A computational study of x-ray emission from laser-irradiated Ge-doped foams

Colvin, Jeffrey D.; Fournier, Kevin B.; May, Mark J.; Scott, Howard A.
July 2010
Physics of Plasmas;Jul2010, Vol. 17 Issue 7, p073111
Academic Journal
New advances in fabrication of low-density high-Z-doped foams have opened new windows on understanding how materials that are not in local thermodynamic equilibrium (LTE) are heated and radiate. Simulations are discussed in this paper of the x-ray spectral emissions from laser-irradiated very low-density Ge-doped silica aerogel targets using a two-dimensional radiation-hydrodynamics code incorporating a modern non-LTE superconfiguration atomic model. Details of the computational model are presented, and it is shown that, for the long-scale-length, subcritical-density, ∼2–3 keV electron temperature plasmas created in experiments at the Omega laser facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)], the simulations provide a close match to both the measured Ge L-shell emission (∼1–1.5 keV) and the measured Ge K-shell emission (∼10–11 keV), but only by accounting properly for nonlocal thermal conduction. The older average-atom atomic model is shown to be inadequate for these non-LTE plasmas.


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