Absorption measurements of radiatively heated low-Z materials

We are studying the opacity of radiatively heated low-Z foils (Z = 5--7) in the spectral region of their K-edges ({approximately}200--500 eV), with the eventual goal of investigating radiative transfer in non-LTE plasmas. In these experiments one arm of the Nova laser (4.2 kJ of 0.53 {mu}m light in a 1-ns pulse) is incident on a Au burn-through foil (0.25 {mu}m thick), producing a soft x-ray source that radiatively heats a low-Z sample. The sample is {approximately}1 {mu}m thick and is placed in close proximity to the Au foil. Absorption spectra are obtained by either viewing the soft x-rays from the Au foil passing through the sample, or by using a second arm of the NOVA laser to create an independent x-ray backlighter pulse from a separate Au foil at a specific time. High resolution spectral measurements ({lambda}/{lambda}{Delta} > 3000) are obtained with a 3-m Rowland circle instrument; data are recorded on Kodak 101-05 photographic plate. Preliminary comparisons with a low-Z opacity code, OPAL, are presented. 4 refs., 9 figs.