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15th International Conference on Plasma Surface Interactions in Controlled Fusion Devices (PSI 15), Gifu, 2002-05-26 to 2002-05-31
Abstract:
Impurity behaviour in advanced scenarios at ASDEX Upgrade and JET has been investigated. For
ASDEX Upgrade improved H-mode plasmas at δ=0.35, accumulation of tungsten and metallic
impurities was observed inside r/a=0.3 in cases with weak central heating. Central ECRH
suppressed the accumulation by increasing the anomalous diffusion and by flattening the profile of
the main plasma density which reduces neoclassical inward convection for the impurities. These
effects are well described by impurity transport simulation and calculated v/D values agree with the
measurements within a factor of 2. In JET reversed shear discharges with internal transport barriers,
metallic impurities accumulate in cases with too strong peaking of the density profile. The peaking
increases with the impurity charge and is low for the low-Z elements C and Ne as expected from
neoclassical convection.
