Characteristics and control of the type I edge localized mode in JT-60U
Characteristics and control of the type I edge localized mode in JT-60U
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DOI：
10.1088/0029-5515/51/3/033009
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发表时间：
2011-03
期刊：
影响因子：
3.3
通讯作者：
N. Oyama;N. Hayashi;N. Aiba;A. Isayama;H. Urano;Y. Sakamoto;Y. Kamada;T. Takizuka
中科院分区：
文献类型：
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作者：
N. Oyama;N. Hayashi;N. Aiba;A. Isayama;H. Urano;Y. Sakamoto;Y. Kamada;T. Takizuka
利用微波反射计、电子回旋发射（ECE）外差辐射计和光栅多色仪等高时空分辨率的诊断仪器，在JT-60 U上研究了I型边缘局域模（ELM）的前体的详细特性。相干密度和温度的前体已经观察到的崩溃阶段的I型ELM。对于几种边缘基座条件，前体的生长速率估计为γ/ωA 10−3。根据在两个环形位置处测量的ECE信号之间的相位延迟和前体的频率，假设前体以与碳杂质相同的环形旋转速度环形地旋转，环形模式数被实验地评估为n = 8-10或14-16。结果表明，在相同的等离子体条件下，各ELM的优势n不同。基座内的压力梯度（WELM）与基座内的压力梯度（WELP）之比已被确认为确定ELM能量损失（ΔWELM）的重要参数，所述ELM能量损失（ΔWELM）被标准化为基座储存能量（Wped），ΔWELM/Wped。从离子温度分布的减少率的比较，由于ELMs，一个较大的减少率内的基座和更广泛的ELM影响的区域中观察到的等离子体与较大的EMPIN/EMPDP。当用1.57 MW的电子回旋波（ECW）加热高场侧基座顶部附近的等离子体时，ΔWELM/Wped减小了约35%，同时ELM频率增加。ELM频率随加热功率的增加速率在ECW注入情况下比在中性束注入情况下观察到的自然功率依赖性大约四倍。
The detailed characteristics of the precursor of the type I edge localized mode (ELM) have been studied in JT-60U using diagnostics with high temporal and spatial resolution such as a microwave reflectometer, electron cyclotron emission (ECE) heterodyne radiometer and grating polychromator. Coherent density and temperature precursors have been observed before the collapse phase of type I ELM. The growth rate of the precursor is evaluated to be γ/ωA ∼ 10−3 for several edge pedestal conditions. From the phase delay between ECE signals measured at two toroidal locations and the frequency of the precursor, the toroidal mode number is experimentally evaluated as n = 8–10 or 14–16 assuming that the precursor rotates toroidally with the same toroidal rotation speed of carbon impurity. It is found that the dominant n varies with each ELM under the same plasma condition. The ratio of the pressure gradient inside the pedestal (∇pin) to the pressure gradient within the pedestal (∇pped) has been confirmed as an important parameter in determining the ELM energy loss (ΔWELM) normalized to the pedestal stored energy (Wped), ΔWELM/Wped. From the comparison of the reduction rate in the ion temperature profile due to ELMs, a larger reduction rate within the pedestal and a wider ELM affected area are observed in the plasma with larger ∇pin/∇pped. When the plasma near the top of the pedestal on the high-field side is heated by an electron cyclotron wave (ECW) power of 1.57 MW, the ΔWELM/Wped is reduced by ∼35%, together with an increase in the ELM frequency. The increasing rate of the ELM frequency with the heating power is about four times larger in the ECW injection case than the natural power dependence observed in the neutral beam injection case.