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Title: Ion cyclotron resonance frequency heating in JET during initial operations with the ITER-like wall

In 2011/12, JET started operation with its new ITER-Like Wall (ILW) made of a tungsten (W) divertor and a beryllium (Be) main chamber wall. The impact of the new wall materials on the JET Ion Cyclotron Resonance Frequency (ICRF) operation is assessed and some important properties of JET plasmas heated with ICRF are highlighted. A ∼ 20% reduction of the antenna coupling resistance is observed with the ILW as compared with the JET carbon (JET-C) wall. Heat-fluxes on the protecting limiters close the antennas, quantified using Infra-Red thermography (maximum 4.5 MW/m{sup 2} in current drive phasing), are within the wall power load handling capabilities. A simple RF sheath rectification model using the antenna near-fields calculated with the TOPICA code can reproduce the heat-flux pattern around the antennas. ICRF heating results in larger tungsten and nickel (Ni) contents in the plasma and in a larger core radiation when compared to Neutral Beam Injection (NBI) heating. The location of the tungsten ICRF specific source could not be identified but some experimental observations indicate that main-chamber W components could be an important impurity source: for example, the divertor W influx deduced from spectroscopy is comparable when using RF or NBI at same power and comparable divertormore » conditions, and Be evaporation in the main chamber results in a strong reduction of the impurity level. In L-mode plasmas, the ICRF specific high-Z impurity content decreased when operating at higher plasma density and when increasing the hydrogen concentration from 5% to 15%. Despite the higher plasma bulk radiation, ICRF exhibited overall good plasma heating performance; the power is typically deposited at the plasma centre while the radiation is mainly from the outer part of the plasma bulk. Application of ICRF heating in H-mode plasmas has started, and the beneficial effect of ICRF central electron heating to prevent W accumulation in the plasma core has been observed.« less
Authors:
; ; ; ; ; ;  [1] ; ; ; ;  [2] ;  [3] ;  [4] ; ;  [5] ;  [1] ;  [6] ;  [7] ;  [8] ;  [9] more »;  [10] ; « less
  1. Euratom/CCFE Fusion Association, Culham Science Centre, Abingdon OX14 3DB (United Kingdom)
  2. Max-Planck-Institut für Plasmaphysik, EURATOM-Assoziation, Garching (Germany)
  3. CEA, IRFM, F-13108 Saint-Paul-Lez-Durance (France)
  4. Association Euratom-IPPLM, Hery 23, 01-497 Warsaw (Poland)
  5. Association EURATOM-Belgian State, ERM-KMS, Brussels (Belgium)
  6. (Germany)
  7. IEK-4, Forschungszentrum Jülich, Association EURATOM-FZJ, Jülich (Germany)
  8. Ecole Nationale des Ponts et Chaussées, F77455 Marne-la-Vallée (France)
  9. Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6169 (United States)
  10. Politecnico di Torino, Department of Electronics, Torino (Italy)
Publication Date:
OSTI Identifier:
22299953
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 21; Journal Issue: 6; Other Information: (c) 2014 Euratom; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BEAM INJECTION HEATING; DIVERTORS; HEAT FLUX; H-MODE PLASMA CONFINEMENT; ICR HEATING; IMPURITIES; ION CYCLOTRON-RESONANCE; ITER TOKAMAK; LIMITERS; L-MODE PLASMA CONFINEMENT; NEUTRAL ATOM BEAM INJECTION; PLASMA DENSITY