Pulse shaping is a powerful tool for mitigating implosion instabilities in direct-drive inertial confinement fusion (ICF). However, the high-dimensional and nonlinear nature of implosions makes the pulse optimization quite challenging. In this research, we develop a machine-learning pulse shape designer to achieve high compression density and stable implosion. The facility-specific laser imprint pattern is considered in the optimization, which makes the pulse design more relevant. The designer is applied to the novel double-cone ignition scheme, and simulation shows that the optimized pulse increases the areal density expectation by 16% in one dimension, and the clean-fuel thickness by a factor of four in two dimensions. This pulse shape designer could be a useful tool for direct-drive ICF instability control.

采用二维磁驱动数值模拟程序（MDSC2）对大电流脉冲功率装置FP-2上的回流罩结构Z-箍缩实验exp90和exp60进行了数值模拟。数值模拟表明，回流罩结构Z-箍缩实验测量电流/回路电流不是负载套筒电流，回流罩结构Z-箍缩实验中回路电流不完全从负载套筒通过，回路电流和负载套筒电流之间存在一个结构系数，提出了边界磁场强度与回路电流关系的新公式。采用具有结构系数的边界磁场强度公式和磁流体力学程序能正确模拟exp90和exp60两个回流罩结构Z-箍缩实验，模拟的套筒内径运动速度和实验测量速度相一致。回流罩结构Z-箍缩实验的结构系数为一常数，仅由回流罩的初始结构确定。90 mm和60 mm内直径套筒的结构系数分别为0.87和0.90。在套筒初始厚度、绝缘材料等其它条件相同的情况下，套筒内径越大，回流罩结构Z-箍缩实验的结构系数越小。

基于拉格朗日描述，建立了水中金属丝电爆炸的单温磁流体动力学模型，并给出一种高阶混合有限元离散求解方法。拉氏可压缩流体方程组中，速度定义在H1连续有限元空间，内能定义在L2间断有限元空间实现物质界面的精确捕捉，存在激波的区域引入张量人工粘性抑制数值振荡。磁扩散方程仅考虑周向磁通量密度，简化为标量方程，使用H1连续有限元方法离散求解。焦耳热和洛伦兹力作为源项引入实现磁流体方程的耦合。数值算例表明：磁扩散求解器能够求解存在不同电导率的多介质磁扩散问题；拉氏流体求解器能够精确追踪物质界面，具有较好的激波分辨能力；耦合RLC电路的磁流体求解器能够复现水中金属丝电爆炸加热相变、冲击波的产生与传播、放电模式转变等物理过程。

Thanks to a rapid progress of high-power lasers since the birth of laser by T. H. Maiman in 1960, intense lasers have been developed mainly for studying the scientific feasibility of laser fusion. Inertial confinement fusion with an intense laser has attracted attention as a new future energy source after two oil crises in the 1970s and 1980s. From the beginning, the most challenging physics is known to be the hydrodynamic instability to realize the spherical implosion to achieve more than 1000 times the solid density. Many studies have been performed theoretically and experimentally on the hydrodynamic instability and resultant turbulent mixing of compressible fluids. During such activities in the laboratory, the explosion of supernova SN1987A was observed in the sky on 23 February 1987. The X-ray satellites have revealed that the hydrodynamic instability is a key issue to understand the physics of supernova explosion. After collaboration between laser plasma researchers and astrophysicists, the laboratory astrophysics with intense lasers was proposed and promoted around the end of the 1990s. The original subject was mainly related to hydrodynamic instabilities. However, after two decades of laboratory astrophysics research, we can now find a diversity of research topics. It has been demonstrated theoretically and experimentally that a variety of nonlinear physics of collisionless plasmas can be studied in laser ablation plasmas in the last decade. In the present paper, we shed light on the recent 10 topics studied intensively in laboratory experiments. A brief review is given by citing recent papers. Then, modeling cosmic-ray acceleration with lasers is reviewed in a following session as a special topic to be the future main topic in laboratory astrophysics research.

