  Two-dimension Particle-in-cell simulations for laser plasma interaction with
laser intensity of $10^{16} W/cm^2$, plasma density range of 0.01-0.28$n_c$ and
scale length of $230 -330 \mu m$ showed significant pump depletion of the laser
energy due to stimulated Raman scattering (SRS) and stimulated Brillouin
scattering (SBS) in the low density region ($n_e=0.01-0.2 n_c$). The
simulations identified hot electrons generated by SRS in the low density region
with moderate energy and by two-plasmon-decay (TPD) near $n_e=0.25n_c$ with
higher energy. The overall hot electron temperature (46 keV) and conversion
efficiency (3%) were consistent with the experiment measurements. The
simulations also showed artificially reducing SBS would lead to stronger SRS
and a softer hot electron spectrum.
