Two dimensional modelling of plasma transport in the scrape-off region of pump limiters

A 2d-transport code based on the fluid equations is presented providing a radial and toroidal resolution of the flux bundle intercepted by the throat of a pump limiter. The continuity equation accounts for the recycling in the throat, the perpendicular particle diffusion, and the parallel convection. The evolution of the parallel velocity is determined by the viscosity, the pressure gradient, and the decelerating effect of the recycled neutrals. The temperature equations account for parallel and perpendicular heat conduction, equilibration and convective heat transport. The boundary conditions stand for a simplified sheath model, for the symmetry with respect to the meridional plasma opposite to the pump limiter and for the density and temperature values at the inner radial boundary of the flux bundle. The neutral plasma reactions, such as ionization, charge exchange or dissociation, are described by the Monte-Carlo code EIRENE. The calculations resort to the data of the advanced limiter test facility ALT-I implemented at the TEXTOR device. The numerical results obtained concern e.g. the mean density (2.7x1012/cm3), the mean temperature (10 eV), the ion flux neutralized at the deflector plate (≅ 110 A) and the flux pumped by the getter panels (≅ 70 A). (orig.)