Advances in the Understanding of ELM Suppression by Resonant Magnetic Perturbations (RMPs)
in DIII-D and Implications for ITER
Authors: R. Nazikian, D. Eldon, T.E. Evans, N.M. Ferraro, B.A. Grierson, R.J. Groebner, et al.
Abstract: Experiments on DIII-D have expanding the operating window for RMP ELM suppression to higher q95 with dominant electron heating and fully noninductive current drive relevant to advanced modes of ITER operation. Robust ELM suppression has also been obtained with a reduced coil set, mitigating the risk of coil failure in maintaining ELM suppression in ITER. These results significantly expand the operating space and reduce risk for obtaining RMP ELM suppression in ITER. Efforts have also been made to search for 3D cause of ELM suppression. No internal nonaxisymmetric structure is detected at the top of the pedestal, indicating that the dominant effect of the RMP is to produce an n=0 transport modification of the profiles. Linear two fluid MHD simulations using M3D-C1 indicate resonant field penetration and significant magnetic stochasticity at the top of the pedestal, consistent with the absence of detectable 3D structure in that region. A profile database was developed to compare the scaling of the pedestal and global confinement with the applied 3D field strength in ELM suppressed and ELM mitigated plasmas. The EPED pedestal model accurately predicts the measured pedestal pressure at the threshold of ELM suppression, increasing confidence in theoretical projections to ITER pedestal conditions. Both the H-factor (H98y2) and thermal energy confinement time do not degrade substantially with applied RMP fields near the threshold of ELM suppression, enhancing confidence in the compatibility of ITER high performance operation with RMP ELM suppression.
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Presented at: the 25th IAEA Fusion Energy Conference, St. Petersburg, Russia, 13-18 October 2014.
Published as: 25th IAEA Fusion Energy Conference Proceedings on IAEA Physics website
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