Uniformity of dielectric barrier discharges using mesh electrodes

In this paper, the uniformities of dielectric barrier discharges (DBDs) produced by different mesh electrodes are studied. If the aperture of the mesh electrode is long enough, the discharge spots are periodic. If the aperture is smaller than 0.5 mm, the discharge spots will be distributed randomly and even more densely than when produced by a planar electrode. Because the evaluation of the uniformity of the DBD, which consists of a large number of microdischarges, is different from that of a glow DBD or a Townsend DBD, the coefficient of variation (CV) of the gray level distribution of the discharge light emission is used to describe the uniformity of the DBD. The smaller the value of CV, the more uniform is the discharge. The experimental results show that the uniformity of the DBD produced by some mesh electrodes is even better than that by a planar electrode if the aperture of the mesh electrode is small enough. On the other hand, a new dimensionless scale invariant (h), which includes the combined effect of the aperture and the normalized change rate of the field strength of the avalanche head, is presented to analyze the physical mechanisms leading to a relatively uniform DBD according to the condition of the slow development of many avalanches at a low electric field. The calculated results show that the variation trend of h for different mesh electrodes is almost the same as that of the CV. This means that the dimensionless scale invariant h can be used to study the discharge uniformity.