Dynamics of the development of ionization fronts and the density distribution of the main plasma parameters in a nanosecond discharge with an extended hollow cathode in argon

Experimental studies and numerical simulation have established the dynamics of the formation and development of an ionization wave front of a nanosecond discharge with a hollow cathode for different cathode cavity profiles. The distributions of the electric field potential, the density of charged particles, and the density of excited atoms in the discharge gap and inside the cathode cavity are calculated for electrode systems with a cathode with a semicircular or rectangular cavity. It is shown that when a certain electron density near the anode surface is reached, ionization waves are formed and, propagating towards the cathode at a speed of $10^7$ cm/s, bridge the discharge gap. The distribution of the density and average electron energy over the center of the discharge gap is calculated. It has been established that the density distribution of charged particles in the gap and discharge structure significantly depends on the geometry of the cathode surface. It is shown that a cathode with the rectangular cavity makes it possible to obtain a uniform flat plasma column at the center of the gap with a higher density of charged particles. The experimental and numerical simulation results are compared, which shows that they qualitatively agree.