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A set of Ce3+ activated silicate- and phosphate-based scintillating glasses were submitted to γ irradiation in the 60Co radioisotope source “Calliope” (ENEA-Casaccia in Rome, Italy) in the dose range between 1 and 250 Gy (3.7 Gy/h). The effect of ionising radiation was probed by transmission measurements performed before and after each irradiation on all analysed samples. From these data, the radiation-induced absorption coefficient was calculated, proportional to the density of colour centres induced by irradiation in the solid matrix. Results are discussed by taking into account the possible dependence of radiation hardness on the composition of glass matrix.

Radiation induced absorption spectra (irradiation up to 500 Gy by 60 Co) and TSL of a set of YAP:Ce crystals co-doped by Zr 4+ were investigated. Positive effect of Zr 4+ co-doping was found, namely reduction of both the defect creation and presence of TSL active traps. Up to three absorption bands were observed in the radiation induced absorption spectra. They probably have different origin - from colour centers in the green part of the spectra to change of the Ce 3+ valency in the near UV.

The effect of γ irradiation on the optical properties of Ce 3+ -doped phosphate and silicate glasses is studied in the 1–250 Gy dose range. Results are discussed by taking into account the possible dependence of radiation-induced effects on the composition of the glass matrix.

The above-mentioned measurements, on crystals, photodetectors and optical couplings, performed at INFN and ENEA laboratories and irradiation facilities, represent a thorough study of options, that will allow the optimal solution for the upgrade of the Belle II end cap calorimeter to be found. © 2014 IEEE.

THE High Luminosity upgrade of the Large Hadron Collider will pose new challenges to the installed detectors. Higher beam background, combined with new requirements in terms of power supply for the upgraded detectors, and the presence of magnetic fields up to 1 T, make the choice of power supply electronic components a crucial point for the successful operation of the detectors for the new physics run. We took the case of the ATLAS New Small Wheel muon detector installation [1], foreseen for the Phase I upgrade, which will integrate over its lifetime a Total Ionizing Dose (TID) of 1.7 kGy, up to 3×1014 1 MeV-equivalent n/cm2, and will operate in a magnetic field ranging between 0.3 and 0.6 T [2], [3], [4]. We carried out a test campaign on different DC-DC power converters and voltage regulators, by exposing test modules to gamma-rays up to 4 kGy TID, neutrons up to 5×1014 n/cm2, protons up to 5×1012 p/cm2, with a wide range of integrated doses and fluences, and magnetic field up to 1 T. A list of candidate devices was identified by a combination of market survey and recommendation. The devices fall into two categories: single-inductor buck converters are intended for one-step reduction of a 12 V-24 V supply voltage to the delivery voltage; low-dropout voltage regulators (LDOs) may optionally follow the buck converters for noise reduction or to provide additional voltages. The selected candidate parts include a variety of desirable features, such as multiple outputs (LTM4619, LTM4628, ADP5052), low radiated noise (LTM8033), or integrated magnetics (LTM8033, LTM4619, LTM4628). © 2014 IEEE.

The effect of 60 Co irradiation (1–250 Gy) on the optical properties of selected phosphate and silicate-based scintillating glasses was investigated by transmission measurements performed at room temperature in the UV–Visible part of the spectra. Samples doped with rare-earth ions (Ce 3+ , Tb 3+ as emission centres, and Gd 3+ as an additional constituent in certain compositions) have been studied. The results are discussed taking into account the possible influence of different glass compositions on radiation induced colour centres.

The influence of different doping ions on the emission and scintillation characteristics of PbWO4 scintillator was studied. In the case of Ce3+ doping, efficient non-radiative recombination at Ce3+ sites takes place resulting in a lower light yield and faster luminescence and scintillation response. Th4+ doping shows all the positive features of trivalent ion doping used previously for PbWO4 scintillator optimisation. Heavily La3+ and Gd3+ doped PbWO4 crystals (up to several molar percent) a suppressed light yield and subnanosecond scintillation response. Finally, Tb3+ and Pr3+ doping results in dominant emission lines at 543 and 602 nm with decay times of about 650 and 61 μs at 295 K, respectively.

