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

TY - JOUR

T1 - Observation and modelling of stimulated Raman scattering driven by an optically smoothed laser beam in experimental conditions relevant for shock ignition

AU - Cristoforetti, G.

AU - Hüller, S.

AU - Koester, P.

AU - Antonelli, L.

AU - Atzeni, S.

AU - Baffigi, F.

AU - Batani, D.

AU - Baird, C.

AU - Booth, N.

AU - Galimberti, M.

AU - Glize, K.

AU - Héron, A.

AU - Khan, M.

AU - Loiseau, P.

AU - Mancelli, D.

AU - Notley, M.

AU - Oliveira, P.

AU - Renner, O.

AU - Smid, M.

AU - Schiavi, A.

AU - Tran, G.

AU - Woolsey, N. C.

AU - Gizzi, L. A.

N1 - © The Author(s), 2021. Published by Cambridge University Press in association with Chinese Laser Press Funding Information: 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.CEA-01 and AWP21-ENR-01-CEA-02, and has received funding from the Euratom research and training programme 2019-2020 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.

PY - 2021/10/18

Y1 - 2021/10/18

N2 - 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 impinging on a hot (1$]]> keV), inhomogeneous and long scalelength pre-formed plasma. Measurements show a significant stimulated Raman scattering (SRS) backscattering (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 (keV), which is well reproduced by numerical simulations.

AB - 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 impinging on a hot (1$]]> keV), inhomogeneous and long scalelength pre-formed plasma. Measurements show a significant stimulated Raman scattering (SRS) backscattering (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 (keV), which is well reproduced by numerical simulations.

KW - inertial confinement fusion

KW - laser-plasma interaction

KW - plasma simulations

KW - shock ignition

KW - stimulated Raman scattering

UR - http://www.scopus.com/inward/record.url?scp=85120533475&partnerID=8YFLogxK

U2 - 10.1017/hpl.2021.48

DO - 10.1017/hpl.2021.48

M3 - Article

AN - SCOPUS:85120533475

SN - 2095-4719

VL - 9

JO - High Power Laser Science and Engineering

JF - High Power Laser Science and Engineering

M1 - e60

ER -