2-D modelling of the JET divertor

The design of the first version (Mk I) of the JET pumped divertor is fixed, but various 'advanced' geometries are being studied for the second phase (Mk II). The two main characteristics that determine a good divertor are the divertor's ability to handle power exhaust at acceptable erosion rates and its control of the impurity production and retention in the scrape-off layer (SOL). A high recycling regime is favourable for both aspects. For modelling studies, the JET code EDGE2D has been updated (EDGE2D/U). The new code treats impurities self-consistently and allows for targets with an arbitrary inclination with respect to the magnetic field lines. We have carried out studies of divertor performance using EDGE2D/U for different geometrical configurations, showing that the geometry of the divertor chamber plays an essential role, because i) it controls the accessibility to the high recycling regime by influencing the return of neutrals to the main plasma, and ii) it can increase the wetted area on targets, thus reducing peak heat load. (author) 3 refs., 6 figs., 1 tab