CNR ExploRA

Articolo in rivista, 2015, ENG, 10.1088/0741-3335/57/1/014033

Sawtooh control in JET with ITER relevant low field side resonance ion cyclotron resonance heating and ITER-like wall

J P Graves 1; M Lennholm 2; I T Chapman 3; E Lerche 4; M Reich 5; B Alper 3; V Bobkov 5; R Dumont 6; J M Faustin 1; P Jacquet 3; F Jaulmes 7; T Johnson 8; D L Keeling 3; Yueqiang Liu 3; T Nicolas 6; S Tholerus 8; T Blackman 3; I S Carvalho 9; R Coelho 9; D Van Eester 4; R Felton 3; M Goniche 6; V Kiptily 3; I Monakhov 3; M F F Nave 9; C Perez von Thun 10; R Sabot 6; C Sozzi 11; M Tsalas 7 and JET EFDA Contributors 12

1) École Polytechnique Fédérale de Lausanne (EPFL), Centre de Recherches en Physique des Plasmas (CRPP), 1015 Lausanne, Switzerland; 2) EFDA-JET CSU, Culham Science Centre, Abingdon, OX14 3DB, UK; 3) CCFE Fusion Association, Culham Science Centre, Abingdon, UK; 4) LPP-ERM/KMS, TEC Partner, Brussels, Belgium; 5) Max-Planck-Institut für Plasma Physik, Boltzmannstr. 2, 85748 Garching, Germany; 6) CEA-Cadarache, F-13108 St. Paul lez Durance, France; 7) FOM Institute DIFFER Dutch Institute For Fundamental Energy Research, FOM, Nieuwegein, The Netherlands; 8) Association VR, KTH, SE-100 44 Stockholm, Sweden; 9) Instituto de Plasmas e Fus ao Nuclear, Instituto Superior Técnico, Universidade de Lisboa, P-1049-001, Lisboa, Portugal; 10) University of Innsbruck, Österreichische Akademie der Wissenshaften (ÖAW), 1010 Wien, Austria; 11) Isituto di Fisica del Plasma CNR, 20125 Milano, Italy: 12) JET-EFDA, Culham Science Centre, Abingdon, OX14 3DB, UK

New experiments at JET with the ITER-like wall show for the first time that ITER-relevant low field side resonance first harmonic ion cyclotron resonance heating (ICRH) can be used to control sawteeth that have been initially lengthened by fast particles. In contrast to previous (Graves et al 2012 Nat. Commun. 3 624) high field side resonance sawtooth control experiments undertaken at JET, it is found that the sawteeth of L-mode plasmas can be controlled with less accurate alignment between the resonance layer and the sawtooth inversion radius. This advantage, as well as the discovery that sawteeth can be shortened with various antenna phasings, including dipole, indicates that ICRH is a particularly effective and versatile tool that can be used in future fusion machines for controlling sawteeth. Without sawtooth control, neoclassical tearing modes (NTMs) and locked modes were triggered at very low normalised beta. High power H-mode experiments show the extent to which ICRH can be tuned to control sawteeth and NTMs while simultaneously providing effective electron heating with improved flushing of high Z core impurities. Dedicated ICRH simulations using SELFO, SCENIC and EVE, including wide drift orbit effects, explain why sawtooth control is effective with various antenna phasings and show that the sawtooth control mechanism cannot be explained by enhancement of the magnetic shear. Hybrid kinetic-magnetohydrodynamic

Plasma physics and controlled fusion (Online) 57 (014033), pp. 014033–?