Langdon效应下离子碰撞对背向散射竞争的影响OA

[Background]Backward stimulated Raman scattering(SRS)and backward stimulated Brillouin scattering(SBS)are two major laser-plasma instabilities that influence the laser-target energy coupling efficiency in inertial confinement fusion(ICF).Hot electrons excited by SRS can preheat the fuel.Their nonlinear competition determines the effectiveness of laser-plasma coupling and thus the performance of laser-driven fusion.In realistic laser fusion conditions,the electron distribution often deviates from a Maxwellian due to strong laser heating,leading to nonthermal effects such as the Langdon effect.Additionally,ion-ion collisions in multispecies plasmas such as CH can alter the damping and dispersion of ion acoustic waves.[Purpose]This study aims to investigate the impact of the Langdon effect and ion-ion collisions on the competition between SRS and SBS in CH plasma,particularly focusing on their respective reflectivities under varying plasma conditions.[Methods]Five-wave coupling equations describing the nonlinear interactions among the pump laser,scattered light,Langmuir wave,and ion acoustic wave were numerically solved.A super-Gaussian electron distribution function was employed to incorporate the Langdon effect,while ion-ion collision effects were included through modifications to the ion susceptibility.The dispersion relations and damping characteristics of both electron plasma waves(EPWs)and ion acoustic waves(IAWs)were analyzed in detail.[Results]The results reveal that the Langdon effect notably reduces Landau damping of EPWs and modifies the dispersion relation of SRS,enhancing its growth rate.Simultaneously,ion-ion collisions increase IAW damping and shift the SBS dispersion curve,weakening its instability.These combined effects lead to a dominance of SRS over SBS at lower electron densities,altering the overall backscattering reflectivity spectrum in laser fusion plasma.[Conclusions]Both the Langdon effect and ion-ion collisions play crucial roles in reshaping the nonlinear dynamics of SRS and SBS.Their influence must be considered in predictive models of laser-plasma interactions.These findings provide insight into optimizing plasma parameters for improved control of backscatter instabilities in inertial confinement fusion experiments.