Düsseldorf 2007 – scientific programme

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P: Fachverband Plasmaphysik

P 22: Poster

P 22.34: Poster

Thursday, March 22, 2007, 16:30–18:30, Poster A

Symmetry and Bias Effects on the Self-Excited Plasma Series Resonance — •Uwe Czarnetzki — Institut für Plasma- und Atomphysik, Ruhr-Universität Bochum, 44780 Bochum

Self-excited Plasma Series Resonances (PSR) are observed in capacitve discharges as high frequency oscillations superimposed on the normal RF current. This high-frequency contribution to the current is generated by a series resonance between the capacitve sheath and the inductive and ohmic bulk of the plasma. The ohmic behavior is caused by elastic collisions between the electrons and the neutral back ground gas and the effective inductive behavior results from the electron inertia. The non-linearity of the sheath leads to a complex dynamic. In a previous work we have described the effect in the frame of a simple one-dimensional model with a single sheath. Here, the model is extended to the case of two sheaths and describes the situation of a discharge of arbitrary area ratio between electrode and ground. The effect of this area ratio can be described by a single symmetry parameter and it is shown how increased symmetry leads to a damping of the PSR oscillation amplitudes. In a similar way also the effect of bias voltage deviations, i.e. a not ideally collapsing sheath, can be described. The derived analytical approximations agree well with numerical solutions.