Mirror-Assisted Radioluminescent Optical Fibers for X-Ray Beam Monitoring

Abstract

In the framework of the current development of optical fiber sensors for dosimetry or beam monitoring applications based on radioluminescence (RL), we propose a method to enhance their radiation-induced light collection efficiency. This method consists in the deposition of a thin metallic layer, acting as a mirror, at the free output extremity of a radioluminescent optical fiber. Emitted visible photons guided in both directions along the optical fiber core can be collected by a single-ended detection system such as a photomultiplier tube. We characterize the impact of depositing two different types of metallic mirrors (Al and Au) on the performances of a RL based dosimeter, constituted by a Nitrogen-doped multimode optical fiber: its sensitivity has been calibrated with 40 keV X-rays at room temperature for dose rates from 0.05 to ~4 Gy(SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> )/s. Also, investigation about the total ionizing dose effects on the mirror has been carried out to understand the evolution of the reflectance of the mirror under radiation exposure. This architecture of sensors appears as very promising, especially for the monitoring of low photon flux.