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Observation and modelling of Stimulated Raman Scattering driven by an optically smoothed laser beam in experimental conditions relevant for Shock Ignition

Abstract : We report results and modelling of an experiment performed at the TAW Vulcan laser facility, aimed at investigating laser-plasma interaction in conditions which are of interest for the Shock Ignition scheme to Inertial Confinement Fusion, i.e. laser intensity higher than 10^16 W/cm2 impinging on a hot (T > 1 keV), inhomogeneous and long scalelength preformed plasma. Measurements show a significant SRS backscattering (4 - 20% of laser energy) driven at low plasma densities and no signatures of TPD/SRS driven at the quarter critical density region. Results are satisfactorily reproduced by an analytical model accounting for the convective SRS growth in independent laser speckles, in conditions where the reflectivity is dominated by the contribution from the most intense speckles, where SRS gets saturated. Analytical and kinetic simulations well reproduce the onset of SRS at low plasma densities in a regime strongly affected by non linear Landau damping and by filamentation of the most intense laser speckles. The absence of TPD/SRS at higher densities is explained by pump depletion and plasma smoothing driven by filamentation. The prevalence of laser coupling in the low density profile justifies the low temperature measured for hot electrons (7 - 12 keV), well reproduced by numerical simulations.
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https://hal.archives-ouvertes.fr/hal-03334746
Contributor : Stefan Hüller Connect in order to contact the contributor
Submitted on : Monday, October 18, 2021 - 3:22:27 PM
Last modification on : Saturday, November 27, 2021 - 10:48:50 AM

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Accepted manuscript file This peer-reviewed article has been accepted for publication but not yet copyedited or typeset, and so may be subject to change during the production process. The article is considered published and may be cited using its DOI. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. 10.1017/hpl.2021.48

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  • HAL Id : hal-03334746, version 1
  • ARXIV : 2108.13485

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G. Cristoforetti, Stefan Hüller, P. Koester, L. Antonelli, S. Atzeni, et al.. Observation and modelling of Stimulated Raman Scattering driven by an optically smoothed laser beam in experimental conditions relevant for Shock Ignition. High Power Laser Science and Engineering, Cambridge University Press, 2021, 9, pp.e60. ⟨hal-03334746⟩

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