Radiation Response of Optical Fibers Loaded with Molecular Oxygen
Résumé
We report an experimental investigation regarding the radiation response of Pure-Silica-Core (PSC) and F-doped Optical Fibers (OFs) previously
subjected to a high pressure O2 loading thermal treatment. First, by micro-Raman spectroscopy we demonstrate the efficiency of the O2 loading
technique we applied. In particular, we showed that high concentrations (~2·10E18 molecules/cm3) of molecular oxygen are incorporated in the
whole OF cross section, almost reaching a saturation condition of the samples. Afterwards, we studied the effects of the O2 loading treatment on
the radiation response of the OFs. For this purpose we carried out a comparative study based on simultaneous online Radiation Induced Attenuation (RIA) measurements of the O2 loaded and unloaded OFs in the UV-Visible spectral domain [1]. The experiments were performed by irradiating with 10keV X-rays. The RIA spectra clearly show a strong impact of the O2 excess. The loading treatment causes an increase of the rad
iation sensitivity of the OFs in the UV-Visible domain.
The presence of radiation induced interstitial ozone molecules is also inferred by decomposition of the RIA spectra. The information gained with the RIA experiments is further supported by Electron Paramagnetic Resonance measurements performed on γ-irradiated samples. As a radiation
hardening effect it is found that the irradiation induces a ten time lower concentration of E’(Si) centers in the O2-loaded OFs.
Another interesting phenomenon detected int he O2-loaded OFs is related to an infrared Radio-Luminescence (iRL) of O2 molecules:
a sharp luminescence at 1272nm was indeed detected during irradiation by 10keV X-rays [2]. We will focus on the applicative aspects related to
this effect: the results we obtained show that the iRL is stable up to doses of 1MGy(SiO2) and is linearly dependent on the dose-rate up to the
maximum investigated dose-rate of ~200kGy(SiO2)/h. On the basis of the obtained results we suggest that the iRL can be exploited for real-time, remote dosimetry in environments characterized by high radiation doses and high dose-rates.
[1] D.Di Francesca, S.Agnello, S. Girard, C. Marcandella, P. Paillet, A. Boukenter, Y. Ouerdane, F. M. Gelardi, IEEE Trans.Nucl. Sci. 61, 3302 (2014).
[2] D. Di Francesca, S. Girard, S.Agnello, C.Marcandella, P. Paillet, A. Boukenter, F. M. Gelardi, Y. Ouerdane, Appl. Phys. Lett. 105 ,
83508 (2014).