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Sep 16

K-shell x-ray spectroscopy: A reliable probe for stimulated Raman scattering in inertial confinement fusion---

Tianluo Luo, Zeyang Li, Yunping Wang, Zhihao Yang, Zhencen He, Dong Yang, Zhimin Hu

arXiv (physics.plasm-ph)Sep 16, 2026Control & Diagnostics AI, Modeling & Simulation Inertial Fusion & HEDP

Accurate characterization of stimulated Raman scattering (SRS) remains a critical challenge in inertial confinement fusion (ICF), as SRS not only scatters laser energy but also generates suprathermal electrons that preheat the fuel and degrade implosion performance. Conventional backscatter diagnostics provide direct measurements of SRS but cannot collect the entire scattered-light signal, limiting the accurate characterization of SRS strength. Using a non-local thermodynamic equilibrium collisional-radiative model with a double-Maxwellian electron distribution, we systematically investigate how suprathermal electrons modify the titanium \textit{K}-shell x-ray emission spectra. The spectra exhibit high sensitivity to the suprathermal-electron fraction at relatively low bulk electron temperatures, making them particularly suitable for diagnosing suprathermal electrons during the early stage of ICF, when even a small suprathermal-electron population can compromise fuel compression. The calculated spectra reproduce experimental measurements from the Nova Laser Facility with good agreement, and the inferred suprathermal-electron fractions show improved consistency with independently measured SRS losses compared with the original spectral analysis by Glenzer~\href{https://doi.org/10.1103/PhysRevLett.81.365} {\text{[S. H. Glenzer \textit{et al}., Phys. Rev. Lett. \textbf{81}, 365(1998)]}}. These results demonstrate that \textit{K}-shell spectroscopy, combined with accurate NLTE collisional-radiative modeling, provides a reliable probe of SRS strength in laser-produced plasmas. Hence, this approach may be extended to spatially resolved diagnosis of SRS strength, offering a promising complement to conventional backscatter diagnostics.

China Academy of Engineering Physics

Sep 1

Ionization potential depression and mechanical-electric coupling in plasma

Yuanjie Huang, Guobin Fan

Physics of PlasmasSep 1, 2026Inertial Fusion & HEDP

Ionization potential depression (IPD) plays an essential role in describing ionization in plasmas. Traditional models like Ecker–Kröll and Stewart–Pyatt relied on screening effects, yet they still fail to adequately interpret the spectroscopic data from the laser-irradiated plasmas. To bridge this gap, we introduce a novel IPD model and the concept of mechanical-electric coupling (MEC) in plasmas. MEC critically influences the electron diffusion, Debye screening, and the electron pressure. Unlike conventional approaches, our IPD model is derived from the downward shift in potential energy of ionized electrons instead of the screening effect. It aligns closely with the spectroscopy and measured IPD values. MEC and the IPD framework provide a foundation for an equation of state that matches the experimental observations. This study offers fresh insight into the plasma ionization and properties, offering a framework for predicting ionization balance and equation of state in dense, non-degenerate plasmas.

China Academy of Engineering Physics

Aug 27

High energy X-ray generation via nanosecond laser irradiation of metal wire-array targets

Chao Tian, Tiankui Zhang, Minghai Yu, Lianqiang Shan, Zhimeng Zhang, Peilin Yao, Feng Zhang, Zongqiang Yuan, Zhongjing Chen, Weimin Zhou

Plasma Physics and Controlled FusionAug 27, 2026Inertial Fusion & HEDP

Experiments were conducted at the SG-III prototype laser facility to generate high-energy X-rays via interaction of focused nanosecond laser beams with wire-array targets of varying materials. X-rays exceeding 10 keV were successfully produced. The energy spectrum was measured using a filtered stack spectrometer and a transmission crystal spectrometer, determining the laser-to-X-ray conversion efficiency. Backlighting radiography of test pattern targets was performed, with image clarity enhanced through source distribution deconvolution, achieving improved spatial resolution of the X-ray source. Additionally, areal density resolution was evaluated through backlighting radiography of stepped objects.

