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Title: Estimation of sheath potentials in front of ASDEX upgrade ICRF antenna with SSWICH asymptotic code

Multi-megawatt Ion Cyclotron Range of Frequencies (ICRF) heating became problematic in ASDEX Upgrade (AUG) tokamak after coating of ICRF antenna limiters and other plasma facing components by tungsten. Strong impurity influx was indeed produced at levels of injected power markedly lower than in the previous experiments. It is assumed that the impurity production is mainly driven by parallel component of Radio-Frequency (RF) antenna electric near-field E// that is rectified in sheaths. In this contribution we estimate poloidal distribution of sheath Direct Current (DC) potential in front of the ICRF antenna and simulate its relative variations over the parametric scans performed during experiments, trying to reproduce some of the experimental observations. In addition, relative comparison between two types of AUG ICRF antenna configurations, used for experiments in 2014, has been performed. For this purpose we use the Torino Polytechnic Ion Cyclotron Antenna (TOPICA) code and asymptotic version of the Self-consistent Sheaths and Waves for Ion Cyclotron Heating (SSWICH) code. Further, we investigate correlation between amplitudes of the calculated oscillating sheath voltages and the E// fields computed at the lateral side of the antenna box, in relation with a heuristic antenna design strategy at IPP Garching to mitigate RF sheaths.
Authors:
 [1] ; ; ;  [2] ;  [3] ;  [4]
  1. LPP-ERM/KMS, Royal Military Academy, 30 Avenue de la Renaissance B-1000, Brussels (Belgium)
  2. Max-Planck-Institut für Plasmaphysik, D-85748 Garching (Germany)
  3. CEA, IRFM, F-13108 Saint-Paul-Lez-Durance (France)
  4. Politecnico di Torino, Corso Duca degli Abruzzi 24, I-10129 Torino (Italy)
Publication Date:
OSTI Identifier:
22496197
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1689; Journal Issue: 1; Conference: 21. topical conference on radio frequency power in plasmas, Lake Arrowhead, CA (United States), 27-29 Apr 2015; Other Information: (c) 2015 EURATOM; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; AMPLITUDES; ANTENNAS; ASDEX TOKAMAK; ASYMPTOTIC SOLUTIONS; COMPARATIVE EVALUATIONS; DIRECT CURRENT; ELECTRIC POTENTIAL; FIRST WALL; ICR HEATING; IMPURITIES; ION CYCLOTRON-RESONANCE; IONS; IPP GARCHING; RADIOWAVE RADIATION; TUNGSTEN