During the implosion of metallic materials, the ejecta formed where the fragments were ejected from the shocked metal surface, and a mixed layer with finite width appears between two fluids, the mixed layer significantly influences the subsequent development of hydrodynamic instabilities and mixing. In inertial confinement fusion (ICF), the shock that passes through the roughened metal interface also causes the formation of ejecta. Therefore, accurate prediction of the growth of Richtmyer-Meshkov (RM) instability involving the mixed layer is crucial for understanding various phenomena in astrophysics and optimizing ICF engineering designs. However, in the experimental studies of RM instability on metal interfaces RM instability with a mixed layer, the opacity difference between the mixed layer and the metal sample is relatively small, this makes it difficult to accurately measure the RM instability growth using traditional X-ray backlighting imaging techniques. To address this issue, this study applies X-ray fluorescence imaging technology to the measurement of RM instability growth. This technique possesses fluid tracing characteristics and localized diagnostic capabilities. The K-shell fluorescence signals of titanium atoms in foam material are obtained by the curved bent crystal imaging system, it enables the measurement of the mixing evolution in low-density regions. More importantly, the signal intensity is approximately proportional to the density of the fluorescing material in X-ray fluorescence imaging, whereas the signal in traditional X-ray backlighting decays exponentially with material density. This allows fluorescence imaging to capture the perturbation structures of the mixing layer under much lower density conditions, obtain higher confidence data on the mixing growth at the interfaces between the mixing layer and the adjacent materials. In laser direct-drive experiments, the hard X-rays and superhot electrons generated by the direct laser loading of CH samples can heat the metal perturbation sample ahead of the shock. Preheating modifies the initial state of the perturbed interface before the shock arrives, thereby complicating the analysis of hydrodynamic instability evolution that depends on these original conditions. A preheat calibration experiment is conducted at the Shenguang-III prototype laser facility, the experimental results show that a 50 mu m thick CH (3% bromine doping) layer and reducing the laser power can block the preheat, the increase in temperature before the arrival time of the shock wave is less than 200 K, which has little influence on the initial state of rear

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.

The time performance of Low Gain Avalanche Diodes (LGADs), designed by the University of Science and Technology of China (USTC) and fabricated by the Institute of Microelectronics of Chinese Academy of Sciences (IME), was characterized at the Shanghai Synchrotron Radiation Facility (SSRF). The experiment was conducted at the BL16B1 beamline, which delivers a focused X-ray beam with a diameter of 500 μm, a repetition period of 2 ns, and a photon energy of 10 keV. Using a fast oscilloscope, waveforms containing continuous signal pulses were recorded within a 50 ns time window. The LGAD under test successfully resolved the 2 ns period of the SSRF. To mitigate pile-up effects and extract pulse-by-pulse information from the acquired waveforms, a waveform-level global template fitting method was employed. The time resolution was then estimated using a combined profile likelihood approach, yielding a value of 126.6 ps. The effect of random photon absorption depth on the time resolution of LGADs was studied through dedicated simulations.

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.

Detailed investigation of the x-ray drive on the capsule at the center of the hohlraum is crucial to solve the "drive deficit" problem in inertial confinement fusion. A pioneering work for probing the drive flux at the hohlraum center by simultaneously measuring the re-emitted flux and shock velocity was reported [X. Xie et al., Phys. Rev. Lett. 128, 075001 (2022)0031-900710.1103/PhysRevLett.128.075001]. However, in the last experiment only two discrete shock velocity values can be obtained, as the streaked optical pyrometer was employed. In this work, we present characterization of the time-dependent x-ray drive on the capsule by simultaneously measuring the time-dependent localized re-emitted flux and the time-dependent shock velocity. The time-dependent localized re-emitted flux was measured by the space-resolving flux detector, while the time-dependent shock velocity was obtained with the velocity interferometer system for any reflector. Two-dimensional radiation hydrodynamic simulations revealed that the time history of the re-emitted flux as well as the shock velocity can be well reproduced. This technique presented a way for the determination of the x-ray drive at the center of the cylindrical hohlraum as well as other novel hohlraums.

