Generation of nonlinear structures,such as stimulated Raman side scattering waves,post-solitons and electron vortices,during ultra-short intense laser pulse transportation in near-critical-density(NCD)plasmas is studi...Generation of nonlinear structures,such as stimulated Raman side scattering waves,post-solitons and electron vortices,during ultra-short intense laser pulse transportation in near-critical-density(NCD)plasmas is studied by using multidimensional particle-in-cell(PIC)simulations.In two-dimensional geometries,both P-and S-polarized laser pulses are used to drive these nonlinear structures and to check the polarization effects on them.In the S-polarized case,the scattered waves can be captured by surrounding plasmas leading to the generation of post-solitons,while the main pulse excites convective electric currents leading to the formation of electron vortices through Kelvin-Helmholtz instability(KHI).In the P-polarized case,the scattered waves dissipate their energy by heating surrounding plasmas.Electron vortices are excited due to the hosing instability of the drive laser.These polarization dependent physical processes are reproduced in two different planes perpendicular to the laser propagation direction in three-dimensional simulation with linearly polarized laser driver.The current work provides inspiration for future experiments of laser-NCD plasma interactions.展开更多
Under Lagrange coordinates, the relativistic spherical plasma wave in a collisional and warm plasma is discussed theoretically. Within the Lagrange coordinates and using the Maxwell and hydrodynamics equations, a wave...Under Lagrange coordinates, the relativistic spherical plasma wave in a collisional and warm plasma is discussed theoretically. Within the Lagrange coordinates and using the Maxwell and hydrodynamics equations, a wave equation describing the relativistic spherical wave is derived. The damped oscillating spherical wave solution is obtained analytically using the perturbation theory. Because of the coupled effects of spherical geometry,thermal pressure, and collision effect, the electron damps the periodic oscillation. The oscillation frequency and the damping rate of the wave are related to not only the collision and thermal pressure effect but also the space coordinate. Near the center of the sphere, the thermal pressure significantly reduces the oscillation period and the damping rate of the wave, while the collision effect can strongly influence the damping rate. Far away from the spherical center, only the collision effect can reduce the oscillation period of the wave, while the collision effect and thermal pressure have weak influence on the damping rate.展开更多
The energy and trajectory of the electron, which is irradiated by a high-power laser pulse in a cylindrical plasma channel with a uniform positive charge and a uniform negative current, have been analyzed in terms of ...The energy and trajectory of the electron, which is irradiated by a high-power laser pulse in a cylindrical plasma channel with a uniform positive charge and a uniform negative current, have been analyzed in terms of a single-electron model of direct laser acceleration. We find that the energy and trajectory of the electron strongly depend on the positive charge density, the negative current density, and the intensity of the laser pulse. The electron can be accelerated significantly only when the positive charge density, the negative current density, and the intensity of the laser pulse are in suitable ranges due to the dephasing rate between the wave and electron motion. Particularly, when their values satisfy a critical condition. the electron can stay in phase with the laser and gain the largest energy from the laser. With the enhancement of the electron energy, strong modulations of the relativistic factor cause a considerable enhancement of the electron transverse oscillations across the channel, which makes the electron trajectory become essentially three-dimensional, even if it is flat at the early stage of the acceleration.展开更多
By using a high-intensity flying focus laser,the dephasingless[Phys.Rev.Lett.124134802(2020)]or phase-locked[Nat.Photon.14475(2020)]laser wakefield acceleration(LWFA)can be realized,which may overcome issues of laser ...By using a high-intensity flying focus laser,the dephasingless[Phys.Rev.Lett.124134802(2020)]or phase-locked[Nat.Photon.14475(2020)]laser wakefield acceleration(LWFA)can be realized,which may overcome issues of laser diffraction,pump depletion,and electron dephasing which are always suffered in usual LWFA.The scheme thus has the potentiality to accelerate electrons to Te V energy in a single acceleration stage.However,the controlled electron injection has not been self-consistently included in such schemes.Only external injection was suggested in previous theoretical studies,which requires other accelerators and is relatively difficulty to operate.Here,we numerically study the actively controlled density transition injection in phase-locked LWFA to get appropriate density profiles for amount of electron injection.The study shows that compared with LWFA driven by lasers with fixed focus,a larger plasma density gradient is necessary.Electrons experience both transverse and longitudinal loss during acceleration due to the superluminal group velocity of the driver and the variation of the wakefield structure.Furthermore,the periodic deformation and fracture of the flying focus laser in the high-density plasma plateau make the final injected charge also depend on the beginning position of the density downramp.Our studies show a possible way for amount of electron injection in LWFA driven by flying focus lasers.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11991074,11774227,12005287,and 12135009)NSAF of China(Grant No.U1930111)+1 种基金the Natural Science Foundation of Shandong Province,China(Grant No.ZR2019ZD44)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDA25000000 and XDA25050800)。
