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
Inverse bremsstrahlung absorption in laser-heated plasmas is studied using the Fokker–Planck equation in the low-field limit.Compared with the commonly used fitting formulas of Langdon and Matte et al.,our work emplo...Inverse bremsstrahlung absorption in laser-heated plasmas is studied using the Fokker–Planck equation in the low-field limit.Compared with the commonly used fitting formulas of Langdon and Matte et al.,our work employs fewer approximations and provides more accurate predictions for the super-Gaussian orderβand the heating rate.Simulation results show that the super-Gaussian order is generally lower than the fitting results of Matte et al.,which leads to an increase in absorption.However,we find two other factors that reduce absorption:the high-order term of the collision frequency and the effects caused by high laser intensity.Therefore,the final simulated absorption can either be higher or lower,depending on the conditions.These phenomena are theoretically analyzed using the Fokker–Planck equation.Fitting formulas are proposed for the super-Gaussian order and the heating rate,showing a discrepancy within∼10%of the simulation results.We also compare the simulation results with the experimental results from several recent papers.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supported by the Natural Science Foundation of China(Grant Nos.12035002,12405235,and U2430207)the China Postdoctoral Science Foundation(Grant No.2023M740336)the CAEP foundation(Grant No.YZJJZQ2023020).
文摘Inverse bremsstrahlung absorption in laser-heated plasmas is studied using the Fokker–Planck equation in the low-field limit.Compared with the commonly used fitting formulas of Langdon and Matte et al.,our work employs fewer approximations and provides more accurate predictions for the super-Gaussian orderβand the heating rate.Simulation results show that the super-Gaussian order is generally lower than the fitting results of Matte et al.,which leads to an increase in absorption.However,we find two other factors that reduce absorption:the high-order term of the collision frequency and the effects caused by high laser intensity.Therefore,the final simulated absorption can either be higher or lower,depending on the conditions.These phenomena are theoretically analyzed using the Fokker–Planck equation.Fitting formulas are proposed for the super-Gaussian order and the heating rate,showing a discrepancy within∼10%of the simulation results.We also compare the simulation results with the experimental results from several recent papers.
