Effects of operational parameters on plasma characteristics and liquid treatment of a DBD-based unipolar microsecond-pulsed helium atmospheric pressure plasma jet

A dielectric-barrier-discharge-based square unipolar microsecond-pulsed helium atmospheric pressure plasma jet (APPJ) was characterized by combining a simplified equivalent circuit model with a transferred charge (Q) measured by introducing an additional capacitance in series with the reactor. From Q-V plots, C-d and C-cell for DBD reactors under pulsed excitation were determined. Q-V plots were drawn for varying operational parameters, and the dissipated energy per cycle was evaluated. Operational parameters, such as the gas flow rate and pulse frequency, were varied, and the resulting changes in the plasma plume length, gas temperature, excitation temperature, discharge current, dissipated power, and optical emission spectra were examined. As an example of the application of the plasma jet, liquid media, including de-ionized water, were exposed to the APPJ, and their properties (pH and electrical conductivity) and concentrations of reactive species generated in the media were measured as functions of the operational parameters. Furthermore, changes in the plasma-activated media after storage for different durations and under different conditions were examined. The correlation between plasma characteristics and properties of plasma-treated liquid is discussed.