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approvedposter.pdf2016-04-06 19:34:20John Omotani


Author: John T. Omotani
Requested Type: Pre-Selected Invited
Submitted: 2016-02-11 11:09:42

Co-authors: I.Pusztai, T.Fülöp

Contact Info:
Chalmers University of Technology
Fysikgården 1
Göteborg,   41296

Abstract Text:
H-mode confinement and the transition to H-mode are vital to future tokamak reactors. Their properties are determined by the behavior of the edge plasma, with flow shear playing a key role. The radial transport of toroidal angular momentum determines the radial electric field and plasma flow and is therefore the key to understanding flow shear.

Even at modest relative concentrations neutral particles can affect transport significantly because of their high cross-field mobility. They are therefore an important factor in edge transport, as has been seen experimentally [1]. However, their interaction with neoclassical and anomalous transport has generally been neglected. We have, for the first time, coupled neutrals to the full ion distribution function numerically, by adding a model for charge-exchange dominated neutrals to the neoclassical solver PERFECT. This allows us to evaluate the momentum transport due to neutrals and hence to compute the flow and radial electric field self-consistently.

There is a rich parameter space of plasma properties, spatial distribution of neutrals and magnetic geometry to be explored with this technique. As one example, we have considered the case of X-point localized neutrals in a model ITER magnetic geometry, where we have investigated the effect of the geometrical parameters on the flow. Notably, moving the X-point inboard generates stronger flow shear by increasing the collisionality dependence of the flow.

[1] E. Joffrin et al. Impact of divertor geometry on ITER scenarios performance in the JET metallic wall. In 25th Fusion Energy Conference (FEC 2014), 2014.