Investigation of transient heat flux redistribution caused by rotating <i>n</i> = 2 RMP in ELM mitigation experiments on EAST

Abstract This study investigates the role of rotating n = 2 resonant magnetic perturbation (RMP) in modifying the transient heat flux distribution during edge localized mode (ELM) mitigation on Experimental Advanced Superconducting Tokamak. During ELM mitigation achieved by the application of a rotating n = 2 RMP, a pronounced reduction in the instantaneous peak heat flux is observed, with a slight increase in the time-averaged peak heat flux. Concurrently, strike point splitting appears in the ELM heat flux profiles, and the split strike points are found to rotate synchronously with the applied RMP field. The qualitative agreement in both the number and locations of strike points between TOP2D vacuum modeling and experimental results indicates that the strike point splitting in ELM heat flux profiles is affected by RMP. Furthermore, the broadening effect of RMP on the heat flux profile is quantified using the power decay length ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mi>λ</mml:mi> <mml:mi>q</mml:mi> </mml:msub> </mml:mrow> </mml:mrow> </mml:math> ). During the mitigated-ELM phase, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mi>λ</mml:mi> <mml:mi>q</mml:mi> </mml:msub> </mml:mrow> </mml:mrow> </mml:math> increases to approximately 6.10 mm, compared to ∼2.86 mm during the inter-large-ELM phase and ∼4.86 mm during the intra-large-ELM phase without RMP. It indicates that the rotating n = 2 RMP significantly broadens the heat flux profiles and reduces the peak heat flux on the divertor target, which is beneficial for the safe operation of tokamaks.