Measuring space charge and electric field in axisymmetric dielectric barrier discharge using EFISH technique

We investigated the dynamic interactions between electric fields and space charges within an axisymmetric dielectric barrier discharge (DBD) configuration. Employing a square-wave AC, the DBD setup ensured spatial and temporal consistency in microdischarge occurrences. The Electric Field Induced Second Harmonic Generation (EFISH) technique was utilized to capture electric fields and space charge distributions, with special emphasis on the theoretical deduction of space charges from Gauss's Law. After a microdischarge occurred, the measured electric fields diminished due to the destructive superposition of external electric fields and the fields induced by space charges. This reduction in electric field intensity prevented subsequent microdischarges from occurring. However, when the polarity changed, our results demonstrated an increase in the electric fields due to constructive reinforcement between the external electric fields and the space-charge-induced electric field. This enhancement in the electric field facilitated the occurrence of subsequent microdischarges. Notably, a dominant excess of negative charges was observed in the negative phase after the microdischarge, indicating a net negative-charge domain likely due to electron emission from a metallic electrode. This study confirmed the effectiveness of the proposed method for estimating space charges by showcasing the inherent operating mechanism of DBD.