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An Investigation of Tungsten-Based Z-Pinch Planar Wire Array and Benchmarking Experiments
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Wire array z-pinches provide an accessible means to research plasmas of high density and temperature and have valuable applications in the fields of inertial confinement fusion (ICF),astrophysics, and radiation studies. The purpose of this work is tungsten/aluminum z-pinch study and to aid in the development of diagnostics for tungsten x-ray radiation from a high-energy-density (HED) plasma, while exploring possible applications to hohlraum-based ICF research. The z-pinch experiments were primarily carried out on Zebra, the 1.0-1.7 MA pulse power generator located at the University of Nevada, Reno (UNR) Physics Department's Nevada Terawatt Facility (NTF), which creates plasmas with typical radiationemission quantum energies up to 2 MeV. This radiation is studied using an extensive suite of diagnostics, including optical imaging systems, x-ray detectors, spectrometers, and more, which yield both temporal and spatial information in the spectral region between 0.01 keV and 2 MeV.This work also includes the results of research into a new and interesting phenomenon in z-pinch plasmas called bubbling. Specifically, planar wire arrays with relatively large interwire gaps where tungsten is placed in the center of a load configuration composed primarily of a single row of aluminum showed unusual characteristics. These loads are shown to generate an effect in which plasma from the ablation of outer aluminum wires is temporarily hindered from converging at the center of the array where the tungsten wire is located. A full investigation of this effect and possible applications to radiation pulse shaping, particularlywith multi-planar arrays, are also discussed. A large number of other z-pinch x-ray radiation pulse shaping experiments with combined tungsten/aluminum planar wire arrays are also surveyed in addition to those included in the bubbling effect study. The generation of prepulses, or small radiation bursts prior to the primary x-ray radiation peak, is important for driving hohlraum-based ICF loads. Additional experiments also explored methods for generating absorption spectra from z-pinch loads without the use of an external source by placing a single Al wire at the end of a W single planar wire array, which allowed the W M-shell emission to act as a semi-backlighter for K-shell Al absorption lines.Data from other types of sources were also included in this study for the purpose of benchmarking and comparison, including experiments carried out on an electron beam ion trap at Lawrence Livermore National Laboratory (named EBIT-I). The EBIT data in particular was useful for the benchmarking of a model that was developed for M-shell W spectra, which utilizes the Theoretical Hebrew University Lawrence Livermore Atomic Code (HULLAC).