In this paper, a number of drawbacks and contradictions of the existing models of charging dielectric targets under irradiation with defocused electron beams of moderate energies (0.2-20 keV) are briefly noted. In order to streamline and coordinate all experimental results and theoretical information concerning the phenomenon of charging under electron irradiation, it was necessary to reconsider some postulates of the standard model based on a simple dependence of the electron emission coefficient sigma on irradiating electron energy E-0. It is shown that the decisive role in establishing the equilibrium state of charging dielectrics is played by not only establishing the equilibrium value sigma = 1, but also by reaching a certain critical value of the field F-in in the near-surface area of the target. This field is due to the generation of the two-layer bipolar distribution of charges. It enhances the electron emission owing to increasing the depth at which secondary electrons emerge and also owing to the previously neglected contribution of primary thermalized electrons. As a result, there occurs a fundamental transformation of the dependence of the total electron emission coefficient sigma(c) for a charged dielectric on the energy of primary electrons as compared to the case of an uncharged dielectric. Consequently, the value of the equilibrium energy E-2C, at which sigma = 1, is changed. It is established that times of reaching equilibrium states for electron emission delta(t) and for surface potentials V-s(t) may differ by orders of magnitude. Also, the charging kinetics is significantly affected by the process of radiation-induced formation of defects in the irradiated dielectric, which results in two charging time constants-fast and long-term ones. Published under an exclusive license by AIP Publishing.
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