China Academy of Engineering Physics

Aug 26

Implosion performance of indirect-drive cryogenic pure deuterium layered targets on the Shenguang laser facility

Yudong Pu, Chuankui Sun, Fengjun Ge, Jiwei Li, Tao Gong, Weiming Yang, Zhebin Wang, Qi Li, Kai Wang, Xiaobo Qi, et al.

Nuclear FusionAug 26, 2026AI, Modeling & Simulation Inertial Fusion & HEDP

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.

China Academy of Engineering PhysicsInstitute of Applied Physics and Computational Mathematics

Evidence for enhanced mass ablation rate driven by a broadband laser

Xichen Zhou, Ning Kang, Huiya Liu, Jiyan Zhang, Ruirong Wang, Guoxiao Xu, Lin Yi, Jian Wang, Honghai An, Jun Xiong, et al.

Nuclear FusionAug 26, 2026AI, Modeling & Simulation Inertial Fusion & HEDP

For laser-driven inertial confinement fusion, implosion performance depends critically on the efficiency of laser energy coupling to mass ablation. Although recent experiments have confirmed that broadband lasers improve energy absorption efficiency by mitigating stimulated Brillouin scattering, evidence for a corresponding increase in mass ablation rate has remained absent. In this paper, we present the first experimental evidence that a broadband laser (0.6% fractional bandwidth) drives a higher mass ablation rate than a narrowband laser on planar titanium foils. Under matched laser intensity, the foil thickness that maximizes the Ti He‑α X-ray yield—the optimal thickness—shifts from ~10 μm for the narrowband case to ~15 μm for the broadband case. Simulations relating optimal thickness to mass ablation rate show that this shift corresponds to an approximately (50 ± 26)% enhancement in mass ablation rate. Analysis suggests that, in addition to the improved laser absorption, the greater nonlocal thermal transport induced by the enhanced hot electron yield from broadband lasers may contribute to this ablation enhancement. These findings provide evidence that a broadband laser can markedly enhance mass ablation, supporting its use as a practical route toward better implosion performance in inertial confinement fusion.

Laser Fusion Research CenterChina Academy of Engineering PhysicsInstitute of Applied Physics and Computational Mathematics

Reconstruction methods for compressed sampling data in the CUP-VISAR system

Lei Zhang, Feng Wang, Zanyang Guan, Yu Long Li, Xin Yulong, Xi Wang, Miao Li, Xinru Zhang, Huaquan Gan

Plasma Physics and Controlled FusionAug 26, 2026Control & Diagnostics AI, Modeling & Simulation Inertial Fusion & HEDP

The temporal evolution of shock wave velocity encodes critical physical information in inertial confinement fusion (ICF) experiments. Integrating a line-imaging velocity interferometer system for any reflector (VISAR) with compressed ultrafast photography (CUP), the resulting CUP-VISAR technique enables promising high spatiotemporal resolution two-dimensional (2D) measurement of continuous shock waves. However, reconstructing time-varying 2D fringe patterns from single-shot, highly underdetermined compressed sampling remains a formidable challenge. To improve reconstruction accuracy of continuous 2D shock wave velocity fields, this work proposes two technical enhancement strategies. First, a deep unfolding network reconstruction scheme for conventional CUP: adopting a hybrid data-and-model-driven approach, it deploys a trainable deep network as a denoiser to capture inherent spatiotemporal correlations in fringe patterns, markedly improving both fringe reconstruction efficiency and velocity field accuracy. Second, a novel integral-camera-based CUP architecture: unlike the conventional coded-aperture/streak-camera configuration, it acquires signals directly via an integral camera, with fringe reconstruction implemented by mixed integer programming guided by discrete phase-space constraints and interference fringe priors, simplifying system structure and enhancing noise robustness. Both schemes effectively improve compressed fringe reconstruction quality and reduce velocity field reconstruction errors, providing more accurate and reliable data support for ICF diagnostic analysis.

