Residual carbon content in the initial ITER-Like Wall experiments at JET

TitleResidual carbon content in the initial ITER-Like Wall experiments at JET
Publication TypeJournal Article
Year of Publication2013
AuthorsS. Brezinsek, S. Jachmich, M.F Stamp, A.G Meigs, J.W Coenen, K. Krieger, C. Giroud, M. Groth, V. Philipps, S. Grünhagen, R. Smith, G.J van Rooij, D. Ivanova, G.F Matthews
JournalJournal of Nuclear Materials
Volume438, Supplement
PaginationS303 - S308

Abstract The residual carbon content and carbon edge flux in JET have been assessed by three independent diagnostic techniques after start of plasma operation with the ITER-Like Wall (ILW) with beryllium first wall and tungsten divertor: (i) in-situ measurements with optical spectroscopy on low ionisation stages of carbon, (ii) charge-exchange recombination spectroscopy, and (iii) residual gas composition analysis in dedicated global gas balance experiments. Direct comparison experiments in L-mode discharges were carried out between references from the previously installed material configuration with plasma-facing components made of carbon-fibre composite (JET-CFC) and the JET-ILW. The temporal evolution of the C divertor flux since installation of the İLW has been studied in the ohmic phase of dedicated monitoring discharges which have been executed regularly throughout the experimental exploitation so far (60000 plasma seconds). The C flux behaviour in the divertor can be divided in three phases: initial fast drop, moderate reduction phase, and a long lasting phase with almost constant C flux. The Be flux in both divertor legs mirrors the behaviour of C. All experiments and diagnostic techniques demonstrate a strong reduction in C fluxes and C content of more than one order of magnitude with respect to JET-CFC which is in line with the reduction in long-term fuel retention due to co-deposition. There is no evidence of an increase in residual carbon in time, thus no indication that a damage of the thin tungsten coatings on CFC substrate in the divertor occurred.







Alternate TitleJ. Nucl. Mater.

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