Dynamics of heavy impurities in non-linear MHD simulations of sawtoothing tokamak plasmas

The effect of sawteeth on impurity dynamics is studied with the XTOR-2F code. Non-linear full 3D MHD simulations including appropriate fluid equations for impurities in the high collisional regime show that the presence of regular sawtooth crashes affects the impurity behaviour. A spatial non-uniformity of 5% in post-crash impurity density profiles persists due to 2D structures of impurity density which appear during sawtooth crashes. They are shown to be mainly driven by the E × B velocity, and are responsible for the sudden impurity transport in the core plasmas.