Aachen PK 2003 – scientific programme

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P: Plasmaphysik

P 5: Basic Plasma Physics, Theory

P 5.3: Talk

Tuesday, March 18, 2003, 12:10–12:30, FO1

Spatial transition of electrons from active to field-free plasma regions through a field reversal range — •D. Loffhagen, F. Sigeneger, and R. Winkler — Institut für Niedertemperatur-Plasmaphysik, 17489 Greifswald, Germany

Reversals of the electric field have repeatedly been suggested in the literature and partly observed in certain discharge conditions, as e.g. in the negative glow or in front of the anode. In generalization of a former study of the spatial transition of the electrons from an active homogeneous to an adjacent field-free plasma region, the impact of a field reversal in the transition zone is now investigated by solving the electron Boltzmann equation and by Monte Carlo simulations. In the one-dimensional model the electric field goes within a transition region from its steady-state value through zero to a reversed field and back to zero. For comparison the field reversal is omitted in a reference case. To get a continuous time-independent transition of the electron gas an electron sink is additionally included in the vicinity of the field reversal describing e.g. the electron extraction by a grid. The results show a considerable impact of the field reversal on the velocity distribution function and the macroscopic quantities of the electrons in the transition region. The occurrence of trapped electrons leads to a much stronger increase of the density and decrease of the mean energy if compared with the reference case. The anisotropic distribution part has a complicated structure which is mainly induced by the backflow of low energy electrons towards the sink. Quite unexpectedly, the backflow is not restricted to the trapped electrons but extends to electrons with a somewhat higher energy too.