Darmstadt 2008 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P II: Poster: Niedertemperaturplasmen, Plasmatechnologie

P II.13: Poster

Dienstag, 11. März 2008, 11:00–13:00, Poster C3

Phase resolved Thomson scattering on an inductively coupled radio-frequency plasma discharge — •Dragos Liviu Crintea, Dirk Luggenhölscher, and Uwe Czarnetzki — Institute for Plasma and Atomic Physics, CPST, Ruhr-University Bochum, Germany

In radio-frequency (RF) discharges the electron energy distribution function is expected to be temporally oscillating. This applies to the homogeneous as well as the inhomogeneous part. The oscillation in the homogeneous part, which is of second order, can be observed by monitoring the phase-resolved emission from highly excited states. The observation of the oscillation of the inhomogeneous part is more difficult to probe. Here, for the first time we demonstrate such a measurement by phase-resolved Thomson scattering in an inductively coupled RF at 13.56 MHz in Argon at pressures of 0.5 Pa and 2 Pa. A displaced Boltzmann distribution is measured, where the displacement oscillates with the RF frequency. The displacement corresponds to a collective drift oscillation with velocity amplitudes of the order of 10^5 m/s. It can be fitted well to a sinus at the RF frequency. Further, the time independent plasma density is inferred from the Thomson spectra and so the local current density can be derived. In addition to the oscillatory drift also a small DC drift is observed with velocities in the range of a few 10^4 m/s. This drift increases with decreasing pressure and vanishes effectively at pressures of about 10 Pa. This work is supported in the framework of SFB 591, GK 1051