High Density H-Mode Discharges with Gas Fueling and Good Confinement on DIII-D

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H-mode operation at high density is an attractive regime for future reactor-grade tokamaks [1]. High density maximizes fusion power output while the high confinement of H-mode keeps the plasma energy loss below the alpha heating power. One concern though is the energy released due to individual ELMs must be kept small to protect the diverter target from excess ablation. We report on discharges in DIII-D with electron densities as high as 1.45 times the Greenwald density, n{sub GW}(10{sup 20}m{sup -3})=I{sub p}(MA)/[{pi}{sup 2}(m)], with good confinement, H{sub ITER89P}=1.9, and ELMs with energy amplitude small enough to protect the divertor. These results ... continued below

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Leonard, A.W.; Osborne, T.H.; Mahdavi, M.A.; Fenstermacher, M.E.; Lasnier, C.J.; Petrie, T.W. et al. August 1, 2000.

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  • General Atomic Company
    Publisher Info: General Atomics, San Diego, CA (United States)
    Place of Publication: San Diego, California

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H-mode operation at high density is an attractive regime for future reactor-grade tokamaks [1]. High density maximizes fusion power output while the high confinement of H-mode keeps the plasma energy loss below the alpha heating power. One concern though is the energy released due to individual ELMs must be kept small to protect the diverter target from excess ablation. We report on discharges in DIII-D with electron densities as high as 1.45 times the Greenwald density, n{sub GW}(10{sup 20}m{sup -3})=I{sub p}(MA)/[{pi}{sup 2}(m)], with good confinement, H{sub ITER89P}=1.9, and ELMs with energy amplitude small enough to protect the divertor. These results were achieved at low triangularity single-null divertor, {delta}{approx}0.0 with a plasma current of 1.2 MA, q{sub 95} {approx} 3-4, and moderate neutral beam heating power of 2-4 MW. The density was controlled by moderate gas puffing and private flux pumping. A typical discharge is shown in Fig. 1 where upon gas puffing the pedestal density, n{sub e,epd}, quickly rises to {approx}0.8 x n{sub GW}. The confinement initially drops with the gas puff, on a longer timescale the central density rises, peaking the profile and increasing the confinement until an MHD instability terminates the high density and high confinement phase of the discharge. In this report we describe in detail edge pedestal changes and its effect on confinement as the density is increased. We then describe peaking of the density profile that offsets degradation of the pedestal at high density and restores good confinement. Finally we describe the small benign ELMs that result at these high densities.

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INIS; OSTI as DE00766692

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  • 27th European Physical Society Conference on Controlled Fusion and Plasma Physics, Budapest (HU), 06/12/2000--06/16/2000

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  • Report No.: GA-A23418
  • Grant Number: AC03-99ER54463
  • Grant Number: W-7405-ENG-48
  • Grant Number: AC04-94AL85000
  • Office of Scientific & Technical Information Report Number: 766692
  • Archival Resource Key: ark:/67531/metadc722686

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  • August 1, 2000

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  • Sept. 29, 2015, 5:31 a.m.

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  • April 18, 2016, 6:06 p.m.

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Leonard, A.W.; Osborne, T.H.; Mahdavi, M.A.; Fenstermacher, M.E.; Lasnier, C.J.; Petrie, T.W. et al. High Density H-Mode Discharges with Gas Fueling and Good Confinement on DIII-D, article, August 1, 2000; San Diego, California. (digital.library.unt.edu/ark:/67531/metadc722686/: accessed August 17, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.