Power balance and wall erosion measurements in a helicon plasma

The power balance measurements in a 1 kW argon helicon plasma discharge are demonstrated. The quantitative wall heat flux measurements using nonintrusive infrared imaging of the glass tube surface, along with data from bolometric probes and calibrated photodiodes to measure heat flux from the rest of the plasma, are shown. For the cylindrical discharge, with radius much less than the axial length, approximately 15% of 1 kW input power is lost in the transmission lines and matching network, 54% is lost through radial particle transport to the walls, 16% is lost through radiation, and 8% is lost through ion impact in the vicinity of the antenna. Wall erosion of the confining glass tube occurs due to sputter etching by ions accelerated in the electrostatic fields produced by the antenna. Wall etch rate measurements are used to quantify particle fluxes to the wall, which are in rough agreement with particle fluxes calculated from thermal flux.

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