Picosecond Breakdown in High-Voltage Open Pulse Discharge With Enhanced Secondary Electron Emission

A 300-ps breakdown was registered in the experiments in the high-voltage open discharge with counter-propagating electron-beams with applying voltage pulses with rise times in 10–20 ns range. Discharge operates between two cathodes and grid-anode in the midplane at 10–35 Torr in helium at voltage 5–13 kV. It is shown in Particle-in-cell Monte Carlo collision (PIC MCC) simulations that the contributions of electrons, ions and energetic atoms in ionization and excitation processes are important for current development. The influence of different emissive cathode materials (titanium, silicon carbide, and CuAlMg-alloy) on evolution of discharge current is studied in the experiment and in kinetic PIC MCC simulations. The secondary electron emission from the cathodes is found to be a dominant process at the final stage of the breakdown. The current growth rate is larger (up to 700 A/cm²ns) for the cathode with a higher secondary electron emission yield. By choosing the cathode material, applied voltage amplitude and gas pressure, the characteristic time of the gas breakdown can be reduced.