We examine the fast-ion driven Alfvén eigenmodes (AEs) in the frequency range 0–500 kHz during the current ramp-up phase of advanced JET plasma before the main heating starts (the preheating phase). Modelling of AEs using equilibrium reconstruction and the ideal MHD spectral code MISHKA shows that three types of mode commonly found during the preheating phase correspond to: global toroidal Alfvén eigenmodes (TAEs) found in regions of moderate to high magnetic shear; core-localized TAEs found in regions of low magnetic shear; and Alfvén cascades found in regions of zero shear. MHD spectroscopy diagnosis of the time evolution of the plasma current within the central region of the plasma and of the minimum safety factor value based upon the frequency evolution of these unstable AEs is discussed.
我们研究了先进JET等离子体电流爬升阶段（主加热开始前的预加热阶段）中，频率范围在0–500 kHz内的快离子驱动阿尔芬本征模（AEs）。利用平衡重建和理想MHD谱代码MISHKA对AEs进行建模，结果表明，预加热阶段常见的三种模分别对应：中等磁剪切区域中的全局环向阿尔芬本征模（TAEs）；低磁剪切区域中的芯部局域TAEs；以及零磁剪切区域中的阿尔芬级联。基于这些不稳定AEs的频率演化，讨论了利用MHD谱诊断等离子体中心区域电流的时间演化以及最小安全因子值。