X-RAY RADIOGRAPHIC IMAGING OF HYDRODYNAMIC PHENOMENA IN RADIATION-DRIVEN MATERIALS - SHOCK PROPAGATION, MATERIAL COMPRESSION, AND SHEAR-FLOW

One- and two-dimensional, time-resolved x-ray radiographic imaging at high photon energy (5-7 keV) is used to study shock propagation, material motion and compression, and the effects of shear flow in solid density samples which are driven by x-ray ablation with the Nova laser. By backlighting the samples with x rays and observing the increase in sample areal density due to shock compression, the trajectories of strong shocks (approximately 40 Mbars) in flight are directly measured in solid density plastic samples. Doping a section of the samples with high-Z material (Br) provides radiographic contrast, allowing a measurement of the shock-induced particle motion. Instability growth due to shear flow at an interface is investigated by imbedding a metal wire in a cylindrical plastic sample and launching a shock in the axial direction. Time-resolved radiographic measurements are made with either a slit-imager coupled to an x-ray streak camera or a pinhole camera coupled to a gated microchannel plate detector, providing approximately 10 mum spatial and approximately 100 ps temporal resolution.