ANALYSIS OF COLD DIVERTOR CONCEPTS FOR ITER

Two different ITER geometries (a V-shaped and a gas-bag like divertor) are analysed with respect to their pure plasma behaviour, ELMs and impurity transport. The V-shaped divertor shows a local balance within each divertor with a rather symmmetric behaviour for pure deuterium plasmas. Being relatively closed, the deep V is able to control the detachment on inner and outer leg separately better. It has easier access to high recycling at lower midplane separatrix densities. It is able to buffer grassy ELMs of some kJ going to the diverters. The gas-bag is dominated by a more global divertor gas balance due to its open configuration. The interaction between inner and outer divertor is complicated, appearing also in the ELM simulation, where the capability to buffer a small ELM is not as good as for the V-shaped configuration. In both configurations for multifluid calculations with beryllium produced by sputtering and neon prescribed by the density of its highest charge state at the innermost flux surface strong radiation close to the X-point develops, however for the V-shaped configuration a much more symmetric situation is obtained, whereas for the gas-bag a strong in-out asymmetry is seen, that means the inner divertor is cooled much more than the outer one.