The kinetic (0-dimensional) model of a pulsed-periodic discharge in mixtures of argon with sulfur vapor, based on solution of the balance equations for plasma species and the electron energy balance equation was developed. The discharge is an effective source of radiation with spectrum, similar to solar spectrum in the wavelength range of 280-600 nm (B3Σ→X3Σ - transition of S2). Variation of plasma species densities during a voltage pulse for various Ar-S2 mixture compositions at different values of the reduced electric field (E/n) under gas pressure ~40 Torr was studied. It is shown, that a breaking field E/n, at which a transition from electronegative to electropositive plasma takes place, increases with sulfur fraction in Ar-S2 mixture. Ar-S2 plasma as simulations show is electronegative; the primary positive ions in Ar-S2 plasma are S2+ and Ar+ ions, the primary negative ions are S2- and S-ions. It is found that during the voltage pulse density of S2 * (B 3Σ ) molecules fast rises and exceeds densities of other excited species; however, when the voltage pulse decreases and, as a consequence, energy of electrons diminishes, density of excited sulfur molecules prompt falls while density of resonance excited argon atoms decreases very slowly. This is a reason for appearance of Ar lines along with S2 bands in spectra of the pulsed-periodic discharge in sulfur vapor argon mixtures.
Power distribution between electrons and positive and negative ions and effect of the distribution on radiative efficiency of XeCl* (308 nm) and Xe2* (172 nm) excimer molecules in the dielectric barrier discharge in Xe-Cl2 at various pressures and supply voltages have been studied and discussed. The discharge characteristics were simulated using the 1D fluid model. It was shown that at small chlorine fraction in the mixture ~0.1–1% the most emission of the DBD is observed in the B→X band of XeCl* molecules at 308 nm: in most cases about 90%–95% of the discharge emission falls on the XeCl* radiation. Highest emission in the B→X band of XeCl* is observed when electrons adsorb about 50 or a bit higher percent of the discharge power. In this case an optimum between emission power and radiative efficiency of XeCl* UV emission is achieved. When the power absorbed by electrons reaches 70%, the radiation efficiency of Xe2* (at 172 nm) sharply increases and riches 10–11% at small increase or even decrease in radiation efficiency of XeCl* (at 308 nm).
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