Large-angle stimulated Raman scattering(LA-SRS)in a longitudinally inhomogeneous plasma with a transverse density modulation is studied using a three-wave coupled model and numerical simulations.The simulations show t...Large-angle stimulated Raman scattering(LA-SRS)in a longitudinally inhomogeneous plasma with a transverse density modulation is studied using a three-wave coupled model and numerical simulations.The simulations show that the scattering angle of SRS in a longitudinally inhomogeneous plasma can be significantly affected by transverse density modulation.Under transverse density modulation conditions,the laser focuses into underdense regions,owing to the transversely modulated refractive index.The angle of LA-SRS,neither a purely 90° angle side scattering nor purely backscattering,is almost consistent with the specific angle at which the density inhomogeneity vanishes.In modulated plasmas,the nonuniform distribution of laser intensity shifts the regions of scattering and gain compared with those in uniform plasmas,ultimately affecting the laser transmission.SRS is suppressed in weakly modulated regimes,whereas it is enhanced under strong modulation conditions,and a theoretical criterion distinguishing between strong and weak modulation is established.展开更多
In this work, characteristics of X/γ-ray radiations by intense laser interactions with high-Z solids are investigated by means of a newlydeveloped particle-in-cell (PIC) simulation code. The PIC code takes advantage ...In this work, characteristics of X/γ-ray radiations by intense laser interactions with high-Z solids are investigated by means of a newlydeveloped particle-in-cell (PIC) simulation code. The PIC code takes advantage of the recently developed ionization and collision dynamicsmodels, which make it possible to model different types of materials based on their intrinsic atomic properties. Within the simulations, bothbremsstrahlung and nonlinear Compton scatterings have been included. Different target materials and laser intensities are considered forstudying the parameter-dependent features of X/γ-ray radiations. The relative strength and angular distributions of X/γ ray productions frombremsstrahlung and nonlinear Compton scatterings are compared to each other. The threshold under which the nonlinear Compton scatteringsbecome dominant over bremsstrahlung is also outlined.展开更多
I.INTRODUCTION Strong interest in the modeling of planetary interiors,dwarf stars,and the physical conditions necessary to achieve inertial confinement fusion(ICF)have driven attention to the properties of matter at h...I.INTRODUCTION Strong interest in the modeling of planetary interiors,dwarf stars,and the physical conditions necessary to achieve inertial confinement fusion(ICF)have driven attention to the properties of matter at high density,temperature,and pressure(beyond the megabar limit).Extreme states of matter have been studied using gas guns,explosives,and Z-pinches,among other methods(see,e.g.,Refs.1–4).However in recent years,lasers have become the most reliable standard tool for creating extreme states of matter.展开更多
We report systematic studies of laser-driven proton beams produced with micrometer-thick solid targets made of aluminum and plastic,respectively.Distinct effects of the target materials are found on the total charge,c...We report systematic studies of laser-driven proton beams produced with micrometer-thick solid targets made of aluminum and plastic,respectively.Distinct effects of the target materials are found on the total charge,cutoff energy,and beam spot of protons in the experiments,and these are described well by two-dimensional particle-in-cell simulations incorporating intrinsic material properties.It is found that with a laser intensity of 8×10^(19) W/cm^(2),target normal sheath acceleration is the dominant mechanism for both types of target.For a plastic target,the higher charge and cutoff energy of the protons are due to the greater energy coupling efficiencies from the intense laser beams,and the larger divergence angle of the protons is due to the deflection of hot electrons during transport in the targets.We also find that the energy loss of hot electrons in targets of different thickness has a significant effect on the proton cutoff energy.The consistent results obtained here further narrow the gap between simulations and experiments.展开更多
Competition among the two-plasmon decay(TPD)of backscattered light of stimulated Raman scattering(SRS),filamentation of the electron-plasma wave(EPW)and forward side SRS is investigated by two-dimensional particlein-c...Competition among the two-plasmon decay(TPD)of backscattered light of stimulated Raman scattering(SRS),filamentation of the electron-plasma wave(EPW)and forward side SRS is investigated by two-dimensional particlein-cell simulations.Our previous work[K.Q.Pan et al.,Nucl.Fusion 58,096035(2018)]showed that in a plasma with the density near 1/10 of the critical density,the backscattered light would excite the TPD,which results in suppression of the backward SRS.However,this work further shows that when the laser intensity is so high(>10^(16)W/cm^(2))that the backward SRS cannot be totally suppressed,filamentation of the EPW and forward side SRS will be excited.Then the TPD of the backscattered light only occurs in the early stage and is suppressed in the latter stage.Electron distribution functions further show that trapped-particle-modulation instability should be responsible for filamentation of the EPW.This research can promote the understanding of hot-electron generation and SRS saturation in inertial confinement fusion experiments.展开更多
