Radiation-induced Absorption Research Articles

Spectrally Resolved Transmission Loss in Gamma Irradiated Yb-Doped Optical Fibers

Yb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped silicate fibers are commonly employed in optical systems utilizing fiber lasers and amplifiers. Deployment of such materials and systems in space-based and other adverse radiation environments requires knowledge of their response to fluxes of ionizing radiation. This paper reports the results of gamma radiation exposures on a suite of passive, modern, highly Yb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped aluminosilicate fibers. Of interest are the effects of total dose and dose rate as well as the development of radiation-induced absorption across a broad spectral window (1.0-1.7 mum). Results indicate that these fibers exhibit reasonable radiation resistance to gamma exposures typical of a five-year low-Earth-orbit environment. Maximum transmittance losses of less than 10% in the 1.0-1.7-mum spectral region for total gamma exposures of 2-5 krad (Si) were observed. In addition, it was found that the dependence of transmittance on radiation dose generally followed a power law that was dependent on dose rate.

Induced absorption in X-ray-irradiated CdS- and CdSSe-doped glasses

Optical transmission spectra of X-ray-irradiated CdS- and CdSSe-doped glasses and undoped glass have been measured. Induced absorption has been observed in these glasses. In addition to the radiation-induced absorption increment, decrease in absorption has been observed near absorption edge in CdSSe-doped glasses. Origin of the decrease in absorption was examined.

Gamma irradiation effects on ZnO-based scintillating glasses containing CeO2 and/or TiO2

Irradiation resistance of as-studied scintillating glass samples were tested under the 60Co γ-ray radiation at doses between 60 and 700Gy. Photoluminescence properties of glasses with and without cerium ions were investigated to show the effect of cerium (III) on the luminescence of ZnO. Ultraviolet and visible optical transmittance spectra were compared before and after irradiation treatment. The so-called radiation-induced absorption coefficient (RIAC) was introduced to compare more effectively the radiation damage on glass samples. The much reduced transmittance change and decreased RIAC value in UV–Vis region indicate that the density of electron centers and hole centers caused by radiation decreased, which helps to confirm that the reduction and oxidation reaction of cerium ions took place in radiation process. From RIAC curves, it can be seen that TiO2 enhances the irradiation resistance of sample in UV region. However, high TiO2 content has negative effect on visible transmittance of glasses after the higher dose irradiation (700Gy).

Radiation assessment of hydrogen-loaded aluminium-coated pure silica core fibres for ITER plasma diagnostic applications

We report on the radiation assessment of hydrogenated aluminium coated 200 μm pure silica core fibres. It is experimentally demonstrated that hydrogen protected the fibres against the radiation-induced absorption. With such appropriate hydrogen treatment the fibres can survive the ITER radiation environment in the vicinity of the labyrinth region of the tokamak reactor.

Reduction of the radiation-induced absorption in hydrogenated pure silica core fibres irradiated in situ with γ-rays

We studied the efficiency of a hydrogen-treatment in different pure silica core fibres irradiated by γ-ray in an attempt to decrease the radiation-induced absorption (RIA). It is observed that the effect of hydrogen already reduces the drawing-induced band commonly observed in low-OH fibres. During irradiation we observe a large increase of the radiation-induced OH growth with a corresponding significant reduction of the radiation-induced absorption at 0.63 μm. The presence of hydrogen also reduces the transient radiation-induced absorption at 0.7 μm sometimes observed in low-OH/low-chlorine fibres and believed to pertain to self-trapped holes (STHs).

Formyl violet cyanide liquid dosimetry system

Aqueous solutions of formyl violet cyanide (FV-CN) have been investigated for potential use in radiation dosimetry using both absorption and fluorescence evaluation. A radiation-induced absorption band peaking at 590 nm was observed and this wavelength was chosen for fluorimetric experiments, where a radiation-induced emission band develops at 600 nm. The useful dose range of the solution was found to be 400–4000 Gy depending on the FV-CN concentration and the evaluation method. The pre- and post-irradiation stabilities of the solutions were found to be satisfactory.

