Strong-field quantum electrodynamics(SF-QED)plays a crucial role in ultraintense laser-matter interactions and demands sophisticated techniques to understand the related physics with new degrees of freedom,including s...Strong-field quantum electrodynamics(SF-QED)plays a crucial role in ultraintense laser-matter interactions and demands sophisticated techniques to understand the related physics with new degrees of freedom,including spin angular momentum.To investigate the impact of SF-QED processes,we have introduced spin/polarization-resolved nonlinear Compton scattering,nonlinear Breit-Wheeler,and vacuum birefringence processes into our particle-in-cell(PIC)code.In this article,we provide details of the implementation of these SF-QED modules and share known results that demonstrate exact agreement with existing single-particle codes.By coupling normal PIC simulations with spin/polarization-resolved SF-QED processes,we create a new theoretical platform to study strong-field physics in currently running or planned petawatt or multi-petawatt laser facilities.展开更多
The rapid development of ultrafast ultraintense laser technology continues to create opportunities for studying strong-field physics under extreme conditions.However,accurate determination of the spatial and temporal ...The rapid development of ultrafast ultraintense laser technology continues to create opportunities for studying strong-field physics under extreme conditions.However,accurate determination of the spatial and temporal characteristics of a laser pulse is still a great challenge,especially when laser powers higher than hundreds of terawatts are involved.In this paper,by utilizing the radiative spin-flip effect,we find that the spin depolarization of an electron beam can be employed to diagnose characteristics of ultrafast ultraintense lasers with peak intensities around 10^(20)–10^(22) W/cm^(2).With three shots,our machine-learning-assisted model can predict,simultaneously,the pulse duration,peak intensity,and focal radius of a focused Gaussian ultrafast ultraintense laser(in principle,the profile can be arbitrary)with relative errors of 0.1%–10%.The underlying physics and an alternative diagnosis method(without the assistance of machine learning)are revealed by the asymptotic approximation of the final spin degree of polarization.Our proposed scheme exhibits robustness and detection accuracy with respect to fluctuations in the electron beam parameters.Accurate measurements of ultrafast ultraintense laser parameters will lead to much higher precision in,for example,laser nuclear physics investigations and laboratory astrophysics studies.Robust machine learning techniques may also find applications in more general strong-field physics scenarios.展开更多
A diamond-like carbon circular target is proposed to improve γ-ray emission and pair production with a laser intensity of 8×1022 W cm-2by using 2D particle-in-cell simulations with quantum electrodynamics.It is ...A diamond-like carbon circular target is proposed to improve γ-ray emission and pair production with a laser intensity of 8×1022 W cm-2by using 2D particle-in-cell simulations with quantum electrodynamics.It is found that the circular target can enhance the density of γ-photons significantly more than a plane target, when two colliding circularly polarized lasers irradiate the target.By multi-laser irradiating the circular target, the optical trap of lasers can prevent the high energy electrons accelerated by laser radiation pressure from escaping.Hence, γ-photons with a high density of beyond 5000 ncare obtained through nonlinear Compton backscattering.Meanwhile, 2.7×1011 positrons with an average energy of 230 MeV are achieved via the multiphoton Breit-Wheeler process.Such an ultrabright γ-ray source and dense positron source can be useful in many applications.The optimal target radius and laser mismatching deviation parameters are also discussed in detail.展开更多
The supersonic gas-jet target is an important experimental target for laser wakefield acceleration(LWFA),which has great potential for driving novel radiation sources such as betatron radiation and Compton scattering ...The supersonic gas-jet target is an important experimental target for laser wakefield acceleration(LWFA),which has great potential for driving novel radiation sources such as betatron radiation and Compton scattering gamma rays.According to different electron acceleration requirements,it is necessary to provide specific supersonic gas jets with different density profiles to generate electron beams with high quality and high repetition rates.In this study,the interference images and density profiles of different gas-jet targets were obtained through a modified Nomarski interference diagnosis system.The relationships between the gas density and back pressure,nozzle structure,and other key parameters were studied.Targets with different characteristics are conducive to meeting the various requirements of LWFA.展开更多
