The article presents the results of an experimental study and numerical modelling for the formation and development dynamics of a high-voltage transverse nanosecond discharge generated by a slot cathode in an argon medium at a pressure range of 1-10 Torr. Numerical modelling was carried out under similar experimental conditions for the processes of formation and propagation of ionisation waves, electron density distribution, excited atom and average electron energy in the discharge gap, including the cavity inside the cathode. At a pressure of p=1 Torr, a classical version of a high-voltage discharge is demonstrated to take place with no penetration of the plasma into the cathode cavity and no observed hollow cathode effect. An increase in gas pressure to 5 Torr leads to a penetration of plasma into the cathode cavity with the formation of a cathodic potential drop (CPD) region. Electrons emitted from the side surfaces of the cavity pass through the CPD region without collisions, oscillate inside the cathode cavity; the hollow cathode effect is fully manifested. At р=10 Torr, the modelling results qualitatively coincide with the results at р=5 Torr; in this case, however, hardly any accelerated electrons are observed in the gap between the electrodes, due to their energetic relaxation both inside the cathode cavity and when exiting from it. In both cases, the plasma structure formed at the exit of the cathode cavity involves a concentration of charged particles an order of magnitude higher than that in the rest of the gap, leading to a self-limiting discharge current effect. The results of the numerical modelling are in good agreement with experimental data.

The article presents the results of an experimental study and numerical simulation of the spatio-temporal dynamics of ionisation processes in the gap between the electrodes and inside the cathode cavity during the formation of a nanosecond discharge in argon at pressures in the chamber from 1 to 10 Torr. The correspondence between the density distribution of charged particles and the optical patterns of the discharge is established. A numerical simulation of the formation of a limited discharge in argon under various external conditions is constructed that accounts for the influence of the charge deposited on the surface of the dielectric wall, the coefficient of secondary emission of electrons from the cathode surface and the effect of the space charge on the distribution of electric potential between the electrodes. The role of the surface charge deposited on the dielectric walls in the formation of the spatial structure of the discharge is determined. The results of numerical simulation are compared with experimental data. It is shown that the electron concentration in a discharge limited by dielectric walls is an order of magnitude higher than in an unlimited discharge under the same external conditions. The general patterns of formation and development of a limited discharge in argon are discussed and the main physical processes affecting the dynamics of development and the spatial structure of the discharge are established.

The work is devoted to the study of the spatiotemporal dynamics of the production of excited atoms in an extended nanosecond discharge with a slot cathode in neon at medium gas pressures. The authors experimentally investigated the frame-by-frame dynamics of the spatiotemporal formation of the discharge optical irradiation with an exposure time of 5 ns and time intervals between frames of 2 ns. Under similar conditions, the concentration of excited neon atoms at metastable levels with a time resolution of about 10 ns was measured by laser absorption spectroscopy, and the current-voltage characteristics of the discharge were experimentally determined in a wide range of amplitudes of voltage pulses and gas pressures in the range of 1–60 Torr. To analyze the kinetic processes in the plasma source under study, numerical simulation of ionization processes in the Comsol Multiphysics software environment was performed using a special Plasma module.