Fiber Bragg Grating Fiber Optic Sensors Measuring Strain & Temperature Changes at the CMS’s Central Beam Pipe

This work tests the reliability and efficacy of the Fiber Bragg Grating (FBG) monitoring system installed around the Compact Muon Selonoid’s (CMS) beam pipe. The FBGs work on measuring Temperature and Strain around the peripherals of the CMS’s BP. The CMS is one of four detectors at the Large Hadron Collider (LHC) operated by CERN around the borders of France and Switzerland. A large particle accelerator that accelerates protons and heavy ions relativistically to high speeds close to the speed of light. Then collides two beams at 4 different detects laid out around the circular collider. ATLAS, LHCb, ALICE, and CMS. The CMS safety team works on systems inside the CMS BP to monitor temperature and strain changes induced in the beam pipe. In hindsight, the FBG sensors use Fiber Optic Sensor (FOS) technology with varying Bragg Gratings inside the glass core of the optical fiber. FBGs work by being exposed to UV light as the result of proton collisions. Then the light is thus reflected back at each grating. The reflected ray’s wavelength changes when being subjected to different levels of temperature and strain. To test the efficacy of the interrogation system, temperature calibration is done and linear and cubic fittings were generated to estimate the temperature through the imputed current. A MATLAB code has been constructed to output the outlined calibration graphs and the fittings.