Abstract—

It is recognized that the filaments have a significant effect on the anomalous energy and particle transport in the tokamak periphery. They are actively investigated using various diagnostics in this regard. Recently studies of filaments using the Doppler backscattering method have been performed in the Globus-M and the ASDEX-Upgrade tokamaks. Backscattering from filaments manifests itself as a burst of quasi-coherent fluctuations of the signals of detectors. Such signals are easy to describe in the Born approximation using the diagnostic weighting function. However, the filaments in tokamaks differ noticeably in their size and intensity. With an increase in the amplitude of the filaments, it is necessary to consider the transition from linear scattering to nonlinear one and further up to the transition from backscattering to reflection from a moving filament. This problem can be solved only using a full wave code. Our simulation was carried out using the finite-difference time-domain code IPF-FD3D in slab geometry. We did not resort to using well-known non-linear MHD codes to determine filament parameters. In the simulation artificial filament-like perturbations were used, the parameters of which varied over a wide range. Modeling Doppler backscattering signal was focused on the identification of the influence of the amplitude of the filament and its size on the shape and the size of the Doppler backscattering output signal. The results obtained largely explain the similarity of the IQ detector data registered in different tokamaks.

中文翻译：

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细丝的多普勒反向散射全波建模

摘要-

公认的是，细丝对托卡马克外围的异常能量和颗粒传输具有显着影响。在这方面，他们使用各种诊断方法进行了积极的调查。最近在Globus-M和ASDEX-Upgrade托卡马克中已经进行了使用多普勒反向散射法研究细丝的研究。灯丝的反向散射本身表现为探测器信号的准相干波动的爆发。使用诊断加权函数可以很容易地在Born近似中描述此类信号。然而，托卡马克中的细丝在尺寸和强度上明显不同。随着细丝振幅的增加，有必要考虑从线性散射到非线性散射的过渡，以及从反向散射到运动的灯丝反射的过渡。仅使用全波码可以解决此问题。我们在平板几何中使用有限差分时域代码IPF-FD3D进行了仿真。我们没有使用众所周知的非线性MHD代码来确定灯丝参数。在仿真中，使用了人造丝状微扰，其参数在很大范围内变化。对多普勒反向散射信号进行建模的重点是确定灯丝幅度及其大小对多普勒反向散射输出信号的形状和大小的影响。