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

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.