Confinement and transport studies of conventional scenarios in ASDEX Upgrade

Confinement studies of conventional scenarios, i.e, L and H modes. in ASDEX Upgrade indicate that the ion and electron temperature profiles are genera lly limited by a critical value of delT/T. When this is the case the profil es are stiff: core temperatures are proportional to pedestal temperatures. Transport simulations based on turbulence driven by all ion temperature gra dient show good agreement with the ion experimental data for H modes, Studi es specifically dedicated to electron transport using electron cyclotron he ating with steady state and modulated powers indicate that the electron tem perature profiles are also stiff. Candidates for turbulence having a thresh old in delT(e)/T-e may be trapped electron modes and electron temperature g radient driven instabilities. The critical threshold (delT(e)/T-e)(c) and t he increase of the stiffness factor with temperature are found experimental ly. In contrast, the density profiles are not stiff, hut the variation in s hape remains moderate in these conventional scenarios. As a consequence of this profile behaviour, the plasma energy is proportional to the pedestal p ressure. The global confinement time increases with triangularity and can b e good at densities close to the Greenwald limit at high triangularity. In this operational corner and at q(95) around 4, the replacement of large typ e I ELMs by small ELMs of type II provides good confinement with very reduc ed peak power load on the divertor plates. This regime is believed to be ad equate for a fusion reactor.