Status of WENDELSTEIN 7-X construction

WENDELSTEIN 7-X (W7-X) shall confirm the favourable plasma properties and the high density and beta limits of the helical advanced stellarator and demonstrate steady-state operation. The magnetic configuration of W7-X is characterized by a set of 50 non-planar and 20 planar superconducting coils. The magnet system will be manufactured and assembled to a precision of a few millimetres and maintain its symmetry during cool-down to cryogenic temperatures. Power supplies allows one to adjust the magnetic field with a precision of a few milli Tesla and safely dump the magnet energy in case of a quench. The plasma vessel gives maximum space for the plasma and is kept symmetrically with respect to the plasma by dedicated means. Steady-state heating is achieved by 10 MW ECRH. Energy and particles are controlled by a continuously working divertor. All plasma-facing surfaces are covered by CFC, graphite or B4C, respectively. The paper reviews the status of the construction and describes details of the design.