ELM Control by Resonant Magnetic Perturbations: Overview of Research by the PEP ITPA Group
Modifications of Edge Localized Modes (ELMs) with Resonant Magnetic Perturbations (RMPs) in H-mode plasmas have been achieved in DIII-D, JET, JFT-2M MAST, NSTX and TEXTOR including (i) suppression of ELM energy losses with internal coils in DIII-D, (ii) mitigation of ELM size with external coils in JET and with internal coils in MAST, DIII-D and TEXTOR, and (iii) pacing of ELMs with modulated RMP pulses in NSTX and DIII-D. The experiments in MAST, JET and NSTX confirm that the island overlap width condition, correlated with ELM suppression in DIII-D and used to guide the design requirements of ITER RMP coils, is not sufficient to assure ELM suppression in multiple devices. They also indicate that the L-H threshold power increases when RMP fields of sufficient amplitude are applied during the L-mode phase of the discharges. For 2011and beyond, upgrades of the internal RMP coil systems are underway on DIII-D, MAST and AUG, and upgrades are under consideration at JET and NSTX, that will permit greater variation of RMP mode spectrum to test ELM control physics models. These systems will greatly increase the capability to test theoretical models of RMP ELM control and the probability of achieving ELM suppression on multiple tokamaks.