Greifswald 2009 – scientific programme
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P: Fachverband Plasmaphysik
P 12: Hauptvorträge Franke, Bronold
P 12.2: Invited Talk
Wednesday, April 1, 2009, 11:40–12:10, HS Biochemie (groß)
A surface-physics inspired model for particle charging in plasmas — •Franz Xaver Bronold1, Holger Fehske1, Hans Deutsch1, and Holger Kersten2 — 1Institut für Physik, Ernst-Moritz-Arndt-Universität Greifswald — 2Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel
Dust particles in a plasma (internal plasma boundaries) are usually negatively charged. They accumulate electrons more efficiently than ions. We propose a microscopic, surface-physics inspired model for charging and shielding of a grain in a plasma which no longer treats the microsphere as a perfect absorber for electrons and ions [1]. Instead, the grain gives rise to external surface states whose temporal occupancies may be characterized by sticking coefficients and residence times. Within our approach the charge of the grain is given by the number of electrons bound in the polarization-induced short-range part of the grain potential. Ions, on the other hand, we expect to be trapped in the shallow states of the long-range Coulomb potential. Hence, they primarily act as screening charges. Using the particle temperature as an adjustable parameter, orbital motion limited electron charging fluxes, and Bohm limited ion charging fluxes, we obtain excellent agreement with experimentally measured grain charges.
[1] F.X. Bronold et al., Phys. Rev. Lett. 101, 175002 (2008).