P2 is the remaining principal asymmetry in laser-driven hohlraums. A simple analytic model for P2 asymmetry on the Shenguang 100 kJ laser facility is presented, which is based on hohlraum geometry, wall albedo, plasma expansion, and shell velocity. The calculated P2 asymmetry from the model is in reasonably good agreement with experimental data from pre-pulse, shell flight and stagnation stages. The P2 model appears to capture the essential physics governing drive symmetry and has been implemented to guide new symmetric implosion designs, enabling a more rapid convergence to a symmetric implosion than the conventional trial-and-error approach.

Collective Thomson scattering (CTS) is crucial for inertial confinement fusion (ICF) hohlraum diagnostics, but measurement of the electron plasma wave (EPW) feature remains challenging. The conventional collisionless model suffers from two critical defects: under low-temperature, high-density conditions it predicts an extremely narrow EPW peak that causes numerical sampling distortion, and it predicts a monotonic increase of peak intensity with decreasing scattering angle, which would mislead experimental design. To overcome these issues, the Bhatnagar–Gross–Krook (BGK) collisional model is introduced. The BGK model predicts a nonmonotonic peak intensity with an optimal angle between 30° and 60°, and yields a finite, resolvable peak width that eliminates sampling artifacts. It also enables reliable assessment of drive-beam backgrounds. Guided by the predicted optimal angle, CTS experiments at 42° were performed on the Shenguang-100 kJ facility. For the first time, both ion and electron features were simultaneously measured in the hohlraum corona, with the electron signal clearly distinguishable from the background. Joint fitting provides the temporal evolution of electron density and temperature. This work establishes a unified, collision-corrected diagnostic framework that overcomes a long-standing obstacle to measuring electron density and temperature in ICF hohlraum plasmas.

In indirect-drive inertial confinement fusion (ICF), the radiation drive temperature of the hohlraum is related to the shock velocity and implosion velocity of the capsule. The radiation drive symmetry on the capsule is the vital parameter for the hotspot symmetry. A new method is proposed to simultaneously determine the radiation temperature and P2 asymmetry on the capsule by measuring the re-emitted x-ray radiation flux along two orthogonal directions. The interaction between the hohlraum and the imploded capsule can be decoupled by employing a high-Z substitute capsule. The effects of opacity and equation of state on the measurement of the P2 asymmetry are given based on the self-similarity theory. The demonstration experiments were conducted on the Shenguang-100 kJ laser facility. The evolutions of the radiation drive temperature and P2 asymmetry are obtained in the experiment. The impact of diagnostic holes and laser beam absences on the P2 asymmetry is quantitatively evaluated with the view-factor calculation. The temporal trend of the symmetry is consistent between the experiment and the integrated simulation (LARED-JC). However, the experimental symmetry differs from the simulation results from the middle of the main pulse. This might be caused by the inverse bremsstrahlung absorption or the crossed-beam energy transfer (CBET) process. The new method can provide both radiation drive temperature and P2 asymmetry for different hohlraumsin experiments. It enables time-resolved determination of both the laser power multiplier and the cone fraction multiplier, which is beneficial for optimizing the innovative hohlraum designs.

In inertial confinement fusion (ICF), Thomson scattering (TS) is a widely used diagnostic technique for probing plasma conditions. We present a first-principles numerical approach to obtaining scattered light signals of ion acoustic features with high resolution in angle and frequency space using particle-in-cell simulations under typical ICF conditions. Our method demonstrates good agreement with existing theories for thermal collective TS. In the super-thermal collective regime, the results align with theory when the driven plasma modes are well-matched in wave vectors to the probe and collecting beams. Moreover, we also find that TS signals can remain significant even under imperfect wave-vector matching-a result that contradicts the conventional expectation that the TS spectrum strictly follows the plasma density spectrum. We attribute this discrepancy to a beating wave mechanism arising from the interaction between the probe beam and driven plasma density modulations. Our work thus provides a practical framework for interpreting TS signals from driven ion modes, a common yet complex feature in ICF plasmas.