Sugar/UV spectrophotometric system for high-energy dosimetry (0.055–160 kGy)

Aqueous solutions of γ -irradiated solid sugar are studied with respect to their dosimetric properties by using UV spectrophotometry. It is shown that radiation-induced absorption at 267 nm linearly increases with absorbed dose, but it is time dependent and reaches ca. 15% higher steady value 10 days after dissolution or 1 h heating the solution at 70 ∘ C . UV response of 1% sucrose solution in 1 cm sample cell is found to be 0.0055/kGy. The lower limit of dose reading is found to be ca. 55 Gy for 20% w/w water solution and 5 cm sample cell.

Kinetic approach to the decomposition of radiation-induced absorption spectra

We propose a kinetic approach to the decomposition of the radiation-induced absorption spectra into individual Gaussian absorption bands. It is based on the correlated analysis of a series of induced absorption spectra obtained in the course of multi-step irradiation and during room temperature long-term post-radiation annealing. The methodology is demonstrated using data on Co60 gamma irradiated samples of commercial boro-silicate glass N-BK7 from SCHOTT. We show that physically meaningful spectroscopic parameters of absorption bands can be obtained without a priori knowledge of the band peak position and bandwidth.

Luminescence and scintillation properties of YAG:Ce single crystal and optical ceramics

We use various techniques to study optical and scintillation properties of Ce-doped yttrium aluminum garnet, Y 3Al 5O 12 (YAG:Ce), in the form of a high-quality industrial single crystal. This was compared to optical ceramics prepared from YAG:Ce nanopowders. We present experimental data in the areas of optical absorption, radioluminescence, scintillation decay, photoelectron yield, thermally stimulated luminescence and radiation-induced absorption. The results point to an interesting feature—the absence of antisite (Y Al, i.e. Y at the Al site) defects in optical ceramics. The scintillation decay of the ceramics is faster than that of the single crystal, but its photoelectron yield (measured with 1 μs integration time) is about 30–40% lower. Apart from the photoelectron yield value the YAG:Ce optical ceramic is fully comparable to a high quality industrial YAG:Ce single crystal and can become a competitive scintillator material.

Thermally stimulated luminescence mechanism of Li 6Y(BO 3) 3:Eu 3+ single crystals

Thermally stimulated luminescence (TSL) of Li 6Y(BO 3) 3:Eu 3+ single crystals has been studied. Radiation-induced absorption of the Li 6Y(BO 3) 3:Eu 3+ crystals in the 320–500 nm region has been attributed to the formation of hole oxygen centers. Three peaks on the TSL curve in the T = 325–525 K range has been ascribed to decay of the radiation defects, which occupy non-equivalent crystallographic positions. The activation energy and frequency factor of the main TSL peak at T = 488 K has been determined: E = 1.25 eV, and s 0 = 1.9 × 10 11 s −1, respectively. It has been shown that TSL spectral composition corresponds to Eu 3+ ions emission. Possible position of localization of radiation defects in Li 6Y(BO 3) 3:Eu 3+ crystals has been proposed on the base of crystal structure analysis.

Radiation-induced differential optical absorption of metal nanoparticles

A method of measuring the temperature of metal nanoparticles under ion bombardment is proposed. Optical absorption in the range of the surface plasmon resonance of metal nanoparticles was measured during implantation of 3MeV Cu2+ ions into silica glass to derive a difference in optical absorption between beam on and off regimes. The radiation-induced differential (RD) spectra were similar to the spectra of thermomodulation (TM) and quite different from the spectra of nonlinear optical response measured by the pump-probe method. Increasing amplitude of RD and TM spectra was assigned to an increase of lattice temperature of Cu nanoparticles.

