Radiation Effects on Silica-Based Preforms and Optical Fibers—I: Experimental Study With Canonical Samples

CEA DIF, Arpajon
IEEE Transactions on Nuclear Science (Impact Factor: 1.28). 01/2009; 55(6):3473 - 3482. DOI: 10.1109/TNS.2008.2007297
Source: IEEE Xplore


Prototype samples of preforms and associated fibers have been designed and fabricated through MCVD process to investigate the role of fluorine (F) and germanium (Ge) doping elements on the radiation sensitivity of silica-based glasses. We characterized the behaviors of these canonical samples before, during and after 10 keV X-ray irradiation through several spectroscopic techniques, to obtain global information (in situ absorption measurements, electron paramagnetic resonance) or spatially-resolved information (confocal microscopy, absorption and luminescence on preform). These tests showed that, for the Ge-doped fiber and in the 300-900 nm range, the radiation-induced attenuation (RIA) can be explained by absorption bands associated with the following radiation-induced point defects: Ge(l); Ge-NBOHC and GeX. Other defects such as GeE' Ge(2); and Ge-ODC are generated but do not contribute in this spectral domain. For the F-doped sample, the different point defects identified, SiE', Si-NBOHC and Si-ODC(II), are unable to reproduce the RIA spectra for energies lower than 4 eV. We suggest that the radiation-induced absorption in this part of the spectrum is due to chlorine-related species, probably CI0 radiolytic groups that absorb at around 3.5 eV. The comparison between the sensitivities of the preform and the fiber reveals the influence of the drawing process on the glass response. Its effect is strongly dose-dependent for the germanosilicate glass. The drawing process seems to be responsible for the main part of the defects generated at low doses (<1 Mrad).

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    • "At lower energies fiber of any core diameter has a greater TL response and greater efficiency than that at higher photon energies (Bradley et al., 2012). The TL response of silica optical fibers under irradiation are influenced by many factors, including: the preform manufacturing conditions, the fabrication parameters used in producing the optical fiber, the preform deposition temperature, fiber drawing process characteristics – drawing speed, fiber drawing tension, furnace temperature, oxygen-to-reagent ratio (Girard et al., 2007), dopants present in the optical fiber core or cladding (pure silica, or doped) (Alawiah et al., 2015a, 2015b; Mady et al., 2010; Paul et al., 2009) and the type of radiation to which the optical fiber is exposed (Girard et al., 2008; Yaakob et al., 2011; Hashim et al., 2010). "
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    ABSTRACT: In regard to thermoluminescence (TL) applied to dosimetry, in recent times a number of researchers have explored the role of optical fibers for radiation detection and measurement. Many of the studies have focused on the specific dopant concentration, the type of dopant and the fiber core diameter, all key dependencies in producing significant increase in the sensitivity of such fibers. At doses of less than 1Gy none of these investigations have addressed the relationship between dose response and TL glow peak behavior of erbium (Er)-doped silica cylindrical fibers (CF). For x-rays obtained at accelerating potentials from 70 to 130kVp, delivering doses of between 0.1 and 0.7Gy, present study explores the issue of dose response, special attention being paid to determination of the kinetic parameters and dosimetric peak properties of Er-doped CF. The effect of dose response on the kinetic parameters of the glow peak has been compared against other fiber types, revealing previously misunderstood connections between kinetic parameters and radiation dose. Within the investigated dose range there was an absence of supralinearity of response of the Er-doped silica CF, instead sub-linear response being observed. Detailed examination of glow peak response and kinetic parameters has thus been shown to shed new light of the rarely acknowledged issue of the limitation of TL kinetic model and sub-linear dose response of Er-doped silica CF. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Full-text · Article · Jul 2015 · Applied Radiation and Isotopes
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    • "It was fabricated and drawn in our lab with the same specifications as the GeD2 fiber, produced by iXFiber SAS. Ge content as well as the doping profiles are quite similar to those already reported [17], [18]. TLD500 is a single crystal ( mm) of anion defective aluminum oxide C. Its mass is 72 mg. "
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    ABSTRACT: One of the main criteria for choosing a thermolumi-nescent dosimeter (TLD) is its sensitivity to the radiations under investigation. Increasing the heating rate during readout often appears necessary to reduce the time between the measurements and the dose evaluation, especially in routine dosimetry. How-ever, doing this degrades the radiation sensitivity of common dosimeters, as illustrated in this work for the TLD500 dosimeter. It is shown that the germanium-doped optical fiber (GDF) is not only more sensitive to radiation than these COTS dosimeters but, unlike them, its sensitivity is enhanced when the heating rate increases. The physical origin of this rare effect of sensitivity enhancement is probably due to the temperature dependence of the recombination rate by which the detrapped electrons upon stimulation are transferred to the luminescent centers. The effect of light exposure on the dose information stored in both GDF and a commercial TLD is also reported.
    Full-text · Article · Dec 2014 · IEEE Transactions on Nuclear Science
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    • "As presented in [3] and [4], comparison between experiments and simulations and validation of new codes and theories necessitate dedicated comparable samples for both approaches. This can be achieved with the so-called canonical samples, consisting in samples of preforms and fibers made by the manufacturer iX- Fiber [5]. "
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    ABSTRACT: We applied theoretical and experimental spectroscopy tools to ad hoc silica-based "canonical" samples to characterize the influence of several dopants and of some drawing process parameters on their radiation sensitivities. We present in this paper, the recent advances and results occurring from our coupled approach. On the experimental side, we studied the doping influence on the response of optical fibers and showed that changing the drawing parameters has a negligible influence on the fiber response in the case of specialty fibers. We focus mainly on the SiE' defect that is observed through Electron Paramagnetic Resonance (EPR) measurements in all canonical samples. On the theoretical side, we exhibit the improvements obtained in the calculations of electronic and optical properties of defects by using Many Body Perturbation Theory through the use of the GW approximation and the resolution of the Bethe-Salpeter equation instead of the Density Functional Theory (Local Density Approximation). To continue to strengthen the link between experiment and simulation, we have performed first-principles calculations of EPR parameters of some silica-based defects. The first results allowing for an attribution of EPR E' signals to structural models are presented. In particular, we confirm that the E-gamma' center is originated by an unpaired electron in a sp(3) state at a three-fold coordinated silicon atom.
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