Ce 3+ and Tb 3+ -doped Na(K)-Gd phosphate glasses were synthesized and their radio-, photo- and thermoluminescence properties were investigated. Increased radioluminescence efficiency with respect to Gd-free glass matrix has been achieved at Gd concentrations above 20 mol%. This is explained by efficient capture of thermalised electrons and holes in the Gd 3+ -sublattice resulting in the formation of Gd 3 excited states followed by Gd 3+ -Gd 3+ energy transfer and single-step transfer to the Ce 3+ (Tb 3+ ) emission centres. In such a way non-radiative losses in the phosphate glass matrix are reduced. Energy migration in Gd-sublattice becomes frozen below 10-15 K due to local field fluctuations in the glass matrix. Thermoluminescence measurements above room temperature show the presence of two groups of traps with concentrations strongly dependent on the glass composition.

In our previous papers we reported that La 3+ , Gd 3+ , Y 3+ , and Lu 3+ dopings significantly improve the optical and scintillation characteristics, including radiation hardness, of PbWO 4 single crystals. The hypothesis of Pb 2+ deficiency in the grown crystals and its charge compensation by the mentioned trivalent ions occupying the Pb 2+ sites has been proposed to explain the observed improvement. Under such assumption, tetravalent-ion doping may be as efficient as or even more efficient than trivalent-ion doping in improving PbWO 4 scintillator. Recently we extended the dopant ions to stable tetravalent ions (Th 4+ , Zr 4+ ) and some other ions (Ce 3+,4+ , Sb 3+,5+ , Mn 2+ ). We have found that the tetravalent-ion (Th 4+ ) doping gives similar improvement compared with the trivalent-ion doping in consistency with the expectation mentioned above. The ions with two different possible charge states (Ce 3+,4+ , Sb 3+,5+ ) gave finite but much less improvement than the trivalent and tetravalent ions. Ce 3+,4+ doping reduced the light yield significantly. Annealing of undoped PWO in PbO vapour was also studied to examine the possibility of reducing the Pb 2+ deficiency

The influence of Gd 3+ doping on the optical properties of PbWO 4 has been investigated by radio- and thermoluminescence, photoluminescence time decay, optical absorption and light yield measurements. The samples were grown by the Czochralski method and the concentration of Gd in the melt was in the range 0 to 135 mol. ppm. The results demonstrate that a dopant concentration of around 100 ppm in the crystal appears as the best one in order to optimise the scintillation performance of the material.

Doping by different trivalent ions (La3+, Lu3+, Gd3+, Y3+, Sc3+) was systematically studied in PbWO4 crystals in the same way, using raw material from the same source. The result was compared with an undoped sample (actually a Pb-rich one) and samples doped with divalent (Cd2+) and pentavalent (Nb5+) ions. All the trivalent ions but Sc3+ gave a significant improvement in transmittance in the short wavelength region (330–450 nm) and in radiation hardness. Among all the tested dopants, Y3+ and Gd3+ showed the best result; these dopants may be worth further studies, since they have another advantage of the segregation coefficient close to unity.

The investigation performed up to now on single crystals of PbWO/sub 4/ (PWO) provides the evidence of the possibility to optimise the optical properties of an intrinsic scintillator such as PWO: the control of essential requirements in the crystal preparation (raw material purity, growing methods and post-growth annealing) as well as the introduction of selected dopants at suitable concentrations (particularly trivalent and pentavalent ions) were found to be very successful in lowering the concentration of point defects in the lattice which strongly affect scintillation properties and radiation hardness. The optical transmission as well as light yield before and after irradiation was measured. The systematic investigation effort to better understand the scintillation characteristics and to improve the quality of PWO crystals is due to their use for the CMS electromagnetic calorimeter.

In this paper gamma-radiation damages and effects on an epoxide matrix and on its particulate composite with coal fly ash have been studied; the curing of both formulations was carried out at room temperature by means of tetraethylenepentamine and of a tailored polyalkylenepolyaminophenolic product. The change on mechanical properties following the irradiation in air at room temperature has been tested as a function of the total absorbed dose. The chemical modification induced by the ionizing radiation on the matrices have been investigated by means of infrared spectrophotometry and differential scanning calorimetry. The high radiation resistance of the matrix and above all of the particulate composite suggests its use for the confinment of low and medium activity radwastes (nuclear or medical).

