Fluid modelling of Stimulated Raman Scattering accounting for trapped particles benchmarked against fully kinetic simulations

International audience; A new fluid model describing backward stimulated Raman scattering (SRS) is presented based on parametric three-wave coupling in multidimensional geometry. It takes into account kinetic effects in the description of the plasma wave via a non linear frequency shift due to trapped electrons. The model is valid in the regime of hot and weakly inhomogeneous plasmas under conditions relevant for inertial confinement fusion with the plasma parameter k L λ De 0.25 (k L standing for the plasma wave number and λ De for the Debye length). Benchmarks of the model have been performed against the Maxwell-particle-in-cell (PIC) code Emi2D in order to calibrate the adjustable parameters controlling the non linear frequency shift. Two major configurations have been tested, one in a homogeneous plasma, with the onset of laser pump depletion and the other in an inhomogeneous plasma, producing auto-resonant growth. Good agreement between fluid and PIC simulations has been found for both configurations, in particular for the growth of SRS, and further on in time for the average backscatter level. The model is a promising tool to be implemented in multi-dimensional laser-plasma interaction packages coupled to hydrodynamics codes in order to compute SRS in mm-size volumes, usually inaccessible with PIC codes.