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)
