REALIZATION OF A HIGH BANDWIDTH BUNCH ARRIVAL-TIME MONITOR WITH CONE-SHAPED PICKUP ELECTRODES FOR FLASH AND XFEL*

In the Free Electron Laser in Hamburg (FLASH), an electro-optical system is used as a Bunch Arrival time Monitor (BAM). The time-of-arrival resolution is proportional to the steepness of the beam pick-up signal at the first zero-crossing. Future experiments will be conducted using significantly lower bunch charges resulting in reduced signal steepness. This requires BAM pickup electrodes with increased bandwidth. This paper presents the realization and measurement results of a high bandwidth cone-shaped pickup system capable of operating in the frequency range up to 40 GHz. The RFmeasurements have been performed using a non-hermetic prototype of the BAM pickups for assessing the influence of manufacturing tolerances on the sensor performance.