Recently, the geodesic acoustic modes (GAMs) induced by negative electrode biasing (EB) are first observed in J-TEXT tokamak, and the electrostatic and magnetic fluctuation characteristics of GAMs and ambient turbulence (AT) are measured by combined Langmuir-magnetic probe. Experimental results reveal that with the ramped up negative biasing, the mean flow shear gradually strengthens, and exciting a high-frequency GAM (H-GAM) and a low-frequency GAM (L-GAM) with frequencies of 24 kHz and 17 kHz respectively. With the combined effects of shear by EB and shear by GAMs, the amplitude of AT is effectively suppressed, leading to an improvement in plasma confinement. This work investigates the relationship between AT, GAM zonal flows and mean flow shear, which provides proper mean flow shear can enhance the Reynolds stress via enhancement of symmetry breaking and thus enhance the amplitude of GAMs, but excessive flow shear can simultaneously suppress AT and GAM zonal flows.
最近，在J-TEXT托卡马克中首次观测到了由负偏压电极引起的测地声模（GAM），并通过组合朗缪尔-磁探针测量了GAM和环境湍流（AT）的静电及磁涨落特性。实验结果表明，随着负偏压的增大，平均流剪切逐渐增强，并激发了频率分别为24 kHz和17 kHz的高频GAM（H-GAM）和低频GAM（L-GAM）。在由偏压引起的平均流剪切和GAM带状流剪切的共同作用下，环境湍流的幅度被有效抑制，从而改善了等离子体约束。本研究探讨了AT、GAM带状流与平均流剪切之间的关系，揭示了适当的平均流剪切可通过增强对称性破缺来增强雷诺应力，进而增强GAM的幅度，但过大的流剪切则会同时抑制AT和GAM带状流。