The use of a novel double-cone funnel target with high density layers （HDL） to collimate and focus electrons is investigated by two-dimensional particle-in-cell simulations. The proposed scheme can guide, collimate ...The use of a novel double-cone funnel target with high density layers （HDL） to collimate and focus electrons is investigated by two-dimensional particle-in-cell simulations. The proposed scheme can guide, collimate and focus electron beams to smaller sizes. The collimation reasons are analyzed by the quasi-static magnetic fields generation inside the beam collimator with HDL. It is found that the energy conversion efficiency is increased by a factor of 2.2 in this new scheme in comparison with the that without HDL. Such a target structure has potential for design flexibility and prevents inefficiencies in important applications such as fast ignition, etc.展开更多
Enhanced photon emission and pair production due to heavy ion mass in the interaction of an ultraintense laser with overdense plasmas is explored by particle-in-cell simulation. It is found that plasmas with heavier i...Enhanced photon emission and pair production due to heavy ion mass in the interaction of an ultraintense laser with overdense plasmas is explored by particle-in-cell simulation. It is found that plasmas with heavier ion mass can excite a higher and broader electrostatic field, which causes the enhancement of backward photon emission. The pair yields are then enhanced due to the increase of backwards photons colliding with the incoming laser pulse. By examining the density evolution and angle distribution of each particle species, the origin of pair yield enhancement is clarified.展开更多
While the traditional trajectory planning methods are used in robotic belt grinding of blades with an uneven machining allowance distribution, it is hard to obtain the preferable profile accuracy and surface quality t...While the traditional trajectory planning methods are used in robotic belt grinding of blades with an uneven machining allowance distribution, it is hard to obtain the preferable profile accuracy and surface quality to meet the high-performance requirements of aero-engine. To solve this problem, a novel trajectory planning method is proposed in this paper by considering the developed interpolation algorithm and the machining allowance threshold. The residual height error obtained from grinding experiments of titanium alloy sample was compensated to modify the calculation model of row spacing, and a new geometric algorithm was presented to dynamically calculate the cutter contact points based on this revised calculation model and the dichotomy method. Subsequently, the off-line machining program is generated based on a double-vector controlling method to obtain an optimal contact posture. On this basis, three sets of robotic grinding tests of titanium alloy blades were conducted to investigate the advantages of the proposed method.The comparative experimental results revealed that the presented algorithm had improved the surface profile accuracy of blade by 34.2% and 55.1%, respectively. Moreover, the average machined surface roughness was achieved to 0.3 μm and the machining efficiency was obviously promoted. It is concluded that this research work is beneficial to comprehensively improve the machined quality of blades in robotic belt grinding.展开更多
Fermion particle pair production in strong SU（2）-gauge chromoelectric fields is studied using the Boltzmann-Vlasov equation in a classical way. The existence of a preproduction process in a classical description is ...Fermion particle pair production in strong SU（2）-gauge chromoelectric fields is studied using the Boltzmann-Vlasov equation in a classical way. The existence of a preproduction process in a classical description is shown using the distribution evolution of non-Abelian particle production. It is interesting to find that the distribution of the particle number density is centered on two islands and shows a split on the color charge sphere as it evolves, ultimately reaching a steady state that is related to the amplitude and variation of the field.展开更多
Massless quark pair production in SU(2) gauge chromoelectric field is investigated by solving the Wigner function with back reaction. The temporal evolution of specific field and its current are obtained self consiste...Massless quark pair production in SU(2) gauge chromoelectric field is investigated by solving the Wigner function with back reaction. The temporal evolution of specific field and its current are obtained self consistently. For the quark distribution function, both its time and momentum dependence are studied. In particular, some interesting phenomena are found, for example, the more abundant symmetry or/and antisymmetry characteristics, the existence of the attractive basin structure and the existence of the momentum "gap" in the quark distribution and so on. All the phenomena are associated with the quark-gluon plasma oscillation, which due to the back reaction effect. The study and analysis qualitatively about the components of the Wigner function are expected to be helpful to deepen the understanding of the QCD vacuum.展开更多
基金The work is supported by the National Natural Science Foundation of China(Grant Nos.12275209,12022506,and U2267204)the Open Foundation of the Key Laboratory of High Power Laser and Physics,Chinese Academy of Sciences(Grant No.SGKF202101)+1 种基金the Foundation of Science and Technology on Plasma Physics Laboratory(Grant No.JCKYS2021212008)the Shaanxi Fundamental Science Research Project for Mathematics and Physics(Grant No.22JSY014).
