EXPERIMENTAL AND THEORETICAL-ANALYSIS OF COLLECTIVE EFFECTS IN ELECTRON-IMPACT IONIZATION PHENOMENA

An experimental analysis of collective effects, depending on the electron-ion mutual interactions, which occur during the ionization of a gas jet by impact with an incident monochromatic pulsed electron beam, is presented. The dependences on the gas pressure of the transmitted current and of the ion yields show a marked deviation, in the same range of gas pressure, i.e., of produced charges, from the expected behavior in the absence of interactions between incident and produced charges. The phenomenon is described by an approximate solution of the two-fluid equation system that takes into account the transient phase, during the impact ionization, and the symmetry of the experiment. The theoretical model well explains the observed dependences. © 1990 The American Physical Society.