Speaker
Mr
Mickey R. Wade
(USA)
Description
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 of the edge response to RMPs as well as expansion of RMP ELM suppression to more ITER-like conditions. Experiments aimed at an improved physics understanding have revealed a complex plasma response in the edge region that combines aspects of ideal MHD, vacuum field penetration, and direct turbulent response to the applied RMP. New observations include RMP-induced helical displacements near the separatrix that increase with q95, a displacement inversion layer in the edge temperature profile response when a rational surface associated with the largest applied RMP poloidal harmonics (m=10-12, n=3 or m=9-11, n=2) is located near the pedestal top, and nearly instantaneous changes in density fluctuations throughout the pedestal region to n=3 RMP amplitude variations. This complex response results in transport modifications near the q_95 window for edge localized mode (ELM) suppression that result in ~30% narrower pedestal width than observed without the RMP applied. These experiments have taken advantage of DIII-D’s unique capability to vary the RMP spectrum (n=3 from one or two internal coils, n=2) as well as toroidal phase variations of n=3 and n=2 RMPs for enhanced diagnostic fidelity, all done at the pedestal collisionality levels expected in ITER. In addition, RMP ELM suppression has been expanded to include the use of n=2 RMPs and has been robustly obtained in the ITER baseline scenario (q_95=3.1) using a single-row n=3 RMP.
Work supported by the US DOE under DE-FC02-04ER54698, DE-AC02-09CH11466, DE-FG02-89ER53296, DE-FG02-08ER54999, DE-FG02-07ER54917, and DE-FG02-08ER54984.
Country or International Organization of Primary Author
USA
Primary author
Mr
Mickey R. Wade
(USA)
Co-authors
Dr
Dmitry M. Orlov
(University of California San Diego)
Dr
George R. McKee
(University of Wisconsin-Madison)
John S. deGrassie
(General Atomics)
Dr
Lei Zeng
(University of California Los Angeles)
Dr
Nathaniel M. Ferraro
(General Atomics)
Dr
Oliver Schmitz
(Forschungzentrum Juelich)
Dr
Philip B. Snyder
(General Atomics)
Dr
Raffi Nazikian
(Princeton Plasma Physics Laboratory)
Dr
Richard A. Moyer
(University of California San Diego)
Dr
Richard J. Buttery
(General Atomics)
Dr
Todd E. Evans
(General Atomics)
