Study of the radioluminesence spectra of doped silica optical fibre dosimeters for stem effect removal

In this study, the spectral emission of Eu3+-doped silica optical fibres is investigated under irradiation with photons and electrons of different energies, field sizes and orientations, in order to discover the origin of stem effect and evaluate its influence on the radioluminescence (RL) spectral shape under experimental conditions. A comparison with previously investigated Ce-doped silica fibres is also made. Below the Cerenkov radiation energy threshold, a slight contribution to the total RL signal is observed. This is due to fluorescence effects occurring in the passive fibre. Above the energy threshold, the stem effect is mainly caused by Cerenkov radiation. A method for removing the stem effect, based on RL spectral analysis, is proposed and validated by measuring the output factors of extended photon fields and by studying the angular dependence of the dosimeter.