Electron Generation and Transport as a Function of Preplasma in Cone-Attached Targets

The underlying physics of laser energy deposition and transport in cone-guided fast ignition is very complex. It has been shown recently that preplasma can significantly affect the generation and transport of electrons in cone targets.\footnote{S. D. Baton, et al., Phys. Plasmas \textbf{15}, 042706 (2008).}$^{,}$\footnote{L. Van Woerkom, et al., Phys. Plasmas \textbf{15}, 056304 (2008).} In integrated FI, prepulse energies of the order of 1 J are expected. Experiments have been performed at the Titan laser (10$^{20}$ W/cm$^{2})$ at LLNL in which prepulse levels were artificially induced at levels of up to 1 J using the long pulse beam into cone-wire targets. By simultaneously using Cu K$\alpha$ imaging, single photon counting cameras, and HOPG crystal spectroscopy, absolute information of spatially resolved K$\alpha$ radiation could give yields of hot electrons and their transport scalelengths as a function of preplasma.