Observation of a quasi-coherent high-frequency electromagnetic mode at the pedestal region in EAST RF-dominant H-modes
Observation of a quasi-coherent high-frequency electromagnetic mode at the pedestal region in EAST RF-dominant H-modes
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DOI：
10.1088/0029-5515/54/4/043014
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发表时间：
2014-04
期刊：
影响因子：
3.3
通讯作者：
H.Q. Wang;G.S. Xu;H. Guo;B. Wan;N. Yan;S. Ding;R. Chen;W. Zhang;L. Wang;S.C. Liu-
中科院分区：
文献类型：
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作者：
H.Q. Wang;G.S. Xu;H. Guo;B. Wan;N. Yan;S. Ding;R. Chen;W. Zhang;L. Wang;S.C. Liu-
在低杂波电流驱动或低杂波与离子回旋共振频率波联合加热的EAST H模中，观察到了频率约为300 kHz的准相干高频模（HFM）。在L-H跃迁后和碰撞强度较高时，HFM的频率和振幅都出现了增长的初始阶段。从边缘朗缪尔探针的详细分析表明，HFM在实验室框架和等离子体框架中的电子反磁方向传播。HFM的解相关速率比陡梯度区的最大E × B剪切速率小一个数量级。此外，HFM的增长，饱和度和振荡，包括频率和振幅，与压力梯度的演变强烈相关。因此，HFM的振幅和频率之间的类似极限环的振荡可能在基座的形成和饱和中起着重要的作用。在基座压力梯度的饱和阶段，HFM，有时伴随着中频（约80 kHz）准相干模式，驱动强的跨场输运，导致压力梯度的小崩溃，并最终限制压力梯度。
A quasi-coherent high-frequency mode (HFM), with frequency ∼300 kHz, has been observed in EAST H-modes obtained by lower hybrid current drive or combined heating of lower hybrid wave and ion cyclotron resonance frequency wave after lithium wall conditioning. The HFM with an initial growing phase in frequency and amplitude appears both following L–H transition and between edge-localized modes at a relatively high-collisionality . Detailed analysis from edge Langmuir probe has revealed that the HFM propagates in the electron diamagnetic direction in both the lab frame and the plasma frame. The decorrelation rate of HFM is smaller than the maximum E × B shearing rate at the steep gradient region by an order of magnitude. Furthermore, the growth, saturation and oscillations of HFM, including both frequency and amplitude, are strongly correlated with the evolution of pressure gradient. Thus, the limit-cycle-like oscillations between the amplitude and the frequency of HFM may play an important role in the formation and saturation of pedestal. During the saturation phase of pedestal pressure gradient, the HFM, sometimes accompanied by a mid-frequency (∼80 kHz) quasi-coherent mode, drives strong cross-field transport resulting in small crashes of pressure gradient and finally limits the pressure gradient.