Fast imaging of edge localized mode structure and dynamics in DIII-D
- University of California at San Diego, La Jolla, California 92093 (United States)
- General Atomics, San Diego, California 92186 (United States)
Fast-framing images of CIII and D{sub {alpha}} emission in the low-field-side plasma boundary of the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] show that edge localized modes (ELMs) rapidly eject multiple field-aligned filaments from the plasma edge. The toroidal and poloidal mode numbers of these filaments depend on normalized plasma density, with measured ELM toroidal mode numbers ranging from {<=}10 to 20 in low-density plasmas and 15 to 35 in high-density plasmas. In high-density plasmas with moderate collisionality {nu}{sub ped}*=0.50, ELMs originate at the low-field-side midplane region and the ion parallel velocity in the scrape-off layer is faster for ELMs with larger D{sub {alpha}} divertor emission, suggesting that large ELMs eject higher-temperature ions from deeper within the plasma compared to small ELMs. In low-density plasmas with collisionality {nu}{sub ped}*=0.25, the midplane and divertor ELM signals appear simultaneously, indicating that ELM behavior depends on collisionality. At all {nu}{sub ped}*, ELMs drive parallel fluxes to the divertor; in addition, ELMs drive cross-field propagation of filaments, which results in plasma-wall interactions that are poloidally localized within 15 cm of the midplane. Using the wall interactions as signatures of the filaments in the scrape-off layer, the measured poloidal width of the filament ranges from 1 to 5 cm.
- OSTI ID:
- 21106170
- Journal Information:
- Physics of Plasmas, Vol. 15, Issue 3; Other Information: DOI: 10.1063/1.2898404; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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