Backscattering due to laser plasma instabilities (LPIs) presents a risk in the laser-driven inertial confinement fusion. Generally, it is assumed that the backscattering of laser beams in the same cone is identical in hohlraum physics studies. In the experiments performed at SG-100kJ laser facility, we find that the backscattering of laser beams in the same cone are quite different. Our investigation reveals the main reason for this phenomenon is that the laser beams in the same cone obtain different power from their neighbor beams via crossed-beam energy transfer (CBET) depending on their polarizations. The dependence of multi-beam CBET on laser polarization arrangement is confirmed in a specially designed experiment. These findings are crucial for understanding the backscattering, CBET, energy deficit and the azimuthal drive asymmetry in cylindrical hohlraums.

The influence of unwanted X-ray background as well as the variation of the physical condition for radiation temperature (Tr) measurement is investigated in this work. Laser clipping by LEH, residual unconverted light striking target support structures and laser energy deposited on the CH membranes will lead to an overestimation of the hohlraum Tr. Laser pointing accuracy and laser power imbalance change the fraction of certain laser spots as well as their energy in the sight of view, causing a deviation in estimating the hohlraum Tr. Besides, LEH closure will lead to an underestimation of the hohlraum Tr.

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.

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.

Based on the experimental conditions of the Shenguang-100 kJ laser facility, the feasibility and applicability of the deep ultraviolet quintuple-frequency Thomson scattering diagnostics are evaluated, and compared with the widely used quadruple-frequency Thomson scattering, so as to provide a reference for the technical route for high-precision diagnosis of inertial confinement fusion plasmas. The probe beam signal, the drive-beam background, and the bremsstrahlung background are evaluated, and the measurement bands of the Thomson scattering ion spectrum and electron spectrum are discussed respectively. The results show that for the ion spectrum, the signal to-background ratio can be significantly improved by using a quintuple-frequency probe beam. For the red peak of the electron spectrum, whether a quintuple-frequency probe beam or a quadruple-frequency probe beam is used, it is strongly disturbed by the intense background of the drive beam. For the blue peak of the electron spectrum, the drive beam background can be avoided by using a quintuple-frequency probe beam, while the bremsstrahlung background will be significantly enhanced. In general, quintuple-frequency Thomson scattering has significant advantages in the measurement of low atomic number plasmas, but not for high atomic number plasmas.

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。

In this article, we present experiments measuring the electron density of a blown-off aluminum plasma created by a 2ω (532 nm) laser using dual-angle Thomson scattering diagnosis. By fitting two ion-acoustic-wave feature spectra collected from two angles simultaneously, in a typical shot, the electron density obtained 400 μm in front of the target as given by Thomson scattering diagnosis was (5.9±0.6)×1018cm−3, which is 35% higher than the average result of (4.4±0.7)×1018cm−3 as measured by digital holography diagnosis. The distribution of the electron density along the laser axis from 400 μm to 700 μm as given by dual-angle Thomson scattering was broadly consistent with that obtained from digital holography diagnosis. At a location of 250 μm in front of the target, a unique set of plasma parameters cannot be obtained by dual-angle Thomson scattering diagnosis. This may be a result of the steep density gradient visible in the hologram in this region. Dual-angle Thomson scattering diagnosis can provide a good estimation of the electron density in plasma parameter regimes similar to those in these experiments, in which the scattering parameter α<2. This technique may be useful for small laser facilities that cannot afford a second probe laser with a different wavelength and for measuring electron density with 4ω Thomson scattering on large laser facilities. This article presents several factors that need to be considered when employing this method.