The aim of this work was to compare the gamma radiation induced effects on samples of an ethylene-propylene copolymer antioxidant free with samples loaded with an antioxidant characterised by the presence of an -NH functional group. The employed techniques were Electron Spin Resonance spectroscopy (ESR) and High Performance Liquid Chromatography (HPLC). Stable radicals RNO° due to the interaction of free radicals produced in the irradiated polymer with the antioxidant have been observed by ESR at room temperature. The time evolution of the ESR signals following the irradiation was examined at different doses. The amount of antioxidant not involved in the oxidation reactions has been determined using HPLC.

A characterization of the radiation hardness of PbWO 4 scintillators by means of transmission measurements will be described. The gamma radiation induced changes in the absorption spectra of PbWO 4 crystals undoped as well as doped with trivalent ions will be illustrated. The characteristics of the room temperature recovery of the radiation induced colour centres in these crystals will be reported.

Recent works show growing interest in optically isolated YAP : Ce single-crystal matrices as high spatial resolution detectors for imaging applications in Nuclear Medicine. Such matrices are manufactured by Preciosa Crytur (Czech Republic) by means of a special sticking procedure of YAP : Ce pillars about 10 mm in length and with cross section ranging between 0.6 mm × 0.6 mm and 3 mm × 3 mm. In this work, we carried out an intensive study on both the complex refractive index of YAP : Ce crystal and the reflectance, versus, the incidence angle, of the coating used as optical insulator in matrix pillar made by Preciosa Crytur.

This work deals with the optical characterisation of the surface of EG&G and Hamamatsu APDs and performance of an antireflection coating made of Y2O3 and deposited on a PWO test piece. The effect of antireflection treatments of PWO and Si surfaces is evaluated in a simplified and a realistic situation by means of the ratio of “detected to emitted photons”.

Gamma-ray irradiations induced various alterations in sulfur- and selenium-based chalcogenide glasses. The absorbed dose was in the range of 0.01–3.6 MGy. The glasses exhibit prominent sensitivity to γ-ray irradiation, characterized by changes in some of the physical properties of the glasses, e.g., optical transmission, optical band gap, density, and thermal expansion coefficient. The effects on glass structure and microscopic morphology were also studied by Raman spectra and scanning electron microscopic observations.

In the present work, series of silver doped Ge-Ga-S-AgI chalcohalide glasses have been prepared and their optical transmission spectra are compared before and after γ-ray irradiation at different doses. The differential transmission spectra of the irradiated samples with and without Ag doping have been compared to characterize the γ-ray irradiation induced red-shift of electronic absorption and formation of color centers. Ag doping plays an important role in increasing γ-ray irradiation resistance of the chalcohalide glasses due to its specific effect on the valence band and the network structure of glasses. © 2014 Elsevier B.V. All rights reserved.

The ordinary and the extraordinary complex refractive index of PbWO4 together with the crystal optical axis orientation are determined on the basis of transmittance and reflectance measurements at normal incidence with polarised light and the measurement of the separation angle between the ordinary and the extraordinary ray at various laser wavelengths. The real part of the extraordinary complex refractive index is lower than the ordinary one (i.e. PbWO4 is a negative uniaxial crystal) and they seem not to be affected by a 30 ppm Nb5+ doping.

A method to determine the photopeak position of the γ absorption spectrum of radioactive sources in low light yield scintillators as lead tungstate is discussed. The method is based on the parametrization of both the Compton and photoelectric contributions to the spectrum and it is proven to be reliable and to give stable and precise results.

This paper reports on the influence that temperature during irradiation and dose-rate have on the radiation-induced free-radical yield and time stability in non de-proteinized bone. Bone from chicken legs was irradiated in the 253-293 K temperature range and with two different sources (60Co, 0.6 Gy/s and 12 MeV electrons, 6 x 10(6) Gy/s). Temperature influences type and number of radicals, while radical concentration seems to slightly decrease with dose rate.

