神光-ⅡU装置的SBS背向散射角分辨诊断系统  

Angle-Resolved Stimulated Brillouin Backscattering Diagnosis System Based on Shenguang-ⅡUpgrade Facility

作　　者：赵闯 袁鹏 李欣焱 郑坚 Zhao Chuang;Yuan Peng;Li Xinyan;Zheng Jian(School of Nuclear Science and Technology,University of Science and Technology of China,Hefei 230026,Anhui,China;Collaborative Innovation Center of IFSA,Shanghai Jiao Tong University,Shanghai 200240,China)

机构地区：[1]中国科学技术大学核科学技术学院,安徽合肥230026 [2]上海交通大学IFSA协同创新中心,上海200240

出　　处：《光学学报》2023年第11期129-137,共9页Acta Optica Sinica

基　　金：中国科学院战略性先导科技专项A类(XDA25010200)。

摘　　要：针对双锥对撞点火方案实验中的受激布里渊散射过程,发展了一套门控角分辨全口径背向散射诊断系统。设计了光纤阵列,对神光-ⅡU装置打靶伺服反射镜上的散射信号进行收集,利用其时间特性,通过相对测量的方式,获得了角分辨的背向受激布里渊散射能量份额,发现其角分布敏感依赖于激光在球壳表面的辐照模式,为深入研究双锥对撞点火方案中的受激布里渊散射过程提供了可靠的实验结果。Objective Stimulated Brillouin scattering(SBS)is an important topic in the field of laserdrive inertial confinement fusion(ICF).SBS can reduce the lasertarget energy coupling efficiency,spoil implosion symmetry,and degrade target gain.The fullaperture stimulated Brillouin backscattering energy fraction diagnosis systems on the main laser fusion devices do not measure the spatial distribution of stimulated Brillouin backscattering signals,which simplifies the diagnosis system but loses the detailed features of stimulated Brillouin backscattering signals.An angleresolved fullaperture backscattering diagnosis system is developed for the Shenguang-ⅡUpgrade(SG-ⅡU)facility to study the SBS process in the integration experiment of the doublecone ignition(DCI)scheme.The evaluation reveals that the angular resolution of the system is about±2°,and the diagnostic accuracy of energy fraction is±15%.Methods The design of the system is guided by the temporal characteristics of the backward reflection signals on the SG-ⅡU facility.It is found that both SBS signals from the target and the third harmonic reflected light from the triplefrequencyconversion crystal(called laser signals in this work)propagate along the same direction but with a fixed time delay dependent on the geometry of the final optical assembly.The level of laser signals is proportional to the incident laser energy and is stable so that it can be used as a reference to infer the SBS energy fraction.An optical fiber array is designed to collect the angleresolved signals reflected from the servo mirror of the SG-ⅡU facility.Then,the signals are split into two beams and recorded with two intensified chargecoupled devices(ICCD)separately.The time delay between the two ICCDs is determined by that between SBS signals and laser signals.To make sure the ICCDs record accurate signal energy and verify the timing and intensity ratio between the SBS signals and laser signals,the temporal characteristics of the ICCDs gating process are tested,and the total signals

关 键 词：激光光学 双锥对撞点火 受激布里渊散射 角分辨全口径背向散射诊断 

分 类 号：O536[理学—等离子体物理]