X-ray spectroscopy on Double Eagle and DM-2

The radial distribution of the ion density and electron temperature in a z-pinch has been inferred by comparing the measured values of the x-ray power and the ratio of optically thick spectral line intensities with calculated ones for a range of assumed radial distributions. This procedure provided evidence for an on-axis dip in the ion density. A complementary procedure is described to analyze spectra obtained on the DM-2 and Double Eagle accelerators at Maxwell Physics International. In this case, the radially resolved intensities of optically thin dopants added to the pinch were measured using a high resolution Johann spectrometer. The line intensities were Abel inverted and the radial distribution of two line ratios [L_α/(He_α+IC) and IC/He_α] were obtained from which the localized electron temperature and density were inferred. Here IC is the intercombination line of the He-like stage. The ion temperature distribution was obtained by Abel inverting each wavelength interval of the ion line profile and determining the Doppler width at each radial position. The density profile inferred for Ar gas puff pinches on DM-2 with 4% Cl and Al wire loads coated with 5% Si on Double Eagle indicated a density dip on-axis similar to that deduced in refs. 1 and 2. The imploded linear mass density was inferred to be about 47% of the initial mass density. Similar on-axis local minima were observed for the ion temperature on both machines. Since different ion temperatures were inferred from the He_α line than from the intercombination line of Cl, opacity and gradients may be affecting these results. These results demonstrate the details of the internal structure of the stagnated pinch that can be inferred from the radially resolved spectral intensities of optically thin dopants.