In the direct drive inertial confinement fusion(ICF)scheme,a rippled interface between the ablator and the deuterium–tritium ice fuel can feed out and form perturbation seeds for the ablative Rayleigh–Taylor instabi...In the direct drive inertial confinement fusion(ICF)scheme,a rippled interface between the ablator and the deuterium–tritium ice fuel can feed out and form perturbation seeds for the ablative Rayleigh–Taylor instability,with undesirable effects.However,the evolution of this instability remains insufficiently studied,and the effects of high-Z dopant on this instability remain unclear.In this paper,we develop a theoretical model to calculate the feedout seeds and describe this instability.Our theory suggests that the feedout seeds are determined by the ablation pressure and the adiabatic index,while the subsequent growth depends mainly on the ablation velocity.Two-dimensional radiation hydrodynamic simulations confirm our theory.It is shown that targets with high-Z dopant in the outer ablator exhibit more severe feedout seeds,because of their higher ionization compared with undoped targets.The X-ray pre-ablation in high-Z doped targets significantly suppresses subsequent growth,leading to suppression of short-wavelength perturbations.However,for long-wavelength perturbations,this suppression is weakened,resulting in increased instability in high-Z doped targets.The results are helpful for understanding the innerinterface-initiated instability and the influence of high-Z dopant on it,providing valuable insights for target design and instability control in ICF.展开更多
The effects of atmosphere conditions on microstructural and mechanical properties of stainless steel 17-4PH components fabricated by laser direct manufacturing (LDM) were investigated through mea-surements on phase co...The effects of atmosphere conditions on microstructural and mechanical properties of stainless steel 17-4PH components fabricated by laser direct manufacturing (LDM) were investigated through mea-surements on phase constitution, porosity, tensile strength, fracture morphology, hardness and evolution of substrate temperature. Results showed that the samples produced in air atmosphere condition pos-sessed higher tensile strength and hardness for both as-deposited and heat-treated states than that in Ar chamber condition, due to dispersion strengthening effect of amorphous oxide particles and nitrogen solution strengthening as a result of higher content of oxygen and nitrogen. The temperature of substrate heat accumulation was higher in Ar chamber condition, leading to dramatically lower porosity and more reverse austenite, which also contributed to the lower strength and hardness.展开更多
In this study,a novel solid-state alloying approach was adopted to fabricate Al-Mg alloys with high Mg contents(C_(Mg)) by accumulative roll-bonding(ARB)of Al and Mg elemental materials to ultrahigh cycles.Experimenta...In this study,a novel solid-state alloying approach was adopted to fabricate Al-Mg alloys with high Mg contents(C_(Mg)) by accumulative roll-bonding(ARB)of Al and Mg elemental materials to ultrahigh cycles.Experimental results showed that the degree of alloying increased with the increase of ARB cycles and a supersaturatedα-Al solid solution accompanied with nanoprecipitates was formed in the Al-Mg alloys by ARB to 70 cycles.The as-prepared Al-Mg alloys exhibited enhanced mechanical properties,with a maximum tensile strength of∼615 MPa and a tensile elongation of∼10%at C_(Mg)=13 wt.%.The high strength can be attributed to different mechanisms,namely solid solution strengthening,grain boundary strengthening,dislocation strengthening,and precipitation strengthening.The Al-Mg alloys showed increased work hardening with increasing C_(Mg),due to the enhanced formation of nanoprecipitates.Meanwhile,no obvious drop in the intergranular corrosion(IGC)resistance was found in the Al-Mg alloys with C_(Mg) up to 13 wt.%.Moreover,sensitization treatment was found to induce little decrease in the IGC resistance of the Al-Mg alloys with C_(Mg)≤13 wt.%.We found that the excellent IGC resistance was due to the suppression of grain boundary precipitation by the preferred formation of precipitates within the grains that were induced by ARB.Our study indicated the novelty of the present solid-state alloying approach to achieving a superior combination of high mechanical properties and IGC resistance in Al-Mg alloys.展开更多