Abstract The technique of indirect-drive cryogenic pure deuterium layered implosion is unique among published works in the research of inertial confinement fusion. After its feasibility was demonstrated recently, we proceeded to improve the implosion performance by using a 2-shock shaped pulse. The target design was evolved from an ignition target design with modifications compatible with current energy scale. The radiation uniformity was confirmed by the dual-axis keyhole targets and cryogenic gas-filled targets. The adiabat of the fuel was controlled by tuning shocks to emerge at the ice-gas interface. The implosion performance of the layered targets were then investigated. The pure deuterium layers of good quality were maintained for a few minutes. The lasers were fired during the survival time of such layer quality. The resulting neutron yield was 9.6×1010, and the hotspot pressure was 30Gbar. Radiative hydrodynamic simulations were carried out using as-shot target and laser parameters, and compared with the experimental measurements. The yield of clean was about 19%. The residual radiation non-uniformity alone cannot explain the observed performance degradation. The hydrodynamic instabilities seeded by ice roughness should play a role in decreasing the hotspot clean volume.

Precise prediction of the hohlraum x-ray drive is essential for target design optimization in indirect-drive inertial confinement fusion. Conventional simulations, however, are often hampered by the hohlraum drive deficit, which limits their predictive power for new experimental configurations. This study focuses on the two-shock implosions of the 100 kJ-level laser facility, aiming to infer the radiation source constrained by multiple diagnostics. A joint inversion method for the radiation source and M -band x-ray power multipliers was developed, leading to the construction of a surrogate model that maps experimental design parameters to radiation source waveforms. Based on this model, a deep learning inference framework, PRISM, was established to achieve precise radiation source prediction. The model exhibits excellent predictive accuracy, and the bang-time prediction error in pre-shot simulations is reduced from about 500 ps to within 200 ps. Its extrapolation capability was validated using transmission grating spectrometer data, demonstrating good agreement between simulated and measured spectra. Shapley Additive Explanations revealed the relative contributions of experimental design parameters to each multiplier. Finally, we used residual-based analysis to quantify engineering accuracy. The analysis indicates improved engineering control of the 100 kJ-level laser facility in 2025, particularly in laser output stability, although pulse synchronization remain areas for refinement.

Abstract Aluminum is the standard material for ultrahigh pressure impedance matching experiments, yet its principal Hugoniot above 50 Mbar, where inner shell ionization dominates, lacks precise experimental data. Here we report laser driven Hugoniot measurements of aluminum at 89 and 93 Mbar using an indirect drive hohlraum on a 100 kJ laser facility. The shock velocities were determined with a combined uncertainty below 0.5% using a dual diagnostic approach. With quartz as the impedance matching standard, the measured compression ratios are 4.47±0.17 and 4.58±0.18. These results agree with models that include shell effects, including extended first principles molecular dynamics, stochastic density functional theory, and the Hartree–Fock–Slater model with charged hard spheres, but deviate by 8–10% from average atom models such as SESAME. These results validate shell‑resolved equation‑of‑state models against average‑atom predictions in the hundred‑megabar regime, and provide a quantitative benchmark confirming that L‑shell ionization softens the aluminum Hugoniot. This establishes a long‑sought high‑precision reference that supports aluminum as a standard for ultrahigh‑pressure impedance matching.

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.

