Speaker
Dr
Ernesto Augusto Lerche
(LPP-ERM/KMS)
Description
Since 2011 JET has been operating with a full-metal ITER-like wall (ILW), with most of the main chamber plasma facing components made from beryllium (Be) and featuring a bulk tungsten (W) divertor [1,2]. In H-modes with PNBI>15MW of neutral beam injection (NBI), accumulation of heavy impurities (in particular W) has become a concern, since aside from degrading the plasma performance it can - in some cases - lead to radiative collapse of the discharges. One efficient way of avoiding this deleterious central impurity accumulation is to provide a localized heat source to the plasma core, since the resulting peaked temperature profiles have a favourable impact on the transport of the high-Z impurities in this region. The main results concerning the use of ICRH for core impurity mitigation in high power H-mode discharges in JET-ILW will be discussed. It will be shown that the ICRH scenario has to be optimized for core electron heating (low minority concentration, central absorption) and that a minimum RF power (~4MW) is needed for achieving sufficiently peaked temperature profiles (Te0>5keV) in typical JET H-mode plasmas (ne0=7-9e19/m3) for effective core impurity mitigation to take place. In these conditions, the W concentration profiles as inferred from soft X-ray tomography are hollow, as opposed to the NBI only heated H-modes, which show a strongly peaked W profile in the plasma centre (r/a<0.2). Aside from assisting the high performance H-mode baseline development and from being routinely used to provide a smooth H-L transition for reliable discharge termination, ICRH has also proven to be essential for achieving steady state nitrogen seeded H-mode discharges in JET-ILW [3].
This work was supported by EURATOM and carried out within the framework of the EFDA. The views and opinions expressed herein do not necessarily reflect those of the European Commission.
[1] G. Matthews et al., Phys. Scr. 2011 (2011) 014001
[2] S. Brezinsek et al., Abs. PSI2014, Karazawa, Japan
[3] C. Giroud et al., this conference
| Country or International Organisation | Belgium |
|---|---|
| Paper Number | EX/P5-22 |
Primary author
Dr
Ernesto Augusto Lerche
(LPP-ERM/KMS)
Co-authors
Dr
Adrianus Sips
(EFDA-JET)
Dr
Agata Czarnecka
(IPP-Warsaw)
Mr
Anthony Shaw
(CCFE)
Dr
Carine Giroud
(CCFE)
Dr
Clive Challis
(Culham Centre for Fusion Energy)
Dr
Costanza Maggi
(Max Planck Institut fuer Plasmaphysik)
Mr
Craig Noble
(CCFE)
Dr
Dirk Van Eester
(LPP-ERM/KMS)
Dr
Dumont Remi
(CEA-IRFM)
Dr
Emmanuel Joffrin
(CEA/IRFM)
Dr
Fernanda Rimini
(CCFE)
Mr
Guy Matthews
(Culham Centre for Fusion Energy)
Dr
Igor Monakhov
(CCFE)
Dr
Isabel Maria Ferreira Nunes
(IPFN/IST)
Dr
Jan Mlynar
(IPP-CR Prague)
Dr
Joerg Hobirk
(IPP-Garching)
Dr
Jonathan Graves
(CRPP-EPFL)
Dr
Kristel Crombe
(LPP-ERM/KMS)
Dr
Laurent COLAS
(CEA, IRFM)
Dr
Leena Aho-Mantila
(VTT Technical Research Centre of Finland)
Dr
Marc Goniche
(CEA, IRFM)
Dr
Marco Valisa
(Consorzo RFX)
Dr
Maria Filomena Nave
(Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico)
Dr
Marie-Line Mayoral
(CCFE)
Dr
Matthias Reich
(Max-Planck-Institut für Plasmaphysik, Garching, Germany)
Dr
Maximus Tsalas
(DIFFER)
Mr
Morten Lennholm
(European Commission)
Dr
Nicolas Fedorczak
(CEA-IRFM)
Dr
Paola Mantica
(ENEA)
Dr
Pascale Monier-Garbet
(CEA, IRFM)
Dr
Peter Lomas
(ccfe)
Dr
Philippe Jacquet
(CCFE)
Dr
Sebastijan Brezinsek
(Forschungszentrum Jülich)
Dr
Thomas Puetterich
(IPP Garching)
Mr
Trevor Blackman
(CCFE)
Vaclav Petrzilka
(IPP-CR Prague)
Dr
Vasili Kiptily
(CCFE)
Dr
Volodymyr Bobkov
(Max-Planck-Institute for Plasma Physics)
