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Suppressing filamentation instability due to laser beam self-filtering

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High Power Laser Science and Engineering 2024年第3期12卷 51-61页

作者： Dmitry Silin Efim Khazanov A.V.Gaponov-Grekhov institute of applied physics of the russian academy of sciences Nizhny NovgorodRussia

The development of small-scale self-focusing in a nonlinear Kerr medium after preliminary self-filtering of a laser beam propagating in free space is studied *** is shown that,under definite conditions,due to self-filtering,filamentation instability(beam splitting into filaments)either occurs at significantly larger values of the B-integral,or does not occur at *** the latter case,there develops the honeycomb instability revealed in this *** instability is the formation of a random honeycomb structure in the beam *** is shown that self-filtering can significantly increase the permissible values of the B-integral,at which the beam quality remains acceptable.

关键词： filamentation instability honeycomb instability self-filtering small-scale self-focusing

Dynamic simulation analysis of molten salt reactor-coupled air-steam combined cycle power generation system

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Nuclear Science and Techniques 2024年第2期35卷 222-233页

作者： Jing-Lei Huang Guo-Bin Jia Li-Feng Han Wen-Qian Liu Li Huang Zheng-Han Yang Shanghai institute of applied physics Chinese Academy of SciencesShanghai 201800China University of Chinese academy of sciences Beijing 100049China

A nonlinear dynamic simulation model based on coordinated control of speed and flow rate for the molten salt reactor and combined cycle systems is proposed here to ensure the coordination and stability between the molten salt reactor and power *** model considers the impact of thermal properties of fluid variation on accuracy and has been validated with *** study reveals the capability of the control system to compensate for anomalous situations and maintain shaft stability in the event of perturbations occurring in high-temperature molten salt tank outlet ***,the control system’s impact on the system’s dynamic characteristics under molten salt disturbance is also *** results reveal that after the disturbance occurs,the controlled system benefits from the action of the control,and the overshoot and disturbance amplitude are positively correlated,while the system power and frequency eventually return to the initial *** simulation model provides a basis for utilizing molten salt reactors for power generation and maintaining grid stability.

关键词： Molten salt reactor Combined cycle Dynamic characteristic Control

Mechanical responses and crystal plasticity model of CoCrNi medium-entropy alloy under ramp wave compression

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Matter and Radiation at Extremes 2024年第5期9卷 93-108页

作者： Jinlei Dong Xuping Zhang Guiji Wang Xianqian Wu Binqiang Luo Xuemiao Chen Fuli Tan Jianheng Zhao Chengwei Sun institute of Fluid physics China Academy of Engineering PhysicsMianyang 621999China institute of Mechanics Chinese Academy of SciencesBeijing 100190China institute of applied Electronics China Academy of Engineering PhysicsMianyang 621999China

It is of substantial scientific significance and practical value to reveal and understand the multiscale mechanical properties and intrinsic mechanisms of medium-entropy alloys(MEAs)under high strain rates and *** this study,the mechanical responses and deformation mechanisms of an equiatomic CoCrNi MEA are investigated utilizing magnetically driven ramp wave compression(RWC)with a strain rate of 105 s^(−1).The CoCrNi MEA demonstrates excellent dynamic mechanical responses and yield strength under RWC compared with other advanced *** characterizations reveal that grain refinement and abundant micromechanisms,including dislocation slip,stacking faults,nanotwin network,and Lomer–Cottrell locks,collectively contribute to its excellent performance during ***,dense deformation twins and shear bands intersect,forming a weave-like microstructure that can disperse deformation and enhance *** the basis of these observations,we develop a modified crystal plasticity model with coupled dislocation and twinning mechanisms,providing a relatively accurate quantitative description of the multiscale behavior under *** results of simulations indicate that the activation of multilevel microstructures in CoCrNi MEA is primarily attributable to stress inhomogeneities and localized strain during *** research offers valuable insights into the dynamic mechanical responses of CoCrNi MEA,positioning it as a promising material for use under extreme dynamic conditions.

