NUMERICAL MODELING OF IMPURITY PRODUCTION IN THE FTU TOKAMAK SCRAPE-OFF LAYER

A 2D multifluid model for deuterium plasma and impurity ions has been applied to study the problem of the plasma and nickel ions transport in the FTU tokamak scrape-off layer (SOL). The model is based on the electron-ion fluid equations for background plasma and rate equations for impurities. An analytical model for neutrals is employed allowing to take into account recycling of hydrogen, sputtering and selfsputtering of nickel atoms at the target in a selfconsistent way with boundary plasma dynamics. Equations of the model are solved in the slab geometry using 2D - multifluid code EPIT. Plasma parameters in the SOL are investigated under conditions when the physical sputtering at the target plate is the only mechanism of the impurity production. Calculations are performed for nickel ions in the simplified poloidal geometry of the FTU tokamak scrape-off layer. The calculated results the existence of a selfregulating mechanism limiting the electron temperature in the SOL below 30 eV. A comparison of the calculated results with the experimental data is also reported.