This paper presents an extension work of the hybrid scheme proposed by Wang et al.[J.Comput.Phys.229(2010)169-180]for numerical simulation of sub-sonic isotropic turbulence to supersonic turbulence regime.The scheme s...This paper presents an extension work of the hybrid scheme proposed by Wang et al.[J.Comput.Phys.229(2010)169-180]for numerical simulation of sub-sonic isotropic turbulence to supersonic turbulence regime.The scheme still utilizes an 8th-order compact scheme with built-in hyperviscosity for smooth regions and a 7th-order WENO scheme for highly compression regions,but now both in their con-servation formulations and for the latter with the Roe type characteristic-wise recon-struction.To enhance the robustness of the WENO scheme without compromising its high-resolution and accuracy,the recursive-order-reduction procedure is adopted,where a new type of reconstruction-failure-detection criterion is constructed from the idea of positivity-preserving.In addition,a new form of cooling function is proposed,which is proved also to be positivity-preserving.With a combination of these techniques,the new scheme not only inherits the good properties of the original one but also extends largely the computable range of turbulent Mach number,which has been further confirmed by numerical results.展开更多
Laser interaction with an ultra-thin pre-structured target is investigated with the help of both two-dimensional and threedimensional particle-in-cell simulations.With the existence of aperiodic structure on the targe...Laser interaction with an ultra-thin pre-structured target is investigated with the help of both two-dimensional and threedimensional particle-in-cell simulations.With the existence of aperiodic structure on the target surface,the laser seems to penetrate through the target at its fundamental frequency even if the plasma density of the target is much higher than the laser’s relativistically critical density.The particle-in-cell simulations show that the transmitted laser energy behind the pre-structured target is increased by about two orders of magnitude compared to that behind the flat target.Theoretical analyses show that the transmitted energy behind the pre-structured target is actually re-emitted by electron’islands’ formed by the surface plasma waves on the target surfaces.In other words,the radiation with the fundamental frequency is actually’surface emission,on the target rear surface.Besides the intensity of the component with the fundamental frequency,the intensity of the high-order harmonics behind the pre-structured target is also much enhanced compared to that behind the flat target.The enhancement of the high-order harmonics is also related to the surface plasma waves generated on the target surfaces.展开更多
The strong-coupling mode,called the"quasimode",is excited by stimulated Brillouin scattering(SBS)in high-intensity laser-plasma interactions.Also SBS of the quasimode competes with SBS of the fast mode(or sl...The strong-coupling mode,called the"quasimode",is excited by stimulated Brillouin scattering(SBS)in high-intensity laser-plasma interactions.Also SBS of the quasimode competes with SBS of the fast mode(or slow mode)in multiion species plasmas,thus leading to a low-frequency burst behavior of SBS reflectivity.Competition between the quasimode and the ion-acoustic wave(IAW)is an important saturation mechanism of SBS in high-intensity laser-plasma interactions.These results give a clear explanation of the low-frequency periodic burst behavior of SBS and should be considered as a saturation mechanism of SBS in high-intensity laser-plasma interactions.展开更多
This paper is concerned with the pattern dynamics of the generalized nonlinear Schrodinger equations(NSEs)relatedwith various nonlinear physical problems in plasmas.Our theoretical and numerical results show that the ...This paper is concerned with the pattern dynamics of the generalized nonlinear Schrodinger equations(NSEs)relatedwith various nonlinear physical problems in plasmas.Our theoretical and numerical results show that the higher-order nonlinear effects,acting as a Hamiltonian perturbation,break down the NSE integrability and lead to chaotic behaviors.Correspondingly,coherent structures are destroyed and replaced by complex patterns.Homoclinic orbit crossings in the phase space and stochastic partition of energy in Fourier modes show typical characteristics of the stochastic motion.Our investigations show that nonlinear phenomena,such as wave turbulence and laser filamentation,are associated with the homoclinic chaos.In particular,we found that the unstable manifolds W(u)possessing the hyperbolic fixed point correspond to an initial phase θ=45° and 225° ,and the stable manifolds W(s)correspond toθ=135° and 315° .展开更多
基金supported by the National Natural Science Foundation of China under Grant Nos.U2430207,12035002,and 12305258by the CAEP Foundation under Grant No.YZJJZQ2023020.
