Investigation of divertor heat flux characteristics under the influence of resonant magnetic perturbations on EAST

Abstract

Controlling the splitting divertor heat flux caused by resonant magnetic perturbations (RMPs) is a topic of concern for fusion devices. As a fundamental prerequisite, it is necessary to understand the characteristics of the heat flux distribution under the applied RMP field, which will be studied in this paper. The nonlinear phenomenon of strike point splitting was found to be strongly dependent on the plasma response under RMP. These splitting heat flux distributions are qualitatively explained by the simulated magnetic footprints. The RMP phase scanning experiment shows that scanning in a certain range of relative phase can maintain good edge-localized mode (ELM) mitigation and simultaneously sweep the striations of heat flux on divertor target. Additionally, even in upper single null (USN) configurations, heat stripes are observed on the lower outer divertor (LO-div), attributed to RMP-induced additional magnetic connections to the LO-div, as confirmed by magnetic topology simulations. A dedicated investigation into the impact of the discrepancy between lower and upper separatrix radii mapped to the low field side mid-plane ( ${\text{d}}{R_{{\text{sep}}}}$ ) reveals its significant influence on both ELM control and heat flux distribution. Within a certain range of ${\text{d}}{R_{{\text{sep}}}}$ , the heat flux distribution is improved while ELM suppression is maintained. These findings contribute to divertor heat flux understanding under RMP conditions in tokamak operations.

Keywords

• tokamak
• resonant magnetic perturbation (RMP)
• strike point splitting
• divertor heat flux
• infrared diagnostic