Stimulated Brillouin Scattering in Shock Ignition

We study laser-plasma interactions and hot electron generation for shock ignition using both fluid and PIC simulations. Typical parameters for OMEGA experiments are used with a density scale length of 170 $\mu $m and a pulse length of $\sim$ 15 ps. A series of simulations with laser intensities between 2 $\times$ 10$^{15}$ and 5 $\times$ 10$^{16}$ W/cm$^{2}$ finds that stimulated Brillouin scattering (SBS) increases significantly with the incident intensity, limiting the transmitted intensity at the 0.17n$_{\mathrm{c}}$ to be under 3 $\times$ 10$^{15}$ W/cm$^{2}$. It is also found that proper modeling of the SBS reflectivity requires realistic flow profiles and seed levels for the electromagnetic fields. The majority of the hot electrons are found to be from stimulated Raman scattering and of moderate energies. However, high energy electrons of preheating threat can still be generated from the two-plasmon-decay instability.