【摘要】 研究了在托卡马克装置中中性束注入时快离子自举电流的产生。利用快离子分布函数在两小增量δ=ρp/a(ρp是极向拉莫尔半径,a是小半径)和δ*=τB/τs(τB是俘获粒子反弹周期,τs是慢化时间)下进行展开的方法求解漂移动力学方程;给出了快离子自举电流的一般表达式。计算了圆截面大纵横比托卡马克中快离子自举电流密度分布和总的快离子自举电流的大小,研究表明:在中性束垂直注入时快离子自举电流约占总电流的10%;自举电流的大小既敏感地依赖于中性束注入的角度——平行注入时较小、接近垂直时迅速增大,同时也较强的依赖于快离子的产生速度与临界速度的比值,即v b vc,而v b2∝E(束能量);自举电流的大小随注入束能量的增加而迅速增大。更多还原

【Abstract】 To investigate the bootstrap current due to fast ions produced by neutral beam injection into tokamak,a drift kinetic equation is established and solved by doubly expanding the fast ion distribution function in two small parameters δ = ρp/a(ρ pis poloidal Larmor radius,a is the minor radius) and δ * = τ B/τs(τB is bounce period of trapped fast-ion,τ s is the slowing down time),then the expression for bootstrap current is derived,and the bootstrap current density and total bootstrap current are obtained numerically in a large aspect ratio tokamak with circular cross section.The results show that the bootstrap current depends strongly on both injection angle and the ratio of v b/vc(v b is birth velocity and v b2∝ E(beam energy),v c is critical velocity),the ratio of the bootstrap current to the total current is about 10% in the perpendicular injection and is small in the parallel injection,the bootstrap current rapidly increases when the injection-angle reaches perpendicular and the beam energy increases.更多还原