Spatial diagnostics of plasma produced by a VHF multi-tile electrode
Ryan, Kevin (2012) Spatial diagnostics of plasma produced by a VHF multi-tile electrode. Master of Science thesis, Dublin City University.
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A scalable multi-tile electrode plasma source operating at 150MHz and 162MHz is described. An investigation into the spatial structure of plasmas produced in such as source is reported. Four dierent plasma diagnostics are applied to examine this spatial structure; they are time-varying magnetic ux probe measurements of the magnetic ux, planar Langmuir probe measurements of the ion saturation cur-
rent density, capacitive probe measurements of the plasma oscillation potential and measurement of rf current and voltage on tiles. Spatial proles of the plasma potential oscillation and the ion saturation high-light the spatial structure imposed on plasmas produced in the PASTIS
source. Analysis of the rf tile current and voltage in the segmented electrode array yields information on the nature of the impedance of both the source and plasma. rf currents in the tiles cause a magnetic dipole to be induced in the regions between tiles. Thus, although the PASTIS source is a capacitive discharge, we must consider a model that includes both capacitively and inductively coupled plasma. This induced dipole moment is measured with a specically designed VHF time-varying magnetic ux probe. Analysis of the diagnostics presented show that there is a well dened spatial structure imposed on the plasma by the segmented electrode tile array.
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