Phenomenology of e-irradiated polymer breakdown

Electronic malfunctions may occur on geostationary satellites when they are immersed in a high energy electron plasma during magnetic substorms. These events are thought to be induced by charges built-up on the various polymer insulators used for the thermal control of the spacecraft and subsequent electrostatic discharges. To understand these discharge mechanisms, laboratory experiments are carried out by irradiating thin FEP films in a vacuum vessel with an electron beam in the energy range 5 keV-50keV. The discharges look like propagating surface discharges in gases at atmospheric pressure and are characterized by a strong electron emission out of the surface known as a 'blowoff emission'. This paper reviews the main characteristics of these surface discharges and a model is proposed for the initiation and propagation processes. The essential idea is that the discharge is the result of the ionization of a thin gas layer created by ionic stimulated desorption of the polymer ahead of the spark. The blowoff emission is then caused by the vacuum expansion of the plasma of the surface discharges. (author)