Time-resolved spectroscopy to advance opacity effort on Z*

Opacity at solar interior conditions has been measured on Z and was found to be higher than predictions. This finding helps resolve the long-standing solar problem although no opacity-model revisions have been found to date. Sandia developed an ultrafast x-ray imager (UXI) that allows time-resolved absorption spectroscopy for the first time. Prior opacity data recorded on x-ray film had duration given by the 3-ns backlighter. One hypothesis for the opacity model-data discrepancy is that the temporal integration influenced the results. Time-resolved conditions have been constrained now and synthetic tests of temporal integration effect on past measurements did not resolve the source of the opacity discrepancy. But only actual time-resolved measurements would provide a model-free evaluation of this effect. So, the focus of the effort is now on measuring absolute time-resolved opacity. Besides, we will also discuss the first results from experiments designed to take advantage of newly acquired time-resolved knowledge to tailor the opacity experimental conditions. The strategy and prospects for obtaining multiple opacity measurements from a single Z experiment will be discussed.