Analysis of cathode pre-ionization in long-gap needle-to-needle air streamer discharges

The investigation of streamer discharge during air gap breakdown under a point-to-point electrode configuration holds significant importance. A numerical model for streamer discharge in a 100 mm air gap with point-to-point electrodes was developed based on the drift-diffusion fluid equations for electrons, positive ions, and negative ions in air discharge. This model incorporates 110 reaction types, including electron impact, recombination, dissociative quenching, attachment reactions, as well as photoionization processes. The study revealed that within the point-to-point structure, a cathode pre-ionization zone forms near the cathode due to the aggregation of particle clouds. Following contact between the propagating streamer and this pre-ionization zone, the discharge exhibits rapid acceleration, culminating in the final breakdown of the gap.