New Al2O3:C,Mg crystals for radiophotoluminescent dosimetry and optical imaging

Optical and dosimetric properties of a new radiophotoluminescent material based on aluminum oxide doped with carbon and magnesium (Al2O3:C,Mg) and having aggregate oxygen vacancy defects are presented. The Al2O3:C,Mg crystals are characterized by several new optical absorption and emission bands. It is suggested that the main optical properties of this material are due to the formation of aggregate defects composed of two oxygen vacancies and two Mg-impurity atoms. Radiation-induced optical absorption bands are centered at 335 and 620 nm and produce fluorescent emission at 750 nm with a 75 +/- 5 ns lifetime. The dose measurements are performed by illumination of the Al2O3:C,Mg crystal with 335 nm or 650 nm light and by measuring the intensity of the 750 nm fluorescence. The detector material is insensitive to room light before and after the irradiation and the traps are stable up to 600 degrees C. A dose measurement range between 5 mGy and 200 Gy, suitable for therapeutic radiology applications, was demonstrated. The short luminescent lifetime and nondestructive readout is favorable for imaging applications.

A study of radiation resistance of silica optical fibers under conditions of reactor irradiation

A measuring system has been developed to investigate the characteristics of radiation-induced optical absorption and radioluminescence in the spectral range of 400–1000 nm for a set of optical fibers being irradiated by fast neutrons and γ rays. This system has been used on the IR-8 research nuclear reactor to perform comparative tests of eight types of silica optical fibers from Heraeus (Germany), Fujikura (Japan), Mitsubishi (Japan), and the Fiber Optics Research Center of the Russian Academy of Sciences’ Prokhorov General Physics Institute. The measured dependences of the induced absorption and radioluminescence intensity versus the nuclear radiation wavelength, flux, and fluence, as well as the temperature, are analyzed. The microscopic mechanisms of induced absorption and radioluminescence are discussed. The values of induced optical absorption and radioluminescence in glass fibers containing H2 gas and having a hermetic coating (the technology for producing such fibers has been developed by the Fiber Optics Research Center) is found to be many times smaller than in other fibers.

Interaction of spermine with DNA, vitamin C and bovine serum albumin in the unirradiated and gamma irradiated states

Structural deformability of spermine with radiation dose (maximum 10 Gy) has been proved. Complex formation of spermine with DNA, vitamin C and BSA took place. Calibration and radiation-induced absorption changes in spermine by ninhydrin reagent has been followed quantitatively. Interaction of vitamin C with DNA and their radiation-induced changes have been reported. Interaction of spermine with DNA in the unlrradiated and gamma irradiated states in 10 -3 M phosphate buffer and water have been compared. Addition of spermine and vitamin C to DNA makes DNA structure more condensed. Bovine serum albumin also binds with spermine and protects it from radiation-Induced degradation.

Radiation defects manipulation by ultrasound in ionic crystals

The radiation-induced optical absorption in ionic crystals is remarkably removed by a room-temperature ultrasonic treatment of the crystals. It is shown that the effect can be explained by defect migration processes occurring in ultrasonic fields. The experimental results display features consistent with a recent theory of the quantum diffusion. This new method of a cold annealing of radiation defects in solids can be termed as ultrasonic defect manipulation.

Setup for the in situ monitoring of the irradiation-induced effects in optical fibers in the ultraviolet-visible optical range

The paper describes a setup for in situ monitoring of the radiation-induced optical absorption and the radiation-induced luminescence, in the UV-visible spectral range (200–800 nm), for large diameter (400μm) optical fibers. Silica and sapphire optical fibers were irradiated, at room temperature, with gamma rays (dose rate of 0.33kGy∕h, total dose of 34.5 kGy) and protons (dose rate of 100Gy∕s, total dose of 1.8 MGy). At several moments, the irradiation was interrupted and the annealing of the radiation-induced optical absorption was observed at room temperature. The setup also makes possible the monitoring of the optical radiation-induced recovery of the optical absorption (the effect of photobleaching), as the optical fiber can be exposed at the same time to both the ionizing radiation (gamma or protons) and to the radiation of a broadband optical source. The optical absorption and radioluminescence were measured with an optical fiber multichannel spectrometer coupled to an optical fiber multiplexer. The equipment control as well as the data collection and processing were performed using the graphical programming environment LabVIEW. The paper includes several graphs illustrating the evolution of the optical absorption and radiation-induced luminescence during gamma and proton irradiation of optical fibers.

