Dynamic evolution investigation on the dielectric surface charging under electron irradiation with various energy distributions

Spacecrafts face various environmental risks in their working durations, thereinto, surface charging, which may result in abnormal operation of devices, is a typical detrimental effect and deserves to be deeply investigated, especially the charging process under various electron energy distributions. In this work, aiming to reveal the evolution process of surface charging in detail, we establish an approach for predicting surface potential under electron irradiation by considering the electron emission process. Mathematical relationships for the dependence of surface charging on the secondary electron yield properties of dielectric surfaces are established. The dynamic process of surface potential evolution is calculated for MgO and Al2O3 when the energy variation of incident electrons obeys uniform distribution, Gaussian distribution, and Maxwell distribution. By analyzing the dynamic equilibrium process of electron incidence/exit in the positively/negatively charged cases, the effect of electron energy on equilibrium surface potential and equilibrium time are quantitatively calculated. It is found that the surface potential will be a dozen volts when the surface is positively charged, surface charging of this magnitude does not have a noticeable effect, and the equilibrium time is short (several microseconds). However, the surface potential may reach very high levels (thousands of volts) leading to breakdowns when the dielectric surface is negatively charged, and its equilibrium time is 3 to 4 orders of magnitude higher than the positively charged case. Via calculating the surface potential under various incident distributions, we acquire the dynamic evolution process of surface potential evolution under different energy distributions, and find its consequence shows a similar tendency for the situation of constant energy irradiation. This work digs into the mechanism of surface charging under various irradiation situations, which makes sense for further works involving surface charging induced by electron irradiation with multiple energy distributions.