Edge-localized mode dynamics and transport in the scrape-off layer of the DIII-D tokamak

Journal Article · Fri Jul 15 04:00:00 EDT 2005 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.1949224· OSTI ID:20764404

Boedo, J A; Rudakov, D L; Hollmann, E; Gray, D S; Burrell, K H; Moyer, R A; McKee, G R; Fonck, R; Stangeby, P C; Evans, T E; Snyder, P B; Leonard, A W; Mahdavi, M A; Schaffer, M J; West, W P; Fenstermacher, M E; Groth, M; Allen, S L; Lasnier, C; Porter, G D ^[1]

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1. General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)

High temporal and spatial resolution measurements in the boundary of the DIII-D tokamak show that edge-localized modes (ELMs) are produced in the low field side, are poloidally localized and are composed of fast bursts ({approx}20 to 40 {mu}s long) of hot, dense plasma on a background of less dense, colder plasma ({approx}5x10{sup 18} m{sup -3}, 50 eV) possibly created by the bursts themselves. The ELMs travel radially in the scrape-off layer (SOL), starting at the separatrix at {approx}450 m/s, and slow down to {approx}150 m/s near the wall, convecting particles and energy to the SOL and walls. The temperature and density in the ELM plasma initially correspond to those at the top of the density pedestal but quickly decay with radius in the SOL. The temperature decay length ({approx}1.2 to 1.5 cm) is much shorter than the density decay length ({approx}3 to 8 cm), and the latter decreases with increasing pedestal (and SOL) density. The local particle and energy flux (assuming T{sub i}=T{sub e}) at the midplane wall during the bursts are 10% to 50% ({approx}1 to 2x10{sup 21} m{sup -2} s{sup -1}) and 1% to 2% ({approx}20 to 30 kW/m{sup 2}), respectively, of the LCFS fluxes, indicating that particles are transported radially much more efficiently than heat. Evidence is presented suggesting toroidal rotation of the ELM plasma in the SOL. The ELM plasma density and temperature increase linearly with discharge/pedestal density up to a Greenwald fraction of {approx}0.6, and then decrease resulting in more benign (grassier) ELMs.

• OSTI ID: 20764404
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 7 Vol. 12; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
COLD PLASMA
DECAY
DOUBLET-3 DEVICE
EDGE LOCALIZED MODES
ELECTRON TEMPERATURE
EV RANGE
ION TEMPERATURE
LENGTH
MAGNETIC CONFINEMENT
PLASMA DENSITY
PLASMA DIAGNOSTICS
PLASMA SCRAPE-OFF LAYER
ROTATION
SPATIAL RESOLUTION
WALL EFFECTS