Slowing down of fast electrons as probe for charging and decharging dynamics of ion-irradiated insulators

Abstract

The slowing down of fast electrons emitted from insulators [Mylar, polypropylene (PP)] irradiated with swift ion beams (C, O, Kr, Ag, Xe; 20--64 MeV/u) was measured by the time-of-flight method at LNS, Catania and GANIL, Caen. The charge buildup, deduced from both convoy- and binary-encounter electron peak shifts, leads to target material-dependent potentials (6.0 kV for Mylar, 2.8 kV for PP). The number of projectiles needed for charging up (charging-up time constant) is inversely proportional to the electronic energy loss. After a certain time, a sudden decharging occurs. For low beam currents, charging-up time, energy shift corresponding to maximum charge buildup, and time of decharging are regular. For high beam currents, the time intervals become irregular (chaotic).