Innovative application of fiber optic sensors in high energy physics experiments

This thesis describes the innovative applications to the monitoring in harsh environment, represented by the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC), of the Fibre Bragg Grating (FBG) technology, which, although invented almost 40 years ago, is currently undergoing an explosion in variant manufacturing technologies and applications. The environment inside a large particle physic experiment like the CMS poses several challenges of monitoring spatially varying quantities in an aggressive environment, with high radiation, high magnetic field, tight electromagnetic compatibility (EMC) requirements, where particle detection priorities require monitoring sensors to have very low mass and associated service volume as well as excellent EMC compliance, conditions that can be very well satisfied by FBG-based sensors inscribed on optical fibres. The particular application described here is the monitoring of strain and temperature variation along the beryllium central beam pipe, a vacuum chamber which carries the counter-rotating proton beams in the Large Hadron Collider (LHC) to collisions within the CMS experiment.