利用多角度散射光研究共用离子声波的多光束受激布里渊散射

A number of laser-driven high enengy density studies will employ multiple laser beams focused to a spatial region of 1mm3. Dozens of beams can collectively excite laser plasma instabilities (LPI) that coupled to a common plasma wave. Even if the individual beam intensity is in sufficient to excite LPI, the cumulative effect of many beams may lead to instability excitation and also produce energy loss in new backward direction. . In this project, we will develop a multiple-direction scattered light method to study multibeam stimulated Brillouin scatterings (SBS) that are collectively coupled to a common ion acoustic wave. The scattered light will be collected by a combination of large solid angle and 4π sampling array. By adjusting the parameter of lasers and targets, the development and amplification of multibeam SBS will be explored from the spatial distribution and spectral feature of the scattered light. Furthermore, the competition and interplay between multiple and single beam SBS will be studied in detail. This work could promote understanding of the current laser-target coupling physics based on single beam LPI studies and contribute to the high energy density experiments from kJ to MJ scale laser facilities.

激光驱动的高能量密度物理过程中，可能会有几十甚至上百路激光重叠在约1mm3等离子体区域内，并共同激发起共用离子声波的多光束受激布里渊散射(SBS)。由于多路激光的协同作用，这类过程不仅激发和增长比单光束SBS更加剧烈，而且还会导致与单光束SBS不同的散射光方向，使激光与等离子体相互作用表现出全新的现象和规律。. 本项目将建立利用多角度散射光研究共用离子声波的多光束SBS的方法，通过散射光方向和光谱变化研究多光束SBS的激发和增长规律，揭示多光束SBS与单光束SBS的相互关系和影响。这将推进以往基于单光束SBS的理解，使人们重新审视目前基于背向散射光实验测量的激光靶耦合物理认识，对大型激光装置上的高能量密度研究应用有重要的意义。

激光驱动的高能量密度物理过程中，由多路激光重叠、协同作用激发的共用离子声波的多光束受激布里渊散射(SBS)过程，使激光与等离子体相互作用表现出不同于单光束SBS的新现象和规律。本项目针对神光180kJ激光装置的激光排布，开展了共用离子声波的多光束SBS的理论研究，建立了针对多光束SBS散射光的两种新型实验测量方法，通过大型物理实验系统评估了神光180kJ激光装置共用离子声波的多光束SBS的激发水平和总体特性，提升了对该装置激光等离子体不稳定性和激光束靶耦合的物理认识。