Objective Single-frequency green lasers with narrow linewidth and high spectral stability are key light sources for space laser communication, precision optical measurement, and related quantum-optical applications. In particular, the 532 nm band is attractive because of its relatively low atmospheric transmission loss. Conventional single-frequency 532 nm lasers are generally realized by frequency doubling of near-infrared solid-state lasers, but such systems typically suffer from large size, high power consumption, and insufficient suitability for lightweight and compact space payloads. Green laser diodes based on the InGaN/GaN material system exhibit the advantages of high integration and low power consumption, yet their native Fabry-P & eacute;rot (FP) cavities tend to support multiple longitudinal modes because of the broad gain bandwidth and comparable modal gains, which leads to poor spectral purity and limited wavelength stability. To address these issues, this work proposes and demonstrates a highly integrated 532 nm single-frequency semiconductor laser for space applications based on volume Bragg grating (VBG) external-cavity feedback. The purpose is to realize wavelength locking and linewidth narrowing of a 532 nm FP laser diode while maintaining a compact package and verifying its feasibility under representative space environmental conditions. Methods A VBG external-cavity diode laser (VBG-ECDL) architecture was developed by combining a 532 nm Fabry-P & eacute;rot laser diode (FP-LD) with a narrowband reflective VBG. To analyze the spectral behavior of the laser under external optical feedback, an external cavity gain model incorporating the VBG spectral response was established. Numerical simulations were carried out to evaluate the influence of key external-cavity parameters, including the external-cavity length, VBG peak reflectivity, and VBG reflection bandwidth, on the longitudinal-mode characteristics and spectral selectivity of the laser. Based on the theoretical analysis and simulation results, a compact VBG-ECDL module was designed and implemented. The optical configuration included beam collimation, VBG feedback, folded external-cavity propagation, and fiber coupling. The spectral characteristics of the fabricated laser were measured using an optical spectrum analyzer, while the longitudinal-mode structure and linewidth were characterized by a scanning FP interferometer. In addition, the wavelength stability under temperature and current variations was evaluated to assess the spectral locking capability of the VBG feedback. To verify the applicability of the proposed laser for space environments, several environmental adaptability tests were conducted, including mechanical vibration tests, vacuum tests, total ionizing dose (TID) irradiation tests, and displacement damage (DD) irradiation tests. The output power characteristics and spectral performance of the laser before and after these tests were measured to evaluate the robustness and reliability of the developed VBG-ECDL under representative space conditions. Results and Discussions Based on the theoretical analysis and simulation results, a compact 532 nm VBG-ECDL was designed and implemented. An FP-LD green laser diode was used as the gain medium, and the emitted beam was collimated along both fast and slow axes. A reflective VBG served as the wavelength-selective feedback element to form the external cavity. The transmitted beam was redirected through a folded optical path and coupled into a multimode optical fiber for output. After introducing the VBG feedback, the cavity gain became concentrated around the main longitudinal mode, and the nearest side-mode gain was significantly suppressed, demonstrating effective spectral selection. Parametric simulations further showed that the external-cavity length, VBG reflectivity, and reflection bandwidth jointly influenced the linewidth of the main-mode gain and the side-mode suppression capability, indicating that proper external-cavity parameter design was critical for achieving stable single-frequency operation. Experimental measurements confirmed the effectiveness of the proposed design. After introducing the VBG external cavity, the emission wavelength was locked at 531.8 nm, and the spectral bandwidth was compressed to below 0.05 nm. The longitudinal-mode structure measured by the scanning FP interferometer showed single-mode operation with a linewidth of 16.64 MHz. The wavelength stability was also significantly improved by the VBG feedback. When the temperature increased from 20 degrees C to 30 degrees C, the wavelength variation of the VBG-ECDL remained within 0.1 nm. Similarly, when the driving current changed from 0.3 A to 1.2 A, the wavelength variation of the VBG-ECDL remained below 0.1 nm. The maximum output power of the developed laser reached 724 mW. Environmental tests further demonstrated the robustness of the proposed laser. After mechanical vibration tests, the laser maintained stable single-mode emission, with the central wavelength remaining at 531.8 nm and the output power exceeding 400 mW at 1 A. After vacuum storage at 1.4 & times;10(-3) for 24 h, no noticeable degradation in spectral or power performance was observed. In the TID irradiation test with a total accumulated dose of 1000 Gy, the slope efficiency of the VBG-ECDL decreased slightly by about 0.06 W /A, which was attributed to radiation-induced degradation of the VBG diffraction efficiency. In the displacement damage test with an equivalent 10 MeV proton fluence of 3.1 & times;10(11)/cm(2), the emission wavelength remained stably locked at 531.8 nm, and the overall performance degradation was negligible. These results indicate that the proposed VBG-ECDL exhibits good spectral stability and environmental adaptability, demonstrating its potential for compact space laser systems. Conclusions A compact 532 nm single-frequency semiconductor laser for space applications is proposed and demonstrated based on VBG external-cavity feedback. By combining theoretical modeling, parameter optimization, device design, and environmental verification, stable injection locking and spectral narrowing of a 532 nm FP laser diode are achieved. The developed VBG-ECDL exhibits a locked center wavelength of 531.8 nm, a linewidth of 16.64 MHz, and a maximum output power of 724 mW. The external-cavity design effectively suppresses multimode oscillation and significantly improves wavelength stability against current and temperature variations. Moreover, the laser maintains good performance after representative vibration, vacuum, TID, and DD tests, demonstrating favorable compactness, robustness, and feasibility for space deployment. This work provides an effective technical route toward lightweight and high-stability 532 nm single-frequency laser sources for future optical systems in space.

