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Abstract

The transport of silicon has been investigated for various heating scenarios in ASDEX Upgrade H-mode discharges. Inside of r ≈ a/4, the diffusion coefficient D is either mainly neoclassical or anomalous depending on the heating method. For all investigated scenarios with NBI-heating and off-axis ECRH or off-axis ICRH, the diffusion coefficient is approximately neoclassical, and the effective heat diffusion coefficient χ_eff is below the neoclassical ion heat diffusion χ_i,neo in the plasma core. When central ECRH is added, χ_eff is above χ_i,neo, and D strongly increases by a factor of 3-10, i.e. becomes predominantly anomalous. For central ICRH, D is above the neoclassical level by a factor of 2. For radii outside of r ≈ a/4, D is always anomalous and increases towards the plasma edge. For r much greater than a/4, we find a clear scaling of D in terms of χ_eff, where D is about equal or above χ_eff. A strong inward drift parameter v/D is only observed in the core and only for cases, when the diffusion coefficient is neoclassical. With central wave heating, the drift parameter decreases to small values.