POF sensors for gas monitoring in the presence of ionizing radiations

This paper describes an innovative sensor for the measurement of low concentrations of hydrogen fluoride (HF) in the insulating gas employed in resistive plate chamber detectors (RPC). RPC detectors are widely used in high energy physics experiments to detect the presence of muons. This application is designed to be installed at the Large Hadron Collider at CERN (European Center for Nuclear Research) and is based on a plastic optic fiber. The sensor is capable of working in the presence of ionizing radiation for periods in excess of 6 months with excellent performance and without transmission lost. The sensitivity to the HF is obtained by deposing a thin SiO_x layer onto the fiber core. The reaction of such layer with the HF alters the fiber light transmission and is revealed by a photodiode.