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Sep 24

Equation of state and transport coefficients of warm dense aluminum from mixed deterministic-stochastic density functional theory

Zi Li, Weijie Li, Cong Wang, Ping Zhang, Xianjue Peng

arXiv (physics.plasm-ph)Sep 24, 2026AI, Modeling & Simulation Inertial Fusion & HEDP

Aluminum is a reference standard in high-energy-density research and serves as a liner material in megampere Z-pinch facilities. Using mixed deterministic-stochastic finite-temperature density functional theory, we compute the equation of state and transport coefficients of liquid aluminum up to temperatures of 1000 eV and compare the results with model-based approaches. We find that for T<200 eV the density-functional results differ from the models by more than 10% at high density, with a maximum deviation of over 30% (at T = 10 eV), leading to significant discrepancies in the Hugoniot curve at high compression; the calculated electrical and thermal conductivities deviate from model predictions by 26% to 63% at T~100 eV. We further employ the Drude model and the Epperlein-Haines framework to examine the magnetic-field dependence of the conductivities. These results can provide valuable input data for radiation-hydrodynamics codes.

Institute of Applied Physics and Computational Mathematics

Sep 9

High-charge, highly polarized positron beams generated from a laser-driven nanowire-array target

De-Sheng Zhang, Cui-Wen Zhang, Kun Xue, Feng Wan, Xue-Ren Hong, Jian-Xing Li, Bai-Song Xie

arXiv (physics.plasm-ph)Sep 9, 2026AI, Modeling & Simulation

The generation of high-charge, highly polarized positron beams in the interaction of a linearly polarized laser pulse with a nanowire-array target is investigated. Here, laser-driven electrons emit high-energy photons through nonlinear Compton scattering (NCS), which subsequently produce electron--positron pairs through the nonlinear Breit--Wheeler (NBW) process. We model this interaction using two-dimensional spin-resolved quantum electrodynamics particle-in-cell (QED-PIC)} simulations. At positron birth, the sign of $S_z$ is statistically correlated with that of the local $B_z$. The spatiotemporal field structure arising from the laser--nanowire interaction strengthens the correlation between the birth spin sign and the direction of the subsequent transverse Lorentz impulse, thereby limiting cancellation between opposite-spin contributions at a given angle. The results show that the average polarization degree reaches $|\bar S_z|\approx0.46$, and the positron charge satisfying $|\bar S_z|>0.3$ is approximately $308\,\mathrm{nC}$. Parameter scans reveal that the high-polarization positron charge is maximized at intermediate target densities and nanowire periods. Such a source could enable polarization-sensitive studies of strong-field QED and spin-dependent phenomena in high-energy and materials physics.

Xi'an Jiaotong UniversityInstitute of Applied Physics and Computational Mathematics

Aug 30

Unified Gas-Kinetic Wave-Particle Method for Multiscale Simulation of Vlasov-Poisson-Fokker-Planck System

Zhigang Pu, Chang Liu, Yixiao Wang, Kun Xu

arXiv (physics.plasm-ph)Aug 30, 2026AI, Modeling & Simulation

A unified gas-kinetic wave--particle method with Fokker--Planck collisions (UGKWP-FP) is developed for the Vlasov--Poisson--Fokker--Planck system. The collision operator is modeled by the Lenard--Bernstein operator, whose stochastic representation corresponds to the Ornstein--Uhlenbeck process in velocity space. To extend the UGKWP framework beyond the conventional Bhatnagar--Gross--Krook (BGK) collision model, the Fokker--Planck operator is decomposed into a nonstiff drift--diffusion contribution and a stiff thermalization contribution. The former is retained in the particle dynamics through a modified Ornstein--Uhlenbeck process, whereas the latter is represented by a BGK-type relaxation toward the local Maxwellian. This decomposition enables an adaptive wave--particle representation: the method follows stochastic particle dynamics in rarefied regimes and increasingly represents the rapidly equilibrating distribution by the analytical wave component as the continuum regime is approached. The modified friction coefficient is constructed to recover the original Fokker--Planck dynamics in the rarefied limit while preserving the hydrodynamic limit under strong collisions. Numerical experiments demonstrate that the proposed method captures velocity-space drift and diffusion, recovers the expected kinetic and continuum behavior across a range of Knudsen numbers, and reproduces the characteristic evolution of collisional plasma phenomena.

