Speaker
Description
Development of an optical fibre-based beam loss monitor (OBLM) is in progress at the Cockcroft Institute, UK. 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.
The OBLM system has shown capability to operate successfully in varied and challenging accelerator and radiation environments, such as attaining full beam loss position resolution despite considerable background signal from dark current in a nearby RF cavity and operating within the undulator section of a free-electron laser.
In these complex situations, it is helpful to use Monte Carlo simulations to estimate and understand potential sources of OBLM signal. Previous simulation work has all been performed using a mix of two codes: the FLUKA particle tracking code and a custom numerical Python code that simulates the propagation of Cherenkov radiation within the fibre.
The Geant4 code supports the simulation of Cherenkov radiation, enabling complete end-to-end simulations of the OBLM system without risk of information loss in the conversion from one simulation code to another. However, Geant4 tracks photons individually using a ray tracing method, which has potential to affect the simulated behaviour of the Cherenkov photons in the fibre.
This work compares the performance of a Geant4-based simulation to existing work performed in FLUKA with a simple beamline model. The differences in the Cherenkov radiation physics between the two codes are investigated and presented.
Preliminary results of Geant4 simulations based on a similar model are also presented, which consider the feasibility of estimating the beam energy from beam loss signals in the OBLM. This is relevant for potential applications of the OBLM system to accelerators with multi-energy beams, such as energy recovery LINACs (ERLs).
