1,721,048 research outputs found
Photodetector R&D for the belle II upgraded forward electromagnetic calorimeter
No full textThe Belle II experiment will operate at the SuperKEKB e+e- collider, designed to reach a peak luminosity of 8×1035 cm-2s-1 at the Γ(4S) resonance. The high background environment of SuperKEKB poses serious challenges to the design of the Belle II detector. In particular, an upgrade of the forward Electromagnetic Calorimeter is foreseen: the new calorimeter will use pure CsI crystals, which have a faster scintillation light emission and lower light yield than the CsI(Tl) crystals presently used. An intense R&D program is ongoing to select the optimal photodetector to meet the stringent requirements set by the use of pure CsI in Belle II. A study of equivalent noise, resolution, radiation hardness and stability of low noise, high-gain avalanche photodiodes obtained by reading single pure CsI crystals is discussed. Our preliminary results indicate that a readout chain using these devices meets the requirements on electronic noise set by the Belle II simulation and could represent a cost-effective choice for the readout of pure CsI crystals in general. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence
Optical characterization of ion-doped crystalline and glassy matrices operating under hostile environmental conditions
No full textThe aim of this work is to give an overall picture of the activity on gamma radiation effects in the field of scintillators (crystals, glasses) with specific mention to the role of ions doped in different crystalline and glassy matrices. Interesting results were obtained in terms of radiation hardness improvement and of physical-chemical properties modification as a function of the nature of dopant (i.e. rare earth as well as metallic ions) and of the scintillating host glassy and glass-ceramic matrix (silicate, phosphate, borate, oxyfluoride and mixed oxides glasses). The research activities were carried out at the 60Co gamma Calliope plant, a pool-type irradiation facility located at the Research Centre ENEA-Casaccia (Rome). Since the eighties, the Calliope facility is deeply involved in radiation processing research on materials and on devices to be used in hostile radiation environment such as nuclear plants, aerospace and High Energy Physics experiments, in the framework of international projects and collaboration with industries and research institutions. © Published under licence by IOP Publishing Ltd
Gamma-ray irradiation induced bulk photochromism in WO3-P2O5 glass
No full textIn the present work, photochromism of WO3-P2O5 glass under gamma-ray irradiation was reported. As-prepared glass samples with different WO3 content are all optically transparent in the visible wavelength range thanks to the addition of a small amount of oxidizing couple Sb2O3-NaNO3. The photochromic properties are identified by transmission spectra of the glasses before and after irradiation. The results show that the irradiation induced darkening results from the reduction of W6+ to W5+ or W4+. The existence of WO6 clusters in glasses of high WO3 content is proved by XPS, which is the main reason for the obvious photochromic effects. The WO3-P2O5 glass is a promising candidate in gamma-ray sensitive detector. © 2015 Published by Elsevier B.V
Gamma-ray irradiation resistance of silver doped GeS2-Ga 2S3-AgI chalcohalide glasses
No full textIn 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
Radiation hardness of Ce-doped sol-gel silica fibers for high energy physics applications
No full textThe results of irradiation tests on Ce-doped sol-gel silica using x- and γ-rays up to 10 kGy are reported in order to investigate the radiation hardness of this material for high-energy physics applications. Sol-gel silica fibers with Ce concentrations of 0.0125 and 0.05 mol. % are characterized by means of optical absorption and attenuation length measurements before and after irradiation. The two different techniques give comparable results, evidencing the formation of a main broad radiation-induced absorption band, peaking at about 2.2 eV, related to radiation-induced color centers. The results are compared with those obtained on bulk silica. This study reveals that an improvement of the radiation hardness of Ce-doped silica fibers can be achieved by reducing Ce content inside the fiber core, paving the way for further material development. © 2018 Optical Society of America
Characterization of γ-radiation induced polymerization in ethyl methacrylate and methyl acrylate monomers solutions