China Academy of Engineering Physics

Aug 20

Enhanced H permeation barrier via sispersed He-irradiation-induced defects in Al 2 O 3 /FeAl coatings

Yulin Wei, Deng Shunjie, Meidie Wu, Ping Peng, Qingjie Zhang, Min Liu

Nuclear FusionAug 20, 2026Materials & Plasma-Facing Components Tritium & Fuel Cycle

The service performance of tritium permeation barriers (TPB) under He irradiation damage is critical to the safe operation of fusion reactors. In this study, He irradiation, annealing, and deuterium (D, H isotope) permeation experiments were performed on Al2O3/FeAl coatings. Systematic characterizations, combined with DFT calculations, were employed to elucidate the mechanisms of He irradiation resistance and irradiation defect-enhanced H permeation barrier. The pronounced crystallographic orientation anisotropy in certain Al2O3 regions may contribute to the formation of high-density grain boundary networks. After irradiation-annealing treatment, the dispersed He distribution may be associated with these anisotropic regions, contributing to the reduced irradiation hardening response. Furthermore, the intrinsic H permeation resistance of Al2O3 originates from the strong orbital hybridization between H and lattice O/Al atoms, while He implantation-induced lattice distortion enhances the H-lattice bonding strength. This enables highly dispersed He-defect clusters to form abundant H-trapping sites, which deflect the H migration path and elevate the H diffusion energy barrier. Consequently, within the temperature range of 500-650 °C, the D permeation resistance of irradiated coatings outperforms that of unirradiated counterparts. At 500 °C, the D permeation reduction factor (PRF) of the irradiated coating reaches as high as 3300, representing an 83% enhancement compared with the unirradiated sample. Under the He irradiation, annealing, and D2 permeation conditions investigated in this study, the coating exhibits certain potential for TPB applications. However, its long-term reliability under the complex service conditions of a fusion blanket remains to be further validated.

China Academy of Engineering PhysicsXi'an Jiaotong University

Aug 18

Tunable high-charge relativistic electron beams via direct laser acceleration in hohlraum-preheated foam targets

Ziyao Wang, Jieru Ren, Zhigang Deng, Wenqing Wei, Wei Qi, Olga N. Rosmej, Nikolay E. Andreev, Sergey Yu. Gus'kov, Rafael Yakhin, Yifang Gao, et al.

arXiv (physics.plasm-ph)Aug 18, 2026AI, Modeling & Simulation Inertial Fusion & HEDP

Direct laser acceleration (DLA) in near-critical-density (NCD) plasmas can efficiently generate high-charge relativistic electron beams, yet beam parameters depend critically on precise plasma state manipulation. Solid-ablation NCD plasmas evolve rapidly, posing severe controllability challenges. We produce NCD plasma via indirectly heating foam targets with ns laser driven hohlraum soft X-ray. Electrons are generated through irradiating the plasma with another picosecond laser. Tuning the laser pulse delay $τ$ enables control of plasma profiles and beam parameters. Experiments show that when the foam is heated ($τ$ = 6 ns, 9 ns), the beam exhibits $T \sim 13$ MeV effective temperature, $E_k \sim 80$ MeV cutoff energy, and hundreds of nC/sr charge for $E_k > 7.5$ MeV. These values are significantly higher than those from solid-foil ($T$ $\sim$ 2.7 MeV, $E_k$ $\sim$ 20 MeV, $Q$ $\sim$ 9 nC/sr) and cold-foam ($T$ $\sim$ 12 MeV, $E_k$ $\sim$ 50 MeV, $Q$ $\sim$ 5 nC/sr) interactions. At a longer delay of $τ$ = 15 ns, the charge increases further while the temperature decreases, and at a shorter delay of $τ$ = 3 ns, both temperature and charge are lower. 3D PIC simulations link these observations to the interplay between the microstructure of the cold foam and the evolving plasma density profile at different delay times, which together determine the beam charge, effective temperature, and divergence. The finding provides a routine to generate and tailor the relativistic electron beams, which is essential for designing laser-driven electron sources for high energy density physics and photonuclear reaction applications.

