Simulation of Stimulated Brillouin Scattering and Stimulated Raman Scattering In Shock Ignition

TL;DR

This study compares fluid and PIC simulations of stimulated Brillouin and Raman scattering in shock ignition, revealing SBS as the dominant instability and emphasizing plasma flow profiles' importance in modeling these effects.

Contribution

It provides a detailed comparison between fluid and PIC simulation results for SBS and SRS in shock ignition, highlighting differences in saturation levels and the role of plasma flow profiles.

Findings

SBS dominates instability at typical shock ignition parameters.

Pump depletion limits transmitted laser intensity to below 3.5×10^{15} W/cm^2.

PIC simulations show higher saturation levels and stronger pump depletion.

Abstract

We study stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) in shock ignition by comparing fluid and PIC simulations. Under typical parameters for the OMEGA experiments [Theobald \emph{et al}., Phys. Plasmas \textbf{19}, 102706 (2012)], a series of 1D fluid simulations with laser intensities ranging between 2$\times$10$^{15}$ and 2$\times$10$^{16}$ W/cm$^2$ finds that SBS is the dominant instability, which increases significantly with the incident intensity. Strong pump depletion caused by SBS and SRS limits the transmitted intensity at the 0.17n$_c$ to be less than 3.5$\times$10$^{15}$ W/cm$^2$. The PIC simulations show similar physics but with higher saturation levels for SBS and SRS convective modes and stronger pump depletion due to higher seed levels for the electromagnetic fields in PIC codes. Plasma flow profiles are found to be important in proper modeling of SBS and limiting its reflectivity in both the fluid and PIC simulations.