skip to main content
Show search Show menu
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Suppression of Large Edge Localized Modes with a Stochastic Magnetic Boundary in High Confinement DIII-D Plasmas

Abstract

Large sub-millisecond heat pulses due to Type-I ELMs have been reproducibly eliminated in DIII-D for periods approaching 7 energy confinement times with small dc currents driven in a simple magnetic perturbation coil. The current required to eliminate all but a few isolated Type-I ELM impulses during a perturbation coil pulse lasting several seconds is less than 0.4% of plasma current. Based on vacuum magnetic field line modeling, perturbation fields from the coil resonate strongly with plasma flux surfaces across most of the pedestal region (0.9 {le} {psi}{sub N} {le} 1.0) when q95 = 3.7{plus_minus}0.2 creating small remnant magnetic islands surrounded by weakly stochastic field lines. Under the best ELM suppression conditions, the stored energy, {beta}N and H-mode quality factor are unaffected by the perturbation field along with the electron pressure profile, radial electric field and poloidal rotation across the pedestal. Consequently, the H-mode transport barrier and global energy confinement time is also unaltered in these cases. Although some isolated ELM-like events typically occur during the perturbation coil pulse, long periods free of large Type-I ELMs ({Delta}t > 4-6 {tau}{sub E}) have been reproduced numerous times, on multiple experimental run days. Several Type-I ELM suppression and modification behaviors have been identifiedmore » and studied over a range of discharge conditions including those matching the ITER scenario 2 flux surface shape and aspect ratio scaled down by a factor of 3.5 to fit in the DIII-D vacuum vessel. Since large Type-I ELM impulses represent a severe constraint on the survivability of the divertor target plates in future fusion devices such as ITER, a proven method of eliminating these impulses is critical for the development of tokamak reactors. Results presented in this paper suggest that non-axisymmetric edge magnetic perturbations could be a promising option for controlling ELMs in future tokamaks such as ITER.« less

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »; ; ; ; ; ; ; « less
Publication Date:
Research Org.:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
15014746
Report Number(s):
UCRL-CONF-207379
Journal ID: ISSN 0022-3115; TRN: US0800913
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Journal Volume: 337-339; Conference: Presented at: 20th IAEA Conference, Vilamoura, Portugal, Nov 01 - Nov 06, 2004
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION; ASPECT RATIO; CONFINEMENT; CONFINEMENT TIME; DOUBLET-3 DEVICE; EDGE LOCALIZED MODES; ELECTRIC CURRENTS; ELECTRIC FIELDS; IAEA; MAGNETIC FIELDS; MAGNETIC ISLANDS; MAGNETIC SURFACES; QUALITY FACTOR; STORED ENERGY

