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Title: Multi-device studies of pedestal physics and confinement in the I-mode regime

This paper describes joint ITPA studies of the I-mode regime, which features an edge thermal barrier together with L-mode-like particle and impurity transport and no Edge Localized Modes (ELMs). The regime has been demonstrated on the Alcator C-Mod, ASDEX Upgrade and DIII-D tokamaks, over a wide range of device parameters and pedestal conditions. Dimensionless parameters at the pedestal show overlap across devices and extend to low collisionality. When they are matched, pedestal temperature profiles are also similar. Pedestals are stable to peeling ballooning modes, consistent with lack of ELMs. Access to Imode is independent of heating method (neutral beam injection, Ion Cyclotron and/or Electron Cyclotron Resonance Heating). Normalized energy confinement H98,y2 ≥ 1 has been achieved for a range of 3 ≤ q95 ≤ 4.9 and scales favourably with power. Changes in turbulence in the pedestal region accompany the transition from L-mode to I-mode. The L-I threshold increases with plasma density and current, and with device size, but has a weak dependence on toroidal magnetic field BT. The upper limit of power for I-modes, which is set by I-H transitions, increases with BT and the power range is largest on Alcator C-Mod at B > 5 T. Finally, issues formore » extrapolation to ITER and other future fusion devices are discussed.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [3] ;  [6] ;  [2] ;  [2] ;  [3] ;  [1] ;  [9] ;  [6] ;  [3] ;  [1] ;  [1] ;  [3] more »;  [10] ;  [11] ;  [1] ;  [11] ;  [12] ;  [3] ;  [1] ;  [1] ;  [1] ;  [1] ;  [3] ;  [10] « less
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  2. General Atomics, San Diego, CA (United States)
  3. Max-Planck-Institut fur Plasmaphysik, Garching (Germany)
  4. Univ. of Texas, Austin, TX (United States)
  5. Max-Planck-Institut fur Plasmaphysik, Garching (Germany); EUROfusion - Programme Management Unit, Garching (Germany)
  6. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  7. Univ. of California San Diego, La Jolla, CA (United States); Univ. of York, York (United Kingdom)
  8. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  9. ITER Organization, St. Paul Lez Durance Cedex (France)
  10. Univ. of Wisconsin, Madison, WI (United States)
  11. Univ. of California, Los Angeles, CA (United States)
  12. Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne (Switzerland)
Publication Date:
Grant/Contract Number:
FC02-04ER54698
Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 56; Journal Issue: 8; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Research Org:
General Atomics, San Diego, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
Contributing Orgs:
Alcator C-Mod, ASDEX Upgrade and DIII-D Teams
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY FEC 2014; tokamak; I-mode; pedestal; threshold
OSTI Identifier:
1373884
Alternate Identifier(s):
OSTI ID: 1373884