Stability of MIR transmittance of silver and thallium halide optical fibres in ionizating β- and γ-radiation from nuclear reactors

In this paper we investigated spectral transmission of irradiated IR fibres derived from single crystals of AgCl-AgBr and AgBr-TlI solid solutions. The fibres were exposed to β- and γ-radiation. The highest absorbed dose was 500 kGy. It was found that even modest radiation doses cause a reduction in transmission in AgCl-AgBr fibres within the entire working wavelength range, while for AgBr-TlI fibres the irradiation causes an increase in transmission when compared to corresponding values of non-irradiated fibres at wavelengths of 4-6 µm. We proposed a mechanism of this radiation-induced translucence and we expect that this phenomenon may be used for improvement of optical fibres. Additionally, we investigated how the transmission of AgCl-AgBr irradiated fibres depends on time after irradiation. Summarizing, both kinds of the fibres are suitable for applications in high radiation environments, for example, as a probe in on-line remote IR spectroscopy.