PICKUP SIGNAL IMPROVEMENT FOR HIGH BANDWIDTH BAMS FOR FLASH AND EUROPEAN - XFEL ∗

In order to measure the arrival time of the electron bunches in low (20 pC) and high (1 nC) charge operation mode, new high bandwidth pickups were developed as a part of the Bunch Arrival-time Monitors (BAMs) for FLASH at DESY [1]. The pickup signal is transported via radiation resistant coaxial cables to the electro-optic modulator (EOM) [2]. Due to the high losses of the 40 GHz RF frontend the signal in the RF path is attenuated well below the optimal operation voltage of the EOM. To improve the overall performance, the signal strength of the induced pickup signal needs to be increased and at the same time the losses in the RF frontend significantly reduced. In this paper, the analysis towards improving the induced pickup signal strength is presented. Simulations are performed with the CST STUDIO SUITE R � package and the results are compared with the state of the art high bandwidth pickups. A non-hermetic demonstrator is built and the measurement results are compared with the simulation.