高功率激光辐照平面靶后辐射冷却效应对等离子体成丝的影响  

Influence of radiative cooling effect on the plasma filamentations in the interaction of high-power laser with planar targets

作　　者：赵鑫[1] 杨晓虎 张国博[1] 马燕云 刘彦鹏 郁明阳[5] Zhao Xin;Yang Xiao-Hu;Zhang Guo-Bo;Ma Yan-Yun;Liu Yan-Peng;Yu Ming-Yang(College of Science,National University of Defense Technology,Changsha 410000,China;IFSA Collaborative Innovation Center,Shanghai Jiaotong University,Shanghai 200240,China;College of Advanced Interdisciplinary Studies,National University of Defense Technology,Changsha 410000,China;State Key Laboratory of Laser Interaction with Matter,Northwest Institute of Nuclear Technology,Xi’an 710024,China;School of Engineering Physics,Shenzhen Technology University,Shenzhen 518000,China)

机构地区：[1]国防科技大学理学院,长沙410000 [2]上海交通大学IFSA协同创新中心,上海200240 [3]国防科技大学前沿交叉学科学院,长沙410000 [4]西北核技术研究所,激光与物质相互作用国家重点实验室,西安710024 [5]深圳技术大学工程物理学院,深圳518000

出　　处：《物理学报》2022年第23期329-338,共10页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:12175309,11775305,11975308,12005297);中国科学院战略先导A类专项(批准号:XDA25050200);激光与物质相互作用国家重点实验室基金(批准号:SKLLIM1908);湖南省自然科学基金(批准号:CX20190001);国防科技大学青年创新奖(批准号:20180104)资助的课题.

摘　　要：基于辐射流体力学程序开展了高功率激光与平面靶相互作用的研究,当激光与钨平面靶相互作用时,由于热成丝不稳定性等原因引起激光能量沉积不均匀,等离子体前沿会出现密度涨落,后期会产生明显的等离子体成丝现象.研究发现,辐射冷却对成丝现象至关重要,在等离子体的辐射流体动力学演化中,辐射冷却效应会导致等离子体压强分布不均匀,影响流体横向运动,进而加强等离子体密度涨落,在激光结束后密度涨落逐渐演变成为成丝现象.通过对铝、铜、钨和金4种材料的研究,发现高Z材料钨和金中,由于辐射冷却效应较强,导致明显的成丝现象.研究结果将对激光聚变、实验室天体物理及强激光驱动的应用等研究具有借鉴意义.Interaction of high-power laser with planar target is studied by using radiation-hydrodynamics simulation.When the laser interacts with the tungsten planar target,the laser energy deposition is uneven due to thermal filamentation instability and other reasons,and density fluctuations will appear in the front of the plasma,resulting in obvious plasma filamentation in the later stage.The researches of four materials,i.e.aluminum,copper,tungsten and gold,show that in the high-Z material tungsten and gold,due to the strong radiative cooling effect,the filamentation phenomena of the density distribution,electron temperature distribution and pressure distribution obviously occur.The order of magnitude of filamentous plasma density is different from that of the surrounding plasma.The filamentation phenomenon is closely related to the non-uniform energy deposition of the laser and the radiative cooling effect,although the ray beam will cause inhomogeneity of the laser irradiation to a certain extent,this is not the main reason for the filamentation phenomenon observed in this paper.Owing to refraction,reflection and the thermal filamentation instability when the laser is transmitted in the ablation plasma,the laser energy is deposited unevenly,which generates instability seeds in the early stage of plasma formation.The radiative cooling effect then amplifies this instability seeds,creating a radiative cooling instability that eventually results in a filamentous distribution of physical quantities such as plasma density,temperature,and pressure.This filamentation phenomenon destroys the uniformity of the plasma to a certain extent,and lays the seeds for the growth of fluid instability,which will seriously affect fusion-related research.It is shown that radiative cooling is crucial to the filamentation phenomenon,which causes uneven distribution of the plasma pressure during the evolution of the plasma,thereby affecting its transverse motion and enhancing the density fluctuation.After the laser irradiation ends,the density

关 键 词：强激光 等离子体 辐射冷却 成丝现象 

分 类 号：O53[理学—等离子体物理] TN248[理学—物理]