Greifswald 2009 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 15: Poster: Diagnostik
P 15.19: Poster
Mittwoch, 1. April 2009, 17:30–19:30, Foyer des IfP
Comparative negative ion density measurements in oxygen dc-glow, rf-CCP and helicon discharges — •Dirk Pasedag1, Holger Testrich1, Kristian Dittmann1, and Nadiya Sydorenko2 — 1University of Greifswald, Institute of Physics, Greifswald, Germany — 2Max-Planck-Insitute for Plasma Physics, EURATOM Association, Greifswald, Germany
Negative ions have a strong influence on the reaction kinetics in molecular electronegative plasmas,
and they drastically modify the plasma properties. Furthermore, the origin of plasma instabilities
is often combined with the generation and loss of negative ions. Their density is beside others
controlled by metastable oxygen molecules as well as the plasma surrounding walls.
To show the influence of these conditions the negative oxygen ion
density in three different discharge types was been measured. In a
dc-glow discharge with low density (ne ∼ 1016 m−3)
and glass walls, a rf-CCP discharge with comparable low density but
walls of stainless steel as well as a high density (ne ∼
1019 m−3) helicon discharge
with a magnetized (B = 100 mT) plasma and relatively large area of stainless steel walls.
The negative oxygen ions (O−) are recorded by the probe assisted laser photo-detachment technique
using a frequency doubled Nd:YAG laser with the same diagnostic equipment. A significant difference
of the electronegativity from less than one in the dc-glow discharge to values considerable greater
than one in rf-CCP discharge was obtained.
Supported by SFB-Transregio 24, projects A1, B1 and B5.