文摘Generation of nonlinear structures,such as stimulated Raman side scattering waves,post-solitons and electron vortices,during ultra-short intense laser pulse transportation in near-critical-density(NCD)plasmas is studied by using multidimensional particle-in-cell(PIC)simulations.In two-dimensional geometries,both P-and S-polarized laser pulses are used to drive these nonlinear structures and to check the polarization effects on them.In the S-polarized case,the scattered waves can be captured by surrounding plasmas leading to the generation of post-solitons,while the main pulse excites convective electric currents leading to the formation of electron vortices through Kelvin-Helmholtz instability(KHI).In the P-polarized case,the scattered waves dissipate their energy by heating surrounding plasmas.Electron vortices are excited due to the hosing instability of the drive laser.These polarization dependent physical processes are reproduced in two different planes perpendicular to the laser propagation direction in three-dimensional simulation with linearly polarized laser driver.The current work provides inspiration for future experiments of laser-NCD plasma interactions.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11865014,11764039,11765017,11475027,11274255 and 11305132the Natural Science Foundation of Gansu Province under Grant No 17JR5RA076the Scientific Research Project of Gansu Higher Education under Grand No 2016A-005
文摘Under Lagrange coordinates, the relativistic spherical plasma wave in a collisional and warm plasma is discussed theoretically. Within the Lagrange coordinates and using the Maxwell and hydrodynamics equations, a wave equation describing the relativistic spherical wave is derived. The damped oscillating spherical wave solution is obtained analytically using the perturbation theory. Because of the coupled effects of spherical geometry,thermal pressure, and collision effect, the electron damps the periodic oscillation. The oscillation frequency and the damping rate of the wave are related to not only the collision and thermal pressure effect but also the space coordinate. Near the center of the sphere, the thermal pressure significantly reduces the oscillation period and the damping rate of the wave, while the collision effect can strongly influence the damping rate. Far away from the spherical center, only the collision effect can reduce the oscillation period of the wave, while the collision effect and thermal pressure have weak influence on the damping rate.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11475027,11765017,11764039,11305132,and 11274255)the Natural Science Foundation of Gansu Province,China(Grant No.17JR5RA076)the Scientific Research Project of Gansu Higher Education,China(Grant No.2016A-005)
文摘The energy and trajectory of the electron, which is irradiated by a high-power laser pulse in a cylindrical plasma channel with a uniform positive charge and a uniform negative current, have been analyzed in terms of a single-electron model of direct laser acceleration. We find that the energy and trajectory of the electron strongly depend on the positive charge density, the negative current density, and the intensity of the laser pulse. The electron can be accelerated significantly only when the positive charge density, the negative current density, and the intensity of the laser pulse are in suitable ranges due to the dephasing rate between the wave and electron motion. Particularly, when their values satisfy a critical condition. the electron can stay in phase with the laser and gain the largest energy from the laser. With the enhancement of the electron energy, strong modulations of the relativistic factor cause a considerable enhancement of the electron transverse oscillations across the channel, which makes the electron trajectory become essentially three-dimensional, even if it is flat at the early stage of the acceleration.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11991074,12225505 and12135009)。
文摘By using a high-intensity flying focus laser,the dephasingless[Phys.Rev.Lett.124134802(2020)]or phase-locked[Nat.Photon.14475(2020)]laser wakefield acceleration(LWFA)can be realized,which may overcome issues of laser diffraction,pump depletion,and electron dephasing which are always suffered in usual LWFA.The scheme thus has the potentiality to accelerate electrons to Te V energy in a single acceleration stage.However,the controlled electron injection has not been self-consistently included in such schemes.Only external injection was suggested in previous theoretical studies,which requires other accelerators and is relatively difficulty to operate.Here,we numerically study the actively controlled density transition injection in phase-locked LWFA to get appropriate density profiles for amount of electron injection.The study shows that compared with LWFA driven by lasers with fixed focus,a larger plasma density gradient is necessary.Electrons experience both transverse and longitudinal loss during acceleration due to the superluminal group velocity of the driver and the variation of the wakefield structure.Furthermore,the periodic deformation and fracture of the flying focus laser in the high-density plasma plateau make the final injected charge also depend on the beginning position of the density downramp.Our studies show a possible way for amount of electron injection in LWFA driven by flying focus lasers.
