The study of overlapping sheath and dust particle structures in dusty plasma.


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Complex (dusty) plasma consists of plasma and dust particles which vary in size from nanometer to millimeter in diameter. Complex plasma exists across many different environments, and can be found in environments from the cosmos to industry. Due to plasma fluxes to its surface, a dust particle embedded in a complex plasma will charge negatively or positively depending on the charging mechanism. It should be noted that unless the electron are very energetic, the dust particle is usually negatively charged.

When a surface is immersed in plasma, the region closest to the surface where a quasi-neutral plasma no longer exists is called the plasma sheath. Due to the perturbative nature of the majority of diagnostics in common use, such sheaths, especially the sheath forming near surfaces, can exhibit complex geometries making their physics difficult to diagnose. In such plasma sheath, the surface most often has a negative electric potential, which allows negatively charged dust particles to levitate against the force of gravity. These dust particles can behave as minimally perturbative electrostatic probes. This technique is relatively simple since the necessary measurements are simply the position of the particle and its motion after perturbation.

A novel plasma diagnostic technique, the freefall particle technique, will be introduced in this thesis. This technique allows measurement of the sheath profile with small perturbations, high spatial resolution and minimal equipment requirements. This technique will be employed to investigate the sheath produced at a planar surface allowing investigation of the overlapping sheaths formed inside a glass box commonly used to confine dust in laboratory experiments. The first experimental measurements of the plasma sheath inside a trench-like structure will also be discussed, as will the ion-wake inside a glass box. Finally, the various dust particle structures will be studied. Through measurement of the external confinement force at each position of the dust particle structures, the relationship between dust particle structure formation and confinement is also examined.