Characteristics of an atmospheric-pressure argon plasma jet excited by a dc voltage

A dc-excited plasma jet is developed to generate a diffuse plasma plume in flowing argon. The discharge characteristics of the plasma jet are investigated by optical and electrical methods. The results show that the plasma plume is a pulsed discharge even when a dc voltage is applied. The discharge frequency varies with a change in the applied voltage, the gas flow rate and the gas gap width. It is found that the discharges at different positions of the plasma plume are initiated and quenched almost at the same time with a jitter of about 10 ns by the spatially resolved measurement. Optical emission spectroscopy is used to investigate the excited electron temperature of the plasma plume. The results show that the excited electron temperature decreases with increasing applied voltage, gas flow rate or gas gap width. These results are analyzed qualitatively.