Structure in Radiative Shock Experiments.

The basic radiative shock experiment is a shock launched into a gas of high-atomic number material (here, xenon) at high velocities (around 200 km/sec), which fulfills the 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 of approximately six hundred microns and length dimensions of two to three millimeters. Repeatable two- and three-dimensional structure was discovered in the experimental data. One form this took was that of radial boundary effects near the tube walls, extended approximately seventy microns into the system. The cause of this effect - low density wall material which is heated by radiation transport ahead of the shock, launching a new converging shock ahead of the main shock - is apparently unique to high-energy-density experiments. Another form of structure is the appearance of small-scale perturbations in the post-shock layer, modulating the shock and material interfaces and creating regions of enhanced and diminished areal density within the layer. This structure formation has been investigated as a variation of the Vishniac instability of decelerating shocks. This instability mirrors (if one uses a suitably deformed reflector) effects believed to be present in astronomically scaled systems 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 experimental campaigns has been undertaken to acquire additional information about the complex structure of the radiating discontinuity.Ph.D.Applied PhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/86388/1/fwdoss_1.pd