On-line gamma dosimetry with phosphorous and germanium co-doped optical fibres

We measured the gamma radiation-induced attenuation in custom made phosphorous and germanium-phosphorous doped fibres at different temperatures for doses up to 360 Gy. Two different components in the recovery kinetics were evidenced. For dosimetry, the phosphorous doped fibre may be interrogated at a single wavelength within an optimal wavelength region of 1200 nm to 1400 nm. Alternatively, we studied the possibility of reconstructing the dose using attenuation data at different wavelengths. The necessary condition for this to work is that enough independent information can be obtained from the attenuation data with respect to the disturbing parameters like temperature, varying dose-rates and recovery. This was only the case for the phosphorous doped fibre and low total doses.