Alfvn eigenmodes (AEs) and energetic particle modes (EPMs) have been observed in EAST neutral beam injection plasma with the presence of heavy tungsten impurity in the core region. The AEs are identified as toroidal Alfvn eigenmodes (TAEs) with roughly constant frequency f _TAE ∼ 100kHz and a special set of AEs with frequency chirping up from frequency f _AE ∼ 70kHz to f _AE ∼ 100kHz. The frequency of EPMs is around f _EPM ∼ 60kHz, exhibiting with frequency chirping down feature. A transition from EPMs to AEs is found, and the location and mode numbers are measured by experimental diagnostics. Hybrid simulations with the global kinetic-magnetohydrodynamic code M3D-K have been carried out to investigate the observed AEs and EPMs, and linear simulations find the EPM with toroidal mode number n = 2 and poloidal mode number m = 3. Nonlinear simulations show that the EPM frequency chirps down nonlinearly, and then two modes emerge with frequencies around 72.7 kHz and 88.0 kHz: the mode with higher frequency is a TAE, and the other mode is an EPM. Afterward, the TAE disappears quickly with the frequency almost unchanged, and the EPM with lower frequency chirps down continuously. The mode frequencies and locations of the simulated EPM and TAE, as well as the chirping down feature of the EPM frequency, are consistent with the experimental measurements. The transition from EPM to TAE is found to be a self-consistent dynamic of nonlinear evolution with the expel of energetic ions due to EPM.

在 EAST 中性束注入等离子体中观察到 Alfvn 特征模式 (AE) 和高能粒子模式 (EPM)，核心区域存在重钨杂质。AE 被识别为环形 Alfvn 特征模式 (TAE)，具有大致恒定的频率f _TAE ∼ 100kHz 和一组特殊的 AE，其频率从频率f _AE ∼ 70kHz上升到f _AE ∼ 100kHz。_EPM的频率约为f _EPM∼ 60kHz，具有频率啁啾下降功能。发现了从 EPM 到 AE 的转变，并且通过实验诊断测量了位置和模式数。使用全局动力学-磁流体动力学代码 M3D-K 进行了混合模拟，以研究观察到的 AE 和 EPM，线性模拟发现环模数n = 2 和极向模数m的 EPM= 3. 非线性仿真表明，EPM 频率非线性啁啾下降，然后出现两种模式，频率约为 72.7 kHz 和 88.0 kHz：频率较高的模式是 TAE，另一种模式是 EPM。之后，TAE 迅速消失，频率几乎没有变化，而低频的 EPM 继续啁啾下降。模拟的 EPM 和 TAE 的模式频率和位置，以及 EPM 频率的啁啾特征与实验测量一致。发现从 EPM 到 TAE 的转变是非线性演化的自洽动态，由于 EPM 会排出高能离子。