Progress in studies of ultra-intense laser plasma interactions for fast ignition FIREX project

It is significantly important to understand the interactions between ultra-intense laser and solid targets or plasmas relevant for fast ignition such as laser light self-focusing over critical density and hot electron behaviors leaving targets under strong electrostatic potential created by themselves. Both these features have been studied using ultra-intense lasers. A PW laser pulse 0.5 psec has been injected into an over-dense plasma and has penetrated through the plasma as a single channel. The total distance of the penetration was over 100 micron in the plasma which was estimate to have 10 times critical density. This penetration was simulated by a PIC simulation which has shown that the relativistic laser self-focusing was responsible for the penetration. Hot electrons can be produced efficiently with an ultra-intense laser pulse irradiation onto an target. The total number of hot electrons created on the target is always about 2 orders of more than the number measured by an electron spectrometer located a meter away from the target. Hot electrons going through the target are under the effect of strong B field as Alfven current limit and electro-static potential. The electro-static potential could be controlled by creating a plasma at the rear side of solid planar target which could supply a return current and could increase the number hot electrons by a factor 2. The retardation of the electro-static potential due to the rear plasma is observed in a 1D PIC simulation and could allow hot electrons restricted by the Alfven limit leaving the target. (author)