Effect of ELMs on the SOL plasma in DIII-D

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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 ... continued below

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6 p.

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Jong, R.A.; Porter, G.D. & Groebner, R.J. May 9, 1995.

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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.

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6 p.

Notes

INIS; OSTI as DE96001718

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  • IAEA technical committee meeting/ US-Japan workshop on H-mode physics, Princeton, NJ (United States), 18-20 Sep 1995

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  • Other: DE96001718
  • Report No.: UCRL-JC--120994
  • Report No.: CONF-9509238--1
  • Grant Number: W-7405-ENG-48;AC03-89ER51114
  • Office of Scientific & Technical Information Report Number: 116704
  • Archival Resource Key: ark:/67531/metadc622943

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  • May 9, 1995

Added to The UNT Digital Library

  • June 16, 2015, 7:43 a.m.

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  • May 31, 2016, 6:22 p.m.

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Jong, R.A.; Porter, G.D. & Groebner, R.J. Effect of ELMs on the SOL plasma in DIII-D, article, May 9, 1995; California. (digital.library.unt.edu/ark:/67531/metadc622943/: accessed December 16, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.