Structure and scaling properties of the geodesic acoustic mode
Structure and scaling properties of the geodesic acoustic mode
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DOI：
10.1088/0741-3335/48/4/s09
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发表时间：
2006-04
影响因子：
2.2
通讯作者：
G. McKee;D K Gupta;R. Fonck;D. Schlossberg;M. Shafer;P. Gohil
中科院分区：
文献类型：
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作者：
G. McKee;D K Gupta;R. Fonck;D. Schlossberg;M. Shafer;P. Gohil
利用时间延迟估计技术，系统地研究了测地线声模的特性和标度特性。测地线声模是一种相干的、径向切变的高频(∼15 kHz)纬向流振荡，应用于DIII-D束流发射光谱获得的局域多点密度起伏测量。GAM幅度随着安全系数q95的增加而显著增加，并且对于q95和4.2同样变得不可检测地小，定性地与基于碰撞衰减的理论预测以及模拟相一致。GAM的径向结构在0.88<；r/a&0.95的径向范围内表现出峰值振幅，并且在该区域内外的振幅迅速减小。实验测得的频率与理论频率接近，但在较低的Q值下有向较高频率的偏移，且GAM幅度随等离子体伸长κ的增大而增大，但其频率减小。
Characteristics and scaling properties of the geodesic acoustic mode (GAM), a coherent, radially-sheared high frequency (∼15 kHz) zonal flow oscillation, are studied systematically using time-delay-estimation techniques applied to localized, multi-point density fluctuation measurements obtained by beam emission spectroscopy on DIII-D. The GAM amplitude is shown to increase strongly with increasing safety factor, q95, and to likewise become undetectably small for q95 < 4.2, qualitatively consistent with theoretical predictions based on collisional damping as well as simulations. The radial structure of the GAM exhibits peak amplitude in the radial range 0.88 < r/a < 0.95 with a rapid amplitude reduction inside and outside this region. The measured frequency is close to the predicted frequency, though some deviation to higher frequency is observed at lower q. The GAM amplitude is also shown to increase with plasma elongation, κ, while its frequency decreases.