Characterization of broadband MHD fluctuations during type-II edge localized modes as measured in 2D with ECE-imaging at ASDEX Upgrade
Characterization of broadband MHD fluctuations during type-II edge localized modes as measured in 2D with ECE-imaging at ASDEX Upgrade
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DOI：
10.1088/0029-5515/52/11/114004
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发表时间：
2012-11
期刊：
影响因子：
3.3
通讯作者：
J. Boom;E. Wolfrum;I. Classen;P. D. de Vries;M. Maraschek;W. Suttrop;C. P. von Thun;A. Donne;B. Tobias;C. Domier;N. Luhmann;H. Park
中科院分区：
文献类型：
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作者：
J. Boom;E. Wolfrum;I. Classen;P. D. de Vries;M. Maraschek;W. Suttrop;C. P. von Thun;A. Donne;B. Tobias;C. Domier;N. Luhmann;H. Park
宽带波动的表征，这是典型的II型ELM制度在ASDEX升级已得到改善，使用二维能力的ECE成像。在从I型到II型ELMy相的过渡期间，已经发现电子温度波动在19-65 kHz范围内形成宽带峰。在II型阶段，这种宽带波动在基座顶部内部达到几乎20%的最大相对幅度。同时，电子温度分布在该位置处完全平坦。该宽带波动的幅度的2D分布使得当随时间平均时，在中平面周围出现最小值。从附近的磁拾波线圈的测量结果来看，在相同的频率范围内似乎可以看到类似的宽带波动。然而，这在稍低的频率处达到峰值，并且不显示类似的最小值。从小时间尺度上的波动分析，极向和环向模数估计为m 100和n 21。此外，活动让人想起拍波已被观察到，这可能部分地解释了波动的宽带性质和表面上的速度变化的单一波动通道。总体而言，这种宽带波动的特征和I型ELMs的各种前兆之间的相似性表明，这种波动可以在调节ELM周期中发挥重要作用。
The characterization of a broadband fluctuation that is typical for the type-II ELM regime at ASDEX Upgrade has been improved using the 2D capabilities of ECE-imaging. During the transition from the type-I to type-II ELMy phase, it has been found that electron temperature fluctuations form a broadband peak in the 19–65 kHz range. In the type-II phase, this broadband fluctuation reaches a maximum relative amplitude of almost 20% just inside the top of the pedestal. Simultaneously, the electron temperature profile is completely flattened at this location. The 2D distribution of the amplitude of this broadband fluctuation is such that, when averaged over time, a minimum occurs around the mid-plane. From the measurements of the nearby magnetic pickup coils, a similar broadband fluctuation seems visible in the same frequency range. However, this is peaked at a slightly lower frequency and does not show a similar minimum. From the analysis of the fluctuations on small timescales, the poloidal and toroidal mode numbers are estimated to be m ∼ 100 and n ∼ 21. Furthermore, activity reminiscent of beat waves has been observed, which might partially account for the fluctuation's broadband nature and the seeming velocity variation of single fluctuation passages. Overall, similarities between the characteristics of this broadband fluctuation and various precursors to type-I ELMs suggest that this fluctuation can play an important role in regulating the ELM cycle.