Effect of island overlap on edge localized mode suppression by resonant magnetic perturbations in DIII-D

Journal Article · Thu May 15 00:00:00 EDT 2008 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2901064· OSTI ID:21120377

Fenstermacher, M E ^[1]; Evans, T E; Osborne, T H; Schaffer, M J; DeGrassie, J S; Gohil, P; Snyder, P B; Groebner, R J; Leonard, A W ^[2]; Aldan, M P ^[3]; Joseph, I; Moyer, R A ^[4]; Jakubowski, M; Schmitz, O ^[5]

---

1. Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
2. General Atomics, P.O. Box 85608, San Diego, California 92186 (United States)
3. University of California-Berkeley, Berkeley, California 94720 (United States)
4. University of California-San Diego, La Jolla, California 92093 (United States)
5. Institut fur Plasmaphysik, FZ-Juelich Euratom Association, 52425 Juelich (Germany)

Recent DIII-D [J. L. Luxon et al., Nucl. Fusion 43, 1813 (2003)] experiments show a correlation between the extent of overlap of magnetic islands induced in the edge plasma by perturbation coils and complete suppression of Type-I edge localized modes (ELMs) in plasmas with ITER-like electron pedestal collisionality {nu}{sub e}*{approx}0.1, flux surface shape and low edge safety factor (q{sub 95}{approx_equal}3.6). With fixed amplitude n=3 resonant magnetic perturbation (RMP), ELM suppression is obtained only in a finite window in the edge safety factor (q{sub 95}) consistent with maximizing the resonant component of the applied helical field. ELM suppression is obtained over an increasing range of q{sub 95} by either increasing the n=3 RMP strength, or by adding n=1 perturbations to ''fill in'' gaps between islands across the edge plasma. The suppression of Type-I ELMs correlates with a minimum width of the edge region having magnetic islands with Chirikov parameter >1.0, based on vacuum calculations of RMP mode components excluding the plasma response or rotational shielding. The fraction of vacuum magnetic field lines that are lost from the plasma, with connection length to the divertor targets comparable to an electron-ion collisional mean free path, increases throughout the island overlap region in the ELM suppressed case compared with the ELMing case.

• OSTI ID: 21120377
• Journal Information: Physics of Plasmas, Vol. 15, Issue 5; Other Information: DOI: 10.1063/1.2901064; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA). DIII-D Team; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
AMPLITUDES
BOUNDARY LAYERS
COLLISIONS
CORRELATIONS
DIVERTORS
DOUBLET-3 DEVICE
EDGE LOCALIZED MODES
ELECTRONS
ITER TOKAMAK
MAGNETIC FIELDS
MAGNETIC ISLANDS
MAGNETIC SURFACES
MAGNETOHYDRODYNAMICS
MEAN FREE PATH
PERTURBATION THEORY
PLASMA