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Spectroscopic study of z-pinch stagnation on Z

Rochau, G.A.; Bailey, James E.; Coverdale, Christine A.; Ampleford, David J.; Cuneo, Michael E.; Jones, Brent M.; Jennings, Christopher A.; Yu, Edmund; Hansen, Stephanie B.

Fast z-pinches provide intense 1-10 keV photon energy radiation sources. Here, we analyze time-, space-, and spectrally-resolved {approx}2 keV K-shell emissions from Al (5% Mg) wire array implosions on Sandia's Z machine pulsed power driver. The stagnating plasma is modeled as three separate radial zones, and collisional-radiative modeling with radiation transport calculations are used to constrain the temperatures and densities in these regions, accounting for K-shell line opacity and Doppler effects. We discuss plasma conditions and dynamics at the onset of stagnation, and compare inferences from the atomic modeling to three-dimensional magneto-hydrodynamic simulations.

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TYPE Conference YEAR 2010
OSTI

Doppler effects on 3-D non-LTE radiation transport and emission spectra

Hansen, Stephanie B.; Jones, Brent M.; Ampleford, David J.; Bailey, James E.; Rochau, G.A.; Coverdale, Christine A.; Jennings, Christopher A.; Cuneo, Michael E.

Spatially and temporally resolved X-ray emission lines contain information about temperatures, densities, velocities, and the gradients in a plasma. Extracting this information from optically thick lines emitted from complex ions in dynamic, three-dimensional, non-LTE plasmas requires self-consistent accounting for both non-LTE atomic physics and non-local radiative transfer. We present a brief description of a hybrid-structure spectroscopic atomic model coupled to an iterative tabular on-the-spot treatment of radiative transfer that can be applied to plasmas of arbitrary material composition, conditions, and geometries. The effects of Doppler line shifts on the self-consistent radiative transfer within the plasma and the emergent emission and absorption spectra are included in the model. Sample calculations for a two-level atom in a uniform cylindrical plasma are given, showing reasonable agreement with more sophisticated transport models and illustrating the potential complexity - or richness - of radially resolved emission lines from an imploding cylindrical plasma. Also presented is a comparison of modeled L- and K-shell spectra to temporally and radially resolved emission data from a Cu:Ni plasma. Finally, some shortcomings of the model and possible paths for improvement are discussed.

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TYPE Conference YEAR 2010
OSTI

Scaling of X pinches from 1 MA to 6 MA

Sinars, Daniel; Mcbride, Ryan; Wenger, D.F.; Cuneo, Michael E.; Yu, Edmund; Harding, Eric H.; Hansen, Stephanie B.; Ampleford, David J.; Jennings, Christopher A.

This final report for Project 117863 summarizes progress made toward understanding how X-pinch load designs scale to high currents. The X-pinch load geometry was conceived in 1982 as a method to study the formation and properties of bright x-ray spots in z-pinch plasmas. X-pinch plasmas driven by 0.2 MA currents were found to have source sizes of 1 micron, temperatures >1 keV, lifetimes of 10-100 ps, and densities >0.1 times solid density. These conditions are believed to result from the direct magnetic compression of matter. Physical models that capture the behavior of 0.2 MA X pinches predict more extreme parameters at currents >1 MA. This project developed load designs for up to 6 MA on the SATURN facility and attempted to measure the resulting plasma parameters. Source sizes of 5-8 microns were observed in some cases along with evidence for high temperatures (several keV) and short time durations (<500 ps).

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TYPE SAND Report YEAR 2010
DOIOSTI
Results 326–350 of 358
Results 326–350 of 358