| Abstract: | Laser Induced Breakdown Spectroscopy (LIBS) is an atomic emission diagnostic which uses a single laser pulse to perform test sample ablation, vaporization, and excitation, all in a single step allowing rapid elemental analysis of any phase of matter. Recently, jet engine manufacturers have expressed concerns regarding the effects of aerosol particulates on component wear and engine lifespan with LIBS systems representing a potential robust approach for exhaust gas monitoring Here, we examine the physics of microparticle ablation and vaporization and the potential for quantitative LIBS analysis of particulates. Micro-particle LIBS is exemplified by a complex plasma initiation on or around the particle surface making experimental investigations probabilistic and non-reproducible due to nearly complete disintegration, especially for particles less than 5 micron. This research discusses the experiments used to study the interactions of micro-particles, much greater than 10 microns, interacting with a laser generated plasma at different distances in a more repeatable and reproducible manner. An electrodynamic balance is designed and constructed to trap a single triboelectrically charged particle and constrain it in space with static and time-varying voltages working in unison. This technique allows for precise localization of the micro-particle in the test section and allows the generation of laser-induced plasmas directly on or in the vicinity of the particle. For the evaluation of three-dimensional effects in the plasma plume, a stereoscopic imaging setup was implemented. The stereo-image technique produces two images on the same camera sensor using a combination of relay optics and pick-off mirrors. Plasma parameters, such as electron temperatures and electron number densities, are determined at various distances between the particle and laser focal point using stereo hyperspectral optical emission spectroscopy coupled with high-speed imaging to visually track particle before and after interaction. Analyzing the data sets provides a good understanding of the effects on the plasma parameters and spectral signatures on breakdown distances relative to the particle and view angles. The electronic version of this dissertation is accessible from https://hdl.handle.net/1969.1/197172 |
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