宽带激光辐照平面厚靶的侧向散射  

Broadband laser driven near-forward scattering light of planar film target

作　　者：龙欣宇 熊俊[1] 安红海[1] 谢志勇[1] 王佩佩 方智恒[1] 王伟[1] 孙今人[1] 王琛[1] Long Xin-Yu;Xiong Jun;An Hong-Hai;Xie Zhi-Yong;Wang Pei-Pei;Fang Zhi-Heng;Wang Wei;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22期198-204,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：激光等离子体不稳定性(laser plasma instability,LPI)是惯性约束聚变(inertial confinement fusion,ICF)点火过程中的关键问题之一,多年来受到了广泛的关注.其中,宽带激光被认为是解决LPI问题的一个有效途径,并且目前已经有了大量的模拟研究和少量背向、近前向散射的实验研究,但是仍然需要侧向散射的实验研究作为补充.因此,基于输出达数百焦耳的宽带二倍频激光装置“昆吾”,本文针对宽带激光与传统窄带激光驱动平面厚靶产生的等离子体不稳定性的侧向散射以及超热电子产额设计实验.实验结果表明,功率密度为1×1015 W·cm-2的宽带激光激发的侧向受激布里渊散射(stimulated Brillouin scattering,SBS)与侧向受激拉曼散射(stimulated Raman scattering,SRS)在不同角度下的光谱和份额与窄带激光存在显著差异.进一步分析发现,宽带条件下侧向的超热电子份额整体高于窄带,而此时宽带条件下小角度近前向、小角度近背向的SRS份额却远低于窄带,初步的定性分析认为此时SRS可能不是超热电子的主要产生机制,认为此时可能是PDI对超热电子的产生起了主导作用.Laser-plasma instability(LPI)is one of the key problems in the ignition process of inertial confinement fusion(ICF),and has been extensively studied in theory,simulation,and experiment for many years.Broadband laser,due to its low temporal coherence,can reduce the effective electric field strength when interacting with plasma and disrupt the phase-matching conditions of LPI,thus an effective approach to solving LPI issues is considered.Current extensive simulation studies indicate that broadband laser can suppress the generation of phenomena such as stimulated Brillouin scattering(SBS),stimulated Raman scattering(SRS),and two-plasmon decay(TPD)to some extent.There are also a few backward scattering experimental studies,but more experimental researches,such as side-scattering,are still needed.Therefore,based on the broadband second harmonic laser facility“Kunwu”,the experiments are designed for studying the lateral scattering of critical density plasma driven by broadband laser and traditional narrowband laser,and the production of hot electrons as well in this work.The experimental results show that the side SBS spectra and side SRS spectra and portions at different angles excited by broadband lasers with a power density of 1×1015 W/cm2 are significantly different from those by narrowband lasers.Further analysis reveals that the overall portion of transverse hot electrons in broadband laser cases is higher than that in narrowband laser case.However,for broadband laser,the portion of SRS at small forward angle and backward angle are significantly lower than that for narrowband laser.Preliminary qualitative analysis suggests that SRS may not be the main mechanism for hot electron generation in this case,and that PDI might play a dominant role in generating hot electrons.

关 键 词：激光等离子体不稳定性 宽带激光 超热电子 

分 类 号：TL632[核科学技术—核技术及应用]