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The possibility to monitor pulsed dose-rate facilities by means of real-time fibered dosimetry is investigated. A system based on the luminescence of the SrS:Ce,Sm is used to monitor pulses from a medical accelerator with four different dose-rates. The RL signal is characterized using a dedicated acquisition system. The RL recorded is linear with dose-rate and dose. The stem effect due to both Cerenkov emission and photoluminescence in the fiber was also investigated with 18 MV photons and 12 MeV electrons. Index Terms--Optical fiber, optically stimulated luminescence (OSL), radiation dosimetry, radioluminescence (RL), real-time dosimetry, stem effect.

In the final objective of elaborating an optical sensor of dimensional change in a nuclear testing reactor, we present extreme high level irradiation tests, up to 1.3 1020 [n.sub.fast]/[cm.sup.2] and 16GGy, conducted on high purity silica and hollow core photonic bandgap (PBG) fibers. These tests are performed in the OSIRIS reactor at CEA Saclay. We measure continuously Radiation Induced Absorption (RIA), at 3 optical wavelengths: 980 nm, 1064 nm and 1310 nm. The evolution with the time of the spectral dependency over larger wavelength range is also reported. As well as reporting RIA up to higher dose than presented before, we demonstrate here the excellent superiority of hollow core PBG fibers over their conventional counterparts in term of radiation resistance up to over [10.sup.20] [n.sub.fast]/[cm.sup.2] and 10GGy. We also report some Optical Time Domain Reflectometry (OTDR) measurements that probe the irradiated parts of the fibers and show a back scattering peak which appears, widens spatially then duplicates. We provide an interpretation based on the change of silica when it turns to metamict phase. Index Terms--Fiber, irradiation, optical sensor, photonics fiber, pure silica.

We compare the E', H(I) and Si-ODC(II) contents in a low-OH high-purity a-Si[O.sub.2] both in bulk and fibre forms. The investigation includes the effects of hydrogen loading of the fibre. We found that the H(I) centre appears during irradiation and that its concentration tends to increase with the dose in fibers impregnated with molecular hydrogen. For the hydrogen-treated fibers, no experimental repeatability could be found in the measurements of E' and Si-ODC(II) although an acceptable agreement was still found in non-hydrogenated samples. This result suggests a possible complex reaction mechanisms under gamma radiation when the glass has a hydrogen excess. Index Terms--Fibre, gamma, hydrogen, point defects, silica.

We evaluated the performances of the hydrogen-loading technique to reduce the radiation-induced absorption in optical fibers in the visible part of the spectrum. A reduction factor as large as one order of magnitude can be obtained in high dose-rate regime. Based on a spectral deconvolution method, we showed that hydrogen preferentially interacts with NBOHC defects while the number of POR defects is not affected. Index Terms--Attenuation, hardening, hydrogen, optical absorption, fiber, radiation.

We compare the E′, 11(I) and Si-ODC(H) contents in a low-OH high-purity a-SiO2 both in bulk and fibre forms. The investigation includes the effects of hydrogen loading of the fibre. We found that the H(I) centre appears during irradiation and that its concentration tends to increase with the dose in fibers impregnated with molecular hydrogen. For the hydrogen-treated fibers, no experimental repeatability could be found in the measurements of E′ and Si-ODC(II) although an acceptable agreement was still found in non-hydrogenated samples. This result suggests a possible complex reaction mechanisms under gamma radiation when the glass has a hydrogen excess. [ABSTRACT FROM AUTHOR]

We compare the E′, 11(I) and Si-ODC(H) contents in a low-OH high-purity a-SiO2 both in bulk and fibre forms. The investigation includes the effects of hydrogen loading of the fibre. We found that the H(I) centre appears during irradiation and that its concentration tends to increase with the dose in fibers impregnated with molecular hydrogen. For the hydrogen-treated fibers, no experimental repeatability could be found in the measurements of E′ and Si-ODC(II) although an acceptable agreement was still found in non-hydrogenated samples. This result suggests a possible complex reaction mechanisms under gamma radiation when the glass has a hydrogen excess. [ABSTRACT FROM AUTHOR]