MODELING IMPURITY CONTROL AT JET

This work compares results from one-dimensional (1D) and two-dimensional (2D) codes that simulate the plasma scrape-off layer in JET discharges. The importance of 2D effects is assessed, with particular emphasis on the screening of impurities from the main plasma. 1D profiles of electron density and temperature along open magnetic field lines agree well with the corresponding 2D profiles, suitably averaged perpendicularly to the magnetic field. Scrape-off layer lengths in agreement with observations are computed by the 2D code with reasonable transport coefficients. In the case of the JET pumped divertor, 2D effects may be beneficial for impurity control since source and flow patterns can prevent sputtered impurities from contaminating the main plasma.