Speaker
Description
Experiments performed at the National Ignition Facility (NIF) have provided evidence that stimulated Raman scattering (SRS) occurs at a level that poses a preheat risk for directly-driven inertial confinement fusion implosions [1]. To help investigate the mechanisms responsible for the generation of this SRS, recent experiments on the OMEGA EP laser (in which similar SRS signatures were observed) were analyzed using a new ray-tracing model. The model is able to explain the time-dependent scattered light spectra from these OMEGA EP experiments: It identifies SRS side-scatter and near backscatter from portions of each incident beam, where either the scattered electromagnetic wave, or the electron plasma wave, are generated in the direction parallel to contours of constant density, as the origin of the major spectral features. As similar effects are known to occur at the ignition scale (on the NIF) [2], it is suggested that the OMEGA EP platform could provide a good surrogate in which to develop SRS mitigation strategies.
This material is based upon work supported by the Natural Sciences and Engineering Research Council of Canada [RGPIN-2018-05787, RGPAS-2018-522497]
[1] M. Rosenberg et al., Phys. Rev. Lett. 120, 055001 (2018).
[2] P. Michel et al., Phys. Rev. E99, 033203 (2019).
