Oxygen opacity experiments to advance our understanding of stellar interiors

Much of our knowledge of the universe stems from our understanding of the Sun. However, updated measurements of abundances have revealed a disagreement between solar models and helioseismic measurements of the interior structure of the Sun. One hypothesis that could resolve this discrepancy is if the opacities of matter at solar interior conditions are higher than models predict. Experiments on the Z Machine and at NIF have been investigating this by studying the opacity of iron and oxygen at stellar interior conditions. These have shown a discrepancy between experiments and models for iron at conditions near the solar convection zone base (CZB). This talk will focus on the progress of the oxygen opacity experiments. Oxygen is the second largest contributor to the opacity at the solar CZB and no experimental benchmark exists to date. In order to produce comparisons of models with the opacity measurements, the plasma conditions within the experiment must be well known. We will discuss the spectroscopic methods used to characterize the plasmas and what has been found.

This work was supported in part by the Wootton Center for Astrophysical Plasma Properties under U.S. DOE cooperative agreement number DE-NA0003843, the Fundamental Science Program of SNL, and NIF’s Discovery Science Program. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.