Radiographic Studies of a Shockwave Interacting with a Counter-Propagating Radiation Flow

The Radishock platform studies the interaction between a radiation wave and a counter-propagating shockwave within a Ti-laden silica aerogel foam using x-ray absorption spectroscopy and point-projection backlighter radiography from the COAX platform [1]. The radiation wave is produced by a laser-driven halfraum, and the shock wave via a directly-driven ablator. These experiments can provide insight into supernova shock breakout emission where the radiation flow breaking out of the star interacts with the circumstellar medium and the relative velocity between this breakout and the medium dictates the degree of heating in the shock. In our Radishock experiments, the radiation flow is not apparent in the radiographic diagnostic and can be directly observed only via the absorption spectroscopy diagnostic, which provides a measure of temperature and position. On the other hand, the shockwave launched from the ablator side of the target is observed in the radiographs, and we extract the full 2D shock front contour using computer vision techniques [2]. In the course of this analysis, we found features present in the late time interaction shots which were not present in the radiation wave only, shockwave only, and early time interaction shots. These features appear to be ablation driven off of the shock front by the interaction with the radiation wave, and it provides an indirect means of probing the radiation wave radiographically, and a direct means of probing the interaction itself.