The effects of particle cluster on streamer discharge considering photoionization

In this study, we investigated the influence of particle clusters on the dynamics of discharge streamers using a pin–plate electrode configuration. By accounting for the charging of particles within the cluster, we observed that an increased particle number density in the cluster region leads to a distortion of the photoionization process. This distortion manifests as a delayed distribution and branching of photoionization, resulting in the formation of two independent sub-streamers along the sides of the particle cluster region. Beyond the altered photoionization, the adsorption of electrons and ions due to particle charging significantly modifies the spatiotemporal distribution of electron density. Notably, a substantial reduction in electron number density is detected within and adjacent to the particle cluster region. The propagation velocity of the primary streamer exhibits a reversal pattern around the particle cluster region: the particle charging generates a relatively high voltage potential near the cluster, which shares the same polarity as the powered pin electrode. Consequently, the electric field strength diminishes between the pin electrode and the particle cluster region but intensifies between the cluster region and the plate electrode. As a result, both photoionization and streamer propagation velocity are delayed prior to reaching the particle cluster region and subsequently accelerate upon exiting it. The asymmetrical distributed particle cluster makes the discharge streamer twisted, as the potential position formed by the charged particles shifts away from the axis.