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(EX2/2) Confinement and Transport Studies of Conventional Scenarios in ASDEX Upgrade

F. Ryter¹⁾, J. Stober¹⁾, A. Stäbler¹⁾, G. Tardini¹⁾, H.-U. Fahrbach¹⁾, O. Gruber¹⁾, A. Herrmann¹⁾, F. Imbeaux²⁾, A. Kallenbach¹⁾, M. Kaufmann¹⁾, B. Kurzan¹⁾, F. Leuterer¹⁾, M. Maraschek¹⁾, H. Meister¹⁾, A. G. Peeters¹⁾, G. V. Pereverzev¹⁾, A. Sips¹⁾, W. Suttrop¹⁾, W. Treutterer¹⁾, H. Zohm^1)
 
1) Max-Planck-Institut für Plasmaphysik, Garching, Germany
²⁾ CEA-Cadarache, DRFC, France

Abstract.  Confinement studies of conventional scenarios, i.e. L and H modes, in ASDEX Upgrade indicate that the ion and electron temperature profiles are generally limited by a critical value of $\nabla$T/T. When this is the case the profiles are stiff: core temperatures are proportional to pedestal temperatures. Transport simulations based on turbulence driven by Ion Temperature Gradient show good agreement with the ion experimental data. Studies specifically dedicated to electron transport using Electron Cyclotron Heating in steady-state and modulated indicate that electron temperature profiles are also stiff, in agreement with recent calculations on transport driven by ETG turbulence with streamers. In particular the predicted threshold and the increase of the stiffness factor with temperature are found experimentally. The density profiles are not stiff. As a consequence of this profile behaviour, the plasma energy is proportional to pedestal pressure and improves with density peaking. The confinement time increases with triangularity and can be good at densities close to the Greenwald limit. In this operational corner and at q₉₅ $\approx$ 4, the replacement of type-I ELMs by small ELMs of type-II provides good confinement with much reduced peak power load on the divertor plates.

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