Kiel 2011 – scientific programme
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P: Fachverband Plasmaphysik
P 20: Simulationsverfahren / Theorie/Modellierung II
P 20.6: Talk
Thursday, March 31, 2011, 12:15–12:30, HS H
Plasma walls beyond the perfect absorber approximation for electrons — •Franz X. Bronold, Rafael L. Heinisch, and Holger Fehske — Institut für Physik, Ernst-Moritz-Arndt-Universität Greifswald, 17489 Greifswald, Germany
Plasma walls accumulate electrons more efficiently than ions leading to wall potentials which are negative with respect to the plasma potential. Theoretically, walls are usually treated as perfect absorber for electrons and ions implying perfect sticking of the particles to the wall and infinitely long desorption times for particles stuck to the wall. For electrons we question the perfect absorber model and calculate, specifically for a planar dielectric wall, the electron sticking coefficient se and the electron desorption time τe. For the uncharged wall [1][2] we find se≪ 1 and τe≈ 10−4s. Thus, in the early stage of the build-up of the wall potential, when the wall is essentially uncharged, the wall is not a perfect absorber for electrons. For the charged wall [3] we find τe−1≈ 0. Thus, τe approaches the perfect absorber value. But se is still only of the order of 10−1. Calculating se as a function of the wall potential and combining this expression with the quasi-stationary balance equations for the electron and ion surface densities we find the selfconsistent wall potential, including surface effects, to be 30% of the perfect absorber value.
[1] R.L. Heinisch et al., Phys. Rev. B 81, 155420 (2010)
[2] R.L. Heinisch et al., Phys. Rev. B 82, 125408 (2010)
[3] F.X. Bronold et al., IEEE Trans. Plasma Science, accepted (2010)