DEVELOPMENT OF A RADIATIVE DIVERTOR FOR DIII-D

We have used experiments and modeling to develop a new radiative divertor configuration for DIII-D. Gas puffing experiments with the existing open divertor have shown the creation of a localized (similar to 10 cm diameter) radiation zone which results in substantial reduction (3-10) in the divertor heat flux while tau(E) remains similar to 2 times ITER-89P scaling. However, n(e) increases with D-2 puffing, and Z(eff) increases with neon puffing. Divertor structures are required to minimize the effects on the core plasma. The UEDGE fluid code, benchmarked with DIII-D data, and the DEGAS neutrals transport code are used to estimate the effectiveness of divertor configurations; slots reduce the core ionization more than baffles. The overall divertor shape is set by confinement studies which indicate that high triangularity (delta approximate to 0.8) is important for high tau(E) VH-modes, Results from engineering feasibility studies, including diagnostic access, will be presented.