High-yield, short-pulse, quasi-monoenergetic neutron and charged particle experimental platforms, developed through laser direct drive implosion of thin-shell targets, are widely used in research areas such as nuclear physics, nuclear astrophysics, and high energy density physics. To achieve high neutron yield in laser direct drive implosion experiments, a data-driven high yield direct drive implosion design method is proposed. When physical understanding and numerical simulations are imprecise, this approach utilizes existing experimental data to establish empirical models and optimize parameters such as pulse shapes, capsule diameter, capsule thickness, fill pressures, and laser spot diameter. It effectively resolves the inherent trade-offs among implosion velocity, hot-spot symmetry, and shell-fuel mixing while balancing the relationship between one-dimensional yield and three-dimensional effects. The design process is initiated by utilizing preliminary experimental data and extensive numerical calculations to calibrate the Multi1D code. This includes refining its physical models of thermal conduction and shell-fuel mixing, as well as adjusting coefficients such as the flux limiter and diffusion multiplier. Furthermore, scaling relations of laser absorption efficiency, yield over clean (YOC), and ion temperature are derived. Subsequently, the calibrated Multi1D code, integrated with these empirical scaling relations, is employed to carry out quantitative simulations to determine the optimal shell thickness and fuel pressure of the glass targets, and to predict experimental yield, ion temperature, and convergence ratio. Validation experiments using 1200 mu m diameter glass targets are conducted on the 100 kJ laser facility. The results demonstrate that a neutron yield of 1.00 & times;10(14) is achieved by applying the data-driven high yield direct drive implosion design and optimizing laser power and wavelength. This is a substantial enhancement over previous results on the 100 kJ laser facility. The fusion conversion efficiency, defined as the fusion output divided by the laser energy incident on the capsule, is 4.5 parts per thousand, slightly higher than that reported for NIF glass targets. It is also found that increasing laser power significantly improves implosion velocity, ion temperature, and neutron yield. Additionally, the use of wavelength separation among the different cone beams effectively suppresses laser losses caused by crossed-beam energy transfer, resulting in significantly improved energy coupling efficiency, hot-spot symmetry, and neutron yield. The four-color laser configuration performs significantly better than the three-color laser. In contrast, various laser repointing strategies show no significant impact on implosion performance, including neutron yield, ion temperature, and hot-spot symmetry.

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 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.

Laser-driven inertial confinement fusion (ICF) is an important experimental platform for high-energy-density physics research under extreme conditions. In ICF research, high-quality shock waves are key to fusion energy release. The velocity interferometer system for any reflector (VISAR) is the most important diagnostic technique for measuring quantities such as shock wave and particle velocities with high precision and high spatiotemporal resolution. This paper provides a detailed introduction to the various configurations of VISAR on 10 and 100 kJ-level laser facilities in China, including Line VISAR, Dual-Axis VISAR, Wide-Angle VISAR, and Compressed Ultrafast Photography-VISAR. Recent advances and applications of VISAR diagnostics at these laser facilities are presented, and the future trend of development of high-spatiotemporal-resolution velocity diagnostic technology is described.

In the field of optical measurement, the inherent edge spectral leakage problem of the Fourier method significantly affects the accuracy of phase extraction. For the velocity measurement scenarios of inertial confinement fusion (ICF) research using a one-dimensional velocity interferometer system for any reflector (VISAR), this issue further undermines the reliability of velocity field calculations. To address this, a data processing method for VISAR image based on four-phase shifting and probability density function (PDF) compensation is proposed in this paper. This method first performs spatial phase-shifting on a single frame original VISAR image to obtain four phase-shifted images with successive phase differences ofπ/2. To compensate for phase-shifting errors introduced during the experimental measurement and phase-shifting process, the standard deviation of the PDF curve is taken as the objective function. An iterative compensation algorithm is employed to adjust the PDF of the wrapped phase to approximate the ideal distribution, thereby determining the compensation amount for phase-shifting errors. Subsequently, the least-squares method is applied to calculate the wrapped phase. Finally, the wrapped phase is unwrapped to obtain the phase distribution of the VISAR image, enabling velocity calculation. The verification results indicate that our method demonstrates robust performance across ideal simulated image, noisy synthetic image, and experimental VISAR image, which is superior to the Fourier method in suppressing edge spectral leakage, providing more reliable data for ICF diagnosis.

