A stationary advanced tokamak scenario with an internal transportbarrier (ITB) for ions and electrons, particles and momentum incombination with an H-mode barrier and flat shear(q0≈1) wasmaintained for 40 confinement times and several internal skintimes with HITERL-89P βN≈5. Raising thedensity by edge gasfuelling close to 50% of the Greenwald density to integrateproper exhaust conditions causes an increase of the thresholdpower to sustain an ITB and a decrease of Zeff below 2. Incontrast, a density increase caused by improved core particleconfinement at more triangular plasma shapes does not change theITB onset conditions. No temporal impurity accumulation evenwith high-Z Ar puffing was observed despite of peaked impuritydensity profiles.MHD modes contribute to the stationarity ofthe shear profile. In the ITB/H-mode scenario (1,1) fishboneswith a large reconnection area `clamp' the q-value in thevicinity of one and avoid sawteeth during the wholehigh-performance phase. In ITB scenarios with reversed shear(qmin ⩾2)fishbones can clamp the current profile development near theq = 2 surface without deteriorating energy confinement, whereasdouble-tearing modes, acting in a similar form, lead tosubstantial confinement losses.Applying central ECRF heatingand current drive to beam heated reversed-shear ITB dischargesshows an substantial effect on MHD stability, affecting thepassage of the q-profile through qmin = 2, and degrading orprolonging the reversed-shear phase depending on the CDdirection. Moreover, reactor relevant Te⩾Ti operation withtemperatures in excess of 10 keV was achieved with internaltransport barriers for both electrons and ions simultaneously.
Turbulence reduction in internal transport barriers on ASDEXUpgrade