强度调制宽带激光对受激拉曼散射动理学爆发的抑制  

Suppression of stimulated Raman scattering kinetic bursts by intensity-modulated broadband laser

作　　者：刘庆康 张旭 蔡洪波[1] 张恩浩 高妍琦 朱少平[1] Liu Qing-Kang;Zhang Xu;Cai Hong-Bo;Zhang En-Hao;Gao Yan-Qi;Zhu Shao-Ping(Institute of Applied Physics and Computational Mathematics,Beijing 100094,China;Graduate School of China Academy of Engineering Physics,Beijing 100088,China;Beijing Computational Science Research Center,Beijing 100088,China;Shanghai Institute of Laser Plasma,Shanghai 201899,China)

机构地区：[1]北京应用物理与计算数学研究所,北京100094 [2]中国工程物理研究院研究生院,北京100088 [3]北京计算科学研究中心,北京100088 [4]上海激光等离子体研究所,上海201899

出　　处：《物理学报》2024年第5期228-236,共9页Acta Physica Sinica

基　　金：国家重点研发计划(批准号:2022YFA1603204);国家自然科学基金(批准号:12325510,12235014,11975055)资助的课题。

摘　　要：激光等离子体不稳定性是困扰惯性约束聚变的难题之一.宽带激光作为抑制激光等离子体不稳定性的有效手段,近年来受到广泛关注.然而,宽带激光在动理学区域驱动的受激拉曼散射等高频不稳定性存在非线性爆发,使抑制效果不及预期.本文提出一种外加强度调制的宽带激光模型.通过选择适当的强度调制包络,能够打断背散光在强脉冲中的放大过程,降低高强度脉冲诱发剧烈爆发的概率,并大幅减少背散光份额和热电子产额.数值模拟表明,强度调制激光对受激拉曼散射具有较好的抑制能力.对于平均功率为1.0×10^(15)W/cm^(2),带宽为0.6%的二倍频宽带激光,使用强度调制技术后,反射率下降了1个数量级,20 keV以上热电子能量份额也由7.34%下降至0.31%.上述研究证实了使用强度调制宽带激光抑制高频不稳定性的可行性,并有望为后续宽带激光驱动聚变实验设计提供参考.Laser plasma instability is one of the difficulties that plague inertial confinement fusion.Broadband laser,as an effective tool for suppressing laser-plasma instabilities,has received a lot of attention in recent years.However,the nonlinear bursts of high-frequency instabilities,such as stimulated Raman scattering driven by broadband laser in the kinetic regime,make the suppression effect less than expected.In this study,a broadband laser model with intensity modulation is proposed.By choosing an appropriate intensity modulation envelope,it is possible to interrupt the amplification process of backscattered light in strong pulses,reduce the probability of high-intensity pulses inducing intense bursts,and drastically reduce the fraction of backscattered light and hot electron yield.Numerical simulations show that the intensity-modulated laser has a good ability to suppress stimulated Raman scattering.For a broadband laser with average power of 1.0×10^(15)W/cm^(2)and a bandwidth of 0.6%,the reflectivity decreases by an order of magnitude and the fraction of hot electron energy above 20 keV decreases from 7.34%to 0.31%by using the intensity modulation technique.The above results confirm the feasibility of using the intensity-modulated broadband laser to suppress the high-frequency instability and are expected to provide a reference for designing the subsequent broadband laser-driven fusion experiments.

关 键 词：惯性约束聚变 动理学效应 宽带激光 受激拉曼散射 

分 类 号：TL632[核科学技术—核技术及应用]