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P: Fachverband Plasmaphysik

P 6: Plasma-surface interaction

P 6.5: Vortrag

Dienstag, 10. März 2020, 12:25–12:40, b302

Interaction of low-energy electrons with metallic walls — •Franz Xaver Bronold and Holger Fehske — Institut für Physik, Universität Greifswald, 17489 Greifswald,

The interaction of electrons with the walls of the discharge vessel is an important surface process in technological low-temperature plasmas. It affects, for instance, the operation modii of dielectric barrier discharges, Hall thrusters, and divertor plasmas in fusion devices. Little is however known quantitatively about the process because it occurs at energies below 50 eV which are hard to access experimentally. There are only a few attempts to measure probabilities for electron absorption, backscattering, or secondary emission in this energy range. A few years ago we presented therefore an approach for calculating the probabilities from a semi-empirical microscopic model and applied it to dielectric walls [1]. The approach is based on an invariant embedding principle for a function Q(Eη|E^′η^′) summing up the backscattering trajectories arising from the interaction of the incoming electron with the excitations and imperfections of the wall. Now we apply the approach to a metallic wall where the dynamic interaction of the penetrating electron with the metal’s Fermi sea and the scattering on imperfections determines the absorption, backscattering, and secondary emission probabilities. Numerical results for the electron absorption probability of a Cu surface are in good agreement with experimental data indicating that the semi-empirical modeling captures in this case the low-energy scattering physics also rather well. [1] F. X. Bronold and H. Fehske, Plasma Phys. Control. Fusion 59, 014011 (2017)