Radiation-Induced Conductivity of Space Used Polymers Under High Energy Electron Irradiation

Abstract

Abstract-Polymers are widely used on spacecraft for different specific functions : thermal and electrical insulation, mechanical support, adhesion... These polymers are highly sensitive to radiation met in space. Their electric properties is especially significantly altered leading to very specific behaviour in term of charge transport and discharge processes. Different dedicated facilities have been developed at ONERA, with CNES support, for the characterisation of space used materials in representative conditions. Thanks to the use of these different facilities, it has indeed been demonstrated that radiation induced conductivity of space polymers strongly affects the charging surface potential and depends on several parameters (radiation dose rate, total radiation dose, temperature and on the induced electric field) through complex physical mechanisms that are described in this paper. The sensitivity of polymers on these different parameters strongly depends upon polymer trap distribution and molecular configuration. Experimental as well as numerical results shall be presented in this paper, coupled with the different experimental techniques developed and applied in this work.

Experimental Investigation of Surface Potentials of Materials Under Electron Spectra Representative of GEO and MEO Worst Case Environments

“…The numerical charging model developed in a previous activity allows predicting charging levels under GEO-like environments with a very limited number of input material properties. However, it is worth noticing that these properties must be measured following a robust and precise procedure in order to be reproducible [14], though versatile enough to adapt to changing environmental conditions (temperature, ageing effects, etc) in order to be representative of space environment conditions. The physical model describing dielectric charging under electron spectra has been successfully compared to ground measurements using electron fluxes representative of kp > 5 and of LANL data at GEO.…”

Analysis of Charge Transport and Ionization Effect in Space-Used Polymers Under High-Energy Electron Irradiation

“…Studying the charging behavior of space polymer in space environment implies to perform thorough analysis on the ionization and charge transport processes in representative conditions. RIC depends on radiation dose, dose rate, temperature, and electric field [1]- [5]. Different experimental procedures have been devised at ONERA for the extraction of RIC and for studying the influence of the different above parameters.…”

“…The first approach is the potential relation (PR) method. For this method, bulk induced conductivity is assessed through the analysis of the surface potential relaxation after charging the sample with low-energy electrons (20 keV) up to a given surface potential [5]. During the electric potential relaxation, a 400-keV penetrating ionizing electron beam (which does not contribute to material charging) is used to stimulate the potential decay through the activation of RIC.…”

Electric field dependence on the conductivity of Kapton-HN: Integration into a 1D physical model used for the description of charge transport in dielectric materials under space environment

“…After few seconds the conductivity slowly decreases due to a slow de-trapping of charges that leads to recombination processes. The presence of the RIC after irradiation is stopped is called delayed RIC (DRIC) and has already been described in another paper [3]. In order to decrease the measured signal noise, the conductivity was averaged over the phase of slow increase of the conductivity during irradiation (between the 10 th and 30 th seconds) for each electric field and plotted in fig.…”