Search results for "irradiation effects"

Effects of high pressure thermal treatments in oxygen and helium atmospheres on amorphous silicon dioxide and its radiation hardness

2009

The effects of thermal treatments at similar to 400 degrees C in oxygen or helium atmospheres at similar to 180 baron the radiation hardness of amorphous SiO(2) are studied. The generation efficiency of several point defects under gamma irradiation is compared to that of the untreated material. All the effects on point defects generation here observed can be explained in terms of changes in the precursor sites. In particular it has been observed that the thermal treatments can change the precursors sites of point defects both through temperature and pressure related processes, not depending on the atmosphere, and through oxygen related processes creating oxygen excess sites. The presence of…

In-situ observation of beta-ray induced UV optical absorption in a-SiO2: radiation darkening and room temperature recovery

2006

International audience; We studied the optical absorption in the 3.0-6.2 eV range induced in bulk amorphous SiO2 by beta-ray irradiation up to similar to 1 MGy at room temperature. The induced absorption was measured in situ both during irradiation and in the post irradiation time. Our data evidence E', center as the main defect induced by irradiation and the partial decay of their absorption band at about 5.8 eV after irradiation. A quantitative analysis of the time evolution of the induced absorption shows that the transmission recovery observed after irradiation is compatible with the reaction of radiation-induced defects with H-related (H-2, H2O) species diffusing in the amorphous matrix

Radiation Response of Ce-Doped Phosphosilicate Optical Fibers

2014

International audience; We report an experimental study of the radiation effects on silica-based multimode optical fibers (OFs) either doped with Phosphorus or with Phosphorus and Cerium. Online Radiation-Induced-Absorption (RIA) measurements were performed in the UV-visible spectral domain under 10 keV X-ray Irradiation. Optical Absorption (OA) in the Near Infrared Region (NIR) and Electron Paramagnetic Resonance (EPR) measurements were also performed on γ-irradiated OFs.

The role of impurities in the irradiation induced densification of amorphous SiO(2).

2011

In a recent work (Buscarino et al 2009 Phys. Rev. B 80 094202), by studying the properties of the (29)Si hyperfine structure of the E'(γ) point defect, we have proposed a model able to describe quantitatively the densification process taking place upon electron irradiation in amorphous SiO(2) (a-SiO(2)). In particular, we have shown that it proceeds heterogeneously, through the nucleation of confined densified regions statistically dispersed into the whole volume of the material. In the present experimental investigation, by using a similar approach on a wider set of materials, we explore how this process is influenced by impurities, such as OH and Cl, typically involved in relevant concent…

Combined High Dose and Temperature Radiation Effects on Multimode Silica-Based Optical Fibers

2013

International audience; We investigate the response of Ge-doped, P-doped, pure-silica, or Fluorine-doped fibers to extreme environments combining doses up to MGy(SiO $_{{{2}}}$) level of 10 keV X-rays and temperatures between 25 C and 300 C . First, we evaluate their potential to serve either as parts of radiation tolerant optical or optoelectronic systems or at the opposite, for the most sensitive ones, as punctual or distributed dosimeters. Second, we improve our knowledge on combined ionizing radiations and temperature (R&T) effects on radiation-induced attenuation (RIA) by measuring the RIA spectra in the ultraviolet and visible domains varying the R&T conditions. Our results reveal the…

Irradiation induced defects in fluorine doped silica

2008

International audience; The role of fluorine doping in the response to UV pulsed laser and c radiation of silica preforms and fibers was studied using electron spin resonance (ESR) spectroscopy. Exposure to radiation mainly generates E0 centers, with the same effectiveness in fibers and in preforms. The E'concentration in F-doped silica fibers is found to increase with UV energy fluence till a saturation value, consistently with a precursor conversion process. These results show the fluorine role in reducing the strained Si–O bonds thus improving the radiation hardness of silica, also after drawing process.

Coupled irradiation-temperature effects on induced point defects in germanosilicate optical fibers

2017

International audience; We investigated the combined effects of temperature and X-rays exposures on the nature of point defects generated in Ge-doped multimode optical fibers. Electron paramagnetic resonance (EPR) results on samples X-ray irradiated at 5 kGy(SiO2), employing different temperatures and dose rates, are reported and discussed. The data highlight the generation of the Ge(1), Ge(2), E0 Ge and E0 Si defects. For the Ge(1) and Ge(2), we observed a decrease in the induced defect concentrations for irradiation temperatures higher than *450 K, whereas the E0 defects feature an opposite tendency. The comparison with previous post-irradiation thermal treatments reveals peculiar effects…

Defect-related visible luminescence of silica nanoparticles

2013

The high photon emissivity in the visible spectral range is one of the most relevant phenomena emerging from the reduction of silica down to nanoscale; hence it is promising for the development of optical nanotechnologies (down converter, probes, display). It is well accepted that the origin of this luminescence is related to the high specific surface (~100 m2/g) that favors the formation of optically active defects at the nanosilica surface. With the aim to clarify the role of specific luminescent defects, here we report a detailed study of spectral and decay features by time-resolved photoluminescence spectra under a visible-UV tunable laser excitation. Our study is carried out on differe…

Luminescence activity of irradiated SiO2-clathrate Melanophlogite

2013

Combined Temperature Radiation Effects and Influence of Drawing Conditions on Phosphorous‐Doped Optical Fibers

2018

International audience; This work focuses on the effects of high dose ionizing radiation, up to 10 MGy(SiO2), on P‐doped multimode optical fibers (OF) at different irradiation temperatures. The investigation is based on two complementary experimental techniques: radiation‐induced attenuation (RIA) measurements and electron paramagnetic resonance (EPR). The latter technique allows measuring the P1, P2, metastable‐POHC and stable‐POHC defects. Three OF samples are drawn from the same preform to evaluate the influence of changing their drawing conditions of the OFs on the radiation responses. This first study is performed under X‐rays at room temperature. The results are compared with the ones…