Opposition Research: A novel platform on the Z Machine to study radiation flow in complex geometries

The dynamics of radiation-driven Marshak waves flowing over opaque obstructions is of interest in astrophysics, for instance to understand how radiation waves from supernova interact with the surrounding, inhomogeneous stellar media. Further, HED experiments studying radiation flow around obstructions can provide valuable data to benchmark numerical models of radiation transport in complex geometries. We present a novel platform on the Z Machine, Opposition Research, to study radiation flow in complex geometries. X-rays from a hohlraum drive radiation waves in two opposing foam packages; one to study complex radiation flow and the other to serve as a fiducial, providing an integrated drive measurement that can be used to calibrate rad-hydro simulations. Radiography is used to measure the position of the blast wave produced in each package as the radiation wave becomes subsonic. We present results showing the left-right drive symmetry of the hohlraum, demonstrating platform viability for experiments with complex radiation flow geometries. We also demonstrate calibration of simulations with a combination of measured blast wave positions and emission-based measurements of the hohlraum x-ray drive.