Effect of ELMs on the SOL plasma in DIII-D

Conference · Tue May 09 04:00:00 EDT 1995

OSTI ID:116704

Jong, R A; Porter, G D; Groebner, R J ^[1]

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1. and others

We have studied the evolution of the edge plasma in VH-mode discharges in DIII-D as the discharge evolves from the ELM-free H-mode phase through the VH-mode phase to the final ELMing H-mode phase, by following the changes in the radial profiles of the density and temperature, in the core plasma near the separatrix and in the scrape-off-layer (SOL) plasma outside the separatrix. The electron density and temperature profiles in the SOL do not show any significant difference between the ELM-free H-mode and VH-mode phases. In the ELMing phase, the, density profile broadens during an ELM, forming a high density (n{sub e} > 1 x 10{sup 19}/m{sup 3}) plateau that extends out into the SOL to the limit of the measurement. This density plateau persists between the ELMs, although the density in the SOL does relax somewhat between the ELMs, with a characteristic time that can be larger than ten milliseconds, much longer than the sonic particle flow time to the divertor plates. The time average density scale length measured at the separatrix increases by about a factor of two after the ELMs begin. This density scale length increases with the ELM background, as measured by the photo-diodes nearest to, but outside the outer strike-point, suggesting that recycling from the divertor targets is supplying particles that maintain the density plateau. The electron temperature profile in the SOL also broadens during an ELM, but relaxes on a much faster time scale and does not persist between ELMs.

• Research Organization: Lawrence Livermore National Lab., CA (United States); General Atomics, San Diego, CA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-48; AC03-89ER51114
• OSTI ID: 116704
• Report Number(s): UCRL-JC--120994; CONF-9509238--1; ON: DE96001718
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
DOUBLET-3 DEVICE
EDGE LOCALIZED MODES
ELECTRON DENSITY
H-MODE PLASMA CONFINEMENT
PLASMA DENSITY
PLASMA DIAGNOSTICS
PLASMA SCRAPE-OFF LAYER
THOMSON SCATTERING