Laboratory tests of astrophysical black hole accretion disk plasma models using the Z-machine at Sandia National Laboratories

The Z-machine at Sandia National Laboratories generates powerful X-ray radiation fluxes. This enables experiments to produce macroscopic quantities of matter at extreme conditions such as those found in accretion powered plasmas around black holes in both active galactic nuclei and x-ray binaries. Complex models for these non-Local-Thermodynamic-Equilibrium (non-LTE) plasmas remain mostly untested with laboratory data. A novel platform developed on the Z-machine for expanding foil photoionized plasma experiments opens a new regime for benchmark measurements of non-LTE plasmas. We use the platform to create plasmas that reach the same photon flux, density, and temperature conditions in black hole accretion disks. The data from these experiments have already shown that an approximation often used for radiation transport in these plasmas was incorrect. They also reveal difficulties in modeling both emission intensities and the level of ionization in the plasma. We will present data of the first ever high S/N iron L-shell x-ray emission spectra from a laboratory photoionized plasma. Such data have been a laboratory astrophysics goal for two decades but are even more critical now because of the "Super-Solar" iron abundance problem (Garcia et al. 2016). Iron abundances in accretion disks inferred from x-ray spectra emitted by photoionized plasma surrounding about a dozen black holes appear to contain 5-20 times more iron than the Sun. This contradicts the widely held expectation that most objects in the universe have the Sun's composition. One prevailing theory is that effects of high electron density are not properly accounted for in the models. Reinterpreting the x-ray spectra with updated models resolved much of that discrepancy. However, a key question still remains: do photoionized plasma spectral models accurately account for x-ray emission? We will describe our progress in using this dataset to evaluate model accuracy and its potential to inform the super-solar iron abundance problem.