Electron acceleration in ultra-intense laser ($>$10$^{18}$ Wcm$^{-2})$ interactions with sub-micron structured targets

The use of sub-micron structure targets is an attractive method for Fast Ignition to enhance energy coupling of the laser into the fast electrons. We have studied electron acceleration using sub-micron structured targets including low-density foam and carbon nano-tube (CNT) in ultra-intense laser plasma interactions. We observe low coupling efficiency of the laser energy into high-energy electrons in present experimental conditions in spite of our previous results showing efficient electron accelerations [1]. Detailed modeling using PIC calculations with various sub-micron structured plasma are presented to understand these results. [1] A.L. Lei et al., Phys. Rev. Lett. 96 (2006) 255006.