Sawteeth and m=1 mode evolution during ECRH/ECCD on FTU tokamak

Journal Article · Mon Sep 20 00:00:00 EDT 1999 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.59746· OSTI ID:21210463

Ramponi, G; Airoldi, A; Bruschi, A; Cirant, S; Granucci, G; Lazzaro, E; Nowak, S; Simonetto, A; Sozzi, C ^[1]; Buratti, P; Kroegler, H; Panaccione, L; Tudisco, O; Zerbini, M ^[2]; Cenacchi, G ^[3]; Gandini, F

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1. IFP, Ass.EURATOM-ENEA-CNR, Via R. Cozzi 53, Milano (Italy)
2. CRE Frascati, Ass.EURATOM-ENEA-CNR (Italy)
3. CRE Bologna, Via Don Fiammelli 2, Bologna (Italy)

Localized ECRH/ECCD has been performed on FTU with the specific aim of shaping the temperature/current density profile for controlling MHD activity. In particular, m=1 mode dynamics and stability are studied during the heating phase, when the steady-state, sawtoothing conditions of the ohmic plasma are modified by a strong off-axis electron heating. Depending on the position of the absorbing layer and on the density of the ohmic target plasma, sawteeth are temporarily suppressed, still in the presence of a slowly growing m=1 oscillation, or a complete quenching of any m=1 activity can be achieved. When direct current, driven by EC waves launched at {+-}10 deg. from the perpendicular in the up-shifted scheme, is added to the pure heating effect, different shapes and periods of relaxation phenomena in the plasma core are observed. Although low values of I{sub ECCD}/I{sub p} are expected because of rather high values of Z{sub eff} during heating, (I{sub ECCD}/I{sub p}=0.04 for p{sub BC}=800 KW, Z{sub eff}=5 and I{sub p}=360 kA), different local changes in the magnetic shear are thought to be responsible of these differences. Time-dependent calculations of current profiles, including transport and diffusion effects, and an analysis of the onset and stabilization of sawtooth oscillations based on the time evolution of s{sub 1} (the magnetic shear value at q=1) compared with that of a suitable critical value are performed.

• OSTI ID: 21210463
• Journal Information: AIP Conference Proceedings, Vol. 485, Issue 1; Conference: 13. topical conference on radio frequency power in plasmas, Annapolis, MD (United States), 12-14 Apr 1999; Other Information: DOI: 10.1063/1.59746; (c) 1999 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
CURRENT DENSITY
CYCLOTRON RESONANCE
DIRECT CURRENT
ECR CURRENT DRIVE
ECR HEATING
ELECTRONS
FT TOKAMAK
MAGNETOHYDRODYNAMICS
PLASMA
PLASMA DIAGNOSTICS
PLASMA INSTABILITY
RF SYSTEMS
SAWTOOTH OSCILLATIONS
SHEAR
STEADY-STATE CONDITIONS
TEMPERATURE MEASUREMENT
TIME DEPENDENCE