Heat flux calculation and problem of flaking of boron carbide coatings on the Faraday screen of the ICRH antennas during Tore Supra high power, long pulse operation

Y. Corre, M. Lipa, G. Agarici, V. Basiuk, L. Colas, X. Courtois, G. Dunand, R. Dumont, A. Ekedahl, J. L. Gardarein, C. C. Klepper, V. Martin, V. Moncada, C. Portafaix, F. Rigollet, R. Tawizgant, J. M. Travre, K. Vulliez

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Reliable and repetitive high power and long pulse tokamak operation is strongly dependant of the ability to secure the Plasma Facing Components (PFCs). In Tore Supra, a network of 7 infrared (IR) video cameras is routinely used to prevent PFCs overheating and damage in selected regions. Real time feedback control and offline analysis are essential for basic protection and understanding of abnormal thermal events. One important limitation detected by the IR real time feed-back loop during high power RF operation (injected power of 9.5 MW over 26 s and 12 MW over 10 s have been achieved respectively in 2006 and 2008) is due to the interaction between fast ions which increase the power flux density and flaking of the boron carbide coatings on the Faraday screen box of the ICRH antennas. An IR-based experimental procedure is proposed in order to detect new flakes during plasma operation. The thermal response of the B 4C coating is studied with and without flaking during plasma operation. The experimental heat flux deposited by fast ion losses on the Faraday screen is calculated for high (3.8 T) and low magnetic field (2 T) during high RF power operation (with fundamental hydrogen minority and second harmonic ICRH heating schemes respectively). The paper addresses both thermal science issues applied to machine protection and limitation due to fast ions issues during high RF power, long pulse operation. Safety margin to critical heat flux and number of fatigue cycles under heat load are presented in the paper.

Original languageEnglish
Pages (from-to)429-441
Number of pages13
JournalFusion Engineering and Design
Volume86
Issue number4-5
DOIs
StatePublished - Jun 2011

Funding

This work, supported by the European Communities under the contract of Association between EURATOM and CEA, was carried out within the framework of the European Fusion Development Agreement. The views and opinions expressed herein do not necessarily reflect those of the European Commission. This work could not have been possible without the Tore Supra IR team, in particular the responsible of the IR system Dr Corinne Desgranges, Colette Balorin and Michel Jouve. The authors gratefully acknowledge Dr André Grosman, Dr. Marc Missirlian, Dr. Pascale Monier-Garbet and Dr. Marianne Richou for useful discussions and Jean-Michel Bernard for the manufacturing of the B 4 C sample used to up-date the measurement of the coating conductivity.

Keywords

  • High power plasma operation
  • ICRH plasma heating
  • IR thermography
  • Thermal calculation

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