关键词： deformation alloy microstructure

A rened analytical model for reconstruction problems in diuse reectance spectroscopy

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Journal of Innovative Optical Health sciences 2024年第5期17卷 33-51页

作者： Ekaterina Sergeeva Daria Kurakina Ilya Turchin and Mikhail Kirillin A.V.gaponov-grekhov institute of applied physics of the russian academy of sciences ulyanov st.46 603950nizhny novgorodrussia

A rened analytical model of spatially resolved diffuse reectance with small source-detector separations(SDSs)for the in vivo skin studies is *** to the conventional model developed by Farrell et al.,it accounts for the limited acceptance angle of the *** rened model is validated in the wide range of optical parameters by Monte Carlo simulations of skin diffuse reectance at SDSs of units of *** of uniform dermis and two-layered epidermis-dermis structures are *** accuracy of the rened model compared to the conventional one is demonstrated in the separate,constraint-free reconstruction of absorption and reduced scattering spectra of uniform dermis from the Monte Carlo simulated *** the case of epidermis-dermis geometry,the recovered values of reduced scattering in dermis are overestimated and the recovered values of absorption are underestimated for both analytical ***,in the presence of a thin mismatched topical layer,only the effective attenuation coe±cient of the bottom layer can be accurately recovered using a diffusion theorybased analytical model while separate reconstruction of absorption and reduced scattering fails due to the inapplicability of the method of ***-ndings require implementation of more sophisticated models of light transfer in inhomogeneous media in the recovery algorithms.

关键词： Diffuse reffectance spectroscopy in vivo skin studies optical properties reconstruction diffuse approximation Monte Carlo simulations method of images

Pulsed THz radiation under ultrafast optical discharge of vacuum photodiode

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Frontiers of Optoelectronics 2024年第2期17卷 99-112页

作者： Aleksandr Ushakov Kseniia Mamaeva Leonid Seleznev Georgy Rizaev Vladimir Bukin Timophey Dolmatov Pavel Chizhov Vladimir Bagdasarov Sergey Garnov Prokhorov General physics institute of the russian academy of sciences Moscow 119991Russia Physical institute Russian Academy of SciencesMoscow 119991Russia Moscow institute of physics and Technology Dolgoprudny 141700Russia russian institute for Scientific and Technical Information Moscow 125190Russia

In this paper,we first present an experimental demonstration of terahertz radiation pulse generation with energy up to 5 pJ under the electron emission during ultrafast optical discharge of a vacuum *** use a femtosecond optical excitation of metallic copper photocathode for the generation of ultrashort electron bunch and up to 45 kV/cm external electric field for the photo-emitted electron *** of terahertz pulses energy as a function of emitted charge density,incidence angle of optical radiation and applied electric field have been *** and polarization characteristics of generated terahertz pulses have also been *** proposed semi-analytical model and simulations in COMSOL Multiphysics prove the experimental data and allow for the optimization of experimental conditions aimed at flexible control of radiation parameters.

关键词： Electron emission Vacuum photodiode Ultrafast excitation Terahertz

Study on the optimal incident proton energy of ^(7)Li(p,n)^(7)Be neutron source for boron neutron capture therapy

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Nuclear Science and Techniques 2024年第3期35卷 170-180页

作者： Yi-Nan Zhu Zuo-Kang Lin Hai-Yan Yu Ye Dai Zhi-Min Dai Xiao-Han Yu Shanghai institute of applied physics Chinese Academy of SciencesShanghai 201800China University of Chinese academy of Science Beijing 100049China

