磁场与密度对等离子体柱中螺旋波及能量沉积影响的数值研究

Effect of Magnetic Field and Radical Plasma Density on Helicon Plasma Wave and Energy Deposition-A Numerical Simulation

考察在高密度、强磁化径向非均匀等离子体柱中,在径向等离子体密度分布呈不同抛物线型轮廓及轴向静磁场不断增大的情况下,等离子体柱内右旋螺旋波与左旋螺旋波的传播性质及其径向、轴向能量沉积特性。采用数值方法求解基于Maxwell方程组的耦合波方程组,得到0.02-0.1 T磁场变化区间与n0=1.2×1013cm-3、α∈（0.36,0.83）径向等离子体密度分布条件下等离子体柱内m=±1角向模螺旋波场幅值及其径向、轴向能量分布情形.计算结果表明,α减小（0.83→0.36）、B0增大（0.02→0.1 T）时,m=＋1模趋于r=0处附近传播,径向能量沉积变化极小,轴向能量沉积逐渐增强;m=-1模在一定B0范围内、α≈0.66时最大幅值传播,径向能量沉积趋向于等离子体柱表面附近,轴向能量沉积逐渐增强.其次,m=＋1模较m=-1模场幅值与能量沉积均占主导地位;m=-1模能量沉积集中于天线电离区,m=＋1模能量沉积远超于天线电离区。

The propagation and energy depositionof the plasma wave,excited by helicon antenna with a parabolic radial electron-density distribution inmagnetic field,were mathematically modeled,theoretically calculated and numerically simulated. The simulated results show that the axial magnetic field（ B0） andradial distribution of plasma density（ α） distribution significantly affect the energy deposition and radial field profile of m = 1 modes.For example,as B0 increases from 0. 02 to 0. 1 T and α decreases from 0. 83 to 0. 36,m = ＋ 1 mode mainly propagates along the axis（ r = 0）,accompanied by an increasing axial energy deposition and an almost constant radial energy deposition. However,only in a given B0 range and at α = 0. 66,the m =-1 mode propagates with its radial energy deposition approaching to the plasma column edge. The dominance of m = ＋ 1 mode includes a stronger fieldamplitude,a higher energy deposition on a much wider volume than m =- 1 mode,whose energy deposits merely around the antenna＇s ionization zone.