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P: Fachverband Plasmaphysik

P 4: Plasma Technology

P 4.1: Hauptvortrag

Montag, 29. Februar 2016, 14:30–15:00, b305

Impact of electron attachment processes on nonthermal plasmas — •Jürgen Meichsner, Sebastian Nemschokmichal, Robert Tschiersch, and Thomas Wegner — Institute of Physics, University of Greifswald, Felix-Hausdorff-Str. 6, 17489 Greifswald, Germany

The electron capture by micro- and nanoparticles in dusty plasmas as well as the formation of negative ions in the volume and on surfaces in low and atmospheric pressure discharges influence the electron kinetics and discharge dynamics. Negative ion formation in single radio frequency oxygen discharges (CCP, ICP) at low pressure was experimentally investigated and their impact on discharge mode transition (low and high electronegativity) and plasma stability is discussed. Furthermore, the formation of negative secondary ions on the powered electrode of an asymmetric CCP is evaluated concerning their contribution to "pseudo secondary electrons" due to collision detachment of negative ions within the rf sheath. In the case of planar helium barrier discharges near atmospheric pressure with small oxygen admixture the influence of negative ions is investigated by laser photodetachment experiments and corresponding simulations. The photodetachment experiments show a change in breakdown voltage and discharge current when firing the laser during the pre-phase of the discharge, but not when firing during the discharge pulse. The comparison with the simulation implies that an additional formation of negative secondary ions on the negatively charged dielectric might be responsible for the large electronegativity in the discharge pre-phase.