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Abstract

The AWAKE project accelerates electrons through proton driven plasma wakefields. The transverse extend of the wakefields is given by the plasma density and is of the order of one millimeter. With external injection, the exact position of the electron bunch in the wakefields determines the acceleration energy and the captured charge. The pointing jitter of the electron beam is on the order of the size of the wakefields, so single event analysis is desired. After the last two beam position monitors (BPMs) the electrons propagate in vacuum. Ballistics can be used to propagate the trajectory to determine the position of the electron bunch with respect to the proton bunch. The co-propagating proton bunch interferes with the electron readings and they cannot be used to determine the electron trajectory for these common events. Therefore, we have to use BPMs upstream of the common beamline. We use a model based on beam-optics to propagate the electron bunch before and towards the plasma and predict its point of closest approach to the proton bunch