Discharge Characteristics of an Atmospheric Dielectric-Barrier Discharge Jet

Abstract

This paper reports that a plasma generator at atmospheric pressure, which is characterized by double dielectric layers and a stable dielectric-barrier discharge (DBD) excited by a sinusoidal power supply of 30 kHz, successfully generates a low-temperature argon plasma jet. The DBD has a coaxial and cylindrical configuration, with an annular gap of 2.35 mm between the inner and outer quartz tubes. The rotational $(T_{\rm rot})$ and vibrational $(T_{\rm vib})$ temperatures of the DBD are measured by fine structure fitting of the emission bands of UV OH, N2 molecules, and the Boltzmann plot method, and in comparison with the data of jet temperature obtained by an optical fiber thermometer. The obtained experimental results suggest that $T_{\rm rot}$ and jet temperature increase with the peak applied voltage $(V_{p})$ . On the other hand, they are inversely proportional to the argon gas flow rate. In addition, $T_{\rm vib}$ is found to be insensitive to $V_{p}$ and gas flow rate. Furthermore, the correlation between electrical diagnosis and ultrahigh-speed photographs shows that there are two plasma jets at the positive and negative half cycles of the applied voltage. And the temporal and spatial evolution of the DBD inside the quartz nozzle and plasma jet is also elucidated.