Stimulated Raman particle-in-cell （PIC） simulations scattering （SRS） in a low-density The backward stimulated Raman plasma slab is investigated by scattering （B-SRS） dominates initially and erodes the head of th...Stimulated Raman particle-in-cell （PIC） simulations scattering （SRS） in a low-density The backward stimulated Raman plasma slab is investigated by scattering （B-SRS） dominates initially and erodes the head of the pump wave, while the forward stimulated Raman scattering （F-SRS） subsequently develops and is located at the rear part of the slab. Two-stage electron acceleration may be more efficient due to the coexistence of these two instabilities. The B-SRS plasma wave with low phase velocities can accelerate the background electrons which may be further boosted to higher energies by the F-SRS plasma wave with high phase velocities. The simulations show that the peaks of the main components in both the frequency and wave number spectra occur at the positions estimated from the phase-matching conditions.展开更多
Stimulated Raman scattering(SRS)in a longitudinal magnetized plasma is studied by theoretical analysis and kinetic simulation.The linear growth rate derived via one-dimensional fluid theory shows the dependence on the...Stimulated Raman scattering(SRS)in a longitudinal magnetized plasma is studied by theoretical analysis and kinetic simulation.The linear growth rate derived via one-dimensional fluid theory shows the dependence on the plasma density,electron temperature,and magnetic field intensity.One-dimensional particle-in-cell simulations are carried out to examine the kinetic evolution of SRS under low magnetic intensity of w_c/w_0<0.01.There are two density regions distinguished in which the absolute growth of enveloped electrostatic waves and spectrum present quite different characteristics.In a relatively low-density plasma(ne~0.20 nc),the plasma wave presents typical absolute growth and the magnetic field alleviates linear SRS.While in the plasma whose density is near the cut-off point(ne~0.23 nc),the magnetic field induces a spectral splitting of the backscattering and forward-scattering waves.It has been observed in simulations and verified by theoretical analysis.Due to this effect,the onset of reflectivity delays,and the plasma waves form high-frequency oscillation and periodic envelope structure.The split wavenumber Dk/k0 is proportional to the magnetic field intensity and plasma density.These studies provide novel insight into the kinetic behavior of SRS in magnetized plasmas.展开更多
Absolute instability modes due to secondary scattering of stimulated Raman scattering (SRS) in a large nonuniform plasma are studied theoretically and numerically. The backscattered light of convective SRS can be cons...Absolute instability modes due to secondary scattering of stimulated Raman scattering (SRS) in a large nonuniform plasma are studied theoretically and numerically. The backscattered light of convective SRS can be considered as a pump light with a finite bandwidth. The different frequency components of the backscattered light can be coupled to develop absolute SRS instability near their quarter-critical densities via rescattering process. The absolute SRS mode develops a Langmuir wave with a high phase velocity of about c/■ with c the light speed in vacuum. Given that most electrons are at low velocities in the linear stage, the absolute SRS mode grows with very weak Landau damping. When the interaction evolves into the nonlinear regime, the Langmuir wave can heat abundant electrons up to a few hundred ke V via the SRS rescattering. Our theoretical model is validated by particle-in-cell simulations. The absolute instabilities may play a considerable role in the experiments of inertial confinement fusion.展开更多
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
Stimulated Raman scattering(SRS)in plasma in a non-eigenmode regime is studied theoretically and numerically.Different from normal SRS with the eigen electrostatic mode excited,the non-eigenmode SRS is developed at pl...Stimulated Raman scattering(SRS)in plasma in a non-eigenmode regime is studied theoretically and numerically.Different from normal SRS with the eigen electrostatic mode excited,the non-eigenmode SRS is developed at plasma density ne>0.25nc when the laser amplitude is larger than a certain threshold.To satisfy the phase-matching conditions of frequency and wavenumber,the excited electrostatic mode has a constant frequency around half of the incident light frequency ω0/2,which is no longer the eigenmode of electron plasma wave ωpe.Both the scattered light and the electrostatic wave are trapped in plasma with their group velocities being zero.Super-hot electrons are produced by the non-eigen electrostatic wave.Our theoretical model is validated by particle-in-cell simulations.The SRS driven in this non-eigenmode regime is an important laser energy loss mechanism in the laser plasma interactions as long as the laser intensity is higher than 10^15 W/cm^2.展开更多
基金supported by National High Technology ICF Committee in Chinathe National Natural Science Fund of China(Nos.10675024,10335020,10375011 and 10576007)the Laboratory of Computational Physics(No.51479050205ZW0905)
文摘Stimulated Raman particle-in-cell （PIC） simulations scattering （SRS） in a low-density The backward stimulated Raman plasma slab is investigated by scattering （B-SRS） dominates initially and erodes the head of the pump wave, while the forward stimulated Raman scattering （F-SRS） subsequently develops and is located at the rear part of the slab. Two-stage electron acceleration may be more efficient due to the coexistence of these two instabilities. The B-SRS plasma wave with low phase velocities can accelerate the background electrons which may be further boosted to higher energies by the F-SRS plasma wave with high phase velocities. The simulations show that the peaks of the main components in both the frequency and wave number spectra occur at the positions estimated from the phase-matching conditions.
