Advances in the physics understanding of ELM suppression using resonant magnetic perturbations in DIII-D. (14th January 2015)

• Record Type: Journal Article
• Authors: Wade, M.R.; Nazikian, R.; deGrassie, J.S.; Evans, T.E.; Ferraro, N.M.; Moyer, R.A.; Orlov, D.M.; Buttery, R.J.; Fenstermacher, M.E.; Garofalo, A.M.; Lanctot, M.A.; McKee, G.R.; Osborne, T.H.; Shafer, M.A.; Solomon, W.M.; Snyder, P.B.; Suttrop, W.; Wingen, A.; Unterberg, E.A.; Zeng, L.
• Is Part Of: Nuclear fusion. Volume 55:Number 2(2015:Feb.)
• Publication Date: 2015-01-14
• Subjects: DIII-D -- resonant magnetic perturbation -- ELM control -- MHD plasma response -- non-axisymmetric fields; 52.55.Fa -- 52.35.Py -- 52.55.Tn -- 52.55.Rk -- 52.30.Cv -- 52.40.Hf; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/0029-5515/55/2/023002
• Languages: English
• ISSNs: 0029-5515

Abstract

Abstract: Recent experiments on DIII-D have increased confidence in the ability to suppress edge-localized modes (ELMs) using edge-resonant magnetic perturbations (RMPs) in ITER, including an improved physics basis for the edge response to RMPs as well as expansion of RMP ELM suppression to more ITER-like conditions. Complete ELM suppression has been achieved utilizing n = 3 RMPs in the ITER baseline scenario. In addition, RMP ELM suppression has been expanded to include plasmas with helium concentrations near 25% and the use of n = 2 RMPs. Analysis of the kinetic profile response suggests that ELM suppression is correlated with the co-alignment of the ω ⊥e = 0 location, an n = 3 rational surface, and the top of the pedestal. Modelling predicts that such a co-alignment could potentially lead to island (or island chain) formation just inside the top of the pedestal, inhibiting the growth of the pedestal and thereby maintaining the ELM-free state. Detailed analysis of data obtained during toroidal phase variations of the applied n = 3 RMPs have provided further evidence of an island-like structure at the top of the pedestal. In addition, nearly matched discharges with co-neutral-beam-injection (co-NBI) and counter-NBI have demonstrated the importance of the presence of the ω ⊥e = 0 location for ELM suppression. In the counter-NBI cases, the toroidal rotation profile is such that there is no ω ⊥e = 0 location and ELMs are not suppressed in conditions in which ELM suppression is generally observed with co-NBI.