Berlin 2005 – scientific programme

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P: Plasmaphysik

P 14: Poster: Niedertemperaturplasmen / Plasmatechnologie 6, Diagnostik 4

P 14.22: Poster

Saturday, March 5, 2005, 14:45–16:45, Poster HU

Electron heating by vibrationally excited molecules in the afterglow of a pulsed, inductively coupled rf discharge — •Deborah O’Connell¹, Mariana Osiac¹, Brian Heil¹, Thomas Schwarz-Selinger², Miles Turner³, Timo Gans¹, and Uwe Czarnetzki¹ — ¹Institut für Plasma- und Atomphysik, Ruhr-Universität Bochum, 44780 Bochum, Germany — ²Max-Planck-Institut für Plasmaphysik, EURATOM Association, 85748 Garching, Germany — ³Plasma Research Laboratory, Dublin City University, Dublin 9, Ireland

Investigations in the afterglow of a pulsed-mode, inductively coupled, hydrogen plasma reveal that the positive space charge sheath does not fully collapse in the post discharge. Time resolved measurements of ion energy distribution functions (IEDFs), using a mass resolved ion energy analyser incorporated into the grounded electrode, exhibit a finite energy of a few eV, for several hundred micro-seconds in the afterglow. This is attributed to electron heating by super-elastic collisions with vibrationally excited molecules. A particle in cell (PIC) simulation confirms electron heating through super-elastic collisions. Measurements of the vibrational temperature, by optical emission spectroscopy, also support this electron heating mechanism. Decay times for the electron density, measured with a Langmuir-probe, are in good agreement with the decay of the ion flux. The project is funded by the DFG in the frame of SFB 591.