Ultra-intense laser-driven fast electron beam propagation in a silicon target is studied by three-dimensional hybrid particle-in-cell–fluid simulations.It is found that the transverse spatial profile of the fast elec...Ultra-intense laser-driven fast electron beam propagation in a silicon target is studied by three-dimensional hybrid particle-in-cell–fluid simulations.It is found that the transverse spatial profile of the fast electron beam has a significant influence on the propagation of the fast electrons.In the case of a steep spatial profile(e.g.,a super-Gaussian profile),a tight fast electron beam is produced,and this excites more intense resistive magnetic fields,which pinch the electron beam strongly,leading to strong filamentation of the beam.By contrast,as the gradient of the spatial profile becomes more gentle(e.g.,in the case of a Lorentzian profile),the resistive magnetic field and filamentation become weaker.This indicates that fast electron propagation in a solid target can be controlled by modulating the spatial gradient of the laser pulse edge.展开更多
The band structure in a kagome lattice can naturally exhibit flat band,Dirac cones,and van Hove singularity,enabling rich interplays between correlation and topology.However,the flat band is rarely detected just at th...The band structure in a kagome lattice can naturally exhibit flat band,Dirac cones,and van Hove singularity,enabling rich interplays between correlation and topology.However,the flat band is rarely detected just at the Fermi level in kagome materials,which would be crucial to realize emergent flat band physics.Here,combining angle-resolved photoemission spectroscopy,transport measurements and first-principles calculation,we observe a striking Fermi-level flat band in paramagnetic YCr_(6)Ge_(6)as a typical signature of electronic kagome lattice.We explicitly unveil that orbital character plays an essential role to realize electronic kagome lattice in crystals with transition-metal kagome layers.We further engineer this material with magnetic rare earth elements to break the time-reversal symmetry of the Fermi-level kagome flat band.Our work establishes a Fermi-level flat band in a kagome magnet as an exciting quantum platform.展开更多
基金supported by the Strategic Priority Research Program of the Chinese Academy of Science(Grant Nos.XDA25050200 and XDA25010100)the National Natural Science Foundation of China(Grant Nos.12175309,12475252,and 12275356)+2 种基金the Defense Industrial Technology Development Program(Grant No.JCKYS2023212807)the Natural Science Foundation of Hunan Province,China(Grant No.2025JJ20007)the Postgraduate Scientific Research Innovation Project of Hunan Province,China(Grant No.CX20230005).
文摘In the direct drive inertial confinement fusion(ICF)scheme,a rippled interface between the ablator and the deuterium–tritium ice fuel can feed out and form perturbation seeds for the ablative Rayleigh–Taylor instability,with undesirable effects.However,the evolution of this instability remains insufficiently studied,and the effects of high-Z dopant on this instability remain unclear.In this paper,we develop a theoretical model to calculate the feedout seeds and describe this instability.Our theory suggests that the feedout seeds are determined by the ablation pressure and the adiabatic index,while the subsequent growth depends mainly on the ablation velocity.Two-dimensional radiation hydrodynamic simulations confirm our theory.It is shown that targets with high-Z dopant in the outer ablator exhibit more severe feedout seeds,because of their higher ionization compared with undoped targets.The X-ray pre-ablation in high-Z doped targets significantly suppresses subsequent growth,leading to suppression of short-wavelength perturbations.However,for long-wavelength perturbations,this suppression is weakened,resulting in increased instability in high-Z doped targets.The results are helpful for understanding the innerinterface-initiated instability and the influence of high-Z dopant on it,providing valuable insights for target design and instability control in ICF.
基金financial support from National Key Research and Development Program of China [grant number 2016YFB1100203]Key Research and Development Program of Jiangxi Province [grant numbers 20171BBE50022, 20151BBE51065]+1 种基金Scientific Research Special Funds of Jiangxi Academy of Sciences [grant numbers 2014-XTPH1-16, 2014-YYB16]Key Research Project of Jiangxi Academy of Sciences [grant number 2016-YZD2-01]
文摘The effects of atmosphere conditions on microstructural and mechanical properties of stainless steel 17-4PH components fabricated by laser direct manufacturing (LDM) were investigated through mea-surements on phase constitution, porosity, tensile strength, fracture morphology, hardness and evolution of substrate temperature. Results showed that the samples produced in air atmosphere condition pos-sessed higher tensile strength and hardness for both as-deposited and heat-treated states than that in Ar chamber condition, due to dispersion strengthening effect of amorphous oxide particles and nitrogen solution strengthening as a result of higher content of oxygen and nitrogen. The temperature of substrate heat accumulation was higher in Ar chamber condition, leading to dramatically lower porosity and more reverse austenite, which also contributed to the lower strength and hardness.
