Effect of nonaxisymmetric perturbations on the structure of a tokamak poloidal divertor

Abstract

The effects of n = 1 nonaxisymmetric perturbations on a tokatnak poloidal divertor are described. Despite the existence of a region of chaotic field line trajectories outside the last closed flux surface, the footprint of the trajectories on the divertor plates is found to be largely coherent, forming a spiral structure. At a fixed toroidal angle, the footprint exhibits a bifurcation similar to that seen experimentally on DIII-D [Nucl. Fusion 28, 902 (1988)]. For field errors of the magnitude that exist in present-day tokamaks, the width of the nonaxisymmetric structure in the divertor footprint is comparable to the width of the scrape-off layer. © 1992 American Institute of Physics.