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.

The novel octahedral spherical hohlraum can provide an ideal and practical approach for the next generation of laser systems to support both direct and indirect drive to achieve predictable and reproducible fusion gain via multiple schemes. To demonstrate its advantage in a naturally high symmetry at a cylindrically configured laser facility, it requires to repoint the laser beams to approach as close as possible the ideal octahedral beam configuration with an injection angle (the angle between a beam and the normal direction of its laser entrance hole (LEH)) ranging from 50° to 60°. We report our investigation and experiment on the optimum repointing scheme at the SGIII facility, which uses 32 beams, with 8 beams entering each polar LEH at 49.5° and 55°, and 4 beams entering each equatorial LEH at 61.5° and 62.1°. It contains residual imbalance between the polar and equatorial beams, leading to an asymmetry dominated by the spherical harmonic Y20 mode, which can be remarkably reduced by the stronger backscatters of equatorial beams. Our experiment demonstrated the feasibility of the 32-beam optimum repointing scheme and generation of 175 eV under 86 kJ inside a 2.4-mm-radius octahedral hohlraum with 0.7-mm-radius LEHs, which provided a strong support for the later experiment on proof-of-concept of octahedral spherical hohlraum [Lan et al., Phys. Rev. Lett. 127, 245001 (2021)]. 2D simulations on LEH closure agree well with the observations. This work opens a novel way of realization of a quasi-spherical irradiation at a cylindrically configured laser facility without supplementary symmetry control.

Both direct and indirect drive concepts of inertial confinement fusion rely on targets with cryogenic thermonuclear fuel shells for ignition. Experiments on the Shenguang-III prototype laser facility using laser-driven gas-filled hohlraums show distinct differences between cryogenic (20 K) and warm hohlraums. Although the measured x-ray flux in the photon range from 1.6 to 4.4 keV (Au M-band) is identical between cryogenic and warm hohlraums, the cryogenic hohlraum has a much slower rate of rise and is 20% lower in peak intensity of x-ray flux in the photon range from 0.1 to 4 keV. The reasons for this drive deficit between cryogenic and warm hohlraums are investigated using a similar series of hohlraum experiments. The experiments employ three types of hohlraums to distinguish the effect of a shroud window membrane and condensates. Warm hohlraums with a shroud window membrane replicate the slower rate of rise of radiation flux of cryogenic targets. When the shroud window is present, the measured x-ray flux in the hohlraum shows a drive deficit that decreases with time. However, the measured deficit increases as the viewing angle increases. All of these results indicate that the portion of the shroud not illuminated by the lasers absorbs the outgoing x-ray flux from the hohlraum.

The ultrastable encrypted storage of X-ray image with quantitative and ultrahigh-spatial resolution are crucial for a wide range of applications in radiation imaging, and it can be achieved by using the radio-photoluminescence (RPL) material, Ag-doped phosphate glass (Ag-PG), which was fabricated via the melt-quenching method. Under X-ray irradiation, Ag-PG produces a luminescence center, obvious 650 nm emission peak, which can be repeatedly excited by ultraviolet light without intensity attenuation. Quantitative X-ray image storage was realized based on the linear relationship between RPL intensity and X-ray irradiation time. X-ray image with a submicron spatial resolution of 0.7 mu m was achieved, which could be stably stored without attenuation for more than 300 days. This submicron level X-ray image can be written into the Ag-PG as an encrypted information, and can only be visualized by an ultraviolet light. Additionally, heat treatment (400 degrees C for 2 h) could eliminate the influence of X-ray radiation on the Ag-PG, and restore the state of the Ag-PG before X-ray irradiation, which allows the recyclability and reusability of the Ag-PG. This research is of great significance for promoting the encrypted storage of X-ray images based on Ag-PG or other RPL materials. (c) 2023 Elsevier B.V. All rights reserved.

