The kinetic theory of cathode plasma expansion in a spatially non-uniform geometric configuration of a vacuum diode

Abstract This paper presents a theoretical explanation for the occurrence of anomalous ion acceleration in vacuum diodes, leading to the expansion of cathode plasma towards the anode, a characteristic phenomenon of vacuum breakdown. The explanation is derived from first principles based on equations of collisionless physical kinetics, using the example of an axisymmetric vacuum diode. The proposed theoretical interpretation convincingly demonstrates that the primary mechanism behind the anomalous ion acceleration of cathode plasma is the collisionless motion of ions in a self-consistent electric field.