Aachen PK 2003 – scientific programme

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P: Plasmaphysik

P 15: Low Temperature Plasmas, Plasma Technology

P 15.4: Talk

Thursday, March 20, 2003, 16:30–16:50, FO1

Distortion of Electron Energy Distribution Functions in a Mixed Mode Discharge — •Ramin Madani and Robert Cherry — Manchester Metropolitan University

The theoretical starting point for the study of low temperature plasmas is the Maxwellian distribution. As a first approximation a Mawellian distribution provides useful information about the dipsersion relationships of surface waves propagating along a cylindrical column. However, under weakly damped conditions practical observations deviate from the theoretical models. The sensitivity of the analysis suggests that a non-Maxwellian distribution may cause this discrepancy.

With a goal of exerting control over the EEDF in an electrodelss discharge a surface wave launcher strikes a discharge through the stray capacitance of a coil, which simultaneously sustains an inductive discharge. The inductive component of the mode is operated at a low frequency of f_H < 100 MHz and the high frequency surface wave mode is launched at f_SW >200 MHz. The experimental configuration favours double probe measurements. Tail measurements of the EEDF obtained from a double probe system have been evaluated with a series of numerically calculated EEDFs mapped for varying electron temperatures and ion densities. The effect of any substantial alterations to the EEDF has been reconstructed from the information obtained by a double probe. These will be compared with measured dispersion relationships and the plasma parameters defining the discharge. A first diagnostic study has already shown very encouraging results.