基金supported by the National Natural Science Foundation of China(Nos.52175358 and 51371128)。
文摘In this study,a novel solid-state alloying approach was adopted to fabricate Al-Mg alloys with high Mg contents(C_(Mg)) by accumulative roll-bonding(ARB)of Al and Mg elemental materials to ultrahigh cycles.Experimental results showed that the degree of alloying increased with the increase of ARB cycles and a supersaturatedα-Al solid solution accompanied with nanoprecipitates was formed in the Al-Mg alloys by ARB to 70 cycles.The as-prepared Al-Mg alloys exhibited enhanced mechanical properties,with a maximum tensile strength of∼615 MPa and a tensile elongation of∼10%at C_(Mg)=13 wt.%.The high strength can be attributed to different mechanisms,namely solid solution strengthening,grain boundary strengthening,dislocation strengthening,and precipitation strengthening.The Al-Mg alloys showed increased work hardening with increasing C_(Mg),due to the enhanced formation of nanoprecipitates.Meanwhile,no obvious drop in the intergranular corrosion(IGC)resistance was found in the Al-Mg alloys with C_(Mg) up to 13 wt.%.Moreover,sensitization treatment was found to induce little decrease in the IGC resistance of the Al-Mg alloys with C_(Mg)≤13 wt.%.We found that the excellent IGC resistance was due to the suppression of grain boundary precipitation by the preferred formation of precipitates within the grains that were induced by ARB.Our study indicated the novelty of the present solid-state alloying approach to achieving a superior combination of high mechanical properties and IGC resistance in Al-Mg alloys.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.12175309,11975308,12005297,and 12275356)the Strategic Priority Research Program of the Chinese Academy of Science(Grant No.XDA25050200)the Fund for NUDT Young Innovator Awards(No.20180104).
文摘Ultra-intense laser-driven fast electron beam propagation in a silicon target is studied by three-dimensional hybrid particle-in-cell–fluid simulations.It is found that the transverse spatial profile of the fast electron beam has a significant influence on the propagation of the fast electrons.In the case of a steep spatial profile(e.g.,a super-Gaussian profile),a tight fast electron beam is produced,and this excites more intense resistive magnetic fields,which pinch the electron beam strongly,leading to strong filamentation of the beam.By contrast,as the gradient of the spatial profile becomes more gentle(e.g.,in the case of a Lorentzian profile),the resistive magnetic field and filamentation become weaker.This indicates that fast electron propagation in a solid target can be controlled by modulating the spatial gradient of the laser pulse edge.
基金supported by the Ministry of Science and Technology of China(Grants No.2018YFA0307000,and No.2018FYA0305800)the Innovation Program for Quantum Science and Technology(No.2021ZD0302802)+1 种基金the National Natural Science Foundation of China(Grants No.U2032128,and No.11874047)the Fundamental Research Funds for the Central Universities(Grant No.2042021kf0210).
文摘The band structure in a kagome lattice can naturally exhibit flat band,Dirac cones,and van Hove singularity,enabling rich interplays between correlation and topology.However,the flat band is rarely detected just at the Fermi level in kagome materials,which would be crucial to realize emergent flat band physics.Here,combining angle-resolved photoemission spectroscopy,transport measurements and first-principles calculation,we observe a striking Fermi-level flat band in paramagnetic YCr_(6)Ge_(6)as a typical signature of electronic kagome lattice.We explicitly unveil that orbital character plays an essential role to realize electronic kagome lattice in crystals with transition-metal kagome layers.We further engineer this material with magnetic rare earth elements to break the time-reversal symmetry of the Fermi-level kagome flat band.Our work establishes a Fermi-level flat band in a kagome magnet as an exciting quantum platform.
