An HED-regime diagnostic to obtain supersonic radiation wavefront profiles using Ti-doped foams on OMEGA

Los Alamos' COAX experimental campaign is developing a Marshak wave diagnostic for constraining HED radflow experiments. COAX uses absorption spectroscopy of backlit Ti-doped foams to infer temperature profiles of the supersonic radiation wavefront propagating down the doped foam tube from a laser-lit halfraum on the OMEGA facility. Radiography shows the blastwave as the radiation goes subsonic. The titanium 1s-2p and 1s-3p absorption lines occur around a frequency of 4400-5400 eV, well above the temperature of the Marshak wave at 50-150eV. Los Alamos custom opacity tables in the OPLIB format with dT_e = 2eV provide the ability to infer the temperature profile of the wavefront in space at multiple snapshots in time. The uncertainty of that final step is a few eV, but the inferred experimental temperatures differ by about 15 eV from Eulerian AMR radiation-hydrodynamics simulations that model the integral setup including laser-ray-tracing into the hohlraum and that are calibrated to the radiographed blastwave. We continue to develop the diagnostic and its overall uncertainty, refine our simulations and their calibration, and seek other physics explanations for the current experiment-simulation inconsistencies, such as the dilute Planckian resulting from one-way radflow.