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Recent results of density ramp-up (< n _e >/ n _GW = 0.5–0.75) experiment in type-I ELMy H-mode on experimental advanced superconducting tokamak are presented, with a focus on pedestal dynamics and turbulence behavior. With the density increase, a general trend is that the pedestal electron pressure ( p _e ^ped ) decreases while the ELM frequency ( f _ELM ) increases. Especially when < n _e >/ n _GW arrives at ∼ 0.68, a sudden decrease of p _e ^ped and an increase of f _ELM are observed. A quasi-coherent mode (QCM) with a frequency of 200–300 kHz is observed in the pedestal region and appears in both density and magnetic fluctuations. The time evolution of p _e ^ped during the inter-ELM phase is analyzed for different densities. The analysis suggests that the pedestal behavior for < n _e >/ n _GW < 0.68 is mainly attributed to pedestal stability but not due to pedestal transport. It is shown that the resistivity effect on the peeling-ballooning (PB) mode (Zhang et al 2017 Phys. Plasmas 24 062108) could be used to explain the present result. But the sudden decrease of p _e ^ped and increase of f _ELM at < n _e >/ n _GW > 0.68 cannot be attributed to the resistivity effect. It is found that for the plasma with < n _e >/ n _GW > 0.68, the QCM disappears just before ELM and the density pedestal becomes steeper. This implies that the QCM can drive outward particle transport. The steeper density pedestal leads to a narrower pedestal width. A narrower pedestal width will lead to a lower pedestal pressure since PB mode limits the pressure gradient and could explain the observed sudden decrease of p _e ^ped and increase of f _ELM .

In a reversed shear discharge in the Experimental Advanced Superconducting Tokamak (EAST), an internal transport barrier (ITB) was formed. For the first time, the turbulence in the plasma core before and after the formation of the ITB in EAST was investigated by microwave reflectometry. It was found that during the formation of the ITB, the turbulence inside the barrier was not completely suppressed. The density fluctuation level decreased in the early phase of ITB and significantly increased later. It was found that the density fluctuation level increased with the density gradient after the appearance of reversed shear Alfvén eigenmodes (RSAEs). The change in turbulence, measurable by the reflectometer, did not affect the rate of increase in core density. Through the measurement of RSAEs, it was found that the formation of this ITB may be related to the minimum q ( q _min ). q _min was close to 2.