Integrated implicit particle-in-cell (PIC) simulations of petawatt laser heating of compressed cores for fast ignition

There has been much interest in the fast heating of compressed matter by short pulse petawatt lasers [1]. Some time ago, we studied the heating process as applied to the GEKKO/PW experiments at Osaka [2] with a 3D hybrid electromagnetic implicit PIC code [3]. One limitation of our analysis was that we legislated the distribution of hot electrons entering the high density region. While the ansantz for the hot electron energy and angular distribution was consistent with experimental data, it clearly lacked rigor. We have now removed that limitation and will present integrated simulations which include the self-consistent laser plasma interaction with the blowoff plasma, as well as the electron transport through the pedestal and deposition in the core. For GEKKO/PW and FIREX [4] phase I scale experiments, the scaling of core temperature with increasing laser energy is nearly linear, and does not appear to have any saturation up to the highest we have considered, a laser energy of 2kJ. The heating profiles in the core show localized heating on the density gradient. Higher laser intensity does create higher energy electrons in the simulations, in agreement with ponderomotive scaling, but this higher mean energy does not appear to directly impact the location of the heating zone at the core edge. From the integrated results of these simulations, a method for igniting a half-moon shaped shell of material and subsequently the entire core is suggested.