On stability of self-sustained volume discharge in working mixtures of non-chain electrochemical HF laser

Burning voltage of a self-sustained volume discharge (SSVD) is studied as a function of the specific energy deposition in SF₅ with C₂—H₆ and H₂ mixtures, which are working media of a non-chain electrochemical HF laser. It is established that the voltage rises linearly with increasing the specific energy deposition, the relative voltage rise in the SF₆—C₂H₆ mixtures being noticeably higher than in pure SF₆ and SF₆—H₂ mixtures. An assumption is suggested and substantiated on determining the role of molecule dissociation by the electron impact leading to the observed voltage rise. From experimental data we have found approximate energy expenditures of producing dissociation fragments including atomic fluorine in a discharge in pure SF₆ Ê_d(F)= 5±1 eV. The values of E_d well agree with literature data obtained by other experimental methods. A conclusion is drawn that the dissociation process is the main mechanism limiting the current density, which implies SSVD realisation without preliminary gas ionisation in working mixtures of a non-chain HF laser and determines a higher stability of the volume discharge in mixtures of SF₆ with hydrocarbons (deuterocarbons) as compared to mixtures with hydrogen (deuterium). A method is suggested and substantiated for numerical estimation of the limitation effect of the current density and its influence on the SSVD stability.