Return To: Session EXP3 - MHD Stability & Alternate Confinement
Prev Page: Session EXP3 - MHD Stability & Alternate Confinement
Next Page: (EXP3/02) Improved Confinement Induced by Tangential CT Injection

(EXP3/01) MHD Studies in FTU Plasmas with Low and Negative Magnetic Shear

P. Buratti, F. Alladio, G. Bracco, S. Cirant¹, F. Crisanti, D. Frigione, E. Giovannozzi, L. Panaccione, O. Tudisco, L. Acitelli, B. Angelini, M. L. Apicella, G. Apruzzese, E. Barbato, L. Bertalot, A. Bertocchi, M. Borra, A. Bruschi¹, G. Buceti, A. Cardinali, C. Centioli, R. Cesario, C. Cianfarani³, S. Ciattaglia, V. Cocilovo, R. de Angelis, F. de Marco, B. Esposito, L. Gabellieri, G. Gatti, C. Gourlan, G. Granucci¹, M. Grolli, A. Imparato, H. Kroegler, M. Leigheb, L. Lovisetto, G. Maddaluno, G. Maffia, S. Mancuso, M. Marinucci, G. Mazzitelli, P. Micozzi, F. Mirizzi, S. Nowak¹, F. P. Orsitto, D. Pacella, M. Panella, V. Pericoli-Ridolfini, L. Pieroni, S. Podda, G. B. Righetti, F. Romanelli, F. Santini, M. Sassi, S. E. Segre², A. Simonetto¹, C. Sozzi¹, S. Sternini, N. Tartoni, A. A. Tuccillo, V. Vitale, G. Vlad, V. Zanza, M. Zerbini, F. Zonca

Associazione Euratom-ENEA sulla Fusione, CRE Frascati, CP 65 00044, Frascati, Roma, Italy
¹ Associazione Euratom-ENEA-CNR, Istituto di Fisica del Plasma, Milano, Italy
² INFM and Dipartimento di Fisica, Il Universitá di Roma `Tor Vergata', Roma, Italy
³ ENEA fellow

Abstract.  Fast current ramps with central ECRH and pellet injection in ohmic plasmas allowed to study several kinds of MHD instabilities in plasmas with peaked pressure profile and low or negative magnetic shear. Double tearing modes were systematically observed when the minimum q value crossed the q_min = 2 value; such modes either ended into full core reconnection, or saturated at a large amplitude, with a displacement involving more than one third of the plasma radius. Macroscopic fluctuations clamp the peak temperature during central ECRH; the cause of such fluctuations is attributed to MHD modes that are excited when q_min is close to a low order rational value; gaps in the distribution of such values can explain the effective transport barriers observed near interger q_min values. When q_min $\approx$ 1 either sawteeth or saturated internal kink modes are observed.

Read the full paper in PDF format.