End to end simulations of a novel optical fibre monitoring system for energy recovery LINACs

Energy recovery LINACs (ERLs) are a type of novel accelerator, which recycle energy from old beams to new beams to increase machine energy efficiency. However, this can heighten beam instabilities, which limits the maximum beam current and increases beam losses. An optical fibre beam loss monitor (OBLM) can provide rapid and reliable beam loss monitoring, which is important for mitigating these instabilities. It obtains the beam loss location via time-of-flight analysis of Cherenkov radiation (CR) produced in optical fibres by relativistic particle showers from beam loss events. Operational demonstration of the OBLM system has previously been shown at several non-ERL facilities, but the multi-energy, fast-repeating beams of ERLs present a unique challenge. Successful interpretation of ERL beam loss signals involves distinguishing losses from beams of different energies, which can be investigated through end-to-end Monte Carlo simulations of the radiation environment and its interaction with the OBLM system. This contribution presents Geant4 simulations of the OBLM response to sample sources of beam loss for beam energies of 7-500 MeV and bunch populations of 1-10M electrons.