Momentum transport by neutrals: Effect of kinetic coupling

Paper in proceeding, 2017

Neutrals couple to the non-Maxwellian as well as (drifting-)Maxwellian parts of the ion distribution function, producing a residual stress that can drive intrinsic rotation. Our modelling predicted a steeper slope of the toroidal rotation profile than observed in dedicated AUG discharges, suggesting the presence of opposing transport mechanisms. Losses from neutrals escaping to the wall which are not captured by the short MFP approximation, neoclassical torque from the toroidal ripple field or turbulent transport are all possibilities. Finally, we did not predict or observe a significant change in the measured rotation profiles when changing the gas fuelling location. This may be due to the modest fuelling possible in the low density discharges used.