Plasma motion and purification in an ergodic divertor

The main problems associated with an ergodic divertor are considered. The pressure gradient in the ergodic layer induces a plasma flow along the flux lines, which allows in principle, control of the energy of the particles reaching the wall. Also the parallel plasma flow tends to drag away the impurity ions and to decontaminate the confined plasma. These effects are considered in the framework of the quasilinear theory. A discussion shows that the real flow pattern consists of quasilinear regions where the flow is limited by transverse and diffusion effects coexisting with regions of free streaming at the sound velocity. (orig.)