EAST反剪切阿尔芬本征模与环向阿尔芬本征模耦合机理实验研究

The reversed shear Alfven eigenmodes (RSAEs) have been observed on some devices in last decades: e. g. JET, ASDEX, DIII-D, NSTX, and HL-2A. Many progress has been made related to RSAEs prediction and their impact on plasma confinement theoretically and experimentally. Generally, RSAEs are observed in tokamak discharges with a nearly flat or reversed q profile. The RSAEs exhibit an upward frequency sweeping, and interact with toroidal Alfven eigenmodes (TAEs). The instabilities have been shown to affect the energetic particle population leading to enhanced transport, losses, and modification of the pressure and current profiles. These issues are critical not only to the performance of future burning plasma experiments, but also to the survivability of first wall components. Although many observations of RSAEs have been reported, the physical mechanism of RSAEs-TAEs transition is still not conclusive. Moreover, less investigation is presented on the electron transport during RSAEs-TAEs transition. Recently, various auxiliary heating methods have been applied on EAST, including LHW, ECCD, ICRF, NBI. Besides, a large set of diagnostics for fast particle mode studies is available, such as reflectometry, ECE, SXR, Mirnov coils array, and so on. Hence, the studies of the triggering mechanism of RSAEs, their interaction with TAEs and the effect of electron transport are at the right time. These studies can also help us to understand the RSAEs-TAEs coupling process including the impact of electron transport in fusion devices.

国内外一些磁约束装置在实验中都观察到了反剪切阿尔芬本征模(RSAEs)，它形成于等离子体芯部弱/反剪切区域，起始频率在GAMs的特征频率附近，演化特征与安全因子极小值有关。通常RSAEs上变频后会逐渐与环向阿尔芬本征模(TAEs)相互耦合。已有结果表明耦合过程快离子再分布导致大量快离子损失，但从实验角度研究耦合机制却结果甚少。. EAST托卡马克已实现了多种波以及中性束加热和电流驱动手段，多项诊断也完成了升级，在实验中初步观测到RSAEs的演化。但实验中关于RSAEs的实验分析以及与TAEs耦合机理方面的实验研究仍处于起步阶段。本项目将利用已有诊断并结合NOVA-K等数值模拟，在EAST上探索RSAEs触发及演化的参数区间，开展RSAEs-TAEs耦合机理的实验研究，分析耦合过程中电子输运的变化。这些研究对于理解RSAEs-TAEs耦合的物理机制及电子输运的影响具有重要意义。

课题研究分为诊断发展和实验研究两个部分。在诊断发展中，我们在EAST装置上研制了多道相关反射计系统，实现了EAST边界湍流径向和极向的同时测量，促进了EAST台基区湍流输运的物理研究。在实验研究方面，本课题分析了EAST首次观测到在H模期间的反剪切阿尔芬本征模（RSAE）结构，并且发现RSAE的特征频率会受到ELM的调制作用。这说明等离子体芯部的RSAE结构与边界的ELM之间存在长程相关作用。引起RSAE特征频率的原因可能是ELM崩塌使得等离子体旋转减小或者安全因子最小值的增加。此外我们发现在内部输运垒行程和演化过程中，RSAE与TAE模的相互转化，这对我们理解内部输运垒的形成和维持提供了丰富的实验依据。.除此之外，在W7-X仿星器装置上我们研究了边界相干模的特征，分析了三维磁拓扑结构对边界湍流结构的影响。