Experimental and numerical investigation of ICRF induced low-frequency turbulence reduction across the scrape-off layer on the EAST tokamak

Abstract

In magnetic confinement fusion devices, the plasma particle and energy transport depend on the turbulence transport. Ion cyclotron range of frequency (ICRF) wave heating can interact with the turbulence in the plasma edge and change the turbulence transport. To understand their interaction/correlation, the radial modification of turbulence by ICRF in the scrape-off layer (SOL) was investigated using midplane reciprocating Langmuir probe, reflectometry, Doppler reflectometry, and Divertor probes on the EAST tokamak. We showed a first demonstration that this interaction occurs at all radii and affects the turbulence across the whole SOL. It was observed that ICRF attenuates the large-scale turbulence structures (usually in the form of blobs) by breaking them into smaller ones, leading to a suppression of low-frequency turbulence in the whole SOL. Moreover, this turbulence reduction is accompanied by an increase in the high-frequency turbulence fluctuations and an increase in the poloidal velocity in the SOL. This poloidal velocity is generated by the radial electric field during ICRF. Following this, BOUT++ simulations were conducted, and the simulations results are in line with the experimental results. They show that the RF-sheath induced radial electric field can explain the increase in high-frequency fluctuations and suppression of turbulence in the SOL.