Raman backscatter as a remote laser power sensor in high-energy-density plasmas

TL;DR

This paper demonstrates using stimulated Raman backscatter as a remote, non-disruptive method to measure instantaneous laser power transfer in high-energy-density plasmas at the NIF, providing new insights into laser coupling.

Contribution

It introduces a novel application of Raman backscatter as a remote sensor for real-time laser power measurement in NIF experiments, enabling non-invasive diagnostics.

Findings

Approximately 50% of outer-cone power transfers to inner cones.

First non-disruptive, instantaneous measurement of power transfer in NIF experiments.

Validated Raman backscatter as an effective remote sensing tool.

Abstract

Stimulated Raman backscatter (SRS) is used as a remote sensor to quantify the instantaneous laser power after transfer from outer to inner cones that cross in a National Ignition Facility (NIF) gas-filled hohlraum plasma. By matching SRS between a shot reducing outer vs a shot reducing inner power we infer that ~half of the incident outer-cone power is transferred to inner cones, for the specific time and wavelength configuration studied. This is the first instantaneous non-disruptive measure of power transfer in an indirect drive NIF experiment using optical measurements.