**2. The effects of electron irradiation and posterior optical bleaching in Ce-doped and Ce/Au-codoped alumino-phospho-silicate fibers**

Development of suitable host glasses and fibers for dosimetry, which are based on formation of radiation-induced defects leading to glass coloration [1–6] or filling pre-existing traps, measured by means of thermally or optically stimulated fluorescence [7], became a hot task. Dosimetry systems can be used in high radiation fields, for example, in proximity to nuclear reactors, hazardous places, and in open space. Fiber-based dosimeters are being intensively investigated and recently a few systems have been proposed, based on versatile physical effects in radiation-sensitive silica fibers [8].

Cerium (Ce)-doped silica glass has interesting fluorescent properties [9], which makes it promising for utilizing as a scintillator for detecting X- and γ-rays, or neutrons [10, 11]. On the other hand, silica glass is known to suffer from the presence of point defects and OH groups, responsible for nonradiative recombination channels competing fluorescence. In turn, Au, when combined with cerium oxide (CeO2) is known to be a promising catalyst for the reaction CO + H2O*→*H2 + CO2 [12, 13], giving a way to remove carbon-related impurities along with OH groups from silica matrix during synthesis. Thus, Ce/Au codoped glass is expected to enhance efficiency of energy transfer from the host matrix to emissive centers. The other motivation for Au codoping is to increase radiation resistance of Ce-doped fiber, as argued in more details below. The refereed properties of alumino-phospho-silicate glass doped with Ce and Ce/Au are also a concern of optical fibers made on its base.

Below, the results of experiments on irradiating Ce-doped alumino-phospho-silicate fibers by energetic β-electrons are highlighted, resulting in the fibers darkening. It is furthermore shown that the irradiated fibers are sensitive to weak light of a He-Ne laser (543 nm) and UV mercury lamp, both leading to partial recovery of their initial properties. The whole of experimental data evidences notable susceptibility of Ce-doped fibers to both kinds of treatment. As well, it is demonstrated that the spectral transformations occurring in Ce fiber codoped with Au are less expressed but more regular upon β-irradiation dose and exposure time when bleaching than those in Au-free fiber. A brief discussion in attempt of a reasonable explanation of the experimental laws completes the study, with the key point being a discussion about the species involved in the processes, which are associated with Ce.

The reported results may have value for using Ce-doped silica fibers for dosimetry in harmful environments [8, 14–20] and inscribing Bragg gratings [21–25]. As well, these results seem to be impactful, given by renewed interest to Ce codoping as a tool for diminishing PD in Ybdoped fibers (we inspect the last effect in detail in Paragraph 3).
