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Langmuir Probe Diagnostics in Dusty, Non-Thermal Plasmas


Non-thermal plasmas, at their most ideal, are well understood; the realistic non-thermal plasma, that which is utilized across nearly all semi-conductor related industries as well as extensively in academia, remains thoroughly lacking that understanding, specifically, the non-thermal plasmas which synthesize and/or contain particulate matter, so-called dusty plasmas. This work addresses the marked difficulty in probing such discharges, presenting a design which results in a much more forgiving and simple system to probe and investigate—one which contains solely conductive dust and inert gases. This work studies potential conductive dust candidates and subsequent synthesis methods that adhere to these restrictions, resulting in a separate non-thermal plasma technique for the synthesis and injection of graphitic nanoparticles, as well as the inert gas, into the probed discharge. This work presents a home-built Langmuir probe capable of comprehensive measurements of the electron energy distribution function and important plasma parameters, with no measured degradation caused by a build-up of graphitic nanoparticles on the probe surface. This work confirms that the presence of dust leads to a decrease in electron density and, thus, an increase in the average electron temperature. Finally, this work studies the phenomenon of nanoparticle trapping, presents the first direct measurement of the particle floating potential in a dusty plasma, and represents a step towards understanding the incredibly complex effect of plasma-dust interactions.

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