基金supported by the National Key Research and Development Program of China (No. 2016YFA0401100)the Strategic Priority Re-search Program of Chinese Academy of Sciences (No. XDA25050700)+1 种基金the Scientific Research Foundation of Hunan Provincial Education Department (No. 20A042)National Natural Science Foundation of China (Nos. 11805062, 11675264, 11774430)
文摘Stimulated Raman scattering(SRS)in a longitudinal magnetized plasma is studied by theoretical analysis and kinetic simulation.The linear growth rate derived via one-dimensional fluid theory shows the dependence on the plasma density,electron temperature,and magnetic field intensity.One-dimensional particle-in-cell simulations are carried out to examine the kinetic evolution of SRS under low magnetic intensity of w_c/w_0<0.01.There are two density regions distinguished in which the absolute growth of enveloped electrostatic waves and spectrum present quite different characteristics.In a relatively low-density plasma(ne~0.20 nc),the plasma wave presents typical absolute growth and the magnetic field alleviates linear SRS.While in the plasma whose density is near the cut-off point(ne~0.23 nc),the magnetic field induces a spectral splitting of the backscattering and forward-scattering waves.It has been observed in simulations and verified by theoretical analysis.Due to this effect,the onset of reflectivity delays,and the plasma waves form high-frequency oscillation and periodic envelope structure.The split wavenumber Dk/k0 is proportional to the magnetic field intensity and plasma density.These studies provide novel insight into the kinetic behavior of SRS in magnetized plasmas.
基金supported by the National Natural Science Foundation of China(Nos.11775144 and1172109)the Natural Science Foundation of Shanghai(No.19YF1453200)
文摘Absolute instability modes due to secondary scattering of stimulated Raman scattering (SRS) in a large nonuniform plasma are studied theoretically and numerically. The backscattered light of convective SRS can be considered as a pump light with a finite bandwidth. The different frequency components of the backscattered light can be coupled to develop absolute SRS instability near their quarter-critical densities via rescattering process. The absolute SRS mode develops a Langmuir wave with a high phase velocity of about c/■ with c the light speed in vacuum. Given that most electrons are at low velocities in the linear stage, the absolute SRS mode grows with very weak Landau damping. When the interaction evolves into the nonlinear regime, the Langmuir wave can heat abundant electrons up to a few hundred ke V via the SRS rescattering. Our theoretical model is validated by particle-in-cell simulations. The absolute instabilities may play a considerable role in the experiments of inertial confinement fusion.
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This work was supported by the Natural Science Foundation of Shanghai(No.19YF1453200)the Strategic Priority Research Program of Chinese Academy of Sciences(Nos.XDA25050800 and XDA25050100)+1 种基金the National Natural Science Foundation of China(Nos.11775144 and 1172109)the National Science and Technology Innovation Foundation of the Chinese Academy of Sciences(No.CXJJ-20S015).
文摘Stimulated Raman scattering(SRS)in plasma in a non-eigenmode regime is studied theoretically and numerically.Different from normal SRS with the eigen electrostatic mode excited,the non-eigenmode SRS is developed at plasma density ne>0.25nc when the laser amplitude is larger than a certain threshold.To satisfy the phase-matching conditions of frequency and wavenumber,the excited electrostatic mode has a constant frequency around half of the incident light frequency ω0/2,which is no longer the eigenmode of electron plasma wave ωpe.Both the scattered light and the electrostatic wave are trapped in plasma with their group velocities being zero.Super-hot electrons are produced by the non-eigen electrostatic wave.Our theoretical model is validated by particle-in-cell simulations.The SRS driven in this non-eigenmode regime is an important laser energy loss mechanism in the laser plasma interactions as long as the laser intensity is higher than 10^15 W/cm^2.
