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P: Fachverband Plasmaphysik

P 8: Haupt- und Preisträgervortrag

P 8.1: Hauptvortrag

Dienstag, 20. März 2007, 10:30–11:00, 6C

Interesting phenomena in high density discharges at extremely low pressure — •Deborah O'Connell^1,2, Timo Gans^1,3, Dragos Crintea¹, Uwe Czarnetzki¹, and Nader Sadeghi⁴ — ¹Institute for Plasma and Atomic Physics, CPST, Ruhr-Universität Bochum, Germany — ²present address: Institute for Electrical Engineering and Plasma Technology, CPST, Ruhr-Universität Bochum, Germany — ³present address: Centre for Plasma Physics, Queen's University Belfast, Northern Ireland — ⁴Laboratoire de Spectrometrie Physique, University Joseph Fourier and CNRS, Grenoble, France

An inductively coupled radio-frequency (rf) magnetic neutral loop discharge allows plasma operation at extremely low pressures, down to 0.01 Pa. In this pressure regime ohmic heating is inefficient and collisionless heating mechanisms become dominant. Collisionless heating in inhomogeneous magnetic field configurations is only rudimentarily understood. Insight into power dissipation requires temporal resolution on various time scales, in particular the dynamics within the rf cycle. Temporal signatures in the electron energy distribution function are investigated using phase resolved optical emission spectroscopy (PROES) and Thomson scattering. In the low pressure regime of the discharge a relatively high degree of ionisation occurs, up to several percent, and an 'electron pressure', exceeding the neutral gas pressure. This can result in interesting phenomena such as localised depletion of the neutral gas in the main plasma production region, around the neutral loop. Laser spectroscopy is used to investigate this depletion of neutral particles. Funding: SFB 591, GRK 1051, MIWFT