The Modified Friction and Diffusion Coefficients of Fokker-Planck Equation and Relaxation Rates for Non-Maxwellian Scattering

作     者：项江 李定 蔡辉山 

作者机构：CAS Key Lab of Basic Plasma PhysicsSchool of SciencesUniversity of Science and Technology of ChinaHefei 230026China 

出 版 物：《Plasma Science and Technology》 (等离子体科学和技术（英文版）)

年 卷 期：2008年第10卷第6期

页      面：661-670页

核心收录：

学科分类：07[理学] 070204[理学-等离子体物理] 0702[理学-物理学] 

基　　金：National High-Tech ICF(Inertial Confinement Fusion)Committee in China National Natural Science Foundation of China(Nos.10475076,10505021,40336052,and 10175065) 

主　　题：Fokker-Planck coefficients non-Maxwellian velocity distribution field particles velocity distribution small-angle scattering small-momentum-transfer collisions 

摘      要：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.