A reshock experiment for investigating the growth of material mixing driven by the Richtmyer-Meshkov instability has been conducted at the SG 100 kJ Laser Facility. We present a novel measurement technique for capturing the density field and the temporal evolution of the mixing width in rough aluminum subjected to reshocks under extreme conditions. The temporal evolution of the aluminum layer width obtained from backlit X-ray radiography demonstrates a sharp increase in width caused by reshocks, and simulations using the BHR-2 turbulent mixing model show excellent agreement with the measured aluminum layer width. Moreover, by utilizing a quasi-monochromatic X-ray imaging system at 5.2 keV, based on Bragg reflection from a spherically curved quartz crystal, we demonstrate direct quantification of the aluminum density field in mixed regions for the first time in a indirectly driven reshock experiment. The deviation between the calculated and actual density values is significantly less than 10% when the density of the aluminum region is below 0.7 g/cm(3). The density field provides further information about variable-density turbulent mixing, which improves the constraints on simulations and enhances predictive capabilities for inertial confinement fusion target design and astrophysical shock scenarios.

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 indirect-drive inertial confinement fusion (ICF) research, the meticulous design and optimization of laser parameters are crucial for achieving high-gain ignition. The intensity of the toe laser, used for ablating the hohlraum sealing membrane, is a subtle but equally critical parameter. This study introduces a novel experimental approach using the Velocity Interferometer System for Any Reflector (VISAR) to assess the impact of toe laser intensity on the compression of fusion capsules. By tracking the reflectivity of tracer layers and shock velocities in liquid deuterium, the adverse effects of insufficient toe laser intensity on capsule compression have been unveiled for the first time. From a comparison with hydrodynamic simulations, we show that below a critical threshold of 0.23 x 10(14) W cm(-2), the adiabat, a measure of the fuel's compression efficiency, increases markedly with the toe laser intensity decreases, whereas it remains stable within the range of (0.23 similar to 7) x 10(14)W cm(-2). Our findings provide critical insights on toe laser parameter design, enhancing our understanding of the role of toe laser intensity in ICF experiments. This research not only refines the parameters for laser operation but also underscores the importance of precision in achieving the desired implosion efficiency, contributing to the development of nuclear fusion as a clean energy source.

