受激布里渊散射的非线性增强和饱和  

Nonlinear enhancement and saturation of stimulated Brillouin scattering

作　　者：郑春阳[1,2] 王清[2] 刘占军[1,2] 贺贤土[1,2] Zheng Chunyang;Wang Qing;Liu Zhanjun;He Xiantu(Institute of Applied Physics and Computational Mathematics,Beijing 100094,China;Center for Applied Physics and Technology,Peking University,Beijing 100871,China)

机构地区：[1]北京应用物理与计算数学研究所,北京100094 [2]北京大学应用物理与技术研究中心,北京100871

出　　处：《强激光与粒子束》2020年第9期116-122,共7页High Power Laser and Particle Beams

基　　金：国家自然科学基金项目(11975059)。

摘　　要：针对典型激光聚变等离子体参数条件,利用弗拉索夫程序研究非均匀流等离子体中受激布里渊散射的非线性行为。在动理学效应占主导的参数区域,观察到受激布里渊散射激发的离子声波由于非线性动理学频移和非均匀流空间失谐相互补偿引起的离子声波自共振增长,这会导致受激布里渊水平量级的增强;提出用光束时间去相干抑制这种绝对增长。在流体非线性占主导的参数区域,观察到由于离子声波谐波导致的孤立波产生、离子加热以及受激布里渊散射饱和现象。The nonlinear evolution of stimulated Brillouin scattering(SBS)in inhomogeneous flowing plasmas is self-consistently investigated by the Vlasov-Maxwell simulations.In the physical regime where ion trapping is dominant,simulations show that the evolution of SBS includes a linear convective stage and a nonlinear stage.In the linear stage,the reflectivity is in good agreement with the theoretical prediction from the Rosenbluth gain.In the nonlinear stage,the reflectivity shows a continuous increase and becomes much larger than the theoretical value.And the auto-resonant growing of ion acoustic wave(IAW)shows a nature of absolute instability,which can be explained as the compensation of the negative kinetic frequency shift from trapped ions and the detuning due to the flow velocity gradient.Methods using the incoherence in the pump waves to mitigate the enhanced SBS are proposed.The saturation of SBS by the decay to solitary turbulence of the IAW is demonstrated in the fluid dominant regime.The formation of solitary structures is due to the generation of harmonics of IAW.

关 键 词：弗拉索夫模拟 受激布里渊散射 离子声波 自共振 孤立波 

分 类 号：O53[理学—等离子体物理]