Design of a Normal Conducting Cavity for Arrival Time Stabilization at FLASH

It has been shown, that beam-based feedback loops stabilize the bunch arrival time in the femtoseconds range. However, further minimizing the bunch arrival time jitter requires a faster actuator that is a normal conducting cavity with higher bandwidth compared to narrow-band superconducting cavities. We present the design of a 4-cell normal conducting cavity that is going to be used in a fast beam-based feedback at free-electron laser FLASH at Hamburg. The input power will be injected to the cavity via a loop coupler from the side of the first cell. The operating frequency of the designed cavity is about 3 GHz with an adjustable bandwidth. The long range longitudinal wakefield calculation results are reported to investigate the cavity performance for multibeam operation up to 3 MHz bunch repetition rate. The results declare that the influence of the long range wakefield on the arrival time jitter is less than 1 fs.