Breakdown Discharge in Submillimeter Gaps: A Study Based on Needle-Needle Electrode Configuration

This study investigates breakdown characteristics and discharge modes in submillimeter needle-needle electrode gaps under low-pressure conditions through a custom-designed experimental system. Initial breakdown voltage, current waveforms, and discharge images were acquired across $100-300 \mu \mathrm{m}$ gaps at pressures ranging from 10 to 101 kPa. Analysis reveals that both breakdown voltage and peak current decrease with reducing pressure at fixed gap distances. Distinct discharge mode transitions were identified: streamer-dominated discharges prevail at $\mathbf{6 0 - 1 0 1 ~ k P a}$, while a distinct current surge at 60 kPa indicates mode transformation to Townsend mechanism-sustained glow-like discharges at $30-60 \text{kPa}$, accompanied by progressive formation of the positive column and expansion of negative glow and Faraday's dark space regions. Stable glow discharges establish below 30 kPa. These findings provide critical references for submillimeter gap insulation design in aerospace power systems.