Citation Formats

Evans, T E, Moyer, R A, Watkins, J G, Osborne, T H, Thomas, P R, Becoulet, M, Boedo, J A, Doyle, E J, Fenstermacher, M E, Finken, K H, Groebner, R J, Groth, M, Harris, J H, Jackson, G L, La Haye, R J, Lasnier, C J, Masuzaki, S, Ohyabu, N, Pretty, D G, Reimerdes, H, Rhodes, T L, Rudakov, D L, Schaffer, M J, Wade, M, Wang, G, West, W P, and Zeng, L. Suppression of Large Edge Localized Modes with a Stochastic Magnetic Boundary in High Confinement DIII-D Plasmas. United States: N. p., 2004. Web. doi:10.1016/j.jnucmat.2004.10.062.
Copy to clipboard
Evans, T E, Moyer, R A, Watkins, J G, Osborne, T H, Thomas, P R, Becoulet, M, Boedo, J A, Doyle, E J, Fenstermacher, M E, Finken, K H, Groebner, R J, Groth, M, Harris, J H, Jackson, G L, La Haye, R J, Lasnier, C J, Masuzaki, S, Ohyabu, N, Pretty, D G, Reimerdes, H, Rhodes, T L, Rudakov, D L, Schaffer, M J, Wade, M, Wang, G, West, W P, & Zeng, L. Suppression of Large Edge Localized Modes with a Stochastic Magnetic Boundary in High Confinement DIII-D Plasmas. United States. https://doi.org/10.1016/j.jnucmat.2004.10.062
Copy to clipboard
Evans, T E, Moyer, R A, Watkins, J G, Osborne, T H, Thomas, P R, Becoulet, M, Boedo, J A, Doyle, E J, Fenstermacher, M E, Finken, K H, Groebner, R J, Groth, M, Harris, J H, Jackson, G L, La Haye, R J, Lasnier, C J, Masuzaki, S, Ohyabu, N, Pretty, D G, Reimerdes, H, Rhodes, T L, Rudakov, D L, Schaffer, M J, Wade, M, Wang, G, West, W P, and Zeng, L. 2004. "Suppression of Large Edge Localized Modes with a Stochastic Magnetic Boundary in High Confinement DIII-D Plasmas". United States. https://doi.org/10.1016/j.jnucmat.2004.10.062. https://www.osti.gov/servlets/purl/15014746.
Copy to clipboard
@article{osti_15014746,
title = {Suppression of Large Edge Localized Modes with a Stochastic Magnetic Boundary in High Confinement DIII-D Plasmas},
author = {Evans, T E and Moyer, R A and Watkins, J G and Osborne, T H and Thomas, P R and Becoulet, M and Boedo, J A and Doyle, E J and Fenstermacher, M E and Finken, K H and Groebner, R J and Groth, M and Harris, J H and Jackson, G L and La Haye, R J and Lasnier, C J and Masuzaki, S and Ohyabu, N and Pretty, D G and Reimerdes, H and Rhodes, T L and Rudakov, D L and Schaffer, M J and Wade, M and Wang, G and West, W P and Zeng, L},
abstractNote = {Large sub-millisecond heat pulses due to Type-I ELMs have been reproducibly eliminated in DIII-D for periods approaching 7 energy confinement times with small dc currents driven in a simple magnetic perturbation coil. The current required to eliminate all but a few isolated Type-I ELM impulses during a perturbation coil pulse lasting several seconds is less than 0.4% of plasma current. Based on vacuum magnetic field line modeling, perturbation fields from the coil resonate strongly with plasma flux surfaces across most of the pedestal region (0.9 {le} {psi}{sub N} {le} 1.0) when q95 = 3.7{plus_minus}0.2 creating small remnant magnetic islands surrounded by weakly stochastic field lines. Under the best ELM suppression conditions, the stored energy, {beta}N and H-mode quality factor are unaffected by the perturbation field along with the electron pressure profile, radial electric field and poloidal rotation across the pedestal. Consequently, the H-mode transport barrier and global energy confinement time is also unaltered in these cases. Although some isolated ELM-like events typically occur during the perturbation coil pulse, long periods free of large Type-I ELMs ({Delta}t > 4-6 {tau}{sub E}) have been reproduced numerous times, on multiple experimental run days. Several Type-I ELM suppression and modification behaviors have been identified and studied over a range of discharge conditions including those matching the ITER scenario 2 flux surface shape and aspect ratio scaled down by a factor of 3.5 to fit in the DIII-D vacuum vessel. Since large Type-I ELM impulses represent a severe constraint on the survivability of the divertor target plates in future fusion devices such as ITER, a proven method of eliminating these impulses is critical for the development of tokamak reactors. Results presented in this paper suggest that non-axisymmetric edge magnetic perturbations could be a promising option for controlling ELMs in future tokamaks such as ITER.},
doi = {10.1016/j.jnucmat.2004.10.062},
url = {https://www.osti.gov/biblio/15014746}, journal = {},
issn = {0022-3115},
number = ,
volume = 337-339,
place = {United States},
year = {Mon Oct 18 00:00:00 EDT 2004},
month = {Mon Oct 18 00:00:00 EDT 2004}
}
Copy to clipboard
Conference:
View Conference (1.51 MB)
https://doi.org/10.1016/j.jnucmat.2004.10.062
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.
Save / Share:
Export Metadata
Save to My Library
You must Sign In or Create an Account in order to save documents to your library.

Works referenced in this record:

Characteristics and scaling of energy and particle losses during Type I ELMs in JET H-modes
journal, August 2002

Characteristics of type I ELM energy and particle losses in existing devices and their extrapolation to ITER
journal, August 2003

Lithium divertor concept and results of supporting experiments
journal, May 2002

ELM particle and energy transport in the SOL and divertor of DIII-D
journal, August 2003

Key ITER plasma edge and plasma–material interaction issues
journal, March 2003

Assessment of erosion of the ITER divertor targets during type I ELMs
journal, August 2003

Improved ELM scaling with impurity seeding in JET
journal, August 2003

ELM frequency control by continuous small pellet injection in ASDEX Upgrade
journal, September 2003

Suppression of Large Edge-Localized Modes in High-Confinement DIII-D Plasmas with a Stochastic Magnetic Boundary
journal, June 2004

Design of a coil to correct magnetic field errors on the DIII-D tokamak
conference, January 1992

Nonlinear Oscillations, Dynamical Systems, and Bifurcations of Vector Fields
book, January 1983

Explicit calculations of homoclinic tangles in tokamaks
journal, September 2003

Homoclinic tangles, bifurcations and edge stochasticity in diverted tokamaks
journal, April 2004

Modeling of stochastic magnetic flux loss from the edge of a poloidally diverted tokamak
journal, December 2002

Analysis and correction of intrinsic non-axisymmetric magnetic fields in high-  DIII-D plasmas
journal, October 2002

Theoretical and experimental investigations of stochastic boundaries in tokamaks
journal, October 1996

    Sort options
    [ × clear filter / sort ]

    Similar records in OSTI.GOV collections: