Applications of autocorrelation function method for spatial characteristics analysis of dielectric barrier discharge

In this paper, spatial characteristics of dielectric barrier discharge (DBD) are analyzed using autocorrelation function (ACF) method. The filamentary, homogeneous and periodic discharge produced in a plate and mesh electrode, respectively, are quantitatively identified by analysis of the spatial structure of the discharge images in DBD with the ACF method. The influences of the size of the mesh electrode on spatial characteristics of discharge in DBD are also investigated by using the ACF, current waveform and Lissajous figures measurements. Moreover, the spatial structure and evolution of patterns in DBD are studied using this method. The results show that an exponential decay and random oscillation are exhibited in the radial and angular distribution of the ACF in a filamentary discharge, respectively. Both the radial and angular distribution of the ACF display a periodic oscillation in a periodic discharge. while the radial and angular distribution of the ACF are both approximately to 1 in a homogeneous discharge. With the decrease of mesh size, it can be seen from the corresponding radial distribution of the ACF that the discharge transits from a periodic discharge with its discharge period gradually decreasing to a filamentary discharge in air at atmospheric pressure when the voltage is kept fixed. It means that there is a optimal mesh size for the formation of the homogeneous spatial structure. Furthermore, the radial distribution of the ACF transits from a exponential decay, an periodic oscillation and into approximately to 1 with the increase of the applied voltage in air/argon mixture. It indicates that the discharge transit from the filamentary mode, the periodic patterned mode into the homogeneous mode. Moreover, two different periodic patterned discharge, the hexagon pattern and the square pattern are recognized quantitatively from the angular distribution of the ACF, which are coincident with the known experimental results. These results demonstrate that the ACF is a simple and effective method to analyze the spatial characteristics of DBD.