Observation and modelling of stimulated Raman
scattering driven by an optically smoothed laser beam in
experimental conditions relevant for shock ignition

Anno: 2021

Autori: Cristoforetti G., Hüller S., Koester P., Antonelli L., Atzeni S., Baffigi F., Batani D., Baird C.,
Booth N., Galimberti M., Glize K., Héron A., Khan M., Loiseau P., Mancelli D., Notley M., Oliveira P., Renner O., Smid M., Schiavi A., Tran G., Woolsey N.C., Gizzi LA.

Affiliazione autori: Intense Laser Irradiation Laboratory, INO-CNR, Pisa, 56124, Italy; Centre de Physique Thyorique CPHT, CNRS, IP Paris, Ecole Polytechnique, Palaiseau, 91128, France; York Plasma Institute, Department of Physics, University of York, York, YO10 5DD, United Kingdom; Dipartimento SBAI, Universita di Roma ?La Sapienza?, Roma, 00161, Italy; University de Bordeaux, CNRS, CEA, CELIA, Talence, 33405, France; STFC Rutherford Appleton Lab, Central Laser Facility, Didcot, SN2 1SZ, United Kingdom; Key Laboratory for Laser Plasmas (MOE), Shanghai Jiao Tong University, Shanghai, 200240, China; CEA, DAM, DIF, Arpajon, 91297, France; University Paris-Saclay, CEA, LMCE, Bruyires-le-Chwtel, 91680, France; Institute of Physics, ELI Beamlines, Institute of Plasma Physics, Czech Academy of Sciences, Prague, 18221, Czech Republic; Helmholtz-Zentrum Dresden-Rossendorf, Dresden, 01328, Germany

Abstract: We report results and modelling of an experiment performed at the Target Area West Vulcan laser facility, aimed
at investigating laser–plasma interaction in conditions that are of interest for the shock ignition scheme in inertial
confinement fusion (ICF), that is, laser intensity higher than 1016 W/cm2 impinging on a hot (T > 1 keV),
inhomogeneous and long scalelength pre-formed plasma. Measurements show a significant stimulated Raman scattering
(SRS) backscattering (∼ 4%−20% of laser energy) driven at low plasma densities and no signatures of two-plasmon
decay (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 becomes 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), which is well reproduced by
numerical simulations.


Volume: 9      Da Pagina: e60  A: e60

Maggiori informazioni: The authors acknowledge financial support from the LASERLAB-EUROPE Access to Research Infrastructure activity within the EC´s seventh Framework Program (Application No. 18110033). This work has also been carried out within the framework of the EUROfusion Enabling research projects AWP19-20-ENR-IFE19.CEA01 and AWP21-ENR-01-CEA-02, and has received funding from the Euratom research and training programme 20192020 and 2021-2025 under grant No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. The authors also acknowledge financial support from the CNR-funded Italian research Network ELI-Italy (D.M. No. 631 08.08.2016) and the Czech Ministry of Education, Youth and Sports, project LTT17015.
Parole chiavi: Laser-Plasma Interaction, Kinetic simulations, Inertial Confinement Fusion
DOI: 10.1017/hpl.2021.48