Electron beam trajectory reconstruction for transfer lines

The goal of the AWAKE Run 2a experiment is to study the electron-seeding of the self-modulation of a proton bunch propagating in plasma. To study the dependence of the electron-seeding on the relative alignment between the beams, a method to measure this alignment has been developed. The electron and proton beamlines are brought together into a common line before they are injected into the plasma. The BPMs within the common line cannot be used for electron measurements in the presence of a proton beam as the signal from the proton beam dominates. In this case, the electron beam trajectory through the common line needs reconstructing, event-by-event, using beam trajectory measurements from the first part of the electron line. Here we describe the use of Physics-Guided Neural Networks to propagate the trajectory of the electron beam through the common line to the entrance of the AWAKE plasma cell.