Institute of Applied Physics and Computational Mathematics

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

Aug 24

Accurate simulation of laser-ablating Ta 2 O 5 foam targets with the hybrid ablation-expansion model

Shiyu Shen, Bo Zeng, Bihao Xu, Wei Xiong, Hanghang Ma, Guobo Zhang, Xin Li, Yan-Yun Ma, Xiaohu Yang

Plasma Physics and Controlled FusionAug 24, 2026AI, Modeling & Simulation Inertial Fusion & HEDP

To improve the modeling of laser ablation of structured high‑Z materials, we extended the hybrid ablation--expansion framework of Hudec et al. (Physics of Plasmas 30, 042704, 2023) to Ta 2 O 5 foam targets, with a key improvement of the explicit coupling of radiation energy from the macroscopic radiation hydrodynamic module into the pore-scale ablation--expansion model. The material thermodynamic properties and radiation–matter interaction are described using tabulated equations of state and opacities. The model is recalibrated using updated Ta 2 O 5 equation-of-state and opacity tables and is quantitatively benchmarked against published X-ray self-emission measurements. It is found that the foam microstructure modifies laser coupling in a non-monotonic manner. The effects of foam density and laser intensity on the laser absorption efficiency and X-ray conversion efficiency are investigated. The laser absorption efficiency exhibits a non-monotonic dependence on the foam density, reaching its maximum at a foam density of ρ=35 mg • cm -3 under a laser intensity of I=10 15 W • cm -2 . The X-ray conversion efficiency also varies non-monotonically with the foam density, but its maximum is shifted to 40 mg • cm -3 . This offset indicates that X-ray conversion efficiency is not controlled by laser absorption alone; it is also affected by the density-weighted radiation generation and optical-depth-limited radiation escape. In addition, the X-ray conversion efficiency decreases with increasing laser intensity, suggesting enhanced radiation losses and reduced conversion efficiency at higher drive conditions. Higher laser intensity, however, produces a larger total X-ray energy output. A maximum X-ray conversion efficiency of 24.8\% is achieved at 40 mg • cm -3 and 10 15 W • cm -2 . The hybrid model provides a physically consistent description of laser--Ta 2 O 5 foam interaction and an effective simulation tool for laser ablation of high--Z foam materials in inertial confinement fusion research.

Institute of Applied Physics and Computational Mathematics

Aug 5

Polarization-resolved attosecond gamma-ray emission from few-cycle laser interactions with cone targets

De-Sheng Zhang, Cui-Wen Zhang, Xue-Ren Hong, Feng Wan, Jian-Xing Li, Bai-Song Xie

arXiv (physics.plasm-ph)Aug 5, 2026Inertial Fusion & HEDP

Linearly polarized attosecond $γ$-ray pulses in the MeV range are generated from a cone target irradiated by a single few-cycle laser pulse. Electron layers are periodically extracted from the cone walls and subsequently accelerated. Their interaction with the counter-propagating reflected attosecond field produces high-energy photons through nonlinear Compton scattering (NCS), forming attosecond $γ$-ray pulses. We model this interaction using two-dimensional quantum electrodynamics particle-in-cell (QED-PIC) simulations that resolve electron spin and photon polarization during emission. The results show a shortest equivalent duration of $300\,\mathrm{as}$, with a corresponding linear polarization degree of 0.78. The photon spectrum extends to $6\,\mathrm{MeV}$, and the linear polarization degree in the high-energy range reaches 0.88. The linear polarization degree remains high when photons from both emission directions are collected over wide momentum-angle ranges. Scans over the cone opening angle and the coupled laser-plasma parameters reveal tradeoffs among photon number, mean photon energy, and polarization. Such highly polarized attosecond $γ$-ray pulses could be used to investigate ultrafast nuclear dynamics and polarization-dependent processes in strong-field quantum electrodynamics.

Xi'an Jiaotong UniversityInstitute of Applied Physics and Computational Mathematics

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 23

Plasma screening and configuration interaction effects induced large enhancement on L-shell photoionization cross sections and opacity

Fuyang Zhou, Shengbo Niu, Simei Lu, Chuangying Li, Xiang Gao, Yong Wu, Yizhi Qu, Jianguo Wang

arXiv (physics.atom-ph)Jul 23, 2026Inertial Fusion & HEDP

An opacity model that incorporates improved treatments of both plasma screening and configuration interaction (CI) effects is proposed, and a 25-30% enhancement on the iron L-shell opacity is predicted at solar interior temperatures. It is originated from the plasma screening induced 14-17% enhancement on the photoionization cross sections and the CI induced 10-20% enhancement on photoexcitation and photoionization cross sections for open L-shell ions. These explain the long-standing discrepancy between theoretical and experimental iron opacity [Nature 517, 56], and the relatively weaker enhancements on chromium and nickel opacity [Phys. Rev. Lett. 122, 235001] due to the sensitivity of these effects to the different L-shell electron population and plasma temperature/density. This letter provides the systematic interpretation of L-shell opacity measurements at solar interior temperatures, and advances the accurate simulation of opacity and radiative transport in high-energy-density plasma.

