Strong impact of neutrals on anomalous inward drift and width of steep gradient zone

The fundamental properties of the anomalous inward drift and the width of t he steep gradient zone in H mode plasmas are explored. A special version of the 1.5-D BALDUR transport code is used to determine the profiles of the e lectron beat diffusivity and upsilon(in)/D by transport analysis. The stron g rise with radius of upsilon(in)/D in the edge region is explained by a li near dependence on the neutral deuterium density n(0), resulting in a new s caling expression upsilon(in)(x)/D(x) = F-0 Z(eff) (x)n(0)(2)2x/(rho(w)x(s) (2)). Applying this in simulations reproduces the empirical fit of the upsi lon(in)/D profile not only in the edge plasma but also in the bulk plasma, Modellings with this scaling yield the observed flattening of density profi les with rising line averaged density. The decreasing penetration of deuter ium atoms to the core causes a decline of the inward drift. The new scaling is shown to be compatible with gas oscillation experiments, while no-indep endent scalings are not. This further explains the strong density profile p eaking and rise of upsilon(in)/D during and after pellet injection by the i ncrease in neutral density. The width of the steep gradient zone is found t o be connected with the penetration of neutrals at the edge and the presenc e of high inward drift velocities. The anomalous inward drift is attributed to ion dynamics, i.e. to the friction between fluctuating deuterons and de uterium atoms diffusing inward. A more general upsilon(in)/D scaling includ ing impurity effects is presented.