Absorption of local thermodynamic equilibrium aluminum at different densities

Increasing the range of plasma parameters accessible for laboratory absorption coefficients measurements is of interest for astrophysical applications. Aluminum is of special interest as its 1s-2p inner shell absorption transitions pen-nit one to precisely determine the ionization balance that is strongly dependent on the electron temperature. A method to increase the density of the probed sample was tested on aluminum confined by carbon tampers of different thickness (8-70 mug/cm(2)). This created a density increase in the aluminum of a factor of similar to10. Measurements showed that the aluminum ionization decreases substantially with increasing carbon thickness. Radiative hydrodynamic simulations showed that density and temperature gradients could not be neglected and had to be taken into account in calculating the absorption structures with the atomic physics code HULLAC. Very good agreement between theory and experiment was obtained by coupling HULLAC with hydrodynamic simulations. (C) 2003 Elsevier Science Ltd. All rights reserved.