron impact dissociation of SF_6 and other mixture components, electron-ion recombination and electron attachment to vibrationally excited SF_6 molecules. Starting from a comparison analysis of the rate coefficients of these processes, it was found that the electron-ion recombination is capable of compensating for electron detachment from negative ions by electron impact. It is established that SIVD can be observed not only in SF_6, but in other strongly electronegative gases, e.g., in C_3F_8 and C_3HCl_3. Analysis is given of the factors determining uniformity of active medium in nonchain HF(DF) lasers. Some special features of operating nonchain HF(DF) lasers with small, 2÷6cm, apertures are carefully examined and the results of measuring the nonchain HF(DF) laser divergence are presented. Consideration is given to the problem increasing the aperture and discharge volume of nonchain HF(DF) lasers and, based from the experimental results, the possibility is shown of increasing their energy to a level of ～1kJ and above.