China Academy of Engineering PhysicsXi'an Jiaotong University

Aug 3

A multi-mass-point model for drive asymmetry of double-shell capsules

Xinrui Chen, Guanqiong Wang, Xindong Li, Wu Wen, Lulu Li, Xiaoguang Wang, Yuanbo Lu, Lixia Huang, Xiangting Yu, Delong Xiao

Physics of PlasmasAug 3, 2026AI, Modeling & Simulation Inertial Fusion & HEDP

Drive asymmetry is one of the main sources that degrade the implosion performance of double-shell capsules in inertial confinement fusion. In this paper a multi-mass-point theoretical model under the time-invariant radiation source is proposed to investigate the transfer of drive asymmetry in double-shell capsules and its impact on the fusion performance. In this model, the capsule is divided into independent azimuthal slices by ignoring the azimuthal motion and then assembled to investigate the effect of drive asymmetry. Each slice is described by different models according to the characteristics of different stages. The theoretical predictions exhibit good agreement with the results from radiation hydrodynamic code MULTI. It is found that the radiation asymmetry generates the asymmetry of the ablated mass and velocity in the outer shell during ablation. Then, the outer shell asymmetry is transferred to the inner shell through the acceleration process due to the shell collision. This method can calculate how drive asymmetry develops, propagates, and affects fusion yield during the implosion process of double-shell capsules, while simultaneously providing scaling laws for the relationship between capsule parameters and the transfer of drive asymmetry.

Xi'an Jiaotong UniversityInstitute of Applied Physics and Computational MathematicsChina Academy of Engineering Physics

Jul 31

Nonlinear polarization effects on plasma screening for thermonuclear reactions

Hanxiang Huang, Binbing Wu, Zhengfeng Fan, Congzhang Gao, Jie Liu, Baisong Xie

arXiv (physics.plasm-ph)Jul 31, 2026Advanced Fuels

We investigate two-center plasma screening effects on thermonuclear reactions of D-T, p-$^{11}$B, and $^{12}$C-$^{12}$C, spanning from classical to degenerate regimes. The two-center screening potential is obtained within a finite-temperature Thomas-Fermi-Dirac framework, capturing two-ion correlations as the leading-order many-body effect. Combining the resulting screened Coulomb potential with a complex Woods-Saxon nuclear potential, we solve the stationary Schrödinger equation to obtain the fusion tunneling probabilities and the corresponding reaction rates. Compared to Debye-Hückel results, the present screening potential is stronger in weakly coupled and weakly degenerate regimes but weaker in strongly coupled and strongly degenerate regimes. Consequently, the fusion enhancement factors are amplified in the former but suppressed in the latter. An underlying interplay between two mechanisms is identified: the nonlinear polarization of ions tends to reduce the screening effect, whereas the nonlinear polarization of electrons tends to enhance it. This subtle competition is governed by the plasma coupling strength and degeneracy. These findings highlight that a two-center treatment is important for predicting fusion rates in dense plasmas.

China Academy of Engineering PhysicsInstitute of Applied Physics and Computational Mathematics

Jul 13

Efficient hot electron generation via low-coherence lasers

Huiya Liu, Yao Zhao, Ning Kang, Fujian Li, Guoxiao Xu, Honghai An, Jun Xiong, Zhiyong Xie, Xichen Zhou, Zhiheng Fang, et al.

arXiv (physics.plasm-ph)Jul 13, 2026Inertial Fusion & HEDP

Hot electrons generated in laser-produced plasmas are a central focus in inertial confinement fusion, laboratory astrophysics, and high-energy-density physics. These electrons originate from instabilities in nonlinear laser-plasma interactions, which are critically modulated by laser bandwidth. Here, we experimentally demonstrate enhanced generation of hot electrons by utilizing instantaneous low-coherence lasers with two bandwidths (0.2% and 0.6%) at intensities of 2-8x10^{14} W/cm^2 and energies up to 620 J. A significant enhancement of hot electron temperature and hard X-ray yield is observed with the broadband lasers compared to a conventional narrowband laser. The results show that the hot electron energy conversion efficiency of the 0.6% broadband laser is approximately 4 times higher than that of the narrowband laser, reaching a maximum value of 2.8%. These findings validate a moderate-bandwidth laser as an efficient hot electron source and support the generation of bright X-ray sources for advanced imaging in high-energy-density physics.

China Academy of Engineering PhysicsInstitute of Applied Physics and Computational MathematicsChinese Academy of Sciences