Great efforts have been made to create a bright K-shell source using the thin metal cylindrical cavities in the past few decades. Several metal materials such as titanium (Ti), iron, and so on have been tested for high x-ray conversion efficiency mainly at the OMEGA and NIF laser facilities. Recently, x-ray sources in Ti K-shell transition energy range were investigated at the Shenguang-III prototype laser facility with ∼5 kJ laser energy. The experiments were aimed to reproduce the previous ones at OMEGA, but with an extraordinarily small volume of cylindrical cavity and detailed characterizations of the x-ray source. The cavities were 800 μm inner diameter, 800 μm length, and 30 μm thick plastic tubes supporting 1 μm thick Ti. Seven laser beams were focused to 200 μm diameter. The combination of the small cavity volume and the focused laser spots is intended to improve the electron temperature with limited laser energy since the electron temperature is a key issue for high x-ray conversion efficiency. Thomson scattering was adopted to experimentally probe the electron temperatures at special time and space zones as well as the average temperature obtained from the Ti K-shell spectrum. The evolutions of the electron temperature and density are predicted by the radiation hydrodynamic simulation. A top view and two photon energy bands of x-ray source images provide a way to directly observe the plasma movement toward the cavity axis and distinguish the different emission mechanisms between the Ti K-shell and lower energy x rays. Six Higher-energy x-ray detectors located at different angles were used to record the Ti K-shell x-ray emission and demonstrate its isotropic feature. The characteristics of the x-ray radiate intensity including the time evolution, the angular distribution, and the total yields for both the photon energy regions above and below 4 keV are compared between the cavity and planar targets. Obviously, different behaviors were found between the two photon energy regions and the two types of targets. The x-ray conversion efficiency of the Ti cylinder was determined to be ∼4% and ∼21% in 4π sr in the Ti K-shell (4–7 keV) and <4 keV range, respectively. The Ti K-shell conversion efficiency obtained in the present experiments is between the ones driven by 13.5 and 4.5 kJ laser energy at OMEGA.

Abstract In inertial confinement fusion, quantitative and high-spatial resolution ( $$< 10\,\upmu $$ < 10 μ m) measurements of the X-rays self-emitted by the hotspot are critical for studying the physical processes of the implosion stagnation stage. Herein, the 8 ± 0.39-keV monochromatic X-ray distribution from the entire hotspot is quantitatively observed in 5- $$\upmu $$ μ m spatial resolution using a Kirkpatrick–Baez microscope, with impacts from the responses of the diagnosis system removed, for the first time, in implosion experiments at the 100 kJ laser facility in China. Two-dimensional calculations along with 2.5% P2 drive asymmetry and 0.3 ablator self-emission are congruent with the experimental results, especially for the photon number distribution, hotspot profile, and neutron yield. Theoretical calculations enabled a better understanding of the experimental results. Furthermore, the origins of the 17.81% contour profile of the deuterium-deuterium hotspot and the accurate Gaussian source approximation of the core emission area in the implosion capsule are clarified in detail. This work is significant for quantitatively exploring the physical conditions of the hotspot and updating the theoretical model of capsule implosion.

Currently, laboratory created energy density of laser-driven inertial confinement fusion (ICF) is extremely close to that for ignition, while the divergence between experiment and simulation is increasing. One of the key issues is the lack of advanced knowledge of laser-hohlraum coupling process, which has shown the complexity of hohlraum environment. Optical Thomson scattering (OTS) becomes the standard technique for diagnosing the ICF hohlraum plasma parameters, due to its capability of providing unperturbed, local and precise measurement. The development of OTS in China is closely related with the Shenguang series laser facilities, on which most of the ICF experiments are carried out. In recent years, 4ω(263 nm) Thomson scattering technique has been set up on Shenguang-III prototype and 100 kJ-level laser facility, the corresponding results help the understanding of ICF physics. In the near future, several novel methods will be developed, for high-precision diagnostics of ICF ignition hohlraum plasmas and the research of new physical phenomena.

