Design of the ECE diagnostic at Wendelstein 7-X

The Electron Cyclotron Emission diagnostic will be the main tool for the measurement of the electron temperature profile in the stellarator Wendelstein 7-X presently under construction in Greifswald, Germany. Design criteria and constraints for the ECE diagnostic are discussed. The resulting set-up is introduced with respect to the line of sight and the in-vessel optics. The 32-channel heterodyne radiometer system already used at the predecessor experiment Wendelstein 7-AS is adapted to the conditions at Wendelstein 7-X.