A new method for measuring the time-dependent drive flux at the hohlraum center is proposed as a better alternative to conventional wall-based techniques. The drive flux here is obtained by simultaneous measurement of the reemitted flux and shock velocity from a three-layered "cakelike" sample. With these two independent observables, the influence induced by the uncertainty of the material parameters of the sample can be effectively decreased. The influence from the closure of the laser entrance hole, which was the main challenge in conventional wall-based techniques, was avoided through localized reemitted flux measurement, facilitating drive flux measurement throughout the entire time history. These studies pave a new way for probing the time-dependent drive flux, for both cylindrical hohlraums and novel hohlraums with six laser entrance holes.

The new hohlraum experimental platform and the quasi-3D simulation model are developed to enable the study of the indirect drive experiment using the six-cylinder-port hohlraum for the first time. It is also the first implosion experiment for the six laser-entrance-hole hohlraum to effectively use all the laser beams of the laser facility that is primarily designed for the cylindrical hohlraum. The experiments performed at the 100 kJ Laser Facility produce a peak hohlraum radiation temperature of ∼222  eV for ∼80  kJ and 2 ns square laser pulse. The inferred x-ray conversion efficiency η∼87% is similar to the cylindrical hohlraum and higher than the octahedral spherical hohlraum at the same laser facility, while the low laser backscatter is similar to the outer cone of the cylindrical hohlraum. The hohlraum radiation temperature and M-band (>1.6  keV) flux can be well reproduced by the quasi-3D simulation. The variations of the yield-over-clean and the hot spot shape can also be semiquantitatively explained by the calculated major radiation asymmetry of the quasi-3D simulation. Our work demonstrates the capability for the study of the indirect drive with the six-cylinder-port hohlraum at the cylindrically configured laser facility, which is essential for numerically assessing the laser energy required by the ignition-scale six-cylinder-port hohlraum.

In order to carry out the experimental study of laser plasma instability (LPI) on the laser device cluster platform with an output energy of 100kJ, a scattered light diagnosis system based on cluster configuration is built. The diagnosis system uses the diffuse reflector as the main light blocking, reflection, and sampling element, the imaging method is used to image the scattered light to the recording components such as iCCD (intensifier Charge Coupled Device) camera, and the sampling measurement method is used to obtain the spatial distribution, energy, spectrum, and time waveform of the scattered light. In the cluster physics experiment, the physical data obtained by the system are in good agreement with the results obtained by the physical simulation program. It shows that the scattering mechanism is mainly subbeam mechanism under the current conditions, and its action process mainly concentrates on the early stage before the plasma empties.

A new diagnostic platform for more accurate diagnosis of the peak radiation temperature on ablator has been proposed. A nearly constant radiation temperature was obtained by two laser entrance holes spherical hohlraum. The peak radiation temperature on ablator was determined by the shock wave technique. A high-quality burn-through image of a two-step-shaped Au ablator was obtained in the experiment. The simulated mass ablation rate agrees well with the experimental result, while the peak radiation temperature measured by flat-response x-ray detectors outside the hohlraum was of ∼20 eV’s lower than that obtained by the shock wave technique. This deviation results in ∼20%’s decrease in the mass ablation rate in the simulation. Thus, the new diagnostic platform can provide more accurate peak radiation temperature diagnosis. This can greatly support the inertial confinement fusion ignition target design.

A high-neutron yield platform imploded by a thin shell target is generally built to probe nuclear science problems, and it has the advantages of high neutron yield, ultrashort fusion time, micro fusion zone, isotropic and monoenergetic neutron. Some analytical models have been proposed to interpret exploding-pusher target implosion driven by a long wavelength laser, whereas they are imperfect for a 0.35 μm laser implosion experiment. When using the 0.35 μm laser, the shell is ablated and accelerated to high implosion velocity governed by Newton’s law, ablation acceleration and quasi-adiabatic compression models are suitable to explain the implosion of a laser direct-drive thin shell target. The new analytical model scales bang time, ion temperature and neutron yield for large variations in laser power, target radius, shell thickness, and fuel pressure. The predicted results of the analytical model are in agreement with experimental data on the Shenguang-III prototype laser facility, 100 kJ laser facility, Omega, and NIF, it demonstrates that the analytical model benefits the understanding of experiment performance and optimizing the target design of high neutron yield implosion.