对国内激光惯性约束聚变(ICF)领域高时空分辨技术的最新进展进行了比较全面的介绍.针对热斑诊断时间分辨优于10 ps、空间分辨优于10μm、能区10～30 keV的需求,从光学、X射线、核诊断和计算成像几个角度,比较系统地介绍了最新的进展.光学领域主要介绍基于泵浦探测技术的全光扫描和全光分幅技术.全光扫描技术的时间分辨可以达到200 fs,全光分幅的时间分辨可以达到5 ps,空间分辨可以达到5μm.该系统的主要部件为光学器件,在ICF未来的强电磁、强电离环境下有很好的应用前景.X射线系统主要介绍最近几年发展的高分辨KB显微镜,其采用STTS构型,可将空间分辨提高到3μm,满足当前高分辨的需求.漂移管技术的时间分辨可以达到10 ps,作为一种正在发展的技术,对此进行了较为全面的分析.中子成像系统主要介绍了高空间分辨的记录系统以及对应的瞄准技术的进展,其空间分辨可以达到20～25μm.计算成像作为一个全新的分支,最近引起了ICF领域的广泛关注.着重介绍了三维光场技术和在高时空分辨领域有很好应用前景的压缩感知超快成像(CUP)技术,对其可能在ICF领域中的应用提出了设想.

Optical Thomson scattering (OTS) diagnostics have been continuously developed on a series of large laser facilities for inertial confinement fusion (ICF) research in China. We review recent progress in the use of OTS diagnostics to study the internal plasma conditions of ICF gas-filled hohlraums. We establish the predictive capability for experiments by calculating the time-resolved Thomson scattering spectra based on the 2D radiation-hydrodynamic code LARED, and we explore the fitting method for the measured spectra. A typical experiment with a simplified cylindrical hohlraum is conducted on a 10 kJ-level laser facility, and the plasma evolution around the laser entrance hole is analyzed. The dynamic effects of the blast wave from the covering membrane and the convergence of shocks on the hohlraum axis are observed, and the experimental results agree well with those of simulations. Another typical experiment with an octahedral spherical hohlraum is conducted on a 100 kJ-level laser facility, and the plasma evolution at the hohlraum center is analyzed. A discrepancy appears between experiment and simulation as the electron temperature rises, indicating the occurrence of nonlocal thermal conduction.

针对传统空间操控装置难以适应未来大型空间设施在轨建设的问题,提出一种能够实现多层次自重构的空间细胞机器人系统,并对其概念体系以及设计理念进行了分析.介绍了空间三角桁架装配场景下的空间细胞机器人系统硬件设计.提出了空间细胞机器人系统关键技术,包括多智能体协同不确定行为规划、多层次机器人系统构型决策、多智能体协同无环境地图自主导航以及多智能体分层协同分布式控制等.最后结合空间细胞机器人系统的特点与优势,对其应用前景进行了展望.

An ultraviolet Thomson-scattering system has been designed and implemented on the Shenguang-III laser facility, a 48-beam, 3ω (351 nm), 180 kJ-level laser driver for high energy density physics and inertial confinement fusion researches. The 4ω (263.3 nm) probe beam of the Thomson-scattering system is injected from the north pole (top) of the target chamber, with an assistant beam-pointing monitor to achieve high pointing accuracy. The Thomson-scattered light is collected by a double-Cassegrain optical transmission system, which provides an achromatic image over a wide wavelength range of 200-800 nm. A novel on-line alignment method is developed and applied to the diagnostic system, ensuring a volumetric positioning accuracy of ∼30 μm for the scattering volume. An online calibration is also conducted to provide the wavelength benchmark and the spectral resolution of the system. This Thomson-scattering system has been tested in a complicated experimental environment with gas-filled hohlraums, and a high-quality ion feature of the scattered light has been obtained.

We report on the first observation, to the best of our knowledge, of soliton explosions in an ultrafast fiber laser mode-locked by nonlinear polarization evolution. The soliton explosion is a transition state between stable mode-locking and noise-like pulses regimes. By tuning the waveplates and the spectral filter, the duration of soliton explosions is widely tunable from ~100 roundtrips to thousands of roundtrips. Our experimental results together with the numerical simulations reveal the dissipative nature of soliton explosions, and may be beneficial for further understanding of this striking phenomenon.