Xiaoxi Duan

The design of inertial confinement fusion implosions relies on the predictable control of shock dynamics, where the first-shock strength is conventionally governed by the initial laser picket intensity. Here, using shock timing experiments at the SG 100 kJ laser facility, we report a distinct deviation from this conventional scaling: when a high-power main pulse precedes shock breakout, the first-shock velocity in liquid deuterium decreases with increasing picket drive. We attribute this anomaly to preheating of the ablator by high-energy X rays from the early main pulse. Integrated simulations and theory reveal that this preheating induces a rapid pressure rise at the ablator fuel interface. The resulting enhanced pressure overrides the picket driven dynamics during shock impedance matching, accelerating the shock into the fuel and thus inverting the expected scaling. Our findings establish a pressure-dominated mechanism that revises the framework for shock tuning in preheat-affected implosions and provides direct guidance for pulse shaping in future high-energy-drive designs.

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 merge 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 × 10 ¹⁰ , and the hotspot pressure was 30 Gbar. 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 (ICF). 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 precisely infer radiation source calibrated by multiple diagnostics. A joint inversion method for the radiation source and M-band 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 provides an efficient method for pre-shot simulations. Its extrapolation capability was validated using transmission grating spectrometer data, demonstrating high consistency 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 significantly improved engineering control of the 100 kJ-level laser facility in 2025, particularly in laser output stability, although pulse synchronization and delays remain areas for refinement.

The melting behavior of tantalum under high pressure is of fundamental importance to materials science and high-energy-density applications. In this study, we investigated tantalum up to 450 GPa by combining in situ x-ray diffraction with ab initio molecular dynamics (AIMD) simulations. Our experiments provide direct evidence that the body-centered cubic phase is retained from ambient conditions to 318 GPa. This conclusion is supported by the observation of multiple diffraction peaks, including Ta(110), Ta(200), and Ta(211). Our findings on the crystal structure are consistent with those reported by recent work [Phys. Rev. Lett. 126, 255701 (2021)]. The melting curve was derived from AIMD simulations based on density functional theory, without the use of empirical potentials. The obtained melting curve shows good agreement with earlier reliable first-principles theoretical studies, suggesting the limitations of empirical models over broad pressure and temperature ranges. Our combined experimental and computational approach provides a robust framework for studying high-pressure melting in refractory metals and is broadly applicable to materials subjected to extreme environments.

Laser absorption in plasma plays a critical role in energy coupling and symmetry driving in laser direct-drive implosions, particularly in polar direct drive. The incidence angle of the laser significantly influences absorption efficiency. In this paper, the absorption of a 351 nm laser in planar CH plasma at oblique incidence is numerically simulated using the one-dimensional radiation-hydrodynamic code MULTI. Scaling laws of total absorption efficiency with varying laser incidence angles and intensities are obtained. The analytical model for laser time-dependent absorption [B. Scheiner and M. Schmitt, Phys. Plasmas 26(2), 024502 (2019)] is modified with the simulation results. Furthermore, a novel design incorporating a prepulse is proposed to enhance laser absorption. These results provide insights into optimizing the design of future polar direct-drive experiments.

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 × 10¹⁴ 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 ∼ 7) × 10¹⁴ 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.

The thermodynamic properties of boron nitride under extreme pressures and temperatures are of great interest and importance for materials science and inertial confinement fusion physics, but they are poorly understood owing to the challenges of performing experiments and realizing ab initio calculations. Here, we report the first shock Hugoniot data on hexagonal boron nitride at pressures of 5–16 Mbar, using hohlraum-driven shock waves at the SGIII-p laser facility in China. Our density functional theory molecular dynamics calculations closely match experimental data, validating the equations of state for modeling the shock response of boron nitride and filling a crucial gap in the knowledge of boron nitride properties in the region of multi-Mbar pressures and eV temperatures. The results presented here provide fundamental insights into boron nitride under the extreme conditions relevant to inertial confinement fusion, hydrogen–boron fusion, and high-energy-density physics.

The investigation of iron under high pressure and temperatures is crucial to understand the Earth’s core structure and composition and the generation of magnetic fields. Here, we present new in situ XRD measurements for iron in an off-Hugoniot state by laser-driven ramp compression at pressure of 200–238 GPa. The lattice parameters for the hexagonal (hcp)-Fe phase and the c/a ratios were obtained to compare them with previous static and dynamical data, which provides the direct confirmation of such parameters via the different compression paths and strain rates. This work indicates that laser ramp compression can be utilized to provide crystal structure information and direct key information on the crystal structure of Fe at the ultrahigh pressure–temperature conditions relevant for planetology.

Tungsten-doped diamond is employed as a promising ablator material in high-gain laser fusion target design. Unlike for pure carbon, reports on the equation of state (EOS) of tungsten-doped carbon are limited, particularly in the high-pressure range over Mbar, which is relevant to laser fusion. To complement the radiation-hydrodynamic simulations of laser fusion, we developed the EOS of tungsten-doped carbon by combining the quotidian EOS model and large-scale atomistic simulations, which provide fundamental material parameters. In this manner, the EOS of doped carbon can be efficiently constructed. The influence of tungsten doping on the diamond material parameters and EOS was observed. The application of the developed EOS was shown via typical radiation-hydrodynamic simulations of laser fusion.

The physical properties of basic minerals such as magnesium silicates, oxides, and silica at extreme conditions, up to 1000 s of GPa, are crucial to understand the behaviors of magma oceans and melting in Super-Earths discovered to data. Their sound velocity at the conditions relevant to the Super-Earth’s mantle is a key parameter for melting process in determining the physical and chemical evolution of planetary interiors. In this article, we used laser indirectly driven shock compression for quartz to document the sound velocity of quartz at pressures of 270 GPa to 870 GPa during lateral unloadings in a high-power laser facility in China. These measurements demonstrate and improve the technique proposed by Li et al. [PRL 120, 215703 (2018)] to determine the sound velocity. The results compare favorably to the SESAME EoS table and previous data. The Grüneisen parameter at extreme conditions was also calculated from sound velocity data. The data presented in our experiment also provide new information on sound velocity to support the dissociation and metallization for liquid quartz at extreme conditions.