Experimental probe-induced complex RF plasma phenomena.
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Access changed 9/30/2016
Harris, Brandon Joseph.
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Plasma has long been studied in its own right as a state of matter, but the addition of particles large compared to its basic constituents yields a host of complicated behavior that was not predicted theoretically. Levitated micrometer-sized particles in the sheath of a RF plasma have previously been shown to form basic symmetry structure, but in this study, formerly undiscovered vertical oscillations, horizontal circular cavities, and waves in chains (longitudinal and transverse) were produced. Though a cylindrical vertical powered probe is used here to arrange and drive the particles in the laboratory, perturbations also exist in plasma formations in space that contain macroparticles. Probe theory is well established as a method to extract plasma parameters, but here the interaction of the probe affects particles directly through the probe’s electric field when nearby, and indirectly affects the particles by changing the local plasma conditions when far away. These effects are first examined independently, and then merged with a mid- range exploration by observing the particle structure formations and their motion. Since the probe extends into the non-uniform plasma sheath, the ubiquitous bulk plasma calculations are not valid, though they can be used as a starting point to facilitate understanding of the plasma and explain its interactions with dust and the probe.