Measuring and controlling the longitudinal phase space and the time-slice emittance of the electron bunch entering at 1.2 GeV in the undulator beam-lines, are crucial to obtain high FEL performances. In the FERMI@Elettra machine, two RF deflecting cavities have been installed at the end of the linac, in order to stretch the electron bunch horizontally and vertically, respectively. The two cavities are individually powered by the same klystron and a switch system is used to choose the deflection plane. This paper reports
the RF measurements carried out during the acceptance test and the RF conditioning including the breakdown rate measurements.
