Impact of the Dynamic Ergodic Divertor DED on the Plasma Edge at TEXTOR - Detection and structure of the laminar zone

The Dynamic Ergodic Divertor (DED) [1] installed at TEXTOR couples a resonant perturbation to the plasma edge in order to modify heat and particle exhaust. The magnetical topology induced was prescribed by field line tracing and mapping methods collected in the ATLAS-Code [2, 3]. In radial outward direction three regions showed up in the perturbed volume: A region with island chains, a region where these islands overlap, called ergodic region and a laminar region, where the field lines before they get decorrelated are deflected towards the DED target tiles with short connection lengths Lc. These laminar field lines form isolated helical flux tubes which are surrounded by ergodic regions and end on the DED target. The intersection of the flux tubes with the DED target at the high field side (HFS) forms four helical strike point patterns with two divertor legs each and a private flux region in between. Ergodic fingers connecting to the inner part of the perturbed edge region are embedded into the flux tubes in front of the target. As a consequence, the heat and particle flux pattern at the DED target can be expected as a superposition of the plasma flow along the laminar flux tubes in the so-called ergodic divertor scrape-off layer (ED-SOL) and within the ergodic fingers as connection to the inner plasma region with higher density and temperature [4, 6]. This contribution discusses the experimental findings on the response of plasma edge parameters ne and Te and the particle flux to the DED target on this complex magnetic topology in the DED m/n = 12/4 base mode configuration.