利用Mirnov探针和静电势涨落测量表征TJ-II仿星器中NBI驱动的剪切阿尔芬波
Characterization of NBI-driven shear Alfvén waves in the TJ-II stellarator using Mirnov probes and electrostatic potential fluctuation measurements
AI总结：
首次实验测量TJ-II仿星器中剪切阿尔芬波的环向模数，通过改变磁位形和旋转变换剖面研究NBI驱动模式，结合Mirnov探针阵列、重离子束探针表征模式结构，建立数据库助力理论验证。
摘要：
我们首次报告了TJ-II仿星器中剪切阿尔芬波环向模数的实验测量结果。在三种不同磁位形下开展了一系列实验，研究反向中性束注入（counter-NBI）驱动的模式。同向和反向电子回旋电流驱动（co- and counter-electron-cyclotron current drive）用于修改旋转变换（\u03c9bar）剖面，从而使不同频率和模数的阿尔芬本来征模集合失稳。为表征模式的空间结构，我们使用了两个Mirnov探针阵列：一个用于测量极向模数，另一个是最近投入使用的螺旋三轴阵列，用于测量环向模数。采用工作在径向扫描模式的重离子束探针（heavy ion beam probe）表征模式的径向位置。我们发现，在验证研究中至关重要的\u03c9bar诱导变化无法通过运动斯塔克效应（motional Stark effect）实验测量，因此转而在柱几何中求解屏蔽电流扩散方程来估算这些变化。我们使用\texttt{STELLGAP}计算了选定案例的不可压缩剪切阿尔芬连续谱，并发现与观测结果具有合理的一致性。我们创建了包含观测模式的数据库，以供未来理论验证工作使用。
英文摘要：
We present the first experimental measurements of the toroidal mode number of shear Alfvén waves in the TJ-II stellarator. A series of experiments were carried out in three different magnetic configurations to investigate counter-NBI driven modes. Co- and counter- electron-cyclotron current drive was used to modify the rotational transform (\iotabar) profile leading to the destabilization of a varied set of Alfvén eigenmodes with different frequencies and mode numbers. To characterize the spatial structure of the modes we have used two Mirnov probe arrays, one dedicated to the measurement of the poloidal mode number and the other, a recently commissioned helical tri-axial array, dedicated to the measurement of the toroidal mode number. A heavy ion beam probe, operated in radial sweep mode, was employed to characterize the radial location of the modes. We show that the induced changes in \iotabar, that are fundamental when it comes to validation studies, cannot be measured experimentally with motional Stark effect so, instead, the shielding current diffusion equation is solved in cylindrical geometry to estimate these changes. We calculate the incompressible shear Alfvén continuum for selected cases using \texttt{STELLGAP} and find reasonable consistency with observations. A database with the observed modes has been created, so that it can be used in future work for theory validation purposes.
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