Controlling the breakdown delay time in pulsed gas discharge

In experiment and 2D3V PIC MCC simulations, the breakdown development in a pulsed discharge in helium is studied for U=3.2 kV and 10 kV and P=100 Torr. The breakdown process is found to have a stochastic nature, and the electron avalanche develops in different experimental and simulation runs with time delays ranging from 0.3 to 8 μs. Nevertheless our experiments demonstrate that the breakdown delay time distribution can be controlled with a change of the pulse discharge frequency. The simulation results show that the breakdown process can be distinguished in three stages with a) the ionization by seed electrons, b) the ions drift to the cathode and c) the enhanced ionization within the cathode sheath by the electrons emitted from the cathode. The effects of variation of seed electron concentrations, voltage rise times, voltage amplitudes and ion-electron emission coefficients on the breakdown development in the pulsed gas discharge are reported.

Current distribution over the hollow-cathode surface for low-pressure glow discharge

The results of investigation of low-pressure glow discharge with the hollow cathode for the conditions when the cathode cavity depth is comparable with cavity diameter are presented. Data on current distribution over the hollow-cathode surface using sectioned electrodes are obtained and the length of the cathode sheath is measured. It is shown that for the regime of suppressed glow discharge the main fraction of the total discharge current closes to the nearest to the anode cathode section. For the regime of ordinary glow discharge, when the cavity depth is equal to cavity diameter, discharge current over the cathode surface is distributed uniformly. The estimations of the discharge parameters and the values of the cathode sheath using the model of hollow-cathode discharge sustainment were done. Model agrees well with the experimental data.