抄録
Many kinds of insulating materials are used outside a spacecraft. Those are FEP films, polyimide films and so on, and are used as thermal control materials. These materials are exposed to charged particles environment around a spacecraft. So these materials charge up due to the charged particles, especially electrons. It is pointed out that charge-up on these materials is likely to cause discharges on the surfaces. From this viewpoint, we have investigated the charging potential characteristics of 127 μm thick FEP film, typical thermal control material, by irradiating electrons with various energies below 20 keV. In the dependence of the charging potential on the electron energy, we found that the electron energy at which no charge-up occurs is about 2.7 keV. It is thought to be the energy at which secondary electron emission yield becomes one. This indicates that electron irradiation to the FEP film with the energy lower than 2.7 keV induces positive charging. From the charge decay characteristics after electron irradiation the volume resistivity of the film was also obtained as a function of electric fields in the bulk of the FEP film.