Ternary Ag-In-S and quaternary Ag-In-Zn-S nanoparticles with different ratio of Ag/In/Zn/S are synthesized. The incorporation of Zn into Ag-In-S nanoparticles leads to the increase in the optical bandgap and the blue shift of photoluminescence (PL). The optical properties of these nanoparticles are significantly dependent on the chemical composition of nanoparticles. Time-resolved PL spectroscopy in nanosecond time regime is used to study the recombination processes of carriers, which involve the surface states and intrinsic crystallographic defects. These measurements support the donor-acceptor model, in which the PL is achieved by radiative recombination of the localized electron and hole.

In inertial confinement approaches to fusion, the asymmetry of target implosion is a major obstacle to achieving high gain in the laboratory. A recently proposed octahedral spherical hohlraum makes it possible to naturally create spherical target irradiation without supplementary symmetry control. Before any decision is made to pursue an ignition-scale laser system based on the octahedral hohlraum, one needs to test the concept with the existing facilities. Here, we report a proof-of-concept experiment for the novel octahedral hohlraum geometry on the cylindrically configured SGIII laser facility without a symmetry control. All polar and equatorial self-emission images of the compressed target show a near round shape of convergence ratio 15 under both square and shaped laser pulses. The observed implosion performances agree well with the ideal spherical implosion simulation. It also shows limitations with using the existing facilities and adds further weight to the need to move to a spherical port geometry for future ignition laser facilities.

One-dimensional line velocity interferometer system for any reflectors (VISARs) acts as a significant diagnostic device in the process of the inertial confinement fusion, which can be used to measure the free surface velocity and the history of shockwave velocity in transparent media over time. But the lack of spatial information makes it impossible to measure the flatness of wavefront. The compressed ultrafast photography (CUP) system developed in recent years can realize two-dimensional ultrafast photography. We have designed a new two-dimensional VISAR diagnosis system by combining the CUP with line-VISAR, called the CUP-VISAR, which will be of great significance in two-dimensional shockwave front measurement. In this paper, a data simulation method of CUP-VISAR is proposed to study the length of diagnostic time window of the device. A series of original VIASR images are firstly generated and then the compressed images are simulated after image encoding and compression. Finally, two-step iterative shrinkage thresholding algorithm is used to reconstruct the compressed images, which results in corresponding reconstructed images. In order to verify the restoration effect of the algorithm, we calculate the velocity error and image correlation coefficient value. Finally the relationship between the image reconstruction quality and the number of images is preliminarily obtained, which provides reference for the actual experiment.

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.

Transmissibility limitation is one of the most important barriers in the use of windows for shock experiments if optical probes are used. In this article, we focus on the widely used window material lithium fluoride (LiF) and investigate its optical response under laser-induced shock-compression conditions. A long-pulse laser is shaped to create a continuous accelerating shock wave propagating through the LiF window in the range of 100–400 GPa. The variation of measured optical transmission with shock pressure shows that the LiF window stays transparent even when the shock stress is higher than 350 GPa and transforms to a total opaque state at about 400 GPa. The present experiment exhibits an obviously higher shock stress for LiF windows to lose transparency compared with previously reported results. The discrepancy in experimental results is considered to be due to the difference in shock thickness for a typical time scale at different experimental platforms. Meanwhile, the possible reasons for the discrepancy between our experimental data and the previous ab initio calculations can be suggested by the effect of thermal relaxation between electrons and ions or the overestimation of the absorption coefficient in theoretical calculations. This finding of higher transmissibility limitation may be of importance to researchers who use LiF as a window material in future shock-compression experiments, especially at the laser platform.

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.