Studies of Electron Transport and Current Diffusion in Switched ECCD experiments on TCV

The aim of the present work is to provide a better insight on the magnetic shear profile modification in the Switched ECCD experiments. Modelling of the plasma current density is carried on by the ASTRA transport code employed in both predictive and interpretative modes, with two shear-dependent models for the calculation of the electron energy diffusion coefficient. In this context, the modulation of ECCD is the only actuator for the transport properties modifications. This study confirms the synergy between electron transport and magnetic shear, both of which are modulated around the EC deposition region. It also allows to completely decouple the effects of the current profile modification from those of slight plasma heating misbalance or non-constant plasma elongation, which are key concepts at the basis of Switched ECCD and can be a rather delicate experimental issue. The numerical results moreover validate a previous rough model based on electrodynamics calculations.