Boron neutron capture therapy(BNCT)is recognized as a precise binary targeted radiotherapy technique that effectively eliminates tumors through the^(10)B(n,α)^(7)Li nuclear *** various neutron sources,accelerator-based sources have emerged as particularly promising for BNCT ***^(7)Li(p,n)^(7)Be reaction is highly regarded as a potential neutron source for BNCT,owing to its low threshold energy for the reaction,significant neutron yield,appropriate average neutron energy,and additional *** study utilized Monte Carlo simulations to model the physical interactions within a lithium target subjected to proton bombardment,including neutron moderation by an MgF_(2)moderator and subsequent BNCT dose analysis using a Snyder head *** study focused on calculating the yields of epithermal neutrons for various incident proton energies,finding an optimal energy at 2.7 ***,the Snyder head phantom was employed in dose simulations to validate the effectiveness of this specific incident energy when utilizing a^(7)Li(p,n)^(7)Be neutron source for BNCT purposes.

关键词： Boron neutron capture therapy ^(7)Li(p,n)7Be neutron source Incident proton energy Monte Carlo simulation

Accelerated generation of holograms with ultra-low memory symmetrically high-compressed look-up table

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Chinese physics B 2024年第4期33卷 466-471页

作者：杨燕朱建英孙敏远毕勇 applied Laser Research Center Technical Institute of Physics and ChemistryChinese Academy of SciencesBeijing 100190China University of Chinese academy of sciences Beijing 100049China

Computer-generated holography technology has been widely applied,and as research in this field deepens,the demand for memory and computational power in small AR and VR devices continues to *** paper presents a hologram generation method,i.e.,a symmetrically high-compressed look-up table method,which can reduce memory usage by50%.In offline computing,half of the basic horizontal and vertical modulation factors are stored,halving the memory requirements without affecting inline ***,its potential extends to various holographic applications,including the production of optical diffraction elements.

关键词： computergenerated hologram look-up table holography

Review on synergistic damage effect of irradiation and corrosion on reactor structural alloys

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Nuclear Science and Techniques 2024年第3期35卷 109-141页

作者： Hui Liu Guan-Hong Lei He-Fei Huang Shanghai institute of applied physics Chinese Academy of SciencesShanghai 201800China School of Nuclear Science and Technology University of Chinese Academy of SciencesBeijing 100049China

The synergistic damage effect of irradiation and corrosion of reactor structural materials has been a prominent research *** paper provides a comprehensive review of the synergistic effects on the third-and fourth-generation fission nuclear energy structural materials used in pressurized water reactors and molten salt *** competitive mechanisms of multiple influencing factors,such as the irradiation dose,corrosion type,and environmental temperature,are summarized in this *** approaches are proposed to alleviate the synergistic damage caused by irradiation and corrosion,thereby promoting in-depth research in the future and solving this key challenge for the structural materials used in reactors.

关键词： Irradiation and corrosion Synergistic effect Austenitic stainless steels Nickel-based alloys Reactors

Experimental observation of the significant difference between surface and bulk Kondo processes in Kondo lattice YbCu_(2)Si_(2)

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Science China(physics,Mechanics & Astronomy) 2024年第4期67卷 154-160页

作者： Yin-Zou Zhao Jiao-Jiao Song Qi-Yi Wu Hao Liu Chen Zhang Bo Chen Hong-Yi Zhang Zhen-Hua Chen Yao-Bo Huang Xue-Qing Ye Ya-Hua Yuan Yu-Xia Duan Jun He Jian-Qiao Meng School of physics Central South UniversityChangsha 410083China Shanghai institute of applied physics Chinese Academy of SciencesShanghai 201204China

Synchrotron-based angle-resolved photoemission spectroscopy was employed to investigate the temperature evolution of the Yb 4 f spectral for surface and bulk in the Kondo lattice YbCu_(2)Si_(2).Our study quantitatively distinguishes between the surface and bulk hybridization processes,revealing that the onset temperatures for both surface and bulk hybridization processes are significantly higher than the Kondo ***,we found that the effective surface Kondo temperature is much lower than that of the *** findings offer valuable insights into the understanding of heavy fermion physics.

关键词： Kondo lattice angle-resolved photoemission spectroscopy electronic structure hybridization surface state