Structural Effects in Deep Charging of Solar Array Dielectrics Irradiated by Energetic Electrons

The charge and discharge characteristics of Solar Array Drive Assembly (SADA) materials in space radiation environments are closely linked to the migration and accumulation of charges on the surface and within the dielectrics, which largely depend on the irradiation parameters, dielectric properties and structures. Accordingly in this work, experimental measurements and simulations are combined to discover the deep charging characteristics with energetic-electron incidence in different configurations of SADA dielectrics, thereby ensuring safe on-orbit operation. The surface potentials of the SADA dielectrics irradiated by 2MeV electrons were firstly measured under three different conditions of the SADA metals: grounded, connected to the high-voltages and floating, each representing the net fluxes of electron current through the dielectric surfaces. GEANT4 and COMSOL were alternately employed to simulate the electron transport and deposition, radiation-induced conductivity, and electric-field on the surface and within the dielectrics. The calculated results are compared with experimental data to verify the modelling accuracy. The results show the dielectric configurations play a significant role in the dielectric deep charging, facilitating a higher electric field building up inside. Specifically in this study, when the ratio of the dielectrics area to the total area exposed to the irradiation environment is reduced from 76.05% to 64.91%, the surface potential drops by 27.69%, and the shares of the secondary-emitted and the back-scattered electrons on the dielectric surface decrease from 20.1% and 0.16% to 18.7% and 0.08 %, efficiently reducing the irradiation dose and the non-elastic scattering of incident electrons in dielectrics. Accordingly, the minimized ratio of the dielectric to total area is recommended. It is further found the positive voltages applied on the SADA metals have a certain offsetting effect on the deep charging due to the accelerated charge leakage. The results of this study provide valuable insights for the rational design of SADA power transmission structure.