# A Frequency Filter of Backscattered Light of Stimulated Raman Scattering due to the Raman Rescattering in the Gas-filled Hohlraums

## TL;DR

This study investigates the interaction between stimulated Raman scattering (SRS) and Raman rescattering (re-SRS) in gas-filled hohlraums, revealing re-SRS as a frequency filter that influences backscattered light and plasma dynamics.

## Contribution

It is the first to use a nonenveloped fluid code to analyze the coupling of SRS and re-SRS in gas-filled hohlraums relevant to inertial confinement fusion.

## Key findings

- re-SRS acts as a frequency filter for backscattered SRS light
- re-SRS depletes low frequency modes at high density regions
- rescattered light energy is rapidly deposited into plasma

## Abstract

The coupling evolutions of stimulated Raman scattering (SRS) and Raman rescattering (re-SRS) are studied under the parameter conditions of relevance to the gas-filled hohlraum experiments at the National Ignition Facility by a nonenveloped fluid code for the first time. It is found that re-SRS works as a frequency filter of backscattered light of SRS in the gas region. The low frequency modes originated from density points higher than about 0.1nc would stimulate re-SRS and be heavily depleted by re-SRS at the region of their effective quarter critical density region. Due to the high collisional damping of the rescattered light, the energy of rescattered light is deposited quickly into the plasmas along with its propagation, which limits the re-SRS in a small region. Large amplitude of the daughter Langmuir wave of re-SRS would stimulate cascade Langmuir decay instabilities and induce obvious low frequency density modulations, which can further result in the inflation of high frequency modes generated at density points lower than the growth region of re-SRS.