Proton Radiation Sensitivity of Fiber Bragg Gratings for Particle Colliders

Abstract

The technology based on Fiber optical Bragg Grating Sensors (FBGS) is very attractive for the structural and environmental monitoring of particle colliders, which require a very precise alignment of their structural components and their sensor elements. Sensors for this purpose need to be unaffected by the extreme radiation cocktail of particles from a collider particle physics experiment and its extremely high magnetic fields. The radiation effects on FBGS with respect to more conventional radiation environments such as space or nuclear installations have been studied for more than a decade and the overall FBGS radiation sensitivity is understood up to a reasonable level. However, significantly fewer studies have been conducted on the sensitivity of FBGSs against proton radiation that is significant in hadronic collider experiments. In this work, the effect of the proton irradiation on the strain and temperature sensitivity were investigated for several FBGS arrays made from different manufactures and with different fiber coatings like Ormocer, acrylic and polyimide. The FBGSs were irradiated with a proton energy of 13.3 MeV in air at room temperature, reaching a total absorbed dose rate of 10 Mrad (100kGy). Based on the positive obtained results, a displacement transducer has been developed for use in the alignment control of the collider sensor elements. The manufactured transducer has a sensitivity of 2,5 pm/micron with a precision of ± 5 microns in a temperature range of -20ºC to 40ºC. and is usable from cryogenic temperatures up to 140ºC.