Extrapolation of implosion performance between different laser energy scales is investigated for indirect drive through a semi-hydro-equivalent design. Since radiation transport is non-hydro-equivalent, the peak radiation temperature of the hohlraum and the ablation velocity of the capsule ablator are not scale-invariant when the sizes of the hohlraum and the capsule are scale-varied. A semi-hydro-equivalent design method that keeps the implosion velocity V_i, adiabat α_F, and PL/Rhc2 (where P_L is the laser power and R_hc is the hohlraum and capsule scale length) scale-invariant, is proposed to create hydrodynamically similar implosions. The semi-hydro-equivalent design and the scaled implosion performance are investigated for the 100 kJ Laser Facility (100 kJ-scale) and the National Ignition Facility (NIF-scale) with about 2 MJ laser energy. It is found that the one-dimensional implosion performance is approximately hydro-equivalent when V_i and α_F are kept the same. Owing to the non-hydro-equivalent radiation transport, the yield-over-clean without α-particle heating (YOC_noα) is slightly lower at 100 kJ-scale than at NIF-scale for the same scaled radiation asymmetry or the same initial perturbation of the hydrodynamic instability. The overall scaled two-dimensional implosion performance is slightly lower at 100 kJ-scale. The general Lawson criterion factor scales as χnoα2D∼S1.06±0.04 (where S is the scale-variation factor) for the semi-hydro-equivalent implosion design with a moderate YOC_noα. Our study indicates that χ_noα ≈ 0.379 is the minimum requirement for the 100 kJ-scale implosion to demonstrate the ability to achieve marginal ignition at NIF-scale.

The first laser–plasma interaction experiment using lasers of eight beams grouped into one octad has been conducted on the Shenguang Octopus facility. Although each beam intensity is below its individual threshold for stimulated Brillouin backscattering (SBS), collective behaviors are excited to enhance the octad SBS. In particular, when two-color/cone lasers with wavelength separation 0.3 nm are used, the backward SBS reflectivities show novel behavior in which beams of longer wavelength achieve higher SBS gain. This property of SBS can be attributed to the rotation of the wave vectors of common ion acoustic waves due to the competition of detunings between geometrical angle and wavelength separation. This mechanism is confirmed using massively parallel supercomputer simulations with the three-dimensional laser–plasma interaction code LAP3D.

A recently proposed octahedral spherical hohlraum with six laser entrance holes (LEHs) is an attractive concept for an upgraded laser facility aiming at a predictable and reproducible fusion gain with a simple target design. However, with the laser energies available at present, LEH size can be a critical issue. Owing to the uncertainties in simulation results, the LEH size should be determined on the basis of experimental evidence. However, determination of LEH size of an ignition target at a small-scale laser facility poses difficulties. In this paper, we propose to use the prepulse of an ignition pulse to determine the LEH size for ignition-scale hohlraums via LEH closure behavior, and we present convincing evidence from multiple diagnostics at the SGIII facility with ignition-scale hohlraum, laser prepulse, and laser beam size. The LEH closure observed in our experiment is in agreement with data from the National Ignition Facility. The total LEH area of the octahedral hohlraum is found to be very close to that of a cylindrical hohlraum, thus successfully demonstrating the feasibility of the octahedral hohlraum in terms of laser energy, which is crucially important for sizing an ignition-scale octahedrally configured laser system. This work provides a novel way to determine the LEH size of an ignition target at a small-scale laser facility, and it can be applied to other hohlraum configurations for the indirect drive approach.

为实现惯性约束聚变（ICF）内爆燃烧停滞阶段过程中最大压缩时刻的冷燃料面密度分布测量，设计了包含字母客体与针孔阵列的照相客体，通过同一发相同视角测量源分布与客体照相技术，首次建立了皮秒激光驱动的高能X射线源编码照相技术。通过星光III实验研究，基于W丝阵靶照相的反演图像空间分辨率5.4 μm±0.7 μm；激光到X射线（50～200 keV）的能量转换效率，W丝阵靶5.4×10⁻⁴，与传统Au单丝靶的转换效率（4.8×10⁻⁴）一致。基于源编码照相解决了传统皮秒激光背光照相中空间分辨率与光源亮度不能兼顾的困难，为强背景干扰下提供高信噪比、高分辨率的ICF靶丸压缩背光图像提供了重要照相方式。

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。

在激光间接驱动的惯性约束聚变（ICF）中，高强度激光与低密度等离子体发生相互作用，会激发两种受激散射过程：受激布里渊散射和受激拉曼散射。它们会损失激光能量、破坏辐射场对称性、产生超热电子，从而危害聚变点火过程。因此，理解受激散射的物理过程并找到抑制其发展的有效方法，是ICF研究中重点关注的问题。介绍了中国激光聚变研究团队为研究受激散射过程而发展的多个理论模型，以及这些模型在实验数据分析中的具体应用。这些理论模型与实验研究一起，为提升受激散射过程的物理理解发挥了重要作用。

高精密的X射线成像诊断是深入理解内爆过程，揭示点火尺度下未知物理问题的关键。基于掠入射反射的X射线显微镜，结合亚纳米级的超光滑球面或非球面反射镜，能够实现空间分辨优于5 μm的高分辨成像。介绍了国际惯性约束聚变领域的X射线显微成像技术发展及应用，重点展示了我国在高分辨X射线（KB）显微镜、多通道X射线KB显微镜以及大视场X射线KBA显微镜方向的进展，分析了下一阶段超高分辨X射线显微成像的研究计划。通过不断的技术创新，我国的X射线显微成像诊断能力已经达到国际先进水平。

介绍了惯性约束聚变研究中X射线线谱诊断与各物理量之间关系，并对X射线晶体谱仪诊断方式及诊断原理进行了简要说明。针对不同类型诊断，介绍了常用不同类型衍射晶体的作用与原理。此外，介绍了最近开展的一种新型变锥面弯晶X射线诊断方法研究，此方法拥有高集光效率的同时，保证了后端接收装置的精巧耦合，减小了像差。以变锥面弯晶衍射特性研究为出发点，开发了一个X射线任意面型晶体衍射追迹仿真软件X-Chase，并以国内某大型激光装置类H、类He线的变锥面晶体诊断为例进行了计算演示，数值模拟结果显示了变锥面晶体具有很好的聚焦效果。

条纹相机（包括X射线条纹相机和可见光光学条纹相机）是一种高时空分辨的诊断设备，在激光惯性约束聚变（ICF）物理实验研究中具有非常重要的应用。介绍了当今国内外激光聚变领域获得广泛应用的两种主要类型条纹相机的技术性能以及各自的技术特点，它们分别采用了同轴电极双聚焦电子光学扫描变像管和双板电极电子光学扫描管。在技术指标方面，重点论述了条纹相机动态范围的判据，分析了激光聚变实验对条纹相机动态范围的需求，介绍了当今国际上高性能条纹相机动态范围指标的现状。文章也介绍了和条纹相机发展应用相关的几项重要技术进展，这些进展包括先进光时标、抗辐射加固记录系统和抑制相机背景噪声的阴极选通技术。