2024 – RMP-ELM Control in ECH-dominated IBS at low torque

RMP-ELM Control in ECH-dominated IBS at low torque

2024 Research Campaign, ITER Integrated Scenarios

Purpose of Experiment

Resonant magnetic perturbation (RMP) driven ELM suppression has been widely demonstrated in NBI heating plasmas. However, it has not been demonstrated in electron cyclotron heating (ECH) plasmas, leaving uncertainty for RMP ELM control in ITER and FPPs with dominant Radio Frequency (RF) heating. This experiment aims to explore approaches to and demonstrate RMP ELM suppression in the EC heated, low torque, low q95, low collisionality ITER similar plasmas. The approach proposed takes advantage of both advances in the understanding of pedestal-top island physics and the specific properties of the ECH ITER baseline scenario.

Experimental Approach

The approach taken in this experiment will be to prioritize applying the predicted methods of achieving ELM suppression in dominantly ECH-heated low torque IBS plasmas. If initial attempts are successful, the day will turn to document the behaviors of ELM suppression in these scenarios. The first stage of the experiment will be applying RMPs in a low βN plasma and then increasing the power to obtain an ITER-relevant βN. Real-time RMP control will also be used to apply the RMP early in the LH transition before the pedestal has fully built up ω*e, using the controller to essentially perform the Moyer strategy without having to tailor the power waveforms. The next stage of the experiment will utilize ECCD near the plasma edge to reduce the RMP ELM suppression threshold. The final stage will then assess the feasibility of using electron root NTV to improve the ωEXB zero crossing conditions. This will essentially involve scans of the non-resonant low-n fields while monitoring the core rotation. If successful low torque suppression is obtained at any point, the remainder of the experiment will document and optimize RMP ELM suppression in this scenario.

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