Expansion of Cone Inner Surface Irradiated by Low intensity Pre-Pulse of Main Heating Laser in Fast-Ignition

We investigated the plasma expansion of the inner surface of the cone used for the fast-ignition scheme (FIS) of the inertial confinement fusion (ICF) by two-dimensional simulation code (Star-2D) with laser-ray tracing. The most intense and short pulse lasers used for the core heating in FIS have a low intensity pre-pulse of several 100ps duration before the main pulse irradiation. The typical contrast of pre-pulse and main pulse ranges from 10$^{-5}$ to 10$^{-9}$. In low contrast cases, the pre-pulse intensity could lead to 10$^{13}$ to 10$^{14}$W/cm$^{2}$ which is high enough to ablate the inner surface of the cone wall made of gold. The profile of this pre-formed plasma on the inner surface of cone has significant effects on interaction between the main high intensity laser pulse and the surface of the cone, and the resulted energetic electron spectrum may change depending on the plasma gradient scale length [1]. We show our simulation results with the various intensity and duration of pre-pulse and discuss their effects on the energetic electron production and core heating REFERENCE [1] T. Johzaki et al., ``Holistic Simulation for FIREX Project withFI3'', Laser Part. Beams. Volume 25, Issue 04, Dec 2007, pp 621-629.