托卡马克低混杂波电流驱动实验中低混杂波传播的解析分析

ANALYTIC STUDY OF LOWER HYBRID WAVE PROPAGATION IN TOKAMAK LHCD EXPERIMENTS

通过对小参量δ =(ω2pe/ω2 ) -1展开 ,导出了简化但普遍的低混杂波电流驱动 (LHCD)参量状态下的低混杂波色散方程 .讨论了环形效应 (环向磁场的R-1关系及磁面的Shafranov位移 )引起的平行折射率的上移或下移及慢波与快波的模转换条件 ,得到一个关于低混杂波可以向等离子体内部传播的充分条件 ,它与LHCD实验中普遍观察到的密度极限现象有密切联系 .预期的临界密度nec∝f4 / 3 B2 / 3 A4 / 3( f ,B ,A分别为波的频率、磁场强度和环径比 ) ,与圆截面托卡马克装置中LHCD实验结果较好地符合 .关于波传播和平行折射率移动的理论结果可作为子程序用于LHCD的大型计算编码 。

General but simplified dispersion relation for the lower hybrid wave in low hybrid current drive (LHCD) regime is derived by expanding technique through the small parameter δ=(ω 2 pe / ω 2) -1 .The upward and the downward shifts of the parallel refractive index,and the relevant mode conversion due to toroidal effects (such as the R -1 dependence of the toroidal magnetic field and the Shafnanov shift of magnetic surfaces) are discussed.A sufficient condition for the wave that is possible to penetrate into the inner region of the plasma column is obtained,which has a relationship with the experimentally observed LHCD density limit.A scaling about the critical density is found to be n ec ∝ f 4/3 B 2/3 A 4/3 ,with f,B,A being the wave frequency,the magnetic field and the aspect ratio,respectively.There exists a quite good agreement between theory and experiments.The simplified equations for wave propagation can be used as a subroutine in a complete LHCD code.