宽带激光辐照平面薄膜靶的近前向散射  

Near forward scattering light of planar film target driven by broadband laser

作　　者：龙欣宇 王佩佩 安红海[1] 熊俊[1] 谢志勇[1] 方智恒[1] 孙今人[1] 王琛[1] Long Xin-Yu;Wang Pei-Pei;An Hong-Hai;Xiong Jun;Xie Zhi-Yong;Fang Zhi-Heng;Sun Jin-Ren;Wang Chen(Shanghai Institute of Laser Plasma,China Academy of Engineering Physics,Shanghai 201800,China)

机构地区：[1]中国工程物理研究院上海激光等离子体研究所,上海201800

出　　处：《物理学报》2024年第12期260-266,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:12074353,12075227)资助的课题。

摘　　要：激光等离子体相互作用(LPI)过程一直以来是惯性约束聚变(ICF)点火中重要的研究内容,宽带激光在理论上一直以来被认为具有抑制LPI的潜力.宽带二倍频激光装置——“昆吾”,为实验研究宽带激光LPI效果提供了可靠的实验研究平台.针对大尺度低密度等离子体的LPI过程中强烈的受激布里渊散射和受激拉曼散射信号,开展了相同条件下宽带和窄带激光驱动C_(8)H_(8)平面薄膜靶的透过激光、前向散射和大角度近前向散射的实验研究.主要针对宽带和窄带激光前向透过信号的组分和近前向散射的光谱及份额信息进行对比研究,发现宽带和窄带激光驱动的LPI过程具有显著差异.同时,初步结果显示宽带激光相比于窄带激光体现出更强的穿透能力,烧蚀靶并穿过等离子体的时间提前了近1 ns,透过能量提升了近10倍,穿透等离子体后有更小的空间发散角.这些结果对于更好地理解宽带激光对于LPI的作用效果具有很好的参考价值.Laser plasma interaction(LPI)has always been an important research topic in the ignition phase of inertial confinement fusion(ICF).Over the years,researchers have attempted to use various laser beam smoothing schemes and optimized light source solutions to suppress the development of LPI.Among them,low-coherence laser drivers have attracted widespread attention in the fields of laser-plasma physics and laser technology in recent years.Recently,a broadband second harmonic laser facility named“Kunwu”has provided a reliable experimental research platform for the LPI process driven by broadband lasers.Aiming at the strong stimulated Brillouin scattering(SBS)and stimulated Raman scattering(SRS)in the LPI process of large-scale low-density plasma,forward scattering experiment and near-forward scattering experiment on C_(8)H_(8) planar film targets driven by broadband laser and narrowband laser under the same conditions are carried out.Based on the“Kunwu”laser facility,two sets of measurement systems are designed,one is centered around fiber-heads and spectrometer,and the other around phototubes and oscilloscope.These systems enable multi-directional precise measurements of scattered lightand a comprehensive analysis of LPI.The main focus is on the comparison of the components and spectral information of the scattering beams between broadband laser and narrowband laser,and it is found that the LPI processes driven by broadband laser and narrowband laser are greatly different.Additionally,preliminary results indicate that broadband laser exhibits a stronger penetration capability than narrowband laser.The time to ablation the target and penetrate the plasma are both nearly 1 ns ahead,with the transmitted energy increased by nearly an order of magnitude.And after penetrating the plasma,there is a smaller spatial divergence angle.These results provide good reference value for better understanding the effect of broadband laser on LPI.

关 键 词：激光等离子体相互作用 宽带激光 受激布里渊散射 受激拉曼散射 

分 类 号：TL632[核科学技术—核技术及应用]