WAKE FIELD MONITORS IN A MULTI PURPOSE X BAND ACCELERATING STRUCTURE

In a collaboration between CERN, PSI and Sincrotrone Trieste (ST), a series of four multipurpose X-band accelerating structures has been designed and fabricated. These feature integrated wake field monitors (WFMs), which are used to measure the alignment (offset and tilt) between structure and beam. One structure has recently been installed in the SwissFEL Injector Test facility (SITF) at PSI. The WFM front end electronics will be developed within the EuCard2 framework, so for the measurements described in this paper we used the raw WFM signals. We compare these measurements to the theoretical results obtained via an equivalent circuit model used in the design and numerical calculations. The beam tests show that by minimizing the WFM signals, the emittance dilution given by the transverse wakes, crucial because of the small aperture of the structure, is minimized as well.