Recent improvements in opacity measurements on the National Ignition Facility*

X-ray opacities of hot dense matter are essential to radiation-hydrodynamic models of stars, other astrophysical objects, inertial confinement fusion, and other high-energy-density experiments. Opacity experiments on the National Ignition Facility (NIF) seek to replicate and extend results from the Sandia Z facility, which often diverge from theory. Promising initial measurements on NIF at temperatures \textasciitilde 150 eV and electron densities \textasciitilde 7x10$^{\mathrm{21}}$/cm$^{\mathrm{3}}$ also revealed areas for improvement. Improvements in backlighting, spatial resolution and signal uniformity, and reduction of backgrounds will be summarized. Recent data from Al:Mg samples will be presented in this context.