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Title: Stabilization of sawteeth with third harmonic deuterium ICRF-accelerated beam in JET plasmas

Sawtooth stabilisation by fast ions is investigated in deuterium (D) and D-helium 3 (He3) plasmas of JET heated by deuterium Neutral Beam Injection combined in synergy with Ion Cyclotron Resonance Heating (ICRH) applied on-axis at 3rd beam cyclotron harmonic. A very significant increase in the sawtooth period is observed, caused by the ICRH-acceleration of the beam ions born at 100 keV to the MeV energy range. Four representative sawteeth from four different discharges are compared with Porcelli's model. In two discharges, the sawtooth crash appears to be triggered by core-localized Toroidal Alfvén Eigenmodes inside the q = 1 surface (also called “tornado” modes) which expel the fast ions from within the q = 1 surface, over time scales comparable with the sawtooth period. Two other discharges did not exhibit fast ion-driven instabilities in the plasma core, and no degradation of fast ion confinement was found in both modelling and direct measurements of fast ion profile with the neutron camera. The developed sawtooth scenario without fast ion-driven instabilities in the plasma core is of high interest for the burning plasmas. Possible causes of the sawtooth crashes on JET are discussed.
Authors:
 [1] ;  [2] ; ; ; ; ;  [3] ;  [4] ; ; ; ;  [5] ;  [6] ;  [7] ;  [8]
  1. EUROfusion Consortium, JET, Culham Science Centre, Abingdon OX14 3DB (United Kingdom)
  2. (France)
  3. CCFE, Culham Science Centre, Abingdon OX14 3DB (United Kingdom)
  4. Max-Planck-Institut für Plasmaphysik, 85748 Garching (Germany)
  5. CEA, IRFM, F-13108 Saint-Paul-lez-Durance (France)
  6. Department of Physics and Astronomy, Uppsala University, 751 20 Uppsala (Sweden)
  7. Catalan Institution for Research and Advanced Studies, 08010 Barcelona (Spain)
  8. (Spain)
Publication Date:
OSTI Identifier:
22493815
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 23; Journal Issue: 1; Other Information: (c) 2016 EURATOM; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ALFVEN WAVES; BEAM INJECTION; DEUTERIUM; HELIUM 3; ICR HEATING; IONS; JET TOKAMAK; KEV RANGE 10-100; MEV RANGE; NEUTRON CAMERAS; PLASMA; PLASMA CONFINEMENT; PLASMA INSTABILITY; SAWTOOTH OSCILLATIONS; STABILIZATION; TOROIDAL CONFIGURATION