Abstract Details
K-shell X-ray Sources at the Z Accelerator
Author: Christine A Coverdale
Requested Type: Oral Only
Submitted: 2009-04-20 08:12:54
Co-authors: B. Jones, D.J. Ampleford, J. Chittenden, C. Jennings, J. Guiliani, J.W. Thornhill, J.P. Apruzese, R.W. Clark, K.G. Whitney, A. Dasgupta, J. Davis, P.D. LePell, C. Deeney, M.E. Cuneo
Contact Info:
Sandia National Labs
P.O. Box 5800, MS 0671
Albuquerque, NM 87185-0
USA
Abstract Text:
The Z accelerator has been used for many years as a research facility for high energy density plasmas, with applications ranging from astrophysics to inertial confinement fusion. The available current at Z (> 15 MA) has also allowed for experiments over a wide range of K-shell x-ray sources, including Al (1.6 keV), Ar (3.1 keV), Ti (4.8 keV), stainless steel (SS, 6.7 keV), and Cu (8.4 keV). The K-shell sources provide excellent opportunities for studying the details of a z-pinch through radiated output in various photon energy regimes, imaging, and spectroscopy. Variations in initial load configurations illustrate the difficulty in achieving appropriate plasma conditions for K-shell emissions, particularly for SS and Cu. The requirement for large diameter loads (> 40mm initial diameter) enhances the growth of the Magnetic Rayleigh Taylor (MRT) instability during the implosion, which can affect the stagnated pinch. Evidence of MRT is present in both the risetime of the radiated power pulse, as well as in time-resolved pinhole imaging. The pinhole images, taken for two different photon energy regimes, show the final stage of the z-pinch implosion and highlight the spatial gradients in the plasma emissivity. This is also evident in time-integrated, spatially resolved K-shell spectroscopy, which can be used to infer plasma temperature and density more directly. The time-integrated spectra also show the effects of opacity for the lower Z materials. The relatively low wire number, large diameter wire arrays fielded also provide views for studying ablation of the wires in the array through radiography. Data from a variety of K-shell sources and load configurations will be shown to illustrate the details of stagnated z-pinches.
The K-shell x-ray source data has been used to benchmark, and improve, phenomenological scaling models for application to higher currents and higher photon energies. The application of these scaling theories to existing data, and for planning future shots, will be discussed. One, two, and three dimensional calculations have also been performed, and comparisons of the measurements to the output of these calculations will also be presented.
The recent refurbishment of the Z accelerator will ultimately increase the coupled energy available to a load, with an anticipated peak current of ~ 26 MA into a wire array. Experiments are in progress to further study K-shell emission with a longer risetime drive current, as well as at higher current levels. Preliminary results will be presented.
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