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Title: Effect of Island Overlap on ELM Suppression by Resonant Magnetic Perturbations in DIII-D

Abstract

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} 3.6). With fixed n = 3 resonant magnetic perturbation (RMP) strength, 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 freemore » path, increases throughout the island overlap region in the ELM suppressed case compared with the ELMing case.« less

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
989346
Report Number(s):
UCRL-JRNL-236424
Journal ID: ISSN 1070-664X; PHPAEN; TRN: US1007069
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 15; Journal Issue: 5; Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
29 ENERGY PLANNING, POLICY AND ECONOMY; 70 PLASMA PHYSICS AND FUSION; DIVERTORS; DOUBLET-3 DEVICE; EDGE LOCALIZED MODES; ELECTRONS; MAGNETIC FIELDS; MAGNETIC ISLANDS; MAGNETIC SURFACES; MEAN FREE PATH; PLASMA; SAFETY; SHAPE; SHIELDING; TARGETS; WINDOWS

Citation Formats

Fenstermacher, M E, Evans, T E, Osborne, T H, Schaffer, M J, Aldan, M P, deGrassie, J S, Gohil, P, Joseph, I, Moyer, R A, Snyder, P B, Groebner, R J, Jakubowski, M, Leonard, A W, and Schmitz, O. Effect of Island Overlap on ELM Suppression by Resonant Magnetic Perturbations in DIII-D. United States: N. p., 2007. Web.
Fenstermacher, M E, Evans, T E, Osborne, T H, Schaffer, M J, Aldan, M P, deGrassie, J S, Gohil, P, Joseph, I, Moyer, R A, Snyder, P B, Groebner, R J, Jakubowski, M, Leonard, A W, & Schmitz, O. Effect of Island Overlap on ELM Suppression by Resonant Magnetic Perturbations in DIII-D. United States.
Fenstermacher, M E, Evans, T E, Osborne, T H, Schaffer, M J, Aldan, M P, deGrassie, J S, Gohil, P, Joseph, I, Moyer, R A, Snyder, P B, Groebner, R J, Jakubowski, M, Leonard, A W, and Schmitz, O. 2007. "Effect of Island Overlap on ELM Suppression by Resonant Magnetic Perturbations in DIII-D". United States. https://www.osti.gov/servlets/purl/989346.
@article{osti_989346,
title = {Effect of Island Overlap on ELM Suppression by Resonant Magnetic Perturbations in DIII-D},
author = {Fenstermacher, M E and Evans, T E and Osborne, T H and Schaffer, M J and Aldan, M P and deGrassie, J S and Gohil, P and Joseph, I and Moyer, R A and Snyder, P B and Groebner, R J and Jakubowski, M and Leonard, A W and Schmitz, O},
abstractNote = {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} 3.6). With fixed n = 3 resonant magnetic perturbation (RMP) strength, 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.},
doi = {},
url = {https://www.osti.gov/biblio/989346}, journal = {Physics of Plasmas},
issn = {1070-664X},
number = 5,
volume = 15,
place = {United States},
year = {Thu Nov 08 00:00:00 EST 2007},
month = {Thu Nov 08 00:00:00 EST 2007}
}