Simulation of fast wave current drive in tokamaks in the ion cyclotron frequency range
Simulation of fast wave current drive in tokamaks in the ion cyclotron frequency range
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DOI：
10.1088/0029-5515/42/9/306
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发表时间：
2002-08
期刊：
影响因子：
3.3
通讯作者：
R. Bilato;M. Brambilla;I. Pavlenko;F. Meo
中科院分区：
文献类型：
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作者：
R. Bilato;M. Brambilla;I. Pavlenko;F. Meo
为了在离子回旋加速器频率范围内对托卡马克中的射频电流驱动进行真实的模拟，利用环面全波代码TORIC评估的波场来建立准线性电子扩散系数，然后利用最近开发的弹平均准线性Fokker-Planck动力学方程求解器QLEFOPS来求解。介绍了ASDEX Upgrade在可能的快波电流驱动实验中的应用。改变目标电子温度，背景欧姆电流，以及在相对有限的可能性，天线的指向性的影响进行了研究。结果与Ehst和Karney基于伴随法求解动力学方程对电流驱动效率参数化的预测基本一致。另一方面，为了保证两个规范之间的一致性，需要进行详细的分析，这表明了该CD方案的特点，这在一定程度上可能会限制实践中所能达到的效率。特别是，实际功率密度的归一化拟线性扩散系数对于拟线性平台的发展来说太小了。在没有超热电子的情况下，只有将天线激发的平行相速度谱定位在理论效率较差的热区附近，才能获得充分的吸收。
To perform realistic simulations of radio-frequency current drive in tokamaks in the ion cyclotron range of frequencies, the wave fields evaluated by the toroidal full-wave code TORIC have been used to build the quasilinear electron diffusion coefficient, which, in turn, is used by a recently developed solver of the bounce-averaged quasilinear Fokker-Planck kinetic equation, QLEFOPS. Applications to possible fast wave current drive experiments in ASDEX Upgrade are presented. The effects of varying the target electron temperature, the background Ohmic current, and, within the relatively limited possibilities, the directivity of the antenna have been investigated. The results are in reasonable agreement with the predictions of the parametrization of the current drive (CD) efficiency proposed by Ehst and Karney based on the adjoint method for the solution of the kinetic equation. The detailed analysis which was necessary to guarantee consistency between the two codes, on the other hand, has put into evidence characteristics of this CD scheme, which, to some extent, are likely to limit the efficiency achievable in practice. In particular, the normalized quasilinear diffusion coefficient for realistic power densities turns out to be far too small for the development of a quasilinear plateau. In the absence of suprathermal electrons, sufficient absorption can be achieved only by positioning the spectrum of parallel phase velocities excited by the antenna close to the thermal region, where the theoretical efficiency is poor.