Runaway Electrons in a Gas Diode with a Wedge-Shaped Cathode

The features of electron runaway in a gas diode with a wedge-shaped cathode providing a sharply inhomogeneous distribution of the electric field in the interelectrode gap are studied. It is shown that the character and conditions of runaway are qualitatively different for wedges with relatively large and small opening angles, i.e., in fact, for different degrees of field inhomogeneity. In the first case, the transition to the runaway mode is determined by the behavior of electrons in the immediate vicinity of their starting point, the vertex of the wedge-shaped cathode. For a wedge close in shape to a blade (opening angle less than 30° degrees), the relative contribution of the braking force for electrons in the gas increases with distance from the cathode, and their behavior at the periphery, near the anode, begins to play a key role in the analysis of runaway conditions. The influence of an external magnetic field on the geometry of the ionized region near the wedge vertex, starting from which the electrons become runaways, is also discussed.