Optical properties and radiation hardness of Pr-doped sol-gel silica: Influence of fiber drawing process

Francesca Cova,Mauro Fasoli,Federico Moretti,Norberto Chiodini,Kristof Pauwels,Etiennette Auffray,Marco Toliman Lucchini,Edith Bourret,Ivan Veronese,Eduardo D’Ippolito,Anna Vedda

doi:10.1016/j.jlumin.2017.07.045

Abstract

The optical emission from the 5d – 4f allowed transition of Pr3+ ions embedded in sol-gel silica is investigated for High Energy Physics applications requiring fast scintillating materials.A complete and detailed characterization of the optical, scintillation and radiation hardness properties of Pr-doped silica is carried out employing different experimental techniques including steady-state and time-resolved photo-luminescence, radio- and thermo-luminescence, scintillation and optical absorption.Optical absorption measurements, performed after X-ray irradiation sequences up to 1kGy, evidence the formation of radiation-induced absorption bands related to point defects acting as color centers. Spontaneous partial recovery of the radiation-induced defects at room temperature, as well as after thermal treatments, is also disclosed.Particular attention is paid to the comparison between bulk silica, both before and after a melting process, and fibers. The results reveal the presence of a lower concentration of optically active defects in melted glass. Such comparison highlights a role of the fiber drawing in modifying the glass defectiveness, consisting in the occurrence of a structural reorganization of the amorphous network during the process.

Highlights

In recent years, the sol-gel technique was demonstrated to allow a good control, at a relatively low densification temperature, of rare earth (RE) ions incorporation and of their dispersion inside the glass matrix
3.1 Luminescence properties RL and Photo-luminescence emission (PL)/PLE spectra are reported in Fig. 2 in order to put in evidence excitation and emission bands of Pr3+ ions inside the silica matrix
The optical, scintillation and radiation hardness properties of Pr-doped sol-gel silica glass have been investigated in view of future applications in High Energy Physics experiments

Summary

Introduction

The sol-gel technique was demonstrated to allow a good control, at a relatively low densification temperature, of rare earth (RE) ions incorporation and of their dispersion inside the glass matrix. The glass synthesis can be performed by using high purity precursors, reducing the level of unwanted impurities [1] This latter factor is an essential feature for the radiation hardness of such materials. The most challenging requirement is expected in the High Luminosity Large Hadron Collider phase [11], in which the radiation induced absorption coefficient of the scintillator material should be kept below 1-2 m-1 even after doses of 300 kGy. Praseodymium dopant can be considered as a suitable luminescent activator, because of its fast (a few tens of ns) 5d - 4f transition leading to an emission band in the UV spectral region [12, 13]. A comparison between bulk preforms and residuals of the fiber drawing process is carried out, in order to disclose the role of this process in the radiation hardness properties of RE-doped silica glasses

Methods

Results

Conclusion