The Pulsed Periodic Discharge in Mixtures of Ar with Sulfur Vapour

Abstract

The discharge in mixtures of inert gas with sulfur vapors is an effective source of radiation spectrum, which is similar to solar in the wavelength range of 280–600 nm due to strong emission of S2 molecules ( $$ B{}^{3}\varSigma \to X{}^{3}\varSigma $$ -transition). This phenomenon is utilized in microwave sulfur lamp. Despite a number of advantages microwave sulfur lamps have disadvantages that prevent their widespread use. This paper presents optical properties of the pulsed-periodic discharge in mixtures of argon with sulfur vapour in UV and visible spectral region and a global model of the discharge. Emission of the pulsed-periodic discharge in argon–sulfur vapour mixtures was studied at argon pressure up to 100 Torr and pressure of sulfur saturated vapors determined by temperature of gas-discharge tube walls varied due self-heating from the room temperature up to 160 °C. It is shown that strong band of S2 molecules are observed in the discharge emission in the wavelength range of 300–600 nm and S and Ar lines are predominate in the wavelength range of 600–1000 nm. Effect of the discharge conditions on emission spectra was investigated. Time profiles of plasma species densities under various Ar–S2 mixture compositions and voltage pulse up to 15 kV with duration ~ 10 μs were calculated using the global model. It is shown, that densities of S2* molecules fast increases at the voltage pulse beginning and reach maximum after ~ 2 μs, so strong radiation of S2* is characteristic for the time interval, then S2* density fast decreases.