Effect of up–down and left–right asymmetry of dust and/or heavy impurity distribution on plasma dynamics in the tokamak edge

Abstract

The potentially important role of dust in future large power wall loadings and long operation times expected for new devices such as ITER is now recognized. In this context, we have studied the effect of the dust poloidal distribution on the plasma dynamics of the plasma edge. This dust spatial distribution can be natural or artificially induced by dust puffing aiming to act on the plasma dynamics. We show that, in the considered range of dust densities, in large-aspect-ratio tokamaks, the poloidal distribution of dust affects only the toroidal velocity. The poloidal velocity and the radial electric field are defined by the ion–dust friction and by the ion–dust thermal forces with the magnetic surface averaged dust density. It also follows from calculations presented in the paper that, in spherical tokamaks, the poloidal distribution of dust can also affect the plasma poloidal velocity and the radial electric field, in addition to affecting the plasma toroidal velocity. These results are also applicable to heavy impurities presented in tokamaks.