Measurements of Particle Emission from Discharge Sites in Teflon Irradiated by High Energy Electron Beams

Anomalous behavior of synchronous orbit satellites manifested by overall degradation of system performance and reduced operating life is associated with electrical discharges resulting from differential charging of the spacecraft surface by fluxes of high energy electrons. During a laboratory simulation silver-backed Teflon samples have been irradiated by electron beams having energies in the range 16-26 keV. Charged particles emitted from the resultant electrical discharges have been measured with a biased Faraday cup and retarding potential analyser. Measurements indicate the presence of two distinct fluxes of particles; the first being an early pulse (0-600ns) of high energy (~7keV) electrons, while the second is a late pulse (1-5 ¿s) of low energy electrons (<1eV) and ions (70eV) leaving the discharge site as a quasi plasma. Calculations indicate an electrostatic field as the dominant accelerating mechanism for charged particles. For high energy (~7keV) electrons, therefore, the potential difference experienced by the particles in arriving at the detector is a measure of the potential existing at the emitting surface. From the surface potentials thereby derived it is concluded that the charged particle release occurs at localized surface sites having potentials well below the predischarge surface potential. The significance of this result can be understood in terms of assessing various discharge models which have been proposed in the literature.