Production quality controls and geometric characterization of the IFMIF-RFQ modules via the usage of a Coordinate Measuring Machine

tThe RFQ of the IFMIF/EVEDA project (Pérez et al., 2015) [1] is a 9.8 m long cavity able to accelerate a125 mA deuteron beam from the input energy of 50 keV/u to the output energy of 2.5 MeV/u. Such RFQoperates at the frequency of 175 MHz and is composed of 18 mechanical modules approximately 0.55long each (Pepato et al., 2010) [2]. The RFQ realization involves the I.N.F.N. Sections of Padova, Torino andBologna, as well as the Legnaro National Laboratories (L.N.L.). The metrological measurements via CMM(Coordinate Measuring Machine) provided to be a very effective tool both for quality controls along theRFQ production phases and in the reconstruction of the cavity geometric profile for each RFQ module.The scans in the most sensitive regions with respect to RF frequency, such as modulation, tips, base-vane width and vessel height provided the values of the cavity deviations from nominal geometry to becompared with design physic-driven tolerances and with RF measurements. Moreover, the comparisonbetween mechanical and RF measurements suggests a methodology for the geometric reconstruction ofthe cavity axis and determines the final machining of the end surfaces of each module in view of thecoupling with the adjacent ones. In this paper a detailed description of the metrological procedures andtests and of the RFQ along its production and assembly phases will be given and it will be shown that theadopted procedure allowed the attainment of the tuning range specifications for each RFQ module.