Radiation-induced absorption in high-purity silica fiber preforms

The effect of the preform fabrication procedure on the radiation-induced absorption in KU-1 and KS-4V high-purity silica glasses was investigated (these glasses are used in fiber preform fabrication via outside fluorosilicate glass deposition on substrate rods and in the rod-in-tube process). The results demonstrate that the deposition of a reflective cladding onto KU-1 rods drastically increases the radiation-induced UV absorption of the rods. In particular, the concentrations of radiation-induced nonbridging oxygen hole centers and E′ centers in gamma-irradiated KU-1 rods with a fluorosilicate cladding are an order of magnitude higher than those in rods that were not heat-treated in plasma torch flames. At the same time, the deposition of a reflective cladding on KS-4V rods has little effect on the concentrations of these radiation-induced color centers. The radiation-induced absorption in KU-1 rods depends on the deposition temperature and duration but is insensitive to the composition of the gas mixture in the torch (in particular, to the presence of fluorination agents) and the presence of a fluorosilicate cladding. It is shown that, in preforms fabricated by the rod-in-tube process, the net concentration of radiation-induced color centers in the substrate rod is lower compared to the outside plasma deposition of fluorosilicate glass on the rod.

Radiation-Induced-Defects Localization in Single-Mode Optical Fibers

We studied the defects at the origins of the permanent radiation-induced attenuation in four g-rays irradiated single-mode germanosilicate optical fibers (~1 MeV; 1.2 kGy; 0.3 Gy/s) in the spectral range 400 - 1700 nm. We determined the wavelength dependence of the following cladding codopant influences: germanium (0.3 %), phosphorus (0.3 %), fluorine (0.3 %) on the germanosilicate (13 %) fiber radiation responses. We identified some of the different color centers produced by g-rays and we evaluated their localization in the fiber cross-section through the determination of the radial distribution of the radiation-induced absorption at 633 nm. We also evidenced the strong interactions between these three codopants. In particular, our results showed that the properties of the phosphorus-related color centers, which mainly determine the fiber infrared radiation sensitivity, are strongly influenced by the germanium- and fluorine-codoping.

Radiation sensitivity of GSO and LSO scintillation detectors

Radiation resistance of 4×4×30 mm 3 GSO and LSO imaging scintillation detectors has been studied for low-energy gamma-ray doses of 10 4 Gy (10 6 rad) and 10 5 Gy (10 7 rad). Radiation hardness was determined by the measurement of optical transmission through GSO and LSO scintillation crystals before and after irradiations with 60Co gamma-rays. The results have been analysed in terms of the radiation-induced absorption coefficients and compared with radiation sensitivity measurements of small BGO scintillation crystals. The recovery time of irradiated small GSO and LSO crystals has also been determined.

On-line measurement of gamma radiation-induced absorption in A3+-codoped PbWO4: Mo crystals

The radiation hardness of the set of seven samples of Mo-doped PbWO4 crystals (from 0 up to 10,000ppm) and further codoped by Y, La, Nb, is investigated. With increasing Mo concentration above 1000ppm radiation hardness increases. Codoping by Y, La can still decrease radiation-induced absorption about several tens percent at least, while influence of Nb is not clear. Induced absorption increases with the dose rate, for dose rates higher than 0.35Gy/min it achieves saturation level. As it is planned to use PbWO4 scintillating crystals at lower temperature in ALICE experiment in CERN, some measurements were performed at temperature −15°C too. Induced absorption coefficient at low temperature is 2–4 times higher with respect to room temperature and kinetic of recovery processes gets slower.