Comparative study of pulsed breakdown processes and mechanisms in self-triggered four-electrode pre-ionized switches

This work investigates the pulsed breakdown processes and mechanisms of self-triggered pre-ionized switches with a four-electrode structure in nitrogen through intensified charge coupled device photographs. The diameter of the trigger plane hole mainly determines the switch's electric field distribution. Two configurations with minimum and maximum trigger plane holes are adopted for comparison. In the switch with a minimum trigger plane hole, the maximum electric field distributes at the surfaces of the main electrodes. Although charged particles in the triggering spark channel cannot drift out, homogeneous discharges can be stimulated from both the cathode and anode surfaces through ultraviolet illumination. Two sub-gaps are likely to break down simultaneously. In the switch with a maximum trigger plane hole, the maximum electric field locates near the trigger electrodes. Discharges in both sub-gaps initiate from the trigger electrodes in the form of a positive or negative streamer. Due to the lower breakdown voltage and electric field threshold for discharge initiation, the cathode side sub-gap breaks down first. The analysis of two extreme examples can be referenced in the future design and improvement of self-triggered four-electrode switches with different trigger electrode structures.