文摘Strong-field quantum electrodynamics(SF-QED)plays a crucial role in ultraintense laser-matter interactions and demands sophisticated techniques to understand the related physics with new degrees of freedom,including spin angular momentum.To investigate the impact of SF-QED processes,we have introduced spin/polarization-resolved nonlinear Compton scattering,nonlinear Breit-Wheeler,and vacuum birefringence processes into our particle-in-cell(PIC)code.In this article,we provide details of the implementation of these SF-QED modules and share known results that demonstrate exact agreement with existing single-particle codes.By coupling normal PIC simulations with spin/polarization-resolved SF-QED processes,we create a new theoretical platform to study strong-field physics in currently running or planned petawatt or multi-petawatt laser facilities.
基金This work is supported by the National Natural Science Foundation of China(Grant Nos.11874295,12022506,U2267204,11905169,12275209,11875219,and 12171383)the Open Fund of the State Key Laboratory of High Field Laser Physics(Shanghai Institute of Optics and Fine Mechanics)+1 种基金the Foundation of Science and Technology on Plasma Physics Laboratory(Grant No.JCKYS2021212008)The work of Y.I.S.is supported by an American University of Sharjah Faculty Research(Grant No.FRG21).
文摘The rapid development of ultrafast ultraintense laser technology continues to create opportunities for studying strong-field physics under extreme conditions.However,accurate determination of the spatial and temporal characteristics of a laser pulse is still a great challenge,especially when laser powers higher than hundreds of terawatts are involved.In this paper,by utilizing the radiative spin-flip effect,we find that the spin depolarization of an electron beam can be employed to diagnose characteristics of ultrafast ultraintense lasers with peak intensities around 10^(20)–10^(22) W/cm^(2).With three shots,our machine-learning-assisted model can predict,simultaneously,the pulse duration,peak intensity,and focal radius of a focused Gaussian ultrafast ultraintense laser(in principle,the profile can be arbitrary)with relative errors of 0.1%–10%.The underlying physics and an alternative diagnosis method(without the assistance of machine learning)are revealed by the asymptotic approximation of the final spin degree of polarization.Our proposed scheme exhibits robustness and detection accuracy with respect to fluctuations in the electron beam parameters.Accurate measurements of ultrafast ultraintense laser parameters will lead to much higher precision in,for example,laser nuclear physics investigations and laboratory astrophysics studies.Robust machine learning techniques may also find applications in more general strong-field physics scenarios.
基金supported by the National Natural Science Foundation of China (Nos.11875007, 11305010)supported by the STFC Cockcroft Institute core grant
文摘A diamond-like carbon circular target is proposed to improve γ-ray emission and pair production with a laser intensity of 8×1022 W cm-2by using 2D particle-in-cell simulations with quantum electrodynamics.It is found that the circular target can enhance the density of γ-photons significantly more than a plane target, when two colliding circularly polarized lasers irradiate the target.By multi-laser irradiating the circular target, the optical trap of lasers can prevent the high energy electrons accelerated by laser radiation pressure from escaping.Hence, γ-photons with a high density of beyond 5000 ncare obtained through nonlinear Compton backscattering.Meanwhile, 2.7×1011 positrons with an average energy of 230 MeV are achieved via the multiphoton Breit-Wheeler process.Such an ultrabright γ-ray source and dense positron source can be useful in many applications.The optimal target radius and laser mismatching deviation parameters are also discussed in detail.
基金This work was supported by the Programs for the National Natural Science Foundation of China(Nos.11975316,11775312,12005305 and 61905287)the Continue Basic Scientific Research Project(Nos.WDJC-2019-02 and BJ20002501).
