Numerical Study of the Dynamics of an Electron Avalanche in the Forming Cathode Sheath of a Self-Sustained Volume Discharge

The dynamics of an electron avalanche starting from the flat cathode surface and from the tops of microtips of different heights on the cathode surface is compared. The dynamics of avalanches was simulated in a changing electric field of the forming cathode sheath of a self-sustained high-pressure volume discharge with preliminary ionization of the gaseous medium. The aim of this work was to study the possibility of the development of instability during the formation of the cathode sheath. It is shown that the start from the top of the microtip gives the avalanche an advantage both in the increase in the number of electrons and in the distance traveled in comparison with the avalanche that started from a flat surface. This advantage is due to the region of enhancement of the electric field produced by the microtip and increases with the height of the tip. Areas of increased plasma density formed by avalanches that start from microtips can create an initial inhomogeneity necessary for the development of instability during the formation of the cathode sheath. The possible mechanisms of the development of instability in the cathode sheath are analyzed.