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Measuring the plasma composition in tokamaks with metallic plasma-facing components

Part of: Focus on Fusion

Published online by Cambridge University Press:  07 October 2019

M. Sertoli Open the ORCID record for M. Sertoli [Opens in a new window] ,
Pedro Jorge Carvalho Open the ORCID record for Pedro Jorge Carvalho [Opens in a new window] ,
C. Giroud ,
S. Menmuir  and
JET Contributors
M. Sertoli*
Affiliation:
Max-Planck-Institut für Plasmaphysik, Boltzmannstrasse 2, D-85748 Garching, Germany CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB, UK
Pedro Jorge Carvalho
Affiliation:
Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
C. Giroud
Affiliation:
CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB, UK
S. Menmuir
Affiliation:
CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB, UK
JET Contributors
Affiliation:
Max-Planck-Institut für Plasmaphysik, Boltzmannstrasse 2, D-85748 Garching, Germany CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB, UK Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
*
†Email address for correspondence: marco.sertoli@ukaea.uk
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Abstract

In present and future magnetic confined fusion devices with metallic plasma-facing components (PFCs) such as JET-ILW and ITER, the calculation of the plasma composition must account for multiple impurities of a wide range of mass and charge, resolve their poloidal asymmetries and account for different central peakings for various elements. Single measurements of radiation and effective charge are not enough to characterize this complex system and a self-consistent analysis of data from multiple diagnostics is required. This contribution describes a method to calculate the plasma composition simultaneously accounting for contributions of up to two low-Z impurities, and two mid-/high-Z impurities. The analysis stems from methodologies explained in Sertoli et al. (Rev. Sci. Instrum., vol. 89 (11), 2018, 113501), expanded to include more impurities and to coherently analyse multiple diagnostics within the same framework. The example Ne-seeded JET-ILW hybrid discharge reported here shows that Be, Ne, Ni and W are necessary to simultaneously explain the observed soft X-ray emission, the W concentration measured by passive vacuum ultra-violet spectroscopy, the line-of-sight integrated measurement of the effective charge, the observed poloidal asymmetry of the soft X-ray (SXR) emission, the Ne density measured by charge-exchange-recombination spectroscopy and the line-of-sight integrals of the total radiation as measured by bolometry. This consistent picture of the elemental composition enables the calculation of the radial profiles of the effective charge, the dilution and total radiation. For the cases analysed up to now, these are often very different from the typical assumptions presently used when modelling JET-ILW discharges. This will affect, among others, the calculation of neutron rates, current density profile and heat transport. These considerations are of course valid for all present and future magnetic-controlled fusion devices which exhibit multi-material plasma-facing components, including ITER.

Keywords

fusion plasmaplasma diagnosticsplasma properties
Type
Research Article
Information
Journal of Plasma Physics , Volume 85 , Issue 5 , October 2019 , 905850504
Copyright
© The Author(s) 2019. Published by Cambridge University Press 

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Footnotes

‡

See the author list of ‘Overview of the JET preparation for Deuterium-Tritium Operation’ by E. Joffrin et al. to be published in Nuclear Fusion Special issue: overview and summary reports from the 27th Fusion Energy Conference (Ahmedabad, India, 22–27 October 2018).

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