Current self-limitation of the nanosecond hollow cathode discharge

The nanosecond hollow cathode discharge in argon gas at the pressure of 1-10 Torr is studied using 2D particle-in-cell Monte Carlo collisions model. We obtain that at the low gas pressure discharge operates in the plane-to-plane mode. This mode allows the generation of energetic electrons (>1 keV) in the gap between the cathode and the anode. However, these electrons do not form the focused beam. At higher pressures, the rather dense plasma penetrates inside the cathode which allows the generation of energetic electrons inside the cathode. However, since the energy relaxation length of 1 keV electrons is shorter than the cathode-anode gap, these electrons dissipate almost all their energy in collisions with neutrals during their propagation toward the anode. Additionally, the optimal conditions necessary for the generation of high-energy electrons are discussed.