文摘Large-angle stimulated Raman scattering(LA-SRS)in a longitudinally inhomogeneous plasma with a transverse density modulation is studied using a three-wave coupled model and numerical simulations.The simulations show that the scattering angle of SRS in a longitudinally inhomogeneous plasma can be significantly affected by transverse density modulation.Under transverse density modulation conditions,the laser focuses into underdense regions,owing to the transversely modulated refractive index.The angle of LA-SRS,neither a purely 90° angle side scattering nor purely backscattering,is almost consistent with the specific angle at which the density inhomogeneity vanishes.In modulated plasmas,the nonuniform distribution of laser intensity shifts the regions of scattering and gain compared with those in uniform plasmas,ultimately affecting the laser transmission.SRS is suppressed in weakly modulated regimes,whereas it is enhanced under strong modulation conditions,and a theoretical criterion distinguishing between strong and weak modulation is established.
基金This work was supported by Science Challenge Project(No.TZ2016005)National Natural Science Foundation of China(No.11605269,11674341 and 11675245)National Basic Research Program of China(Grant No.2013CBA01504).
文摘In this work, characteristics of X/γ-ray radiations by intense laser interactions with high-Z solids are investigated by means of a newlydeveloped particle-in-cell (PIC) simulation code. The PIC code takes advantage of the recently developed ionization and collision dynamicsmodels, which make it possible to model different types of materials based on their intrinsic atomic properties. Within the simulations, bothbremsstrahlung and nonlinear Compton scatterings have been included. Different target materials and laser intensities are considered forstudying the parameter-dependent features of X/γ-ray radiations. The relative strength and angular distributions of X/γ ray productions frombremsstrahlung and nonlinear Compton scatterings are compared to each other. The threshold under which the nonlinear Compton scatteringsbecome dominant over bremsstrahlung is also outlined.
文摘I.INTRODUCTION Strong interest in the modeling of planetary interiors,dwarf stars,and the physical conditions necessary to achieve inertial confinement fusion(ICF)have driven attention to the properties of matter at high density,temperature,and pressure(beyond the megabar limit).Extreme states of matter have been studied using gas guns,explosives,and Z-pinches,among other methods(see,e.g.,Refs.1–4).However in recent years,lasers have become the most reliable standard tool for creating extreme states of matter.
基金The simulations were performed on the Qilin-2 supercomputer at Zhejiang University.This work was supported by the Science Challenge Project(No.TZ2016005)the National Natural Science Foundation of China(Grant Nos.119210067,11605269,11721091,11775144)the National Grand Instrument Project(Nos.2019YFF01014400,2019YFF01014404).
文摘We report systematic studies of laser-driven proton beams produced with micrometer-thick solid targets made of aluminum and plastic,respectively.Distinct effects of the target materials are found on the total charge,cutoff energy,and beam spot of protons in the experiments,and these are described well by two-dimensional particle-in-cell simulations incorporating intrinsic material properties.It is found that with a laser intensity of 8×10^(19) W/cm^(2),target normal sheath acceleration is the dominant mechanism for both types of target.For a plastic target,the higher charge and cutoff energy of the protons are due to the greater energy coupling efficiencies from the intense laser beams,and the larger divergence angle of the protons is due to the deflection of hot electrons during transport in the targets.We also find that the energy loss of hot electrons in targets of different thickness has a significant effect on the proton cutoff energy.The consistent results obtained here further narrow the gap between simulations and experiments.
基金supported by the National Natural Science Foundation of China(Nos.12205274,12275251,12035002,11975215)
文摘Competition among the two-plasmon decay(TPD)of backscattered light of stimulated Raman scattering(SRS),filamentation of the electron-plasma wave(EPW)and forward side SRS is investigated by two-dimensional particlein-cell simulations.Our previous work[K.Q.Pan et al.,Nucl.Fusion 58,096035(2018)]showed that in a plasma with the density near 1/10 of the critical density,the backscattered light would excite the TPD,which results in suppression of the backward SRS.However,this work further shows that when the laser intensity is so high(>10^(16)W/cm^(2))that the backward SRS cannot be totally suppressed,filamentation of the EPW and forward side SRS will be excited.Then the TPD of the backscattered light only occurs in the early stage and is suppressed in the latter stage.Electron distribution functions further show that trapped-particle-modulation instability should be responsible for filamentation of the EPW.This research can promote the understanding of hot-electron generation and SRS saturation in inertial confinement fusion experiments.
