Shadowgraphy Imaging to Infer Electron Density Profiles in High Energy Density Plasmas on Sandia's Z machine

Shadowgraphy and schlieren imaging use a probing beam to determine the spatial variation of the refractive index of a medium — which in a plasma is directly proportional to the electron density — by measuring how the photons are deflected. Using numerical ray-tracing techniques, we have developed a synthetic diagnostic that calculates the ray deflection angles of an incident laser beam after it has traversed a given 3-D electron density profile. We apply this to simulate shadowgraphy and schlieren images across the reconnection layer produced by high energy density (HED) experiments on Sandia's Z machine, as a part of the "Magnetically Ablated Reconnection on Z" (MARZ) collaboration. We take 2-D and 3-D simulations of dual exploding aluminium wire arrays using the Gorgon magnetohydrodynamic (MHD) code, which produces a radiatively-cooled reconnection layer at the midplane. Strong radiative cooling results in a sharp increase in the electron density due to the compression of the layer, which results in larger deflection angles than the non-radiatively cooled case. Using this synthetic diagnostic code, we will assess the viability of using shadowgraphy and schlieren techniques to diagnose the reconnection layer in the MARZ experiments.