Pump depletion and hot-electron generation in long-density-scale-length plasma with shock-ignition high-intensity laser.

Two-dimensional particle-in-cell simulations for laser plasma interaction with laser intensity of 10^{16}W/cm^{2}, plasma density range of 0.01-0.28n_{c}, and scale length of 230-330μm 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}=0.01-0.2n_{c}). The simulations identified hot electrons generated by SRS in the low-density region with moderate energy and by two-plasmon-decay 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's measurements. The simulations also showed artificially reducing SBS would lead to stronger SRS and a softer hot-electron spectrum.