Greifswald 2009 – scientific programme

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P: Fachverband Plasmaphysik

P 15: Poster: Diagnostik

P 15.22: Poster

Wednesday, April 1, 2009, 17:30–19:30, Foyer des IfP

Radio Frequency Modulation Spectroscopy (RF-MOS) in Inductively Coupled Plasmas — •Dominik Winter, Yusuf Celik, Dirk Luggenhölscher, and Uwe Czarnetzki — Institute for Plasma and Atomic Physics, Ruhr-University Bochum

Radio-frequency modulation spectroscopy is a recently developed emission spectroscopic diagnostic in inductively coupled plasmas. It measures primarily the temporal modulation of the local electron energy distribution function (EEDF) by detecting small modulations in the percentage range of the optical line emission from the plasma. The measured quantities are the oscillatory velocity amplitude and its phase. Further, constant drifts in the same direction as the oscillatory drift can be detected. The analysis requires, in addition to the optical measurements, knowledge on the form of the EEDF around the excitation threshold of the measured emission line. In the simplest approximation the EEDF in that energy range can be represented by a Maxwellian distribution characterized by an effective electron temperature parameter. The general theory is based on a Fourier solution of the local Boltzmann equation. The solution connects the first and second harmonic of the distribution function with the static and isotropic velocity distribution. Only elastic collisions have an explicit influence of the amplitudes. In case of vanishing collisions the result is equivalent to an expansion of the general solution of Vlasov*s equation in the small drift velocity. Provided that the local approximation holds, the velocity amplitude can be linked directly to the local electric field. The theoretical basis, experimental requirements and results are presented.