Fast dynamics of type I and grassy ELMs in JT-60U
Fast dynamics of type I and grassy ELMs in JT-60U
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DOI：
10.1088/0029-5515/49/11/115008
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发表时间：
2009-11
期刊：
影响因子：
3.3
通讯作者：
A. Kojima;N. Oyama;Y. Sakamoto;Y. Kamada;H. Urano;K. Kamiya;T. Fujita;H. Kubo;N. Aiba
中科院分区：
文献类型：
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作者：
A. Kojima;N. Oyama;Y. Sakamoto;Y. Kamada;H. Urano;K. Kamiya;T. Fujita;H. Kubo;N. Aiba
为了理解ELM触发器的物理特性并确定ELM的尺寸，已经在JT-60 U中使用具有高空间和时间分辨率的新的快速诊断（例如锂束探针）研究了I型ELM和草状ELM的快速ELM动力学（Δt ≤ 0.5 ms）和电荷交换复合光谱（Δt ≤ 2.5 ms），它们可以分别测量电子密度和离子温度。在基座区域的离子压力分布的演变已被评估为第一次详细的边缘轮廓测量。在此基础上，研究了ELM循环中离子密度、离子温度和离子压力的动态变化规律。为了理解环向旋转效应，将同向旋转等离子体与反向旋转等离子体进行了比较。在同向旋转等离子体中观察到的I型ELM的影响面积（Δnped/nped ≥ 30%，径向范围>15 cm）比在反向旋转等离子体中观察到的I型ELM的影响面积（Δnped/nped ≥ 20%，径向范围≥ 10 cm）大且宽。在I型ELM碰撞前，同向旋转等离子体中的基座离子压力和最大梯度分别比反向旋转等离子体中的高20%和12%。发现同向旋转等离子体中基座区离子压力梯度的径向范围比反向旋转等离子体中宽14%。实验结果表明，ELM的尺寸与整个基座区的等离子体压强结构有关。在电子温度基台的崩塌过程中，草型ELMs密度基台的崩塌比Ⅰ型ELMs小（<20%），宽度也比Ⅰ型ELMs窄（<1.5 cm）。因此，它被证实，由于长满草的ELMs的传导和对流损失是小的。
In order to understand the physics of the ELM trigger and determine the ELM size, the fast ELM dynamics of type I and grassy ELMs have been studied in JT-60U, using new fast diagnostics with high spatial and temporal resolutions such as a lithium beam probe (Δt ∼ 0.5 ms) and a charge exchange recombination spectroscopy (Δt ∼ 2.5 ms), which can measure the electron density and the ion temperature, respectively. The evolution of the ion pressure profile in the pedestal region has been evaluated for the first time by detailed edge profile measurements. Then, the dynamics of the density, the ion temperature and the ion pressure in the ELM cycle has been investigated. The co-rotating plasmas are compared with the counter (ctr)-rotating plasmas for the understanding of the toroidal rotation effects. Type I ELMs observed in co-rotating plasmas exhibit a larger and wider ELM affected area (Δnped/nped ∼ 30%, radial extent >15 cm) than ctr-rotating plasmas (Δnped/nped ∼ 20%, radial extent ∼10 cm). Just before a type I ELM crash, the pedestal ion pressure and its maximum gradient in co-rotating plasmas are 20% and 12% higher than those in ctr-rotating plasmas, respectively. It is found that the radial extent of the ion pressure gradient at the pedestal region in co-rotating plasmas is 14% wider than that in ctr-rotating plasmas. The experimental results suggest that the ELM size is connected with the structure of the plasma pressure in the whole pedestal region. As for the dynamics of grassy ELMs, the collapse of density pedestal is smaller (<20%) and narrower (∼5 cm) than those of type I ELMs, as observed in the collapse of the electron temperature pedestal. Thus, it is confirmed that both conductive and convective losses due to grassy ELMs are small.