Fig. 1. Fundamental evolution stages and multi-timescale physical processes in repetitively pulsed streamer discharge^[21-22]

Fig. 2. Breakdown characteristics of plate-plate electrode and tip-plate electrode under repetitive nanosecond pulses^[29]

Fig. 3. Number of nanosecond pulses required for conversion to spark discharge and relationship between discharge interval and repetition frequency^{[12, 30]}

Fig. 4. Three-stage formation process of spark discharge under repetitive nanosecond pulses^[31]

Fig. 5. Effect of the pulse delay time on variations of positive streamer channels (gas pressure: 13.3 kPa, voltage amplitude: 13.6 kV, pulse width: 200 ns). Images were created by superimposing two streamer discharge channels. Areas that only emitted during the first pulse are blue, areas that only emitted during the second pulse are yellow, and areas that emitted during both two pulses are white

Fig. 6. The “self-focusing” phenomenon of spark discharge channel under repetitive pulses^[43]

Fig. 7. The electron density and electric field distribution: electron-ion plasma cloud interacting with the streamer

Fig. 8. Space charge separation under residual voltage^[61]

Fig. 9. Temporal evolution of the estimated charge in the half-space near the cathode, evaluated from the electric field and charge on the cathode (the background is the optical emission)^[64]

Fig. 10. Uniform DBD glow discharge under repetitive nanosecond pulses in atmospheric pressure air^[70]

Fig. 11. Effect of pulse repetition frequency on pre-breakdown and post-breakdown axial electric field strengths of fast ionization wave^[72]

Fig. 12. Evolution tendency of repetitively sub-microsecond pulsed streamer channel in N₂ (gas pressure: 0.2 MPa)