We present an experimental study of the dynamics of shocks generated by the interaction of a double-spot laser in different kinds of targets: simple aluminum foils and foam–aluminum layered targets. The experiment was performed using the Prague PALS iodine laser working at 0.44 μm wavelength and irradiance of a few 10¹⁵ W/cm². Shock breakouts for pure Al and for foam-Al targets have been recorded using time-resolved self-emission diagnostics. Experimental results have been compared with numerical simulations. The shocks originating from two spots move forward and expand radially in the targets, finally colliding in the intermediate region and producing a very strong increase in pressure. This is particularly clear for the case of foam layered targets, where we also observed a delay of shock breakout and a spatial redistribution of the pressure. The influence of the foam layer doped with high-Z (Au) nanoparticles on the shock dynamics was also studied.

激光聚变有望一劳永逸地解决人类的能源问题，因而受到国际社会的普遍重视，一直是国际研究的前沿热点。目前实现激光惯性约束聚变所面临的最大科学障碍（属于内禀困难）是对内爆过程中高能量密度流体力学不稳定性引起的非线性流动的有效控制，对其研究涵盖高能量密度物理、等离子体物理、流体力学、计算科学、强冲击物理和高压原子物理等多个学科，同时还要具备大规模多物理多尺度多介质流动的数值模拟能力和高功率大型激光装置等研究条件。作为新兴研究课题，高能量密度非线性流动问题充满了各种新奇的现象亟待探索。此外，流体力学不稳定性及其引起的湍流混合，还是天体物理现象（如星系碰撞与合并、恒星演化、原始恒星的形成以及超新星爆炸）中的重要过程，涉及天体物理的一些核心研究内容。本文首先综述了高能量密度非线性流动研究的现状和进展，梳理了其中的挑战和机遇。然后介绍了传统中心点火激光聚变内爆过程发生的主要流体力学不稳定性，在大量分解和综合物理研究基础上，凝练出了目前制约美国国家点火装置（NIF）内爆性能的主要流体不稳定性问题。接下来，总结了国外激光聚变流体不稳定性实验物理的研究概况。最后，展示了内爆物理团队近些年在激光聚变内爆流体不稳定性基础性问题方面的主要研究进展。该团队一直从事激光聚变内爆非线性流动研究与控制，以及聚变靶物理研究与设计，注重理论探索和实验研究相结合，近年来在内爆重要流体力学不稳定性问题的解析理论、数值模拟和激光装置实验设计与数据分析等方面取得了一系列重要成果，有力地推动了该研究方向在国内的发展。

在二维磁驱动数值模拟程序MDSC2中增加了LiF材料的材料参数和功能模块，使MDSC2程序具有了求解带窗口磁驱动准等熵压缩实验的能力。采用MDSC2程序，对大电流脉冲功率装置上的exp-3-window、exp-6-window带窗口磁驱动准等熵压缩实验进行了模拟。数值模拟结果表明，二维磁驱动数值模拟程序MDSC2能正确模拟带窗口磁驱动准等熵压缩实验exp-3-window和exp-6-window的全过程，模拟的飞片/窗口界面速度在飞片/窗口界面速度的上升阶段、峰值附近和卸载阶段与实验测量基本一致，验证了新程序的计算有效性。MDSC2程序对带窗口磁驱动准等熵压缩实验的正确模拟有助于磁驱动样品物性实验的研究。

为了确定磁驱动飞片发射实验结构系数的范围、影响因素、结构系数与影响因素的关系，对聚龙一号装置上的磁驱动飞片发射实验进行了数值模拟和分析。数值模拟表明，磁流体力学程序能正确模拟聚龙一号装置上各个磁驱动飞片发射实验；磁驱动双侧飞片发射实验的结构系数为0.7～0.8；磁驱动单侧飞片发射实验的结构系数为0.80～0.85。磁驱动飞片发射实验的结构系数与实验加载电流无关，仅由磁驱动飞片发射实验的负载结构决定。磁驱动飞片发射实验的结构系数取决于阴阳电极极板的初始宽度、阴阳电极之间的初始间隙以及阴阳电极上飞片厚度之和等三个因素。在磁驱动飞片发射实验中，电极初始宽度、阴阳电极之间的初始间隙不变的情况下，结构系数由阴阳电极上飞片厚度之和确定，阴阳电极上飞片厚度之和越大，结构系数越大。