Hannover 2016 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 5: Poster Session- Helmholtz Graduate School for Plasma Physics

P 5.13: Poster

Montag, 29. Februar 2016, 16:30–19:00, Empore Lichthof

Neutralization of positive ions at metallic and dielectric plasma walls — •Mathias Pamperin, Franz Xaver Bronold, and Holger Fehske — Institut für Physik, Universität Greifswald, 17489 Greifswald, Germany

The main loss channel for positively charged ions in bounded low temperature plasmas is the recombination of ions with the wall. It is often driven by Auger processes and thus accompanied by electron emission. The emission efficiency depends on the electronic structure of the wall and the ion. It is expected to be high in cases where resonant charge transfer initially creates a metastable relay state which then Auger de-excites releasing thereby an electron. For helium ions hitting metallic walls this two-step process leads to robust secondary electron emission due to wall recombination. If however resonant charge transfer is blocked, as it may happen for dielectric walls, secondary electron emission due to ions is much smaller. Secondary electrons result then solely from impacting metastable species produced in the discharge volume. With an eye on tailoring electron emission from the wall, we studied theoretically–using a semi-empirical Anderson-Newns model and non-equilibrium Green function techniques–the interaction of inert gas ions with dielectric and metallic surfaces. Our results demonstrate the importance of metastable relay states and may thus help to design wall materials with custom-made electron emission properties.

Supported by the DFG through CRC/Transregio TRR24 and the Federal State of Mecklenburg-Western Pomerania through the International Helmholtz Graduate School.