Modification of the target design of the W7-X divertor for steady-state operation

Actively-cooled divertor and wall protection systems are planned to be installed from start of operation in 2010 in the stellarator WENDELSTEIN 7-X (W7-X). The W7-X plasma facing components are designed to remove up to 10 MW stationary power. To reduce the actively-cooled target areas, the local angle of incidence of the field lines to the target areas has been increased by 1°. This modification makes it possible the keeping of the full range of plasma and magnetic parameters to be studied experimentally. Two different loaded zones are defined: the higher loaded zone of about 20 m² designed to withstand a maximum stationary heat flux up to 10-12 MW/m², and the lower loaded zone of about 6 m² designed to withstand a maximum stationary heat flux up to 1 MW/m². The selected technology for the higher loaded zone is based on CFC flat tiles bonded on water cooled CuCrZr heat sink. For the lower loaded zone, graphite tiles are clamped on a CuCrZr heat sink which is brazed on a stainless steel water cooling tube. The design is now sufficiently detailed to start the fabrication.