Radiation from Precursor Plasmas of Cylindrical Wire Array and X-pinch Plasmas at 1-1.7 MA Current and Notable Spectroscopic Signatures of fs Laser Produced Plasmas
AdvisorSafronova, Alla S
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My research began with studying precursor plasma from cylindrical wire array (CWA) Z-pinches. Z-pinches are efficient X-ray generators which makes them interesting to many research fields including high energy density (HED) physics, inertial confinement fusion, and astrophysics. Precursor plasmas play an important role in the implosion dynamics of Z-pinches and have been studied extensively. While many important aspects of precursor plasmas column have been studied, the electron temperatures of the precursor plasma was originally estimated using extreme ultraviolet spectra and were inferred to be ~50-60 eV. In later experiments on the Zebra Generator, X-ray time gated spectrometers were implemented to observe L-shell radiation from Ni-60 (94% Cu and 6% Ni) CWAs. Modeling of the spectra suggested electron temperatures of the precursor plasma exceeded 300 eV. My research continues from this point by studying precursor plasmas from CWAs using Cu, Ni, and Al wires to observe precursor plasma conditions, sensitivity to current changes, and effects of non-uniform wire material configurations. Experimental data from time resolved diagnostics including X-ray spectrometers, X-ray pinhole cameras, and diode signals were analyzed to understand precursor plasma evolution. Additional exploration into plasmas from pulse powered devices included experiments with pure Ti and Ti alloy X-pinch experiments. The goal of these experiments was to optimize the experimental parameters, most notably the array mass, to best take advantage of the current that is increased by the Load Current Multiplier (LCM) and determine the limits for the Zebra Generator with the enhanced current. Having investigated K-shell and L-shell radiation from pulsed power created plasma, it was desired to further investigate the results of notable spectroscopic signatures from HED plasmas. In order to focus on specific interactions that affect plasma radiation, ultrashort fs pulse lasers were used to create plasma that interact with the laser pulse on such small time scales that specific relativistic atomic processes can be much more noticeable. Flat Mg targets were irradiated by 350 fs laser pulses from the Leopard Laser producing dielectronic satellite lines from K-shell plasmas. Dielectronic recombination is an important atomic process for populating atomic states with transitions that produce satellite lines and has a large influence on the ionization balance for a plasma. Analysis of the satellite lines provided information on the significance of dielectronic recombination and identified the transitions associated with the satellite structure. Lastly, K-shell Fe spectra were analyzed that were collected from 35 fs pulse laser irradiation from the J-KAREN Laser to investigate hot electron interaction and X-ray pumping effects in the formation of K-shell Fe radiation. Results included observing three distinct plasma regions and identifying hot electron presence.