双锥对撞点火实验中的交叉束能量转移与背向受激布里渊散射  

Cross beam energy transfer and backward stimulated Brillouin scattering in double-cone ignition experiment

作　　者：高凡 袁鹏 黄浩彬 寇琦 贾青 远晓辉 张喆[3,4,5] 张杰[2,3,4] 郑坚[1,3] Gao Fan;Yuan Peng;Huang Hao-Bin;Kou Qi;Jia Qing;Yuan Xiao-Hui;Zhang Zhe;Zhang Jie;Zheng Jian(School of Nuclear Science and Technology,University of Science and Technology of China,Hefei 230026,China;Key Laboratory for Laser Plasmas,Ministry of Education,School of Physics and Astronomy,Shanghai Jiao Tong University,Shanghai 200240,China;Collaborative Innovation Center of IFSA(CICIFSA),Shanghai Jiao Tong University,Shanghai 200240,China;Beijing National Laboratory for Condensed Matter Physics,Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China;Songshan Lake Materials Laboratory,Dongguan 523808,China)

机构地区：[1]中国科学技术大学核科学技术学院,合肥230026 [2]上海交通大学物理与天文学院,激光等离子体教育部重点实验室,上海200240 [3]上海交通大学IFSA协同创新中心,上海200240 [4]中国科学院物理研究所,北京凝聚态物理国家研究中心,北京100190 [5]松山湖材料实验室,东莞523808

出　　处：《物理学报》2023年第17期254-260,共7页Acta Physica Sinica

基　　金：中国科学院战略性先导科技专项(A类)(批准号:XDA25010200)资助的课题.

摘　　要：在直接驱动激光聚变研究中,激光辐照靶丸会激励起受激布里渊散射(SBS)和交叉束能量传递(CBET)等过程,降低激光与靶丸的能量耦合效率以及激光辐照均匀性,导致靶丸内爆品质下降.本文使用一套基于光纤收集信号的背向散射诊断系统,诊断了双锥对撞点火(DCI)实验中波长在351 nm附近的时间分辨背向散射光谱.通过对比不同激光辐照条件下散射光谱的特征,结合光谱强度与入射激光能量以及激光偏振态的相关性分析,确认背向散射信号中包含了分别来自CBET和背向SBS过程的散射成分,确认镜像激光束之间的偏振夹角对CBET的影响.实验结果表明,在当前DCI实验中,在351 nm附近的背向反射率不高于3%,显著低于球对称辐照直接驱动中心点火方案的实验结果.In the research of direct-drive laser fusion,laser irradiation of a target pellet can stimulate various laser plasma instabilities,such as stimulated Brillouin scattering(SBS)and cross-beam energy transfer(CBET),which significantly reduce the energy coupling efficiency between the laser and target pellet as well as the laser irradiation uniformity,leading the implosion quality to degrade.In the double-cone ignition(DCI)scheme of laser fusion scheme,the diagnosis of SBS and CBET is important owing to the different target configurations and oblique incident laser irradiation from the traditional spherically symmetric direct-drive central ignition scheme.In this paper,a simple and reliable backscattering diagnostic system is developed and applied to the diagnosis of the time-resolved backscattering spectrum at wavelength near 351 nm in a DCI experiment on the Shenguang-II upgrade(SG-IIU)facility.We use the system to carry out an experimental study of the SBS process and CBET process in DCI.The backscattering diagnostic system collects the backscattered light signal through the scattered light by reflector mirror via an optical fiber.The signal is dispersed by a spectrometer and then recorded by a streak camera.The signal contains both the laser reference signal from the frequency doubling crystal and the backscattered light.With the help of the reference signal,the diagnostic system can reliably give the energy fraction of backscattered light.The experimental results show that the energy fraction of backscattered light around 351 nm is not higher than 3%,which is significantly lower than the experimental result of the spherically symmetric irradiation direct-drive central ignition scheme.By analyzing the correlation between the backscattered signal and the laser irradiation conditions and combining the results of a set of comparative experiments,we determine that the backscattered signal contains both CBET and SBS.There is a significant difference in the CBET fraction between the backscattered signal of the #5 laser

关 键 词：双锥对撞点火方案 交叉束能量转移 背向受激布里渊散射 

分 类 号：TL62[核科学技术—核技术及应用]