基金supported by National Natural Science Foundation of China(Grant Nos.11702127,11521091,91752202)Science Challenge Project(No.TZ2016001).
文摘This paper presents an extension work of the hybrid scheme proposed by Wang et al.[J.Comput.Phys.229(2010)169-180]for numerical simulation of sub-sonic isotropic turbulence to supersonic turbulence regime.The scheme still utilizes an 8th-order compact scheme with built-in hyperviscosity for smooth regions and a 7th-order WENO scheme for highly compression regions,but now both in their con-servation formulations and for the latter with the Roe type characteristic-wise recon-struction.To enhance the robustness of the WENO scheme without compromising its high-resolution and accuracy,the recursive-order-reduction procedure is adopted,where a new type of reconstruction-failure-detection criterion is constructed from the idea of positivity-preserving.In addition,a new form of cooling function is proposed,which is proved also to be positivity-preserving.With a combination of these techniques,the new scheme not only inherits the good properties of the original one but also extends largely the computable range of turbulent Mach number,which has been further confirmed by numerical results.
基金supported by the Science Challenge Project(No.TZ2016005)China Postdoctoral Science Foundation(No.2017M620430)+1 种基金National Natural Science Foundation of China(Nos.11435011,11575035,11705180,and 11875241)the National Basic Research Program of China(No.2013CB834101)
文摘Laser interaction with an ultra-thin pre-structured target is investigated with the help of both two-dimensional and threedimensional particle-in-cell simulations.With the existence of aperiodic structure on the target surface,the laser seems to penetrate through the target at its fundamental frequency even if the plasma density of the target is much higher than the laser’s relativistically critical density.The particle-in-cell simulations show that the transmitted laser energy behind the pre-structured target is increased by about two orders of magnitude compared to that behind the flat target.Theoretical analyses show that the transmitted energy behind the pre-structured target is actually re-emitted by electron’islands’ formed by the surface plasma waves on the target surfaces.In other words,the radiation with the fundamental frequency is actually’surface emission,on the target rear surface.Besides the intensity of the component with the fundamental frequency,the intensity of the high-order harmonics behind the pre-structured target is also much enhanced compared to that behind the flat target.The enhancement of the high-order harmonics is also related to the surface plasma waves generated on the target surfaces.
基金supported by the National Natural Science Foundation of China(Nos.11875091,11575035,11875093,11475030 and 11435011)National Postdoctoral Program for Innovative Talents(No.BX20180055)+1 种基金China Postdoctoral Science Foundation(No.2018M641274)Science Challenge Project(No.TZ2016005).
文摘The strong-coupling mode,called the"quasimode",is excited by stimulated Brillouin scattering(SBS)in high-intensity laser-plasma interactions.Also SBS of the quasimode competes with SBS of the fast mode(or slow mode)in multiion species plasmas,thus leading to a low-frequency burst behavior of SBS reflectivity.Competition between the quasimode and the ion-acoustic wave(IAW)is an important saturation mechanism of SBS in high-intensity laser-plasma interactions.These results give a clear explanation of the low-frequency periodic burst behavior of SBS and should be considered as a saturation mechanism of SBS in high-intensity laser-plasma interactions.
基金This work is also supported by the National Natural Science Foundation of China grant Nos.10575013 and 10576007partially by the National Basic Research Program of China(973)(2007CB814802 and 2007CB815101).
文摘This paper is concerned with the pattern dynamics of the generalized nonlinear Schrodinger equations(NSEs)relatedwith various nonlinear physical problems in plasmas.Our theoretical and numerical results show that the higher-order nonlinear effects,acting as a Hamiltonian perturbation,break down the NSE integrability and lead to chaotic behaviors.Correspondingly,coherent structures are destroyed and replaced by complex patterns.Homoclinic orbit crossings in the phase space and stochastic partition of energy in Fourier modes show typical characteristics of the stochastic motion.Our investigations show that nonlinear phenomena,such as wave turbulence and laser filamentation,are associated with the homoclinic chaos.In particular,we found that the unstable manifolds W(u)possessing the hyperbolic fixed point correspond to an initial phase θ=45° and 225° ,and the stable manifolds W(s)correspond toθ=135° and 315° .
