Monochromatic 8.05-keV Flash Radiography of Imploded Cone-in-Shell Targets

Fast ignition has the potential of high fusion gains through the ignition of massive DT fuel assemblies. The cone-in-shell target concept might be one way of achieving this goal. Integrated experiments on OMEGA have demonstrated $\sim $4{\%} coupling efficiency of short-pulse laser energy into the compressed target.\footnote{W. Theobald \textit{et al.}, Phys. Plasmas \textbf{18}, 056305 (2011).} An improved target design has been developed with a low-$Z$ cone tip. The goal was to validate 2-D radiation--hydrodynamic modeling predictions of the new target design. The technique used was flash radiography from a monochromatic 8.05-keV x-ray source.\footnote{ J. A. King\textit{ et al.}, Appl. Phys. Lett. \textbf{86}, 191501 (2005).} Cu foils were irradiated by the 1.5-kJ, 10-ps OMEGA EP short-pulse laser to generate a bright Cu K$_{\alpha }$ area backlighter source, which was used in combination with monochromatic imaging with a spherical Bragg crystal to backlight the cone-in-shell implosions at various times around peak compression. Flash radiography provides high-quality images of the fuel assembly with $\sim $10-ps time resolution and $\sim $10-\textit{$\mu $}m spatial resolution. This work was supported by the U.S. Department of Energy under Cooperative Agreement Nos. DE-FC52-08NA28302 and DE-FC02-04ER54789.