Simulation analysis of effectiveness of deep dielectric charging in ground tests

The deep charge-discharge effect in dielectrics induced by high-energy electrons is a major cause of spacecraft anomalies and failures in geosynchronous orbit (GEO) and medium earth orbit (MEO). To evaluate the in-orbit deep charging and discharging behavior of satellite dielectric materials, ground-based simulation testing is essential. However, due to limitations in ground test conditions, it is necessary to conduct a comprehensive analysis of the effectiveness of such evaluations. This paper introduces the key physical model of deep dielectric charging, taking a grounded planar dielectric with an irradiated inner surface as a representative case to analyze the internal charging process and the evolution of critical physical quantities governing deep charging phenomena. In this study, the DICTAT simulation tool is used to investigate the charging effects of three distinct electron sources: strontium-90 decay electrons, monoenergetic electron beams, and GEO ambient electrons. In ground-based simulations, researchers typically use monoenergetic or continuous-spectrum electron beams with flux intensities on the order of pA·cm<sup>–2</sup> to irradiate test specimens with varying shielding configurations, dielectric thicknesses, and material compositions, aiming to replicate <i>in-situ</i> deep charging phenomena and assess associated risks. Therefore, the simulations are conducted under electron flux levels representative of GEO orbital conditions. This study focuses on polytetrafluoroethylene (PTFE) dielectric samples under three typical spacecraft shielding configurations: 1) externally mounted on the cabin surface, 2) housed inside the pressurized cabin, and 3) embedded within standalone electronic subsystems, while systematically incorporating variations in dielectric thickness. The results show that the disparity between the electron flux deposited within the dielectric bulk and the flux at dielectric interfaces critically governs the severity of charging under varying irradiation conditions. Two key findings emerge as follows. 1) Discrepancies in electron energy spectra and their influence: the differences in energy spectra between the test electron source and the actual space environment lead to variations in deposited electron flux across different aluminum shielding thicknesses and dielectric depths. This discrepancy influences the equilibrium charging state by changing the current density and conductivity in sub-region-<i>n</i> (the dielectric-ground interface), potentially resulting in either underestimation or overestimation of deep charging effects compared with true space conditions. 2) Effectiveness of different electron sources for simulation: strontium-based sources (e.g. Sr-90 β-decay spectra) effectively replicate the internal charging behavior of Teflon (PTFE) materials on cabin exteriors and inside pressurized compartments under GEO-like electron flux conditions. 0.5 MeV monoenergetic electron beams are suitable for simulating surface dielectric charging on cabin exteriors. However, higher-energy monoenergetic beams exhibit limited applicability at varying dielectric thicknesses. Despite the similar flux intensity used in the tests compared with that in the actual space environment, the differences in energy distribution between the test beams and space electrons can lead to underestimation or overestimation of the charging effects. Based on the simulation results, this work provides recommendations for selecting appropriate test beam parameters under different shielding conditions to improve the accuracy of ground-based evaluations of in-orbit deep dielectric charging.