Effect of powered electrode configuration on plasma structure of surface micro-discharge array

Abstract

Surface micro-discharge (SMD) has received growing interest for its great prospect in various emerging applications spanning the fields of biomedicine, manufacturing, and agriculture. Discharge properties and the nature of the chemical species are heavily dependent on the electrode configuration. However, insight into the effect of electrode configuration on SMD remains scarce. This paper reports on the effect of the geometry of the powered planar electrode on the dynamic evolution of plasma in a helium SMD array at atmospheric pressure. The observed symmetric and asymmetric luminous patterns correspond to odd and even numbered current pulses in negative half-cycle, respectively. When the powered electrode is not covering the full area of the mesh unit of the grounded electrode, the luminous pattern dominated by the negative pattern consists of three parts: the distinct luminous channel, the flabelliform luminous area, and the discontinuous cambered channels under the incomplete powered electrode condition. The distinct luminous channel is ascribed to the propagation of the bullet-like plasma volume originated at the middle part of the mesh side before merging with other plasmas. The merging plasma forms a cambered front and continuous to propagate, leading to the formation of a flabelliform area. The discontinuous cambered channels result from the propagation of bullets ignited at the mesh corners, especially the slide of luminous area with maximum emission intensity along the streamer. Moreover, the mesh element without a powered electrode can also initiate breakdown due to the sufficiently high voltage and the propagation of surface charges, suggesting that the grounded mesh electrode should be extended to avoid redundant discharges.