Stuttgart 2012 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 7: Diagnostik (von Niedertemperaturplasmen)
P 7.3: Vortrag
Dienstag, 13. März 2012, 11:15–11:30, V57.01
Electron kinetics in 10 Hz pulsed cc-rf plasmas studied by 160 GHz Gaussian beam microwave interferometry — •Christian Küllig, Kristian Dittmann, and Jürgen Meichsner — Institute of Physics, University of Greifswald
The line integrated electron density was measured in the bulk plasma of a 10 Hz (50 % duty cycle) pulsed cc-rf plasma in argon and oxygen by means of 160 GHz Gaussian beam microwave interferometry. The on-phase electron density is between 1015 and 3×1016 m−2 in argon and is significantly higher compared with the electron density in oxygen which is between 1014 and 1016 m−2. In the oxygen plasma it was observed an overshoot of electron density in the early afterglow phase for low rf power over a wide pressure range from 20 to 100 Pa. In this case it is important to note that the electron density is nearly the same as the density of negative atomic oxygen ions, which was measured by simultaneous laser photodetachment. A 0D model for the afterglow phase was applied considering particle balance equations for six species (O2+ , O2−, O−, e, O2(a1Δg), O) and eight elementary reactions. The measured steady state density of negative ions and electrons as well as plausible assumptions concerning the density of atomic oxygen and metastabels are taken into account as initial conditions. The model fits very well the measured temporal behaviour of the electron density. A main result from the model is that the O2(a1Δg) are the dominant species for detachment of the negative oxygen ions and electron production in the afterglow. //Funded by the DFG Collaborative Research Centre TRR24, project B5.