Energy loss for grassy ELMs and effects of plasma rotation on the ELM characteristics in JT-60U
Energy loss for grassy ELMs and effects of plasma rotation on the ELM characteristics in JT-60U
复制标题
DOI：
10.1088/0029-5515/45/8/014
复制
发表时间：
2005-07
期刊：
影响因子：
3.3
通讯作者：
N. Oyama;Y. Sakamoto;A. Isayama;M. Takechi;P. Gohil;L. Lao;P. Snyder;T. Fujita;S. Ide;Y. Kamada;Y. Miura;T. Oikawa;T. Suzuki;H. Takenaga;K. Toi
中科院分区：
文献类型：
--
作者：
N. Oyama;Y. Sakamoto;A. Isayama;M. Takechi;P. Gohil;L. Lao;P. Snyder;T. Fujita;S. Ide;Y. Kamada;Y. Miura;T. Oikawa;T. Suzuki;H. Takenaga;K. Toi
研究了ITER中草缘局域模的能量损失，探讨了草缘局域模在ITER中的适用性。长满草的榆树的特征是800-1500 Hz的高频率周期性崩溃，这比I型榆树快10.15倍。偏滤器的峰值热流密度是由于草ELMs小于10%的I型ELMs。该较小的热通量是由温度基座的塌陷的较窄径向范围引起的。I型ELMs和草ELMs之间的不同径向范围定性地同意由理想MHD稳定性分析确定的本征函数的不同径向分布。草地榆树的主要能量损失是由温度降低引起的，其占基台储存能量的比例为0.4- 1%。该比率比I型ELM的比率低约10倍，I型ELM通常具有2-10%的基座能量分数损失。在JT-60 U装置上，采用切向和垂直中性束注入相结合的方法，系统地研究了计数器（CTR）等离子体旋转对ELM特性的影响。在高等离子体三角形度（δ）区域中，随着CTR等离子体旋转增加，ELM特性（例如振幅、频率和类型）可以从I型ELM改变为高频草状ELM。另一方面，在低δ状态下，当在应用CTR-NBIs期间根据第一壁和等离子体分界线之间的间隙优化等离子体位置时，完全ELM抑制（QH模式）可以维持长达3.4 s（Δ 18τE或能量约束时间）的长时间。在JT-60 U中，在CO-NBI相期间也观察到瞬态QH相，在等离子体边缘几乎没有净环向旋转。
The energy loss for grassy edge localized modes (ELMs) has been studied to investigate the applicability of the grassy ELM regime to ITER. The grassy ELM regime is characterized by high frequency periodic collapses of 800–1500 Hz, which is ∼15 times faster than that for type I ELMs. The divertor peak heat flux due to grassy ELMs is less than 10% of that for type I ELMs. This smaller heat flux is caused by a narrower radial extent of the collapse of the temperature pedestal. The different radial extent between type I ELMs and grassy ELMs agrees qualitatively with the different radial distribution of the eigenfunctions as determined from ideal MHD stability analysis. The dominant ELM energy loss for grassy ELMs appears to be caused by temperature reduction, and its ratio to the pedestal stored energy was 0.4–1%. This ratio is lower by a factor of about 10 than that for type I ELMs, which typically have between 2–10% fractional loss of the pedestal energy. A systematic study of the effects of counter (CTR) plasma rotation on the ELM characteristics has been performed using a combination of tangential and perpendicular neutral beam injections (NBIs) in JT-60U. In the high plasma triangularity (δ) regime, ELM characteristics (e.g. amplitude, frequency and type) can be changed from type I ELMs to high frequency grassy ELMs as the CTR plasma rotation is increased. On the other hand, in the low δ regime, complete ELM suppression (QH-mode) can be sustained for long periods up to 3.4 s (∼18τE or energy confinement times), when the plasma position in terms of the clearance between the first wall and the plasma separatrix is optimized during the application of CTR-NBIs. In JT-60U, a transient QH phase was also observed during the CO-NBI phase with almost no net toroidal rotation at the plasma edge.