The ultraviolet absorption and emission spectra of Ce3+ doped phosphate glasses based on gadolinium and sodium phosphates are studied in the present work. Compared with the cerium-free phosphate glass matrixes, CePO4 doping shifts the ultraviolet absorption edge of glasses into the longer wavelength because of the 4f–5d absorption transition of Ce3+. The emission spectra correlate such red-shift with glass compositions. Explanations are based on variation in the optical basicity of glasses, which corresponds not only to the alkali content but also to the O/P ratio. The latter is proportional to the number of nonbridging oxygen in the oxyanion unit (PO4), and most likely plays an overwhelming role in the overall optical basicity of glasses.

The CMS electromagnetic calorimeter (ECAL) comprises 75848 scintillating lead tungstate crystals. 61200 crystals are contained in the ECAL Barrel section and are read out by avalanche photodiode (APD) with internal gain of about 50. This gain is achieved with a high voltage (HV) of about 400 Volts. The gain stability requirement implies a supply voltage stable to within 0.01%. We describe our experience with the installed Barrel HV power supply system, which has been used for data taking since 2008.

Most of the high energy physics experiments require their detectors to be embedded in a high intensity magnetic field. In particular the biggest of them, ATLAS, running in the CERN Large Hadron Collider (LHC) particle accelerator, generates a field of 2 T by means of a gigantic toroidal magnet working in open air. Its future phase 2 upgrade plans to move the DC/DC power supplies from the present positions on the external balconies directly on the detectors, where the field is of the order of 1 T. This presentation describes the development of samples made of special magnetic material for inductor cores suitable to work in such an environment. Starting from iron-silicon powders, at FN plant a plastic forming process, based on powder extrusion, injection moulding and sintering, was developed. To get the best compromise between the forming process requirements (good coupling among the metallic powder and the organic components to assure the right mouldability) and the debinding and sintering conditions, several mixtures (with different percentages and kind of organic additives) were experimented. A proper mould was designed and realized to get torous-shaped prototypes. The preliminary results of the physical-microstructural characterization performed on the first prototypes made will be shown. © 2013 Owned by the authors, published by EDP Sciences.

The influence of γ-ray irradiation on the optical properties of Bi2O3-B2O3-SiO2 glass has been investigated. Broadband infrared (IR) emission at 1310 nm with a FWHMover 200 nm is observed in the γ-ray irradiated glass. The IR luminescence depends on the γ-ray irradiation dose and the concentration of Bi 2O3. The thermal stability of the γ-ray irradiated IR luminescence center is studied, and the origin of the IR luminescence center has been suggested. © 2013 Optical Society of America.

Graft copolymerization of hydrophilic monomers onto thin plates of ethylene-propylene rubber by the direct irradiation method was carried out. Experimental conditions ensuring a surface grafting reaction were ascertained. Slices of the grafted samples were analyzed by ER absorption spectroscopy and the distribution of the grafted chains across the plate thickness was evaluated.

The Calliope plant, a pool-type irradiation facility located at the Research Centre ENEA-Casaccia (Rome), is equipped with the 60 Co γ source in a high-volume shielded cell. Calliope facility is involved in radiation processing research on materials (polymers and optical components) and on devices to be used in hostile radiation environment such as nuclear plants, aerospace experiments and High Energy Physics experiments. The aim of this work is to give an overall picture of the activity we are carrying on at our laboratories with a mention to the possible applications in the field of scintillators and glasses, like doping effect to induce radiation resistance in scintillators, glasses for safe nuclear fuel disposal, suitable substitute oxides which can replace PbO in the preparation of lead-free glasses complying environmental regulations.

Infrared absorption spectroscopy has been used to investigate the effect of γ-radiation on ethylene-propylene copolymer loaded with different amount of antioxidant. The oxidation profiles were obtained analyzing slices of the samples by an IR microscope. The IR spectra have shown that the antioxidant content does not affect the shape of the oxidation profiles; their dependence on thickness and dose rate is in good agreement with the Clough and Gillen model. Our results indicate that the antioxidant does not affect the reactions involved in the oxidation process and the oxygen distribution on the sample.

