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

TL;DR

This study uses 2D Particle-in-cell simulations to analyze laser-plasma interactions at high intensities, revealing significant pump depletion, hot electron generation mechanisms, and the effects of scattering processes relevant to shock ignition.

Contribution

It provides new insights into pump depletion and hot electron generation in long scale length plasmas under high-intensity laser conditions, with implications for shock ignition.

Findings

Significant pump depletion due to SRS and SBS in low-density plasma regions.

Hot electrons generated by SRS and TPD with energies up to 46 keV.

Reducing SBS enhances SRS and results in a softer hot electron spectrum.

Abstract

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.