Optical characteristics of dielectric barrier uniform discharge at atmospheric pressure

Abstract

Dielectric barrier uniform discharges have attracted considerable interest because this type of discharge requires practically no vacuum devices and plasma with good uniformity can be generated at high pressure. In this paper, discharges are initiated in air at atmospheric pressure in a dielectric barrier discharge setup composed of two parallel planar electrodes separated by two layers of dielectric. The characteristics of dielectric barrier discharge are studied through collecting the emission signals from the discharge with a photomultiplier tube and a spectrometer, respectively. The results show that the discharge consists of many micro-discharge filaments when the applied voltage is slightly above the breakdown voltage, and the discharge is uniform when the applied voltage is very high. The waveform of discharge emission consists of many pulses with duration of several tens nanoseconds in the filamentary discharge mode. However, it only consists of a single broad electrical pulse (hump) lasting approximately a quarter of a discharge time period on which significant narrow pulse peaks are superposed. Streamer breakdown mechanism is involved in the discharge of not only filamentary discharge but also uniform discharge. Spectral emission spectroscopy is used to study the discharge transition. The intensity ratio of 391.4nm to 337.1nm represents electron energy that is mainly determined by the electric filed applied to the gas gap. With increasing the applied voltage, the intensity ratio of 391.4nm to 337.1nm decreases. This experimental result indicates that electron energy decreases with the increasing of the applied voltage.