| Bibliographic Citation | |
| Full Text |  0 K |
|---|---|
| Title | Suppression of Large Edge Localized Modes with a Stochastic Magnetic Boundary in High Confinement DIII-D Plasmas |
| Creator/Author | 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 |
| Publication Date | 2004 Oct 18 |
| OSTI Identifier | OSTI ID: 15014746 |
| Report Number(s) | UCRL-CONF-207379 |
| DOE Contract Number | W-7405-ENG-48 |
| Other Number(s) | TRN: US200802%%1391 |
| Resource Type | Conference |
| Resource Relation | Conference: Presented at: 20th IAEA Conference, Vilamoura, Portugal, Nov 01 - Nov 06, 2004 |
| Research Org | Lawrence Livermore National Laboratory (LLNL), Livermore, CA |
| Sponsoring Org | USDOE |
| 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 |
| Description/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 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. |
| Country of Publication | United States |
| Language | English |
| Format | Medium: ED; Size: PDF-file: 11 pages; size: 1.5 Mbytes |
| System Entry Date | 2008 Feb 04 |
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Last Updated: 11/20/2009