摘要
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 10^(16) W/cm^(2) impinging on a hot(T>1 keV),inhomogeneous and long scalelength pre-formed plasma.Measurements show a significant stimulated Raman scattering(SRS)backscattering(;%-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.
基金
financial support from the LASERLAB-EUROPE Access to Research Infrastructure activity within the EC’s seventh Framework Program(Application No.18110033)
carried out within the framework of the EUROfusion Enabling research projects AWP19-20-ENR-IFE19.CEA01 and AWP21-ENR-01-CEA-02
funding from the Euratom research and training programme 20192020 and 2021-2025 under grant No.633053
financial support from the CNR-funded Italian research Network ELI-Italy(D.M.No.63108.08.2016)
the Czech Ministry of Education,Youth and Sports,project LTT17015。
作者简介
Correspondence to:G.Cristoforetti,Istituto Nazionale di Ottica-CNR,area della ricerca,Via Moruzzi 1,56124 Pisa,Italy.Email:gabriele.cristoforetti@cnr.it。
