Poloidally localized edge density fluctuation with applied and spontaneous 3-D fields in experimental advanced superconducting tokamak (EAST)

Poloidally localized density fluctuation with applied and spontaneous 3-D fields in high-confinement mode (H-mode) plasma is observed by using poloidally distributed multichannel interferometer diagnostics in the experimental advanced superconducting tokamak. With the application of an n = 1 rotating nonaxisymmetric magnetic perturbation (NAMP) field, a density fluctuation appears on different interferometer channels sequentially. Evidence shows that this fluctuation is located at the plasma edge. When an n = 1 static NAMP field is applied, the density fluctuation amplitude increases in parts of channels but decreases in other channels, implying a poloidal localization. This localization is enhanced with the increase in the NAMP field. In addition, when a spontaneous n = 1 external kink mode with a frequency of ∼3.5 kHz appears in the plasma edge, the amplitude of density fluctuation is modulated by the n = 1 kink. This modulation could be attributed to the localization effect on fluctuation by the 3-D fields of the spontaneous kink mode.Poloidally localized density fluctuation with applied and spontaneous 3-D fields in high-confinement mode (H-mode) plasma is observed by using poloidally distributed multichannel interferometer diagnostics in the experimental advanced superconducting tokamak. With the application of an n = 1 rotating nonaxisymmetric magnetic perturbation (NAMP) field, a density fluctuation appears on different interferometer channels sequentially. Evidence shows that this fluctuation is located at the plasma edge. When an n = 1 static NAMP field is applied, the density fluctuation amplitude increases in parts of channels but decreases in other channels, implying a poloidal localization. This localization is enhanced with the increase in the NAMP field. In addition, when a spontaneous n = 1 external kink mode with a frequency of ∼3.5 kHz appears in the plasma edge, the amplitude of density fluctuation is modulated by the n = 1 kink. This modulation could be attributed to the localization effect on fluctuation by the 3-D fi...