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Title: Enhanced H-mode pedestals with lithium injection in DIII-D

Periods of edge localized mode (ELM)-free H-mode with increased pedestal pressure and width were observed in the DIII-D tokamak when density fluctuations localized to the region near the separatrix were present. Injection of a powder of 45 μm diameter lithium particles increased the duration of the enhanced pedestal phases to up to 350 ms, and also increased the likelihood of a transition to the enhanced phase. Lithium injection at a level sufficient for triggering the extended enhanced phases resulted in significant lithium in the plasma core, but carbon and other higher Z impurities as well as radiated power levels were reduced. Recycling of the working deuterium gas appeared unaffected by this level of lithium injection. The ion scale, kθ ρs ~ 0.1–0.2, density fluctuations propagated in the electron drift direction with f ~ 80 kHz and occurred in bursts every ~1 ms. The fluctuation bursts correlated with plasma loss resulting in a flattening of the pressure profile in a region near the separatrix. This localized flattening 2 allowed higher overall pedestal pressure at the peeling-ballooning stability limit and higher pressure than expected under the EPED model due to reduction of the pressure gradient below the “ballooning critical profile”. Furthermore, reductionmore » of the ion pressure by lithium dilution may contribute to the long ELM-free periods.« less
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [3] ;  [3] ;  [4] ;  [5] ;  [5] ;  [3] ;  [6] ;  [5] ;  [2] ;  [1]
  1. General Atomics, San Diego, CA (United States)
  2. Univ. of Wisconsin, Madison, WI (United States)
  3. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  4. Univ. of California San Diego, La Jolla, CA (United States)
  5. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  6. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
OSTI Identifier:
1353120
Grant/Contract Number:
FC02-04ER54698; FG02-89ER53296; FG02-08ER54999; AC02-09CH11466; FG02-99ER54917; AC52-07NA27344; AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 55; Journal Issue: 6; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Research Org:
General Atomics, San Diego, CA (United States)
Sponsoring Org:
USDOE Advanced Research Projects Agency - Energy (ARPA-E)
Contributing Orgs:
The DIII-D Team
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; DIII-D; pedestal; H-mode; lithium