Microparticle Dynamics in the Presence of Externally Imposed, Ordered Structures in a Magnetized Low-Temperature Plasma

Abstract

Dusty plasmas are a type of plasma which consists of charged microparticles suspended in a background plasma. In the presence of a strong magnetic field, dusty plasmas have been observed to develop new patterned formations in which the pattern corresponds to the shape of a conducting element within the plasma. These formations are given the name imposed, ordered structures. Originally discovered in the Magnetized Dusty Plasma Experiment (MDPX), dust particles were shown to take on the pattern of a conducting wire mesh present in one of the experiments bounding electrodes. This dissertation presents new results from the examination of these imposed, ordered structures in more depth. A two-parameter method for describing the particle organization will be introduced. Using these methods, it will be shown how various types of particle dynamics associated with the onset of imposed, ordered structures are correlated to the increasing magnetization of the background plasma.

In order to better understand the physical mechanism behind the imposed, ordered structures three separate experiments are performed using a new “waffle”-shaped electrode which consists of a large conducting surface with a series of holes through the electrode. When using this electrode, dust particles are observed to become confined to regions beneath the holes in the electrode. Additionally, plasma probe diagnostics show electron density and electric field structures beneath the hole regions of the electrode. A comparison of effective electric potential profiles within the plasma, calculated from three independent experiments, provide strong evidence of magnetically modified plasma sheaths within the plasma.