In this paper, a new method to derive the Fokker-Planck coefficients defined by a non-Maxwellian velocity distribution function for the field particles is presented. The three- fold integral and the new Debye cutoff p...In this paper, a new method to derive the Fokker-Planck coefficients defined by a non-Maxwellian velocity distribution function for the field particles is presented. The three- fold integral and the new Debye cutoff parameter, which were introduced by CHANG and LI, are applied. Therefore, divergence difficulties and the customary replacement of relative velocity g by thermal velocity vth are naturally avoided. The probability function P（v, Av） for non- Maxwellian scattering is derived by the method of choosing velocity transfer Av, which is a true measure of collision intensity, as an independent variable. The method enables the difference between small-angle scattering and small-momentum-transfer collisions of the inverse-square force to be well clarified. With the help of the probability function, the Fokker-Planck coefficients are obtained by a normal original Fokker-Planck approach. The friction and diffusion coefficients of the Fokker-Planck equation are modified for non-Maxwellian scattering and are used to investigate the relaxation processes for the weakly coupled plasma. The profiles of the relaxation rates show that the slowing down and deflection processes are weakened in the conditions of non-Maxwellian scattering.展开更多
Effect of electron-ion collision on stimulated Raman backward scattering （SRBS） spectrum are investigated by numerical simulations. In the given parameters and plasma condition, the growth rates of SRBS are found to...Effect of electron-ion collision on stimulated Raman backward scattering （SRBS） spectrum are investigated by numerical simulations. In the given parameters and plasma condition, the growth rates of SRBS are found to strongly depend on the electron density, and the gap in the SRBS spectrum corresponding to the high electron density could be explained by the collisional damping. In the low density region, a much higher Landau damping estimated by the linear theory makes the collisional damping negligible. However, the present results show that, collisions play a even more important role than known in the linear theory.展开更多
In this paper, a solution to the Fokker-Planck equation is presented, which is extended to the field particles＇ high-energy-tail non-Maxwellian velocity distribution function in transport theory. Based on the correct...In this paper, a solution to the Fokker-Planck equation is presented, which is extended to the field particles＇ high-energy-tail non-Maxwellian velocity distribution function in transport theory. Based on the correct physical concept of collision intensity, introduced by CHANG and LI, the electrical conductivities for like-particles collisions are obtained in different conditions. The modified Fokker-Planck coefficients for non-Maxwellian scattering are applied in the study. It is found that the parallel part of the collision operator plays an important role. The non-Maxwellian scattering will stimulate the transport processes in various degrees with mutative deviation parameters.展开更多
The propagation of light waves in an underdense plasma is studied using one-dimensional Vlasov-Maxwell numerical simulation. It is found that the light waves can be scattered by electron plasma waves as well as other ...The propagation of light waves in an underdense plasma is studied using one-dimensional Vlasov-Maxwell numerical simulation. It is found that the light waves can be scattered by electron plasma waves as well as other heavily and weakly damping electron wave modes, corresponding to stimulated Raman and Brilluoin-like scatterings. The stimu- lated electron acoustic wave scattering is also observed as a high scattering level. High frequency plasma wave scattering is also observed. These electron electrostatic wave modes are due to a non-thermal electron distribution produced by the wave-particle interactions. The collision effects on stimulated electron acoustic wave and the laser intensity effects on the scattering spectra are also investigated.展开更多
基金National High-Tech ICF(Inertial Confinement Fusion)Committee in ChinaNational Natural Science Foundation of China(Nos.10475076,10505021,40336052,and 10175065)
文摘In this paper, a new method to derive the Fokker-Planck coefficients defined by a non-Maxwellian velocity distribution function for the field particles is presented. The three- fold integral and the new Debye cutoff parameter, which were introduced by CHANG and LI, are applied. Therefore, divergence difficulties and the customary replacement of relative velocity g by thermal velocity vth are naturally avoided. The probability function P（v, Av） for non- Maxwellian scattering is derived by the method of choosing velocity transfer Av, which is a true measure of collision intensity, as an independent variable. The method enables the difference between small-angle scattering and small-momentum-transfer collisions of the inverse-square force to be well clarified. With the help of the probability function, the Fokker-Planck coefficients are obtained by a normal original Fokker-Planck approach. The friction and diffusion coefficients of the Fokker-Planck equation are modified for non-Maxwellian scattering and are used to investigate the relaxation processes for the weakly coupled plasma. The profiles of the relaxation rates show that the slowing down and deflection processes are weakened in the conditions of non-Maxwellian scattering.
基金supported by National Natural Science Foundation of China (Nos. 10975023, 10935003)the Sci. & Tech. Funds of CAEP (No. 2010A0102004)the State Key Development Program for Basic Research Program of China(No. 2007CB814802)
文摘Effect of electron-ion collision on stimulated Raman backward scattering （SRBS） spectrum are investigated by numerical simulations. In the given parameters and plasma condition, the growth rates of SRBS are found to strongly depend on the electron density, and the gap in the SRBS spectrum corresponding to the high electron density could be explained by the collisional damping. In the low density region, a much higher Landau damping estimated by the linear theory makes the collisional damping negligible. However, the present results show that, collisions play a even more important role than known in the linear theory.
基金supported by National High-Tech ICF Committee in ChinaNational Natural Science Foundation of China(Nos.10475076,10505021,40336052,and 10175065)
文摘In this paper, a solution to the Fokker-Planck equation is presented, which is extended to the field particles＇ high-energy-tail non-Maxwellian velocity distribution function in transport theory. Based on the correct physical concept of collision intensity, introduced by CHANG and LI, the electrical conductivities for like-particles collisions are obtained in different conditions. The modified Fokker-Planck coefficients for non-Maxwellian scattering are applied in the study. It is found that the parallel part of the collision operator plays an important role. The non-Maxwellian scattering will stimulate the transport processes in various degrees with mutative deviation parameters.
基金supported by the National High-Tech ICF Committee of China,the National Natural Science Foundation of China(Grant Nos. 10975023,10835003,10935003 and 10974022)the National Basic Research Program (Grant Nos. 2007CB815101,2007CB814802 and 2010CB832904)
文摘The propagation of light waves in an underdense plasma is studied using one-dimensional Vlasov-Maxwell numerical simulation. It is found that the light waves can be scattered by electron plasma waves as well as other heavily and weakly damping electron wave modes, corresponding to stimulated Raman and Brilluoin-like scatterings. The stimu- lated electron acoustic wave scattering is also observed as a high scattering level. High frequency plasma wave scattering is also observed. These electron electrostatic wave modes are due to a non-thermal electron distribution produced by the wave-particle interactions. The collision effects on stimulated electron acoustic wave and the laser intensity effects on the scattering spectra are also investigated.
