Kögler, U.FZJ* ; Winter, J.FZJ*

1997
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Report No.: Juel-3361

Abstract: The ERO-TEXTOR code is described in detail. The code solves the kinetic equations of impurities in the scrape-off layer of a tokamak plasma in the vicinity of material surfaces like limiters or divertors. A relaxation time ansatz in the traced impurity limit is chosen, taking the gyromotion of the particles into account. Since the background plasma is slightly non-maxwellian at the plasma edge higher order corrections (thermal [orces) to the relaxation time ansatz are also considered. Background plasma parameters are calculated from a simple plasma model, i.e. the one dimensional continuity and moment um equations are used to derive the local electron density, the local fiow velo city and the pre-sheath and sheath electric fields. Since these calculations are not done in a selfconsistent way, the measured values of electron density and temperature are used as basic input to derive the dependency of these quantities. The regarded magnetic topology is still straight and uniform. Also detailed account is given to the plasma surface inter action and the erosion/deposition processes. A linear differential equation model for multi species impact on a material surface has been developed and is used in a discrete time step approximation. External databases include the ionization rates for atomic species, molecular pro ces ses of methane and silane molecules and the sputtering and refiection yields, which are taken from binary collisi on calculation codes (e.g. TRIM) or from semi-empirical fits (e.g. the Bodhansky and Yamamura fits).

1. Institut für Plasmaphysik (IPP)