EU ITER TF coil: Dimensional metrology, a key player in the Double Pancake integration

• Published in: Fusion engineering and design 2015-10, Vol.98-99, p.1135-1139
• Main Authors: Poncet, L., Bellesia, B., Oliva, A. Bonito, Boter Rebollo, E., Cornelis, M., Cornella Medrano, J., Harrison, R., Bue, A. Lo, Moreno, A., Foussat, A., Felipe, A., Echeandia, A., Barutti, A., Caserza, B., Barbero, P., Stenca, S., Da Re, A., Silva Ribeiro, J., Brocot, C., Benaoun, S.
• Format: Article
• Language: English
• Subjects: Coils (windings); Conductors (devices); Dimensional metrology; Domestic; Grooves; Intermediate frequency; ITER; Metrology; Monitors; Strategy; Superconducting coil
• ISSN: 0920-3796; 1873-7196
• DOI: 10.1016/j.fusengdes.2015.06.073

•Development and qualification of a dimensional metrology procedure on wound superconductor trajectory based on Laser scanning system.•Dimensional control of the conductor centreline during winding, before and after heat treatment.•Radial Plate groove centreline length controlled using Laser Trackers.•Full scale wound Double Pancake prototype transferred inside Radial Plate prototype without any issues. The ITER Toroidal Field (TF) magnet system consists of 18 “D” shaped coils. Fusion for Energy (F4E), the European Domestic Agency for ITER, is responsible for the supply of 10 out the 19 TF coils (18 installed plus one spare coil). Each TF coil, about 300 t in weight, is made of a stainless steel case containing a Winding Pack (WP). The European manufacturing of the Radial Plates (RPs) and WPs has been awarded to two different industrial partners, whose activities are strongly linked with each other. In order to manufacture a Double Pancake (DP), first, the conductor has to be bent onto a D-shaped double spiral trajectory, then heat treated and inserted in the grooves of the RP. This represents the most challenging manufacturing step: in order to fit inside the groove, the double spiral trajectory of the conductor must match almost perfectly the trajectory of the groove, over a length above 700m. In order to achieve this, the conductor trajectory length must be controlled with an accuracy of 1mm over a length of 350m while the radial plate groove has to be machined with tolerances of ±0.2mm over dimensions of more than 10m. In order to succeed, it has been essential to develop a metrology process capable to control with high accuracy both the DP conductor and the RP groove trajectories. This paper reports on the work carried out on the development and qualification of the dimensional metrology to monitor the manufacturing of the conductor. Reference is made to the final dimensional check of the RP focusing on the groove centreline length. In addition the results obtained on the one to one scaled prototype DP are described. Finally, the strategy and foreseen improvements for the production of DPs are discussed.