The capabilities of steady state operation at the stellarator W7-X with emphasis on divertor design

The stellarator Wendelstein 7-X (W7-X) is presently under construction at G reifswald, Germany, and the start of operation is planned in 2006. W7-X is a large 'advanced stellarator' of the HELIAS type (R = 5.5 m, a = 0.55 m, B -o = 3 T, five periods, moderate shear and variable rotational transform 5/ 6 less than or equal to iota less than or equal to 5/4 at the boundary) wit h the aims of demonstrating the reactor potential of this stellarator line in steady state operation close to fusion relevant parameters. The capabili ty of stationary operation requires the realization of a superconducting ma gnet system consisting of 50 modular coils and 20 planar coils, the operati on of a 140 GHz ECR CW heat source of 10 MW, the installation of a divertor to handle the power and particle flux, and to limit the impurity fraction to tolerable levels. Additional heating schemes, ICRF and NBI, will be prov ided for flexible experimentation.