The ESR technique was used to investigate the time evolution of a γ-irradiated model rubber (ethylene-propylene copolymer loaded with antioxidant containing NH functional group ). Measurements have been performed at different temperatures in the (77–333) K range. Two different kinds of radicals (polymer and NO°) have been identified and their activation energy, related to the post-irradiation behaviour, evaluated. The results suggested the formation of NO° through a bimolecular process.

The ESR technique was used to investigate the resonant paramagnetic properties of an ethylene-propylene based material and of its basic components irradiated with a 60 Co source up to 0.1 MGy. A qualitative model for the radical formation in a polymeric material with antioxidant as an additive is proposed.

Optical absorption, photo- and thermo-luminescence measurements were performed on (NaPO3)x(GdPO4)y(TbPO4)z (x=60– 77 mol % ; y=20– 30 mol % ; z=3– 10 mol %) glasses. Pronounced changes of photoluminescence intensity of the leading 542 nm emission line of Tb3+ were observed during prolonged excitation (irradiation) by 308 nm XeCl excimer laser line into the Gd 3+ 6 P 5/2 excited state. Laser irradiation also gave rise also to optical absorption that peaks at around 5.4 MeV and to a thermoluminescence glow peak at 195°C. Similar optical absorption and thermoluminescence features were found by ionising (X-ray) irradiation. The results are explained by taking into account energy exchange between the Gd-sub-lattice and deep traps in the glass matrix.

Infrared absorption spectroscopy has been used to investigate the effect of γ-radiation on copolymer ethylene-propylene (EPR). The IR spectra showed that exposure of EPR samples to gamma doses from 50 kGy to 0.6 MGy results in noticeable changes in their absorption bands, in particular an appearance of a CO band at 1720 cm -1 and O—H band at 3450 cm -1 . The dependence of the 1720 cm -1 band as a function of dose and dose rate is reported and discussed in terms of a simple model for the oxidation process.

International audience; Nanophase separation in the bulk Ge-As-Se chalcogenide glasses was observed by SEM and supported by XRD and IR measurements. Effects of nanophase separation on glass transition temperature (Tg), microhardness (Hv), optical band gap (Eopt) and thermal expansion coefficient (α) were investigated in terms of glass rigidity transitions. According to the correlations between the properties and average coordination number Z, it is established that nanophase separation becomes more intensive when Z is larger than 2.64.

International audience; In this work, multiple effects of γ-ray irradiation on properties of bulk Ge-As-Se chalcogenide glasses were studied. Increased density (ρ), thermal expansion coefficient (α) and decreased optical band gap (Eopt) were observed after irradiation, depending on glass compositions. Glasses with stoichiometric (GeSe2)100−x(As2Se3)x compositions showed linear correlations between As2Se3 proportion x and irradiation sensitivity, which is expressed by Δρ/ρ, Δα/α and ΔEopt/Eopt. Nonstoichiometric glasses (Ge2Se3)100−x(As2Se3)x exhibited irregular variations. The phenomena are discussed in terms of chemical bonds transition and structural evolution under γ-ray irradiation.

Gamma radiation induced absorption processes of various scintillating materials were studied at room temperature. Single crystal of PbWO 4 , Ce-doped YAlO 3 and Ce(Pr)-doped Y(Lu) 3 Al 5 O 12 were irradiated by 60 Co and doses ranging between 1-500 Gy. Broad induced absorption spectra obtained were decomposed into separate Gaussian components and tentatively ascribed to specific color centres. Supporting thermoluminescence and electron paramagnetic resonance experiments were performed to reveal the nature of charge carrier traps. The influence of codoping by aliovalent ions is also shown and discussed.

We investigated Czochralski-grown YAG:Pr single crystal as a potential novel scintillator. Optical characteristics including photoluminescence, radioluminescence, scintillation decay, radiation damage and thermoluminescence were measured. Their dependence on the dopant concentration was studied. The radiation damage results show that with increasing concentration of Pr the radiation damage reduces. Thermoluminescence above room temperature shows the dominant glow curve peak around 250 °C. Comparing to YAG:Ce scintillator an advantage of YAG:Pr is its much faster scintillation decay (16-17 ns at room temperature) and an absence of slow components in the decay. Therefore YAG:Pr appears as potentially interesting scintillator material. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

ZnO-based silicate glasses are studied in the present paper. Irradiation resistance of glass samples is tested under the /sup 60/Co /spl gamma/-ray radiation at the doses of 71 and 262 Gy. Ultraviolet and visible transmission spectra of glass samples are compared before and after irradiation treatment. Test results show that radiation damage of ZnO-based glasses increases with dose while the glass with the Al/sub 2/O/sub 3/ donor dopants exhibits improved radiation resistance. The latter can be correlated to bandgap broadening effect due to Al/sub 2/O/sub 3/ doping in the ZnO-based glass and to the role of Al/sup 3+/ as the network intermediate to enter partially the tetrahedral structure of silicate glass.

