CNR ExploRA

Articolo in rivista, 2017, ENG, 10.1088/1361-6587/aa60d2

Ion cyclotron resonance heating for tungsten control in various JET H-mode scenarios

By:Goniche, M (Goniche, M.)[ 1 ] ; Dumont, RJ (Dumont, R. J.)[ 1 ] ; Bobkov, V (Bobkov, V.)[ 2 ] ; Buratti, P (Buratti, P.)[ 3 ] ; Brezinsek, S (Brezinsek, S.)[ 4 ] ; Challis, C (Challis, C.)[ 5 ] ; Colas, L (Colas, L.)[ 1 ] ; Czarnecka, A (Czarnecka, A.)[ 6 ] ; Drewelow, P (Drewelow, P.)[ 2 ] ; Fedorczak, N (Fedorczak, N.)[ 1 ] ; Garcia, J (Garcia, J.)[ 1 ] ; Giroud, C (Giroud, C.)[ 5 ] ; Graham, M (Graham, M.)[ 5 ] ; Graves, JP (Graves, J. P.)[ 7 ] ; Hobirk, J (Hobirk, J.)[ 2 ] ; Jacquet, P (Jacquet, P.)[ 5 ] ; Lerche, E (Lerche, E.)[ 8 ] ; Mantica, P (Mantica, P.)[ 9 ] ; Monakhov, I (Monakhov, I.)[ 5 ] ; Monier-Garbet, P (Monier-Garbet, P.)[ 1 ] ; Nave, MFF (Nave, M. F. F.)[ 10 ] ; Noble, C (Noble, C.)[ 5 ] ; Nunes, I (Nunes, I.)[ 10 ] ; Putterich, T (Puetterich, T.)[ 2 ] ; Rimini, F (Rimini, F.)[ 5 ] ; Sertoli, M (Sertoli, M.)[ 2 ] ; Valisa, M (Valisa, M.)[ 11 ] ; Van Eester, D (Van Eester, D.)[ 8 ] ;Group Author(s): JET Contributors

[ 1 ] CEA, IRFM, F-13108 St Paul Les Durance, France [ 2 ] Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany [ 3 ] ENEA, CR Frascati, Via E Fermi 45, I-00044 Frascati, RM, Italy [ 4 ] Forschungszentrum Julich, Trilateral Euregio Cluster, Inst Energie & Klimaforsch Plasmaphys, D-52425 Julich, Germany [ 5 ] CCFE, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England [ 6 ] IPPLM, Hery 23, PL-01497 Warsaw, Poland [ 7 ] Ecole Polytech Fed Lausanne, Ctr Rech Phys Plasmas, CH-1015 Lausanne, Switzerland [ 8 ] 1LPP ERM KMS, Trilateral Euregio Cluster, Brussels, Belgium [ 9 ] CNR, Ist Fis Plasma P Caldirola, Milan, Italy [ 10 ] Univ Lisbon, IST, Inst Plasmas & Fusao Nucl, Lisbon, Portugal [ 11 ] CNR, Consorzio RFX, Padua, Italy [ 12 ] EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England

Ion cyclotron resonance heating (ICRH) in the hydrogen minority scheme provides central ion heating and acts favorably on the core tungsten transport. Full wave modeling shows that, at medium power level (4MW), after collisional redistribution, the ratio of power transferred to the ions and the electrons vary little with the minority (hydrogen) concentration n(H)/n(e) but the high-Z impurity screening provided by the fast ions temperature increases with the concentration. The power radiated by tungsten in the core of the JET discharges has been analyzed on a large database covering the 2013-2014 campaign. In the baseline scenario with moderate plasma current (I-p. =. 2.5 MA) ICRH modifies efficiently tungsten transport to avoid its accumulation in the plasma centre and, when the ICRH power is increased, the tungsten radiation peaking evolves as predicted by the neo-classical theory. At higher current (3-4MA), tungsten accumulation can be only avoided with 5MW of ICRH power with high gas injection rate. For discharges in the hybrid scenario, the strong initial peaking of the density leads to strong tungsten accumulation. When this initial density peaking is slightly reduced, with an ICRH power in excess of 4 MW, very low tungsten concentration in the core (similar to 10(-5)) is maintained for 3 s. MHD activity plays a key role in tungsten transport and modulation of the tungsten radiation during a sawtooth cycle is correlated to the fishbone activity triggered by the fast ion pressure gradient.

Plasma physics and controlled fusion (Print) 59 (5)