Sol–gel silica glasses for radiation dosimetry

Nissrine Al Helou (1) , Jessica Bahout (1) , Hicham El Hamzaoui (1) , Bruno Capoen (1) , Géraud Bouwmans (1) , Geneviève Chadeyron (2) , Rachid Mahiou (2) , Youcef Ouerdane (3) , Aziz Boukenter (3) , Sylvain Girard (3) , Claude Marcandella (4) , Olivier Duhamel (4) , Mohamed Bouazaoui (1)

1 PhLAM - Laboratoire de Physique des Lasers, Atomes et Molécules - UMR 8523
2 ICCF - Institut de Chimie de Clermont-Ferrand
3 LHC - Laboratoire Hubert Curien
4 DAM/DIF - DAM Île-de-France

In the field of new techniques for radiotherapy, also in harsh environment such as in nuclear facilities or in space industry, ionizing radiation dosimetry requires monitoring over long distances and/or with high space resolution of the measurement. For these applications, fibered solutions seem particularly adapted, but in this domain, new sensitive materials, able to be drawn into fibers, are needed. Indeed, scintillating fibers already exist, generally made of tissue-equivalent organic materials, which are particularly interesting to remotely measure real-time X-ray doses in radiotherapy applications. However, these plastic optical fibers exhibit rather poor guiding properties and could suffer from radiation in hostile environment. Thereby, increased attenuation losses and degradation of the scintillating dopant may occur in those devices when exposed to high dose rates, which is a problem in nuclear industry where radiation hardening of the safety or radioprotection devices is a crucial point. Inorganic radio-sensitive optical elements, like doped silicate glasses, can overcome these drawbacks. Moreover, compared to their crystalline counterpart, the glassy scintillators show higher mechanical and thermal stabilities, facilitating their shaping as optical fibers. Hence, this presentation will focus on the potentialities of doped sol-gel silica glasses for in-vivo / in-situ or high dose rate remote measurements. This work deals with the spectroscopic and optical properties of a bulk cerium-doped sol–gel vitreous glass, obtained by densification either in air or in helium atmosphere. In comparison with the glass densified under air atmosphere, the one obtained after sintering the xerogel under helium gas presents improved optical properties, with an enhancement of the photoluminescence quantum yield up to 33 %, which is attributed to a higher Ce3+ ions concentration. The second kind of samples are sol-gel silica glasses activated with various concentrations of Cu+ ions. Here again, we show that the densification atmosphere has a decisive impact on the visible luminescence performance of the glass. The exposition of these Cu-doped samples to high doses of X-ray or -radiation induces point defects, a visible darkening and a strong reduction of their photoluminescence quantum yield. However, the materials remain optically active and can be used in a dosimetry setup. Such glassy cylindrical samples have been drawn at high temperature into thin canes, pieces of which have been used as active materials in fibered remote X-ray radiation dosimeters. The samples exhibited a reversible linear radioluminescence intensity response versus the dose rate up to 50 Gy s−1. The optically stimulated luminescence properties of these doped silica rods have also been investigated using the same fibered setup. These results confirm the potentialities of such materials for in- vivo / in-situ or high dose rate remote dosimetry measurements.

Domaines: Optique [physics.optics]

Nissrine Al Helou, Jessica Bahout, Hicham El Hamzaoui, Bruno Capoen, Géraud Bouwmans, et al.. Sol–gel silica glasses for radiation dosimetry. The 5th International Conference on the Physics of Optical Materials and Devices (ICOM 2018), Aug 2018, Igalo, Montenegro. ⟨hal-01885385⟩