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Title: Extending the physics basis of quiescent H-mode toward ITER relevant parameters

Recent experiments on DIII-D have addressed several long-standing issues needed to establish quiescent H-mode (QH-mode) as a viable operating scenario for ITER. In the past, QH-mode was associated with low density operation, but has now been extended to high normalized densities compatible with operation envisioned for ITER. Through the use of strong shaping, QH-mode plasmas have been maintained at high densities, both absolute ($$\bar{n}$$e ≈ 7 × 1019 m₋3) and normalized Greenwald fraction ($$\bar{n}$$e/nG > 0.7). In these plasmas, the pedestal can evolve to very high pressure and edge current as the density is increased. High density QH-mode operation with strong shaping has allowed access to a previously predicted regime of very high pedestal dubbed “Super H-mode”. Calculations of the pedestal height and width from the EPED model are quantitatively consistent with the experimentally observed density evolution. The confirmation of the shape dependence of the maximum density threshold for QH-mode helps validate the underlying theoretical model of peeling- ballooning modes for ELM stability. In general, QH-mode is found to achieve ELM- stable operation while maintaining adequate impurity exhaust, due to the enhanced impurity transport from an edge harmonic oscillation, thought to be a saturated kink- peeling mode driven by rotation shear. In addition, the impurity confinement time is not affected by rotation, even though the energy confinement time and measured E×B shear are observed to increase at low toroidal rotation. Together with demonstrations of high beta, high confinement and low q95 for many energy confinement times, these results suggest QH-mode as a potentially attractive operating scenario for the ITER Q=10 mission.
 [1] ;  [2] ;  [3] ;  [2] ;  [1] ;  [4] ;  [5] ;  [1] ;  [2] ;  [2]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. General Atomics, San Diego, CA (United States)
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  4. ITER Organization, St. Paul Lez Durance (France)
  5. Univ. of Wisconsin-Madison, Madison, WI (United States)
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0029-5515
Grant/Contract Number:
AC52-07NA27344; AC02- 09CH11466; FC02-04ER54698; FG02-95ER54309; FG02-89ER53296; FG02- 08ER54999
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 55; Journal Issue: 7; Journal ID: ISSN 0029-5515
IOP Science
Research Org:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24); USDOE Advanced Research Projects Agency - Energy (ARPA-E)
Country of Publication:
United States
70 PLASMA PHYSICS AND FUSION TECHNOLOGY ELM-free regimes; pedestal pressure; confinement studies; edge modes