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Title: L to H mode transition: Parametric dependencies of the temperature threshold

The L to H mode transition occurs at a critical power which depends on various parameters, such as the magnetic field, the density, etc. Experimental evidence on various tokamaks (JET, ASDEX-Upgrade, DIII-D, Alcator C-Mod) points towards the existence of a critical temperature characterizing the transition. This criterion for the L-H transition is local and is therefore easier to be compared to theoretical approaches. In order to shed light on the mechanisms of the transition, simple theoretical ideas are used to derive a temperature threshold (Tth). They are based on the stabilization of the underlying turbulence by a mean radial electric field shear. The nature of the turbulence varies as the collisionality decreases, from resistive ballooning modes to ion temperature gradient and trapped electron modes. The obtained parametric dependencies of the derived Tth are tested versus magnetic field, density, effective charge. Furthermore, various robust experimental observations are reproduced, in particular Tth increases with magnetic field B and increases with density below the density roll-over observed on the power threshold.
Authors:
 [1] ;  [2] ;  [1] ;  [1] ;  [3] ;  [4] ;  [3] ;  [5] ;  [6] ;  [6] ;  [1] ;  [7] ;  [8] ;  [1]
  1. CEA, IRFM, Saint-Paul-lez-Durance (France)
  2. CEA, IRFM, Saint-Paul-lez-Durance (France); Aix-Marseille Univ., CNRS, Marseille Cedex (France)
  3. Aix-Marseille Univ., CNRS, Marseille Cedex (France)
  4. CEA, IRFM, Saint-Paul-lez-Durance (France); FOM Institute DIFFER-Dutch Institute for Fundamental Energy Research, Nieuwegein (The Netherlands)
  5. ITER Organization, Saint Paul Lez Durance (France)
  6. Culham Centre for Fusion Energy, Abingdon (United Kingdom)
  7. Ecole Polytechnique, Palaiseau (France)
  8. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
OSTI Identifier:
1263860
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 55; Journal Issue: 7; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY plasma physics; L H transition; tokamak