# Nonlinear Fluid Simulation Study of Stimulated Raman and Brillouin Scatterings in Shock Ignition

## TL;DR

This study introduces a nonlinear fluid simulation code to analyze laser-plasma instabilities in shock ignition, revealing mechanisms of SRS and SBS saturation, re-scattering phenomena, and agreement with PIC simulations.

## Contribution

A new nonlinear fluid code (FLAME) for laser-plasma instability simulation, providing insights into SRS and SBS behaviors in shock ignition.

## Key findings

- SRS modes saturated by LDI and pump depletion
- Ion-acoustic waves seed SBS with bursting patterns
- Re-scattering of SRS observed at 1/16th-critical surface

## Abstract

We developed a new nonlinear fluid laser-plasma-instability code (FLAME) using a multi-fluid plasma model combined with full electromagnetic wave equations. The completed one-dimensional (1D) version of FLAME was used to study laser-plasma instabilities in shock ignition. The simulations results showed that absolute SRS modes growing near the quarter-critical surface were saturated by Langmuir-wave Decay Instabilities (LDI) and pump depletion. The ion-acoustic waves from LDI acted as seeds of stimulated Brillouin Scattering (SBS), which displayed a bursting pattern and caused strong pump depletion. Re-scattering of SRS at the 1/16th-critical surface was also observed in a high temperature case. These results largely agreed with corresponding Particle-in-Cell simulations.