Imaging of Transient Analytical Plasmas Using Charge-Coupled Device Detectors
Mork, Brian James
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https://hdl.handle.net/2142/70430
Description
Title
Imaging of Transient Analytical Plasmas Using Charge-Coupled Device Detectors
Author(s)
Mork, Brian James
Issue Date
1988
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Analytical
Physics, Fluid and Plasma
Computer Science
Abstract
The goal of this work has been to better understand analytical atomic emission sources. Heavy reliance on engineering designs of predecessors is exhibited, with the exception of charge coupled device (CCD) detection technology. The incorporation of a CCD into a high energy source spectroscopy laboratory is documented, considering device selection, hardware and software engineering, operating procedures, importance of simultaneous multi-dimensional detection, and system performance.
Problems are uncovered with extending Czerny-Turner based methods to design magnifying transfer optics for spectrographic imaging. Abel inversion processing has been improved by accommodating the suspected condition of concomitant emission and absorption. A model appropriate for discrete element array detectors is designed and characterized.
A variety of experiments are done to document behavior of the high voltage atmospheric pressure spark with the new assemblage of facilities. A spectral survey using a copper electrode is done over the range of 4700-5300 A. Time and two-dimensionally resolved emission spectra are recorded showing results similar to that already in the literature, but offering improved confidence over previous data, which was recorded on photographic plates. Spectral features are shown to vary in significant and unexpected ways as a function of peak current passing through the spark gap. Time differentiated images from an electrode wear study are presented and discussed, revealing subtleties not discernible in any image form previously available. Data recorded in a streak camera mode shows behavior similar to that which others have published, but differing in the presence of on-axis lack of intensity. Single shot spark data at three separate repetition rates indicates a wide range of emission distributions contribute to any data averaged from a train of sparks.
Results collectively reveal the lack of interpretability of most data collected with previous technology. Currently available technology has yielded original insight via a well-characterized detector and the ease of processing large amounts of information, but more critically important research will be possible only when CCDs (or replacement technology) allow time dissection of a single spark in a spatially and temporally resolved manner. However, the data that have been collected point to a less stepwise sparking process than others have concluded. The entire spark gap volume is inundated from within with tremendous energy, stochastically deposited into an existing gap environment.
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