Influence of Resonant Magnetic Perturbation (RMP) on the Turbulence in the Edge Pedestal on JET
The influence of an n = 2 Resonant Magnetic Perturbation (RMP) field on the density fluctuation in the edge pedestal has been investigated using correlation reflectometry in type-I ELMy H-mode plasma on JET. Without the n = 2 field, the frequency spectrum of the density fluctuation shows two broadband fluctuation components: one is with Low Frequency (LF) less than 200kHz and another is with High Frequency (HF) from 200kHz to 400kHz. A correlation between the density and magnetic fluctuations has been observed. With the n = 2 field applied, an increase of ELM frequency and a drop of electron density (so called density pump-out) have been observed. The electron density (gradient) and pressure (gradient) in the edge pedestal decrease with the application of the n = 2 field while the electron temperature profile shows no change. The experimental observations show that both the density and magnetic fluctuation levels in the edge pedestal are reduced after applying the n = 2 field. This result implies that the ion-scale turbulence in the edge pedestal is not the responsible mechanism for the density pump-out observed during the application of the n = 2 field.