Structure in Radiative Shock Experiments.

[摘要] The basic radiative shock experiment is a shock launched into a gas of high-atomic numbermaterial (here, xenon) at high velocities (around 200 km/sec), which fulfillsthe conditions for radiative losses to collapse the post-shock material to high densities(over 20 times the initial gas density). The experiment has lateral dimensions ofapproximately six hundred microns and length dimensions of two to three millimeters.Repeatable two- and three-dimensional structure was discovered in the experimentaldata. One form this took was that of radial boundary effects near the tubewalls, extended approximately seventy microns into the system. The cause of thiseffect - low density wall material which is heated by radiation transport ahead of theshock, launching a new converging shock ahead of the main shock - is apparentlyunique to high-energy-density experiments. Another form of structure is the appearanceof small-scale perturbations in the post-shock layer, modulating the shock andmaterial interfaces and creating regions of enhanced and diminished areal densitywithin the layer. This structure formation has been investigated as a variation ofthe Vishniac instability of decelerating shocks. This instability mirrors (if one uses a suitably deformed reflector) effects believed to be present in astronomically scaledsystems involving decelerating, diverging supernova remnants.This thesis gathers data from Omega laser campaigns of July 17, 2007; July 10,2008; October 23, 2008; July 21, 2009; and August 6, 2010. Each of these experimentalcampaigns has been undertaken to acquire additional information about the complexstructure of the radiating discontinuity.

[发布机构] University of Michigan

[效力级别] Physics

[关键词] Radiation Hydrodynamics;Physics;Science;Applied Physics