Relaxation Electron Surface Emission From Space Used Polymers

Dedicated experiments have been developed at ONERA to characterize the charging and relaxation behavior of irradiated space polymers. Postirradiation analyses have been performed through potential kelvin probe and leakage or displacement current measurements. We have been able to demonstrate that polymers are submitted, after irradiation, to electron emission from their surface during the relaxation phase. This electron emission presents very low kinetics and can be intense enough to contribute at significant level to the surface potential drop of these materials. A parametric study has been performed to confirm electron relaxation emission and get a better understanding of the underlying steering mechanisms. This emission process is strongly dependent on the energy of the incident electrons used during irradiation and nature of the irradiated material. We present here the experimental results on electron emission from Kapton and Teflon and discuss the different physical mechanisms that could account for this process. The influence of charge double layer and injected radiation dose could especially explain electron emission from the surface through bulk diffusion and energy release by electron-hole recombination process.