Areal density evolution of isolated surface perturbations at the onset of x-ray ablation Richtmyer-Meshkov growth

Isolated defects on inertial confinement fusion ignition capsules are a concern as defects taller than a few hundred nanometers are calculated to form jets of high-Z material, which enter the main fuel. If this mixing of high-Z material is not controlled, a serious degradation in thermonuclear burn can occur. A path towards controlling the growth of defects on the outer surface of plastic capsules is currently under development, but requires accurate predictions of defect evolution driven by the early time ablative Richtmyer-Meshkov (RM) effect. The chief uncertainty is the Equation of State (EOS) for polystyrene and its effect on ablative RM. We report on measurements of the growth of isolated defects made at the onset of ablative RM oscillations driven by x-ray ablation to differentiate between EOS models used in design calculations. Experiments at the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] used on-axis area backlighting radiography and x-ray framing cameras to determine bump ar...