skip to main content

SciTech ConnectSciTech Connect

Title: ICRF 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 material on the JET Ion Cyclotron Resonance Frequency (ICRF) operation was assessed and also the properties of JET plasmas heated with ICRF were studied. No substantial change of the antenna coupling resistance was observed with the ILW as compared with the carbon wall. Heat-fluxes on the protecting limiters close the antennas quantified using Infra-Red (IR) 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 well 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. Some experimental facts indicate that main-chamber W components could be an important impurity source: the divertor W influx deduced from spectroscopy is comparable when using RF or NBI at same power and comparable divertor conditions; the W content is also increased in ICRF-heated limiter plasmas; and Bemore » evaporation in the main chamber results in a strong and long lasting reduction of the impurity level. The ICRF specific high-Z impurity content decreased when operating at higher plasma density and when increasing the hydrogen concentration from 5% to 20%. Despite the higher plasma bulk radiation, ICRF exhibited overall good plasma heating efficiency; The ICRF power can be deposited at plasma centre and the radiation is mainly from the outer part of the plasma. Application of ICRF heating in H-mode plasmas started, and the beneficial effect of ICRF central electron heating to prevent W accumulation in the plasma core could be observed.« less
Authors:
; ; ; ; ; ;  [1] ; ; ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ; ;  [8] ;  [9] ;  [10] ;
  1. Euratom/CCFE Fusion Association, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom)
  2. Max-Planck-Institut für Plasmaphysik, EURATOM-Assoziation, Garching (Germany)
  3. IEK-4, Forschungszentrum Jülich, Association EURATOM-FZJ (Germany)
  4. Ecole Nationale des Ponts et Chaussées, F77455 Marne-la-Vallée (France)
  5. CEA, IRFM, F-13108 Saint-Paul-Lez-Durance (France)
  6. Association Euratom-IPPLM, Hery 23, 01-497 Warsaw (Poland)
  7. Oak Ridge National Laboratory, Oak Ridge, TN 37831-6169 (United States)
  8. Association EURATOM-Belgian State, ERM-KMS, Brussels (Belgium)
  9. Politecnico di Torino, Department of Electronics, Torino (Italy)
  10. Association EURATOM-IPP.CR, Za Slovankou 3, 182 21 Praha 8 (Czech Republic)
Publication Date:
OSTI Identifier:
22267804
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1580; Journal Issue: 1; Conference: 20. topical conference on radiofrequency power in plasmas, Sorrento (Italy), 25-28 Jun 2013; Other Information: (c) 2014 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; BEAM INJECTION HEATING; EFFICIENCY; HEAT FLUX; H-MODE PLASMA CONFINEMENT; ICR HEATING; ION CYCLOTRON-RESONANCE; ITER TOKAMAK; PLASMA; PLASMA DENSITY; THERMOGRAPHY