Photoionized Neon Plasma Experiments at Z: Data Processing and Analysis Development
AuthorMayes, Daniel Christopher
AdvisorMancini, Roberto C
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Photoionized plasmas are a special class of plasma common in astrophysical environments, such as x-ray binaries and active galactic nuclei, but they are a relatively unexplored regime of laboratory plasmas. This thesis discusses an experimental effort using the Z-Machine at Sandia National Laboratories to study the atomic kinetics in photoionized plasmas via K-shell line absorption spectroscopy. The experiment employs the intense x-ray flux emitted by the collapse of a Z-pinch to heat and backlight a neon photoionized plasma contained within a cm-scale gas cell placed at various distances from the Z-pinch and filled with neon gas with pressures in the range from 3 torr to 30 torr. High-resolution spectra show absorption by several ionization stages of neon, including Be-, Li-, He-, and H-like ions. A suite of IDL programs have been developed to process the experimental data to produce transmission spectra. Analysis of these spectra yields ion areal-densities and charge state distributions, which can be used to benchmark atomic kinetics codes. In addition, the electron temperature is extracted from level population ratios of Li- and Be-like ions, which can be used to test heating models of photoionized plasmas. Multiple aspects of the processing and analysis methods are tested to identify areas that show improvement or must be improved upon. These include the method of zero-level of absorption estimation, correspondence between known gas filling pressure and measurements totals, temperature extraction from Li-like and Be-like level populations, and the use of Voigt line profiles and Stark broadened line profiles to model the absorption spectra. Finally, we discuss trends visible in the analysis results.