Institute of Applied Physics and Computational Mathematics

Jul 16

Mitigation of stimulated Brillouin scattering in two-color lasers via shared-trapping-induced frequency shift

D.J. Liu, Qing Wang, Q.S. Feng, S.T. Zhang, R.J. Cheng, X.X. Li, S.Y. Lv, Z.M. Huang, Z.J. Chen, Z.Y. Xu, et al.

Nuclear FusionJul 16, 2026AI, Modeling & Simulation Inertial Fusion & HEDP

A novel coupling mechanism for stimulated Brillouin scattering (SBS) in two-color laser systems with large frequency separation is proposed, using a representative combination of 527 nm and 351 nm beams. Owing to the near-linear dispersion of ion-acoustic waves (IAWs), both lasers excite IAWs with similar phase velocities. Consequently, the strong IAW driven by the high-intensity 351 nm laser induces pronounced particle trapping, which in turn generates a significant nonlinear frequency shift in the IAW driven by the 527 nm laser. The frequency shift from Vlasov simulation shows excellent quantitative agreement with our shared-trapping-induced nonlinear frequency-shift theoretical model. This newly identified mechanism suppresses the linear growth of SBS driven by the 527 nm laser, thereby providing a lower initial SBS level when the previously proposed two ion decay (TID) coupling mechanism (2024 Nucl. Fusion 64 126020) becomes active in the nonlinear stage, and enabling the total SBS reflectivity to be suppressed to an even lower level. The mechanism operates within a well-defined parameter window, where the SBS growth rate of the 527 nm laser lies between that of the TID instability and the higher growth rate driven by the 351 nm laser. For fixed total intensity, increasing the fraction of 527 nm light causes the total reflectivity to first decrease and then increase. When the SBS reflectivities driven by the two lasers become comparable, the shared-trapping-induced frequency-shift mechanism and the TID coupling act cooperatively, yielding the minimum total reflectivity. At the optimal intensity fraction, the simulation results show that the total SBS reflectivity is reduced by ∼ 40 % compared with a pure 351 nm laser at the same total intensity, with the instantaneous reflectivity remains no higher than that of the corresponding single-color cases throughout the simulation. These results demonstrate the potential of large-frequency-separation two-color lasers for improving laser–target coupling efficiency in future high-gain laser fusion schemes.

Institute of Applied Physics and Computational MathematicsChinese Academy of Sciences

Forward stimulated Brillouin scattering driven by shared ion-acoustic wave mode in dual orthogonally polarized beams

S.Y. Lv, Qing Wang, X.X. Li, D.J. Liu, R.J. Cheng, Z.M. Huang, Z.Y. Xu, Z.J. Chen, S.T. Zhang, Qiang Wang, et al.

Nuclear FusionJul 16, 2026Inertial Fusion & HEDP

This study proposes a novel mechanism for exciting forward stimulated Brillouin scattering (FSBS) using two orthogonally polarized laser beams. We demonstrate that, when a shared ion-acoustic wave (IAW) mode is excited, beat waves generated by the interaction between the scattered light and the IAW can seed FSBS. Simulations show that the developed FSBS suppresses backward SBS (BSBS) and the shared IAW mode by driving energy transfer between their scattered light and competing for pump energy. As a result, the total backscattering reflectivity in the dual-beam configuration is reduced to a level comparable to that of single-beam incidence. This work identifies FSBS not merely as an instability, but also as a potential mechanism for mitigating collective instability. However, its influence on beam propagation and frequency shift may also affect implosion symmetry and energy deposition in inertial confinement fusion configurations.

Institute of Applied Physics and Computational Mathematics

Jul 13

Measurement of the radiation drive temperature and P2 asymmetry on the capsule

Yaoyuan Liu, Qi Li, Tao Gong, Jinhua Zheng, Xuelong Qin, Changshu Wu, Xin Li, Longfei Jing, Lifei Hou, Sanwei Li, et al.

Nuclear FusionJul 13, 2026Control & Diagnostics Inertial Fusion & HEDP

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.

Institute of Applied Physics and Computational MathematicsLaser Fusion Research Center

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