文摘The supersonic gas-jet target is an important experimental target for laser wakefield acceleration(LWFA),which has great potential for driving novel radiation sources such as betatron radiation and Compton scattering gamma rays.According to different electron acceleration requirements,it is necessary to provide specific supersonic gas jets with different density profiles to generate electron beams with high quality and high repetition rates.In this study,the interference images and density profiles of different gas-jet targets were obtained through a modified Nomarski interference diagnosis system.The relationships between the gas density and back pressure,nozzle structure,and other key parameters were studied.Targets with different characteristics are conducive to meeting the various requirements of LWFA.
基金supported by National Natural Science Foundation of China(NSFC)under Grant Nos.11475026,11664039 and 11305010
文摘The use of a novel double-cone funnel target with high density layers （HDL） to collimate and focus electrons is investigated by two-dimensional particle-in-cell simulations. The proposed scheme can guide, collimate and focus electron beams to smaller sizes. The collimation reasons are analyzed by the quasi-static magnetic fields generation inside the beam collimator with HDL. It is found that the energy conversion efficiency is increased by a factor of 2.2 in this new scheme in comparison with the that without HDL. Such a target structure has potential for design flexibility and prevents inefficiencies in important applications such as fast ignition, etc.
基金supported by National Natural Science Foundation of China (NSFC) under Grant No. 11475026
文摘Enhanced photon emission and pair production due to heavy ion mass in the interaction of an ultraintense laser with overdense plasmas is explored by particle-in-cell simulation. It is found that plasmas with heavier ion mass can excite a higher and broader electrostatic field, which causes the enhancement of backward photon emission. The pair yields are then enhanced due to the increase of backwards photons colliding with the incoming laser pulse. By examining the density evolution and angle distribution of each particle species, the origin of pair yield enhancement is clarified.
基金supported by the National Natural Science Foundation of China(No.52075059)the Natural Science Foundation of Chongqing(No.cstc2020jcyj-msxm X0266)。
文摘While the traditional trajectory planning methods are used in robotic belt grinding of blades with an uneven machining allowance distribution, it is hard to obtain the preferable profile accuracy and surface quality to meet the high-performance requirements of aero-engine. To solve this problem, a novel trajectory planning method is proposed in this paper by considering the developed interpolation algorithm and the machining allowance threshold. The residual height error obtained from grinding experiments of titanium alloy sample was compensated to modify the calculation model of row spacing, and a new geometric algorithm was presented to dynamically calculate the cutter contact points based on this revised calculation model and the dichotomy method. Subsequently, the off-line machining program is generated based on a double-vector controlling method to obtain an optimal contact posture. On this basis, three sets of robotic grinding tests of titanium alloy blades were conducted to investigate the advantages of the proposed method.The comparative experimental results revealed that the presented algorithm had improved the surface profile accuracy of blade by 34.2% and 55.1%, respectively. Moreover, the average machined surface roughness was achieved to 0.3 μm and the machining efficiency was obviously promoted. It is concluded that this research work is beneficial to comprehensively improve the machined quality of blades in robotic belt grinding.
文摘Fermion particle pair production in strong SU（2）-gauge chromoelectric fields is studied using the Boltzmann-Vlasov equation in a classical way. The existence of a preproduction process in a classical description is shown using the distribution evolution of non-Abelian particle production. It is interesting to find that the distribution of the particle number density is centered on two islands and shows a split on the color charge sphere as it evolves, ultimately reaching a steady state that is related to the amplitude and variation of the field.
基金Supported by the National Natural Science Foundation of China under Grant No.11475026
文摘Massless quark pair production in SU(2) gauge chromoelectric field is investigated by solving the Wigner function with back reaction. The temporal evolution of specific field and its current are obtained self consistently. For the quark distribution function, both its time and momentum dependence are studied. In particular, some interesting phenomena are found, for example, the more abundant symmetry or/and antisymmetry characteristics, the existence of the attractive basin structure and the existence of the momentum "gap" in the quark distribution and so on. All the phenomena are associated with the quark-gluon plasma oscillation, which due to the back reaction effect. The study and analysis qualitatively about the components of the Wigner function are expected to be helpful to deepen the understanding of the QCD vacuum.
