ELM mitigation via rotating resonant magnetic perturbations on MAST

TL;DR

This paper demonstrates that rotating resonant magnetic perturbations (RMPs) on MAST can effectively mitigate edge localized modes (ELMs) by rotating strike point splitting, doubling ELM frequency, and reducing peak heat flux by 50%.

Contribution

It introduces the use of rotating RMPs with n=3 in MAST to control ELMs, showing how rotation distributes heat flux and halves ELM energy, a novel approach for ELM mitigation.

Findings

ELM frequency doubled with rotating RMPs while maintaining H mode.

Peak heat flux reduced by 50% during mitigation.

Strike point splitting rotation observed with high-resolution IR thermography.

Abstract

The application of resonant magnetic perturbations (RMPs) produces splitting of the divertor strike point due to the interaction of the RMP field and the plasma field. The application of a rotating RMP field causes the strike point splitting to rotate, distributing the particle and heat flux evenly over the divertor. The RMP coils in MAST have been used to generate a rotating perturbation with a toroidal mode number n=3. The ELM frequency is doubled with the application of the RMP rotating field, whilst maintaining the H mode. During mitigation, the ELM peak heat flux is seen to be reduced by 50% for a halving in the ELM energy and motion of the strike point, consistent with the rotation of the applied RMP field, is seen using high spatial resolution (1.5mm at the target) heat flux profiles measured using infrared (IR) thermography.