Theory and Modeling of Blast-Wave–Driven Perturbation Growth in OMEGA Planar Experiments*

Decaying shock waves play an important dynamic and energetic role in a variety of contexts, from expanding supernova-remnant outflows to imploding inertial confinement fusion targets. In the latter, decaying shocks are used to set the fuel and ablator adiabats but also result in instability growth and potential mixing at the fuel–ablator interface. We report here on 2-D modeling with radiation-hydrodynamics code DRACO of instability growth of an interface between a doped-plastic pusher and low-density foam caused by a laser-generated blast wave in planar OMEGA experiments. Simulated radiographs generated with Spect3D were compared with high-resolution 4.75-keV experimental radiographs obtained using a Fresnel phase zone-plate imaging system. Images obtained many nanoseconds after the end of the laser pulse reveal comparable, highly nonlinear growth caused by both the Richtmyer–Meshkov and Rayleigh-Taylor instabilities during a phase in which the vorticity is effectively “frozen” into the plasma. Discrepancies in the observed and modeled post-shock compressibility will also be discussed.