Design and Development of an Optical Beam Loss Monitor Based on Cherenkov Light Detection for the CERN Super Proton Synchrotron Accelerator

As a result of the harsh LSS2 radiation conditions in SPS at CERN, exhaustive monitoring of beam losses, including a study of the loss source localisation, is required. According to studies conducted in particle accelerators worldwide, an optical Beam Loss Monitor (oBLM) composed primarily of a quartz multimode optical fibre and two photo-sensors is an appropriate candidate for loss mapping. This beam loss monitor is based on the Cherenkov light generation, which is emitted by high-energetic particles reaching the fibre. The interaction between particles and silica produces Cherenkov photons that propagate along the fibre until they are detected by the photo-sensors. The most critical factors introduced by the characteristics of the fibre are examined to determine the quality of the signal obtained by the system. Before the development of the oBLM prototype, a computational tool was developed to simulate Cherenkov light generation in optical fibres. With this model, it is possible to quantify the number of photons detected by the Cherenkov oBLM in any accelerator geometry simulated in FLUKA. Through experimental campaigns in CLEAR accelerator facilities, the computational model, the system components, and the PCB design for the signal readout were validated. Additionally, the oBLM prototype was installed in the beamline of LSS2. The system and cabling setup, the difficulties encountered in their implementation, and further optimisation are discussed.