W7-X precision metrology

Metrology at W7-X is an integral part of device assembly. Lots of assembly steps are guided by metrology. In addition to that metrology performs final geometry checks at the end of most of assembly steps. This paper presents some general assembly tolerances and the metrology equipment which founds the accuracy basement to gain these tolerances. Exemplified by magnet system assembly metrology methods used and the alignment as well as the measurement accuracies achieved are presented. It is shown that the final geometric position accuracy of the main field coils meet the requirements at a high quality of the magnet field. A procedure to transfer co-ordinates from the main co-ordinate system, fixed on the torus hall building, into the vacuum vessel is given in detail. The accuracy obtained for the coordinate transfer is presented. At the moment 248 out of 254 ports of W7-X have been assembled. Final measurements of port positions have been completed at 4 out of 5 modules. The metrology methods used for ports assembly as well as the final port positions are presented.