Cylindrical vector (CV) gamma rays can introduce spatially structured polarization as a new degree of freedom for fundamental research and practical applications. However, their generation and control remain largely unexplored. Here, we put forward a novel method to generate CV gamma rays with tunable hybrid polarization via a rotating electron beam interacting with a solid foil. In this process, the beam generates a coherent transition radiation field and subsequently emits gamma rays through nonlinear Compton scattering. By manipulating the initial azimuthal momentum of the beam, the polarization angle of gamma rays relative to the transverse momentum can be controlled, yielding tunable hybrid CV polarization states. Three-dimensional spin-resolved particle-in-cell simulations demonstrate continuous tuning of the polarization angle across (-90°, 90°) with a high polarization degree exceeding 60

Obtaining inertial fusion energy requires higher gain in laser indirect drive inertial confinement fusion(ICF), but traditional cylindrical hohlraums face two persistent challenges: low energy coupling efficiency from the hohlraum to the capsule and severe inner beam interception by outer gold bubbles, both needing optimization for improved ICF performance. In this paper, a new domed-rugby hohlraum design is proposed. The novel and optimized hohlraum configuration increases the energy coupling efficiency by reducing the wall surface and energy loss with a rugby-shaped geometry, thereby enhancing the radiation source temperature.Simultaneously, through a special toroidal dome structure, the interaction between the outer bubble plasma and inner laser beams is mitigated, allowing the inner laser beams to reach the waist of the hohlraum. As a result, more spherical implosions are obtained and the quality of the radiation source is improved. It has been simulated that on the 100 kJ class laser facility, there is a 20% higher neutron yield. The integrated implosion performance is expected to be significantly advanced in such a novel configuration, providing a new concept for hohlraum configuration designs with a high-temperature and high-quality radiation source.

Stimulated Raman scattering (SRS) under a new ignition path that combines the advantages of direct-drive (DD) and indirect-drive (ID) schemes is investigated experimentally at the Shenguang-100 kJ facility. The results show that collective SRS in the plasma produced by ablating a polyimide film is detected for the ID beams, but is suppressed by adding a toe before the main pulse of the ID beams. The toe also strongly influences SRS of both the ID and DD beams excited in the plasma generated in the hohlraum. When a toe is used, the SRS spectra of the DD beams show that SRS tends to be excited in lower plasma density, which will result in a lower risk of super-hot electrons. Measurements of hot electrons support this conclusion. This research will help us produce a better pulse design for this new ignition path.

Early hot electron can preheat the pellet fuel and thus lead to lower implosion performance. The properties of hot electrons in early stage of implosion experiments in Shenguang-100 kJ laser facility were investigated. It was shown that both the temperature and the energy of early hot electrons were very low. The upper limit of the temperature and the energy of early hot electrons in our experiments were only 7.7 keV and 0.35 J, respectively. Besides, the generation mechanisms of early hot electrons were also different from NIF experiments according to the results of the hard X-ray imager (HXI). In NIF experiments, two-plasmon decay and multi-beam stimulated Raman scattering (SRS) were dominate mechanisms that generate early hot electrons. However, SRS of the outer beams was our dominant mechanism. Spectrum of the scattered light of SRS was obtained by radiative hydrodynamic and ray-tracing simulations. The result showed that the spectrum was peaked at λ _s=482 nm , which meant hot electrons with the temperature near 7keV can be generated. And from the result of HXI, hot electrons deposited onto the pellet were estimated to less than 6.8× 10^-3 J. Deeper analysis showed that, in the beam overlapping region, the plasma density was unsuitable for multi-beam SRS, so no hot electrons with larger temperature were generated.

A reduced dispersion relation for multibeam laser-plasma instability is derived. The dispersion relation includes the combined effects of self-coupling and interaction with other beams by sharing a common scattered light (SL modes) and by sharing a common plasma wave (SP modes). The latter two have the most prominent collective effects of all. We have solved the dispersion relation numerically for stimulated Raman scattering, and set different beam configurations and polarizations to discuss the spatial distributions of the temporal growth rate. The instability in the beam overlapping region is complicated, but there are still a few simple rules that govern the system, such as the dominancy of SL modes and subdominancy of backscattering and SP modes. The maximum growth rate always occurs at these special modes, or a new mode formed by combining two or three of the special modes. The reduced model provides us with the ability to understand the underlying physics of multibeam instabilities under general laser and plasma conditions.