Experimental study on the impedance of atmospheric radio-frequency glow discharges

A method for studying the influences of plasma working-gas compositions (helium and argon)on the impedance of the atmospheric radio-frequency glow discharges is presented. According to the dielectric properties of plasmas, an equivalent circuit model of resistance-capacitance serial-parallel-connection is proposed to describe the plasma region. The root-mean-square (rms) values of the discharge current and voltage are measured by using an oscilloscope with a current probe and a high voltage probe. The electron number density, as well as the impedance of the generator, during the discharge process is obtained based on the equivalent circuit model. The experimental measurements show that, for the α-mode helium and argon discharges, the resistance and the absolute value of the reactance of the plasmas decrease with increasing in the discharge current, while the electron number density increases almost linearly with the increase of the discharge current. The resistance and the capacitance of the argon plasmas are higher than those of the helium plasmas at the same discharge current. These results will provide guidance for the impedance matching of the discharges using different plasma working-gases.