Specific Features of Electron Runaway in a Gas Gap with a Conical Cathode

The conditions and dynamics of electron runaway in a gas gap with an inhomogeneous electric field distribution due to the use of a conic cathode are analyzed. Significant distinctions in the behavior of electrons at cone opening angles larger and smaller than the threshold value of 98.6° are revealed. For a weakly inhomogeneous field distribution (cones with angles above the threshold), electrons are continuously accelerated throughout the entire gap. In a strongly inhomogeneous field (cones with comparatively small opening angles), electrons may gain a maximum energy within the gap and start to decelerate in the near-anode area. However, they reach the anode with high energies comparable to the electric field work. Such a difference necessitates the use of different criteria for the runaway of free electrons in the gas gap.