3-dimensional model for Trichel pulses: results of numerical studies for air

It is known that an electric current in a negative corona for pin-to-plane configuration in a wide range of parameters has a form of periodic peaks, which are called Trichel pulses. Recently, authors reported about development of 3-D axially symmetric model intended for numerical simulations of Trichel pulses. In this paper authors present results of numerical simulations of a long train of pulses for pin with hemispherical cap to plane anode configuration in ambient air at atmospheric pressure. These calculations provide information about dynamics of Trichel pulse starting from step-wise voltage applying. Calculations clearly demonstrate that regular current oscillations are established after 4-5 pulses. Space-time evolution of electric field and charged species densities within one cycle of regular oscillations is described in detail. In particular, distributions of specific components of current density over the cathode and anode surfaces were found in dependence on time. Comparison is made with experimentally available data. In contrast to simplified 1.5-D model predicting two-peak shape of Trichel pulse, the exact 3D model predicts single-peaked pulses when ion induced secondary emission processes are included, and photo-emission is neglected. On the anode surface, radial profiles of electric field and ion and electron current components were calculated. Variations of individual current pulse amplitude and shape with discharge voltage growth are studied, too. (author)