The effect of the magnetic topology on particle recycling in the ergodic divertor of TEXTOR M. Lehnen a, * , S.S. Abdullaev a , S. Brezinsek a , K.H. Finken a , D. Harting a , M. von Hellermann b , M.W. Jakubowski a , R. Jaspers b , A. Kirschner a , A. Pospieszczyk a , D. Reiter a , U. Samm a , O. Schmitz a , G. Sergienko a , B. Unterberg a , R. Wolf a , The TEXTOR Team a Institut fu ¨ r Plasmaphysik, Forschungszentrum Ju ¨ lich, Association EURATOM-FZJ, Germany 1 b FOM-Rijnhuizen, Association EURATOM-FOM, The Netherlands 2 Abstract The influence of the divertor geometry of the dynamic ergodic divertor (DED) in TEXTOR on particle recycling is discussed. The geometry can be varied by the choice of the base mode, the edge safety factor and the divertor coil current. The divertor volume is split into the upstream and the downstream area. Strong plasma flows in the downstream area, essential for high screening efficiency, are predicted. The source strength of deuterium and carbon in the downstream area is estimated by using the two-dimensional distribution of D a and CIII emission in front of the target. The results are compared to EMC3 and ERO-code calculations. Ó 2007 Elsevier B.V. All rights reserved. PACS: 52.55; 52.25; 52.40 Keywords: Divertor; Edge plasma; Stochastic boundary; Textor 1. Introduction In this paper, the influence of the DED divertor geometry on the particle recycling behaviour is dis- cussed. Especially the radial extent of the divertor volume with respect to the mean free path of neu- trals plays an important role for the control of the recycling in a divertor. Such a control is essential to achieve divertor regimes like high-recycling and improve the impurity screening in the divertor. These properties were first studied in limiter and poloidal divertor machines. More recently these studies were also intensified for helical, island and ergodic divertor geometries [1–4]. The higher com- plexity of these configurations makes the analysis more challenging. The ergodic divertor at TEXTOR generates a resonant magnetic perturbation which focuses the 0022-3115/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jnucmat.2007.01.125 * Corresponding author. Tel.: +49 2461 615102; fax: +49 2461 615452. E-mail address: m.lehnen@fz-juelich.de (M. Lehnen). 1 www.fz-juelich.de/ipp. 2 www.rijnh.nl. Journal of Nuclear Materials 363–365 (2007) 377–381 www.elsevier.com/locate/jnucmat