Manufacturing of X-band Accelerating Structures: Metrology Analysis and Process Capability

The fabrication tolerances of RF components are essential for CLIC X-band accelerating structures to perform efficiently. On one hand, the capability of high power accelerating structures depends on the shape accuracy and the asperity of the inner surfaces, when microwaves pass through the cavity. On the other hand, surface flatness and dimensional tolerances are necessary to guarantee a correct assembly process. Hence, the discs that build up the structure require sub-micrometre specifications and, in order to meet all the needs, ultra-precision machining using single crystal diamond tools is mandatory. This paper shows the analysis of the metrology results of the fabrication of 118 discs (4 accelerating structures). Dimensional and form tolerances are studied following the production order to find drifts in the production and to predict the impact on the assembly process. Finally, process capability is evaluated.