A New Scenario for the Kinetics of Charging Dielectrics under Irradiation with Medium-Energy Electrons

Based on a critical analysis of previous studies on the charging mechanisms of dielectric targets under the action of medium-energy (1−30 keV) electron beams, a significant number of conflicting data have been revealed in models of charging, both theoretical and experimental. The cause-and-effect relationships of the physical phenomenon of charging have been revised and refined aiming to eliminate the contradictions that have arisen in the interpretation of the processes of electronic charging of dielectrics. After extensive experimental studies of a wide class of dielectrics, general regularities of the kinetics of charging dielectric targets have been established depending on the number of initial and radiation-induced traps, the density j 0 of current of irradiating electrons and their energy E 0 . The secondary emission properties of a charged dielectric are shown to be fundamentally different from those of an uncharged one, and the electron emission coefficient σ, depending on E 0 , is not the only determining factor of positive or negative charging. When considering the processes of charging, for the first time, primary thermalized electrons are taken into account, which significantly change the general charging scenario, and the key role of the density of the formed radiation defects in charging kinetics is shown. In the proposed model, the decisive stabilizing effect of the onset of equilibrium state charging is the internal electric field F dip generated during irradiation between the positive and negatively charged layers in the near-surface region of the dielectric. The main driving factor of the self-regulating self-consistent process of charging dielectrics under electron irradiation is not only the electron emission coefficient, as has been generally believed earlier, but the formation of the electric field of the dipole layer of charges. This critical control field F cr is of the order of 0.5 MV/cm. This field is approximately the same for all dielectrics at any values of E 0 .