No full textThe present work is focused on the γ-radiation induced polymerization of ethyl methacrylate (EMA) and methyl acrylate (MA) monomers mixture to obtain a co-polymer with specific features. The effect of the irradiation parameters (radiation absorbed dose, dose rate) and of the environmental atmosphere on the features of the final products was investigated. Attenuated Total Reflectance - Fourier Transform Infrared Spectroscopy (ATR-FTIR) and Nuclear Magnetic Resonance high-resolution analyses of hydrogen and carbon nuclei (1H and 13C NMR) were applied to follow the γ-induced modifications by monitoring the co-polymerization process and allowed the irradiation parameters optimization. Diffusion-Ordered NMR (DOSY-NMR) data were used to evaluate the co-polymers polydispersity and polymerization degree. Since the last parameter is strongly influenced by the γ radiation and environmental conditions, a comparison among samples prepared and irradiated in air and under nitrogen atmosphere was carried out. In presence of oxygen, higher radiation was required to obtain a full solid co-polymer since a partial amount of energy released to the samples was involved in competitive processes, i.e. oxygen-containing free radicals formation and primary radicals recombination. Irrespectively to the environmental atmosphere, more homogeneous samples in term of polymerization degree dispersion was achieved at lower dose rates. At radiation absorbed doses higher than those needed for the formation of the co-polymer, while in case of samples irradiated in air heavy depolymerization was verified, a sensible increase of the samples stability was attained if the irradiation was performed under nitrogen atmosphere. © 2017 Elsevier Lt
Gamma-ray induced reversible photochromism of Mn2+ activated borophosphate glasses
No full textPhotochromic glasses have attracted increasing interests as switchable lenses and radiation dosimeters. Here, we report on a new and cheap photochromatic material, Mn2+ activated borophosphate glass which can be readily prepared by the conventional melt-quenching method. The photochromic properties are characterized by differential absorption spectra, and the photochromism stems from the conversion of Mn2+ to Mn3+ when the glass samples are exposed to gamma-rays. Our results show that the photochromism can be controlled by modifying the glass structure and optical basicity through adding of alkali (Na2O) and alkali-earth (SrO, BaO and CaO) oxides. © 2014 Elsevier B.V. All rights reserved
Characterization of polysiloxane organic scintillators produced with different phenyl containing blends
No full textAiming at the fabrication of elastomeric organic scintillators for the detection of ionizing particles and neutrons with good light yield, mechanical robustness and radiation resistance, several samples of polysiloxane added with suitable amounts of fluorophores, such as 2,5-diphenyloxazole (PPO) and Lumogen Violet (LV), have been herein produced starting from either the copolymer polydiphenyldimethylsiloxane with 22 mol% of diphenyl groups or from blends of this precursor with different amounts of the homopolymer polymethylphenylsiloxane, thereby ultimately obtaining, after room temperature vulcanization (RTV), siloxane scintillators bearing different amounts of phenyl side groups. The scintillators have been characterized as for optical properties by excitation and fluorescence spectroscopy, while their performances as radiation detectors have been derived from light yield measurements upon irradiation with α particles. Ion beam-induced luminescence (IBIL) has been also applied using a proton beam of 2 MeV to compare the behavior of the different compositions by observing the in-situ degradation rate of the emitting species under ion irradiation. The samples and commercial scintillators (EJ-212 and EJ-200) used as a standard underwent heavy irradiation with γ-rays from a 60Co source at different doses, up to 54 kGy. Then, the ex-situ light yield toward α particles for each scintillator was collected twice again: immediately after the irradiation stage and after one month, in order to characterize the stability and the radiation hardness of scintillators produced with the different blends. © 2012 Elsevier B.V. All rights reserved
Study on optical properties and γ-ray irradiation resistance of heavy metal oxide tellurite glasses
No full textOptical properties and irradiation resistance of heavy metal oxide tellurite glasses in the TeO2-PbO-Bi2O3-B2O3 system doped with different ions are investigated. The results indicate that the matrix glass has a moderate UV cut-off edges at about 386 nm wavelength. The UV cut-off positions are obviously shifted to red by the addition of Ce4+. The introduction of Cr3+, Ce4+ and Ni2+ into the matrix glass exerts positive influences on irradiation resistance of glasses and cerium plays the most pronounced role. Such phenomena are mainly attributed to the variable valences of these cations. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Radiation hardness and stability of optical coupling materials for BelleII electromagnetic calorimeter
No full textOptical coupling materials are usually applied to ensure good optical matching in the APD-scintillating crystal detection system. High transparency at the scintillating emission wavelength and material stability under irradiation are recommended requirements. In this work, silicon optical grease (BC630) and two-component epoxy resins (Epo-tek 301-2FL and Epo-tek 305), to be employed in the electromagnetic calorimeter of the BelleII experiment at the Super-KEKB collider, were investigated to establish their radiation hardness and stability under gamma and neutron irradiation. Optical transmittance measurements were performed in the UV-VIS range, paying particular attention to the materials behavior in the range around 315nm (CsI scintillating emission wavelength). © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence
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