In an experiment performed on the Shenguang-III prototype laser facility, collective Thomson scattering (TS) is used to study the spatial growth of stimulated Brillouin scattering (SBS) in a gas-filled hohlraum by detecting the SBS-driven ion acoustic wave. High-quality time-resolved SBS and TS spectra are obtained simultaneously in the experiment, and these are analyzed by a steady-state code based on the ray-tracing model. The analysis indicates that ion–ion collisions may play an important role in suppressing SBS growth in the Au plasma; as a result, the SBS excited in the filled gas region is dominant. In the early phase of the laser pulse, SBS originates primarily from the high-density plasma at the edges of the interaction beam channel, which is piled up by the heating of the interaction beam. Throughout the duration of the laser pulse, the presence of the TS probe beam might mitigate SBS by perturbing the density distribution around the region overlapping with the interaction beam.

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 new mechanism for the generation of high intensity speckles by coupling of overlapping beams is discovered and studied in detail. Using three-dimensional simulations, the coupling of overlapping beams smoothed by phase plates and by polarization smoothing are investigated in the regime relevant to inertial confinement fusion studies. It is found that the intensity distribution of the laser beam spot can be changed by nonuniform spatial phase modulation, and the speckles formed by the phase plate can be split into smaller speckles with higher intensities, which is favorable for the generation of laser plasma instabilities. Stimulated Brillouin scattering is compared in simulations with and without coupling of the overlapping incident beams, and the results confirm the enhancement of stimulated Brillouin scattering due to this mechanism.

冬季牧草即枯草的存量是生态补偿计算与畜牧生产科学管理的关键基础, 而对青藏高原枯草关键参数认识的不足, 直接限制了高寒冬季枯草监测研究与应用发展。 PROSAIL是一种光学辐射传输模型, 它可以定量描述植被参数与冠层反射率的关系。 利用最新版本PROSAIL模型, 结合野外实测的枯草光谱及叶面积、 叶绿素等10个性状参数数据, 模拟生成了15 000组潜在的枯草光谱数据序列。 通过冬、 夏实测枯草与绿草样方的反射光谱特征分析, 揭示了枯草在可见光波段与近红外波段与绿草的显著差异性, 描述了青藏高原冬季枯草在400~1 300 nm波段近似线性的独特光谱分布特征。 在此基础上, 提出了以红光与绿光波段差值为依据的鲜/枯草光谱区分方法, 并据此实现了15 000组模拟光谱中枯草光谱的初级与二级筛选, 建立了枯草模拟光谱数据序列集。 该模拟光谱数据序列集与实测光谱在400~2 500 nm全波段明显相关, 所有模拟谱线R²均在0.904~0.994之间, 表明该模型能够很好地模拟高寒冬季枯草的反射率光谱。 进一步采用EFAST方法, 对枯草模拟光谱数据序列进行全局敏感性分析, 识别出棕色素、 类胡萝卜素、 花青素、 叶片结构、 热点5个对枯草光谱变化不敏感的参数, 并在此基础上优化枯草敏感参数阈值区间。 最终, 以99%置信区间为标准、 余弦距离为评价函数, OFAT方式再次运行模型, 界定了枯草敏感的参数阈值: 叶面积指数阈值区间为0.2~0.89、 叶绿素含量为0~1.29 μg·cm^-2、 平均叶倾角为11°~90°、 等效水厚度为0.000 1~0.005 cm、 干物质含量为0.008~0.05 g·cm^-2。 通过对10个枯草性状参数及其取值区间的率定, 提出了枯草光谱关键参数数值区间参考表, 为提高对高寒冬季枯草性状特征的科学认识及探究遥感反演应用技术方法提供理论依据与基础数据。

在神光III原型装置上，利用8束三倍频（351.0 nm）激光注入充气黑腔产生大尺度高温等离子体并激发高水平受激布里渊散射（SBS）过程。利用1束四倍频（263.3 nm）探针束和1套广角汤姆逊散射诊断系统，获得了三倍频激光SBS过程驱动的离子声波的超热相干汤姆逊散射（STS）光谱。通过对STS光谱和背向SBS光谱进行联合分析，揭示了SBS的时空演化过程。