Analyzing spatially resolved line spectra emitted by Z pinches

Abstract

The spatial profiles of key physical variables such as electron temperature and density are crucial in determining the overall radiating efficiency of a Z pinch as well as the emitted photon energy distribution. The present work uses spatially resolved x-ray lines emitted from shots taken on the 4 MA Double EAGLE generator [C. Deeney et al., Phys. Rev. A 44, 6762 (1991)] at Maxwell Physics International to infer such profiles. The loads were arrays of 15 wires consisting of 95% Al, 5% Si, producing nearly 50 kJ of K-shell radiation with relatively long pulsewidths of 41–43 ns. It is found that the spatial profile of the He-like intercombination to resonance line ratio is critically affected by self-absorption and re-emission (scattering) of resonance line photons emitted from the hot, dense interior of the pinch. This ratio cannot be correctly interpreted without taking the scattering into account. Also, at densities somewhat lower than those achieved by these pinches, this line ratio becomes more temperature than density dependent. The inferred temperature gradient is much less steep than that which had been diagnosed previously for a pinch emitting a much shorter x-ray pulsewidth of 13 ns.