Discharge characteristics in a nonchain HF(DF) laser

It is found that for SF₆—hydrocarbon (deuterocarbon) mixtures having a composition typical for nonchain HF(DF) lasers, the electric field strength reduced to the partial pressure of SF₆ (p_SF6) in the quasistationary phase of a volume self-sustained discharge (E/p_SF6)_st=92 V m^–1 Pa^–1 is close to the known critical value (E/p)_cr=89 V m^–1 Pa^–1, which is specified by the condition that the electron-impact ionisation rate of SF₆ is equal to the rate of electron attachment to SF₆ molecules. This testifies to the decisive role of these two processes and allows the use of the known approximations of the effective ionisation coefficient and the electron drift velocity for pure SF₆ when calculating the discharge characteristics. The oscilloscope traces of voltage and current calculated in this approximation for lasers with apertures ranging from 4 to 27 cm deviated from the experimental data by no more than 10%.