Laser-plasma interactions and hot electron generation in shock ignition

We present 2D Particle-in-cell (PIC) simulations, including electron-ion collisions and lasting more than 10 ps, on laser-plasma interactions for two sets of shock ignition (SI) parameters. The first is for conditions relevant to the Omega laser facility with a spike intensity of $I=2\times {10}^{15}$W/cm$^{2}$ and the density scale length at the quarter critical surface of L $\sim$ 170microns. The second is relevant to NIF conditions with $I=5\times {10}^{15}$W/cm$^{2}$ and L$\sim$400microns. Under the Omega conditions, the simulations show a bursting pattern in both plasma waves and hot electron fluxes, which is attributed to the interplay between stimulated Raman scattering (SRS) and two-plasmon decay (TPD) instabilities. The observed hot electron temperatures compare favorably to those measured in the 40$+$20 spherical SI experiments (Theobald et al. 2012). SRS is the main source for hot electrons but TPD can produce \textgreater 100 keV ones. Similar bursting patterns are also observed in the NIF-relevant simulations. However, these simulations show strong SBS in rather low density region ($\sim$ 0.1$n_{cr})$.