Abstract
We investigated the electrostatic charging phenomena of polymer films used for the thermal control materials of spacecrafts by electron-beam irradiation simulating the hot plasma in space. Three kinds of polymer films, Teflon FEP (flurinated ethylene-propylene), Kapton PI (poly imide) and Mylar PET (poly ethylene telephthalate) of the thickness of 13-75μm, were tested under the irradiation conditions of the electron energy E lower than 50keV and the beam current density Jb lower than 1nA/cm2. The surface potentials Vs of the films were obtained as functions of E and Jb at the constant irradiation time.
The obtained experimental results are as follows.
(1) Vs increases with increase of Jb. When Vs∞Jbn is assumed, the n value is different during the films: n=1 for FEP film, n_??_0.5 for PI film and 0.5_??_n_??_0.8 for PET film.
(2) In Vs-E characteristics, Vs has the peak at some electron energy which is dependent on the material and the thickness.
These results were explained by an one-dimensional charging model in which one charge deposition layer is assumed to be formed in the bulk of the film and the volume resistivity and the secondary electron emission coefficient of the material are considered.
