Metrology In-Process Control for the European Toroidal Field Coil Project

To guarantee the required performances stringent dimensional tolerances have been defined for the ITER Toroidal Field (TF) coils. The process has been divided in the following stages: reception of the parts, insertion of the Winding Pack (WP) into the Coil Cases (CC), closure welding, gap filling and final machining. At each of the production stages, metrological surveys are carried out in order to check the compliance with the defined requirements: fiducials positions, gap evaluation, virtual fit, welding distortion. In particular, one of the key elements of the magnets is the position of the Current Center Line (CCL). The CCL has to be kept under control during the production and linked to the external TF coil case interfaces. A rigid metrology process has been put in place, assuring reliable results in terms of repeatability and accuracy of the measurement. Laser tracking, sided when possible by photogrammetry technologies, have been chosen for the scope.