Optical coatings are widely used in optical instrumentation for astronomical and space applications. The required optical components are similar to the ones necessary for ground-based instrumentation: antireflection coatings, mirrors, transmission filters. In addition, depending on the specific application, resistance to the radiation induced damage is needed. The analysis here is limited to optical components for instruments to be used for Earth observation from the polar sun-synchronous orbit, where they will withstand a total radiation dose of 50 Gy accumulated during a typical lifetime of 5 years. In this work a set of optical coating materials were submitted to γ irradiation at the 60Co radioisotope source (ENEA Research Center) in order to simulate the hostile radiation environment in which they will be employed. The selected coatings are made with a multilayer structure that contains oxide layers and/or metal layers. Before the coating irradiation, the behavior of single-layer materials was investigated by comparing their reflectance and transmittance before and after the γ-ray exposure. Results are reported for a number of oxide single layers (SiO2, HfO2, Y2O3), metal layers (Ag, Al) and multilayer coatings made with these materials, by the physical vapor deposition (PVD) technique. The behavior of different substrates (glass, quartz) is also compared.

The barrel part of the CMS electromagnetic calorimeter consists of about 75 000 Lead Tungstate (PbWO 4 ) crystals arranged in 36×4 modules which are assembled in two Regional Centres, in Rome and at CERN. Two automatic machines have been designed to check the crystal quality before assembly. The main crystal characteristics are compared to a set of specifications included in the contract with the crystal producers. The measurement stability and cross-calibration between the two machines is a fundamental issue, which has to be monitored throughout the construction phase. This paper describes comparisons between measurements made at the two regional centres to ensure a consistent and reliable crystal quality control.

Commercial spectrophotometers are basically designed to measure the absorbance of solutions contained in transparent cuvettes. Although their functions can be generally extended by means of a variety of accessories, these instruments are generally not flexible and do not fit solid samples thicker than some centimeters. This paper describes a highly versatile spectrophotometer, named Lumen, composed of discrete components and suitably arranged on a large breadboard. Two noticeable instrument configurations are discussed: the first allows to measure the transmittance through long samples, like crystals of lengths up to 23 cm; the second was developed to perform the same measurement in microstructures a few tens of micrometers wide, like those obtained in insulating materials by focused radiation beams. The data acquisition software, written in LabVIEW, adopts some original solutions that make Lumen unique.

Mechanical properties of polyvinylpyrrolidone hydrogel dressings were investigated as a function of production factor combinations. The experimental results show that the peak-load depends strongly on the PVP concentration, the break-strain is inversely dependent on the radiation dose and the modulus of elasticity depends mainly on the PVP concentration.

The ESR technique was used to study the influence of dose rate and oxygen on the radiation induced effects on an ethylene-propylene loaded with antioxidant characterized by an NH functional group. It was shown that the oxidative degradation takes place during irradiation and the oxidation products increase with decreasing dose rate [H. Kashiwabara and T. Seguchi, in: Radiation Processing of Polymers, eds. A. Singh and J. Silverman (Hanser, 1992)].

A group of of heavy germanate glasses containing BaO and/or Gd 2 O 3 , La 2 O 3 , SnO and doped with the scintillating rare earth Tb 3+ are presented. Photoluminescence measurements are made on these glasses. The intensity of emission peaks is found proportional to the contents of Tb 3+ dopants as well as of Gd 3+ : the former indicates that no obvious concentration quenching effect is visualized within the limits of present Tb 3+ dopant while the latter is related to the enhanced energy transfer process from Gd 3+ to Tb 3+ centers.