Return To: Session EX/P4 - AUG, TORE SUPRA, FT-U, TRIAM-1M,
Prev Page: (EX/P4-02) Investigation of High Density Regimes in FTU
Next Page: (EX/P4-04) Particle Fuelling for Long Pulse with Standard

(EX/P4-03) Internal Transport Barriers in ASDEX Upgrade

A.G. Peeters¹⁾, A.C.C. Sips¹⁾, E. Quigley²⁾, O. Gruber¹⁾, V. Igochine¹⁾, P. McCharty²⁾, F. Ryter¹⁾, R. Wolf^1)
 
1) Max Planck Institut für Plasmaphysik, Garching bei Muenchen, Germany
²⁾ University of Cork, Ireland

Abstract.  This paper gives an overview of all the experiments on transport barriers performed on ASDEX Upgrade. Strong ( R/L_Te = 25 T_e(0) = 20 keV) transport barriers in the electron heat channel are generated with counter electron cyclotron current drive in low density plasmas n_e = 1 - 2.5x10¹⁹m^{- 3}. Ion barriers are generated using neutral beam heating in the current ramp up. Correlation with plasma parameters, shows that a sufficiently low density is a necessary condition for barrier formation. A new scenario with delayed heating in the current ramp has broken all the ASDEX Upgrade records of central ion temperature (now 21 keV) and beta normalised (now 3.2). Pre-heating with ECRH delays the barrier formation, which forms at the same radial position. Broader barriers can be generated with more NBI power. A study of the barrier position with respect to the q-profile reveals that the foot of the barrier is not well correlated with the minimum q position. Also turbulent fluctuations are reduced at the barrier foot, but not completely suppressed. The new scenario often does not show any external kink activity and can reach $\beta_{N}$ values of 3.2. They however, often have a (3,1) tearing mode.

Read the full paper in PDF format.