No abstract

Dielectric barrier discharges (DBDs) occur in the presence of at least one insulating layer in contact with the discharge between two planar or cylindrical electrodes connected to a high voltage supply. A quartz coaxial DBD tube, filled with argon, has been studied and an electrical model characterizing the discharges has been proposed. The proposed model considers the geometry of the DBD tube, gas gap spacing and the properties of the dielectric barrier material. A sinusoidal voltage up to 2.4 kV peak with frequencies from 20 to 100 kHz has been applied to the discharge electrodes for the generation of microdischarges. By comparisons of visual images and electrical waveforms, the filamentary discharges have been confirmed. The simulated discharge characteristics have been validated by the experimental results. A good correlation between the experimental and simulated results was found, which is used to deduce the circuit impedance and other electrical parameters, in particular, the conduction current, charge accumulation, energy deposited and consumed power during discharges.

A structurally simple dielectric barrier discharge based mercury-free plasma UV-light source has been developed for efficient water disinfection. The source comprises of a dielectric barrier discharge arrangement between two co-axial quartz tubes with an optimized gas gap. The outer electrode is an aluminium baked foil tape arranged in a helical form with optimized pitch, while the inner electrode is a hollow aluminium metallic rod, hermetically sealed. Strong bands peaking at wavelengths 172 nm and 253 nm, along with a weak band peaking at wavelength 265 nm have been simultaneously observed due to plasma radiation from the admixture of xenon and iodine gases. The developed UV source has been used for bacterial deactivation studies using an experimental setup that is an equivalent of the conventional house-hold water purifier system. Deactivation studies for five types of bacteria, i.e., E. coli, Shigella boydii, Vibrio, Coliforms and Fecal coliform have been demonstrated with 4 log reductions in less than ten seconds.