Evaluation of the theta pinch as a sampling and excitation source for elemental analysis of solid refractory materials
Miller, Duane L.
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https://hdl.handle.net/2142/20355
Description
Title
Evaluation of the theta pinch as a sampling and excitation source for elemental analysis of solid refractory materials
Author(s)
Miller, Duane L.
Issue Date
1996
Doctoral Committee Chair(s)
Scheeline, Alexander
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
Language
eng
Abstract
Studies of a theta pinch discharge device were performed to assess its effectiveness as a sampling and excitation source for elemental analysis of refractory solids. Previous work demonstrated the ability of the discharge to produce spectra suitable for qualitative analysis, but quantitation could not be demonstrated due to insufficient and irreproducible sampling. It was deemed necessary to gain more information about the plasma dynamics to further optimize discharge parameters for improved sampling. Conclusions are based on measurements of plasma shock wave propagation, argon ion excitation temperature, and plasma sampling efficiency as they relate to alterations in induction coil geometry, discharge energy, discharge gas pressure, and sample positioning. A dual grating Echelle spectrometer with charge coupled device detection was constructed and characterized for obtaining spectroscopic data, and is discussed in detail.
Results show that parameter changes which increase the rate of change in magnetic field strength (dB/dt) will increase the plasma energy coupling efficiency, plasma excitation temperature, and sampling efficiency. The absence of an external longitudinal electric field decreases energy coupling efficiency, increases excitation temperature, and has no observable effect on sampling efficiency. Streak photography shows that plasma motion resembles shock wave propagation rather than a magnetically compressed current sheet. Sample positioning affects shock wave propagation, but sample relocation to a shock wave reflection node produces insignificant improvement in sampling efficiency.
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