2024 – Pursuing RMP ELM suppression in ECH dominated ITER-like scenarios

Pursuing RMP ELM suppression in ECH dominated ITER-like scenarios

2024 Research Campaign, Transient Control

Purpose of Experiment

Resonant magnetic perturbation (RMP) driven suppression of Edge-Localized modes (ELMs) has been widely demonstrated in the plasma with mainly neural beam injection (NBI) heating. However, it has not been demonstrated in plasmas with dominantly electron cyclotron heating (ECH), leaving uncertainty for RMP ELM control in ITER and FPPs with significant ECH heating. The goals of this experiment series are to probe the impact ECH heating on the access RMP ELM suppression and test methods to reinstate ELM suppression in case it is lost.

Experimental Approach

Scans of the RMP amplitude with toroidal mode number n=3 will be performed during constant ECH power application for different levels of ECH power to investigate the effect that ECH has on the access to ELM suppression: is it gradual or sudden? The NBI power will be the same in every scan to ensure about constant plasma beta and the RMP amplitude scan will be performed stepwise in order to to properly measure relevant quantities through the scan. At a certain level of ECH power, ELM suppression is expected to be denied. In this heating mix, we will develop and optimize the following approaches to achieve RMP-driven ELM suppression: 1) Leveraging a hysteresis effect in the edge safety factor by triggering a magnetic island further in the plasma and move it to the pedestal, 2) apply counter-current electron cyclotron current drive near the pedestal top to lower the RMP penetration threshold, 3) use boron dropper to improve wall conditions reducing the RMP amplitude threshold for ELM suppression.