MODELING EFFORTS ON THE HELICAL NEAR-FIELD DIVERTOR OF THE DYNAMIC ERGODIC DIVERTOR (DED) FOR TEXTOR-94

As a first step for the modelling of the plasma-wall interaction of th e proposed Dynamic Ergodic Divertor (DED) of TEXTOR-94, the topology o f the magnetic field lines of the divertor is analysed. Despite the st rong ergodization, the magnetic field lines intersecting the wall in o ne poloidal turn form continuous sets. These sets are visualised by a 2-D imaging technique; the field lines of each set of starting values is traced one poloidal turn clockwise and ctr. clockwise, marking thos e lines intersecting the wall. An overlay of the marked starting point s defines areas with properties of a scrape-off layer and areas with f ield lines ending on one side in the ergodic layer and one side on the wall. The edge plasma can be described by a 2-D model; the model trea ts a part of the plasma as that of a conventional scrape-off laver and another part with ''half open'' field lines connecting the divertor t arget plate with the ergodic layer. Calculations of the power flux dis tribution in the DED-near field divertor are presented.