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(EXP2/06) H-mode and Confinement Studies in ASDEX Upgrade

W. Suttrop, F. Ryter, V. Mertens, O. Gruber, H. Murmann, H. Salzmann, J. Schweinzer and ASDEX Upgrade Team

Max-Planck-Institut für Plasmaphysik, EURATOM-IPP Association, D-85740 Garching, Germany

Abstract.  H-mode operational boundaries and H-mode confinement are investigated on ASDEX Upgrade. The local edge parameter threshold for H-mode holds independent of divertor geometry and changes little with ion mass. The deviation of the H-mode power threshold at densities near the Greenwald limit can be understood as a consequence of a confinement deterioration, caused by ``stiff'' temperature profiles and lack of core density gradients in gas puff fuelled discharges. Ion and electron temperature profiles can be described by a lower limit of gradient length L_T = T/T'.

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