Absorption of LTE aluminum and nickel at different densities

Absorption coefficients are of interest for inertial fusion and astrophysics in a wide range of plasma parameters. The absorption of 2-3 transitions of nickel has been measured for a density varying by a factor of 10. The density of radiatively heated sample was increased by tamping the absorbing sample by thick carbon layers. This method was tested on aluminum in a previous experiment and applied here for pure nickel and Al/Ni mixtures. Results on 2p-3d Ni absorption in the 12 - 14 Å and 1s-2p Al absorption near 8.0 Å spectral range were measured and compared to calculations performed with the LTE superconfiguration code SCO. When the tamper thickness was increased, the plasma was less ionized, due to the higher density and a lower temperature. Comparison of the data with 1D radiative Lagrangian code calculations gives a good description of the parameters inside the absorption sample.