The thermoluminescence response of oxygen-doped optical fibres subjected to photon and electron irradiations

The work describes an attempt to increase the thermoluminescence (TL) yield of pure silica optical fibres, introducing oxygen concentrations through to a depth of 160 nm by means of an ion implantation technique. Subsequent investigation of TL yield was performed by irradiating the O2-doped optical fibres to 6 MV photons and separately to 6, 9 and 12 MeV electrons. To allow comparison, equivalent irradiations were also performed on Ge- and Al-doped silica and pure silica (Ps) fibres, the TL response of these being the subject of previous investigations. The results show the superior TL response to be that of the Ge-doped optical fibres followed by that of the O2-doped fibres. As an example, at 6 MV for doses of up to 4 Gy, the response of the Ge-doped fibres was found to be four times that of the O2-doped fibres, while the response of the O2-doped fibres was around 68 times that produced by the Al-doped fibres. As a consequence of the variability of defect concentration obtained in the process of ion implantation, the O2-doped fibres showed greater fluctuation in dose response than the Ge-doped fibres. O2-doped fibres are observed to provide promising sensitivity on first use, subsequent annealing leading to the loss of practically all added dopants.