Dosimetry with optical fibres: Results for pure silica, phosphorous and erbium doped samples

The potential for intrinsic dosimetry with three different fibre types through the gamma ray radiation induced attenuation is investigated with respect to annealing, temperature dependencies, photo-bleaching and, to a limited extent, dose-rate. The radiation sensitivity of these three fibres covers an effective dose range of 0.1 Gy to 100 kGy which makes them suitable for a broad range of nuclear applications. With detailed analysis in both the spectral and temporal domain, it is shown that the long-term annealing effects can be suppressed by exploiting the stability of certain colour centres in the fibre core and adequate interrogation of the induced attenuation at a discrete set of wavelengths. Photo-bleaching is observed by employing a low power white light source (a few microwatts in the fibre) with Erbium doped fibres and when Germanium is added as a co-dopant with phosphorous fibres. Temperature dependencies during irradiation and annealing are addressed from room temperature to 80°C. The Phosphorous and Erbium doped samples exhibit a reverse behaviour: the optical absorption increases with temperature.