Internal measurements of electromagnetic geodesic acoustic mode (GAM) in EAST plasmas

作者：Y. H. Wang, Weixing Ding, Chu Zhou, A. D. Liu, Xi Feng, Hui Lian, Haiqing Liu, Yuqi Chu, D. L. Brower, Wenzhe Mao, Jinlin Xie, Lifu Gao, Ruiping Zhu, X. Zhong, Haijun Ren, Zhe Chen, W. X. Shi, S. F. Wang · 发表于：Physics of Plasmas · 年份：2024 · DOI：10.1063/5.0211489 · 被引用次数：5 · 研究领域：Magnetic confinement fusion research、Ionosphere and magnetosphere dynamics、Laser-Plasma Interactions and Diagnostics

Velocity, density, and magnetic fluctuations of the geodesic acoustic mode (GAM) have been measured using the Doppler backscattering system, Faraday-effect polarimeter-interferometer, and external pick-up coils in the Experimental Advanced Superconducting Tokamak. Simultaneous measurements of density and velocity fluctuations at the midplane and top of plasmas demonstrate that m = 1 density fluctuations are quantitatively balanced by the compression of perpendicular flow fluctuations. Furthermore, internal magnetic fluctuations associated with GAM have now been directly measured by laser-based Faraday-effect polarimetry for the first time. Line-averaged magnetic fluctuations (up to 16 Gauss, B̃¯R,GAMBT∼0.066%) are significantly larger than those extrapolated from edge coils (a few Gauss) and that magnetic fluctuations increase with β. The observed discrepancy between finite β theory and experimental data indicates the need for further theoretical investigations.