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The identification of the center acting as electron source for the well-known 110 °C thermoluminescence (TL) peak of quartz is of fundamental importance for practical applications in dating and dosimetry. This TL peak was studied in parallel with the electron paramagnetic resonance (EPR) signal of the [GeO4]− center on natural colourless quartz irradiated at room temperature. Immediately after irradiation, the signals of the 110 °C TL peak and of [GeO4]− center decay exponentially in the same way, yielding a lifetime of 50.4 ± 0.9 min at room temperature. Besides, we acquired the isothermal decay curves for the 110 °C TL peak and [GeO4]− center at different temperatures (the samples were held at the selected temperature in the range of 260–308 K). The lifetimes extracted by the isothermal decays were plotted as a function of reciprocal temperature, revealing again the same behavior of the 110 °C TL peak and [GeO4]− center, both characterized by activation energies very close of 0.76 ± 0.07 eV and 0.77 ± 0.07 eV, respectively. All results of the present work clearly show the role of electron source of [GeO4]− center in the emission mechanism of the 110 °C TL peak in quartz.

Wavelength-shifting materials in the form of optical fibers are requested in order to both convert UV scintillation light produced by fast scintillators into a more easily detectable visible light, and to efficiently transport it to the detectors. In the present investigation we have considered glasses with composition 3CaO-2SiO2 and 3CaF2-2SiO2 doped with 0.05, 0.5 and 1 at% of Ce3+ ions, prepared by an original method consisting in a combination of co-precipitation and sol-gel approaches. The glasses have been investigated by Raman scattering, as well as by photo- and radio-luminescence. The glasses are characterized by complex Raman features. Composite photo-luminescence excitation and emission spectra are also detected in all cases, depending upon glass composition and Ce concentration. Broad excitation spectra extend from approximately 260 nm to 360 nm, while the composite Ce3+ emission is detected in the blue spectral region at around 400 nm. A satisfactory matching between the excitation spectra of the glasses and the emission spectrum of CeF3 scintillator occurs, confirming their potential application as wavelength shifters of CeF3 UV scintillation light. Moreover, bright photo-luminescence signals are accompanied by a very poor radio-luminescence. The results are discussed by taking into account the presence of different silicate clusters embedded in the glass network, as well as the role of point defects in the radio-luminescence process.

FLARES is an innovative project in the field of rare events searches, such as the search for the neutrinoless double beta decay. It aims at demonstrating the high potential of a technique that combines ultra-pure scintillating crystals with arrays of high performance silicon drift detectors, operated at about 120. K, to reach a 1% level energy resolution. The proposed technique will combine in a single device all the demanding features needed by an ideal experiment looking for rare events. The performance of a first production of matrices of silicon drift detectors as well as first measurements of the low temperature light yield of a selection of high purity scintillating crystals will be presented and discussed

The radioluminescence (RL) spectra of three types of quartz have been compared to those obtained from wavelength resolved thermally stimulated luminescence (TSL) measurements. A detailed numerical deconvolution into Gaussian components allowed to identify which of the bands are involved in either types of luminescence processes. The blue "A band" at 2.51 eV was confirmed to dominate both RL and TSL spectra in samples exposed to prolonged irradiation. The UV emission of the 110°C TSL peak was found to be composite. Analogously to what previously reported for RL spectra, an annealing at 500°C for 10 min induced a strong enhancement of the "C band" at 3.42 eV. This effect was particularly evident in natural and pre-irradiated quartz. A second intense UV component, the "M band" at 3.7 eV, was found to contribute to both TSL and RL spectra of samples annealed at 1000°C for 10 min. A further broad UV emission seems to be involved only in RL emission but not in the TSL one.

TiO2 nanoparticles were supported on a new persistent luminescence (3ZnO:Ga2O3:2GeO2):Cr3 + material. The sample was characterized by means of X-ray powder diffraction, scanning electron microscopy and radioluminescence. The photoactivity was evaluated for the degradation of methylene blue (MB) in aqueous solution especially in the darkness. A MB photodegradation occurred also in the absence of an external illumination. In fact, the persistent luminescence material stores and provides the necessary photons to the TiO2 allowing the photocatalysis process even in the darkness.

Future research in High Energy Cosmic Ray Physics concerns fundamental questions on their origin, acceleration mechanism, and composition. Unambiguous measurements of the energy spectra and of the composition of cosmic rays at the "knee" region could provide some of the answers to the above questions. Only ground based observations, which rely on sophisticated models describing high energy interactions in the earth's atmosphere, have been possible so far due to the extremely low particle rates at these energies. A calorimeter based space experiment can provide not only flux measurements but also energy spectra and particle identification, especially when coupled to a dE/dx measuring detector, and thus overcome some of the limitations plaguing ground based experiments. For this to be possible very large acceptances are needed if enough statistic is to be collected in a reasonable time. This contrasts with the lightness and compactness requirements for space based experiments. A novel idea in calorimetry is discussed here which addresses these issues while limiting the mass and volume of the detector. In fact a small prototype is currently being built and tested with ions. In this paper the results obtained will be presented in light of the simulations performed.

The process of hole and electron localization in LuAG:Ce,Mg ceramics is studied by electron spin resonance (ESR) and thermally stimulated luminescence (TSL). Hole traps, which are created by UV irradiation, are detected in the form of O- centers. Mg-perturbed variants of O- centers are proposed to exist. The thermal stability of such defects is studied, proving that they are stable up to room temperature. The interaction between O- centers and shallow electron traps is studied by thermally stimulated luminescence (TSL) and phosphorescence experiments, which reveal the occurrence of an a-thermal tunneling process between trapped electrons and randomly distributed Ce centers. By correlating the TSL-derived trap parameters and temperature dependent ESR intensities, it is found that O- centers compete with Ce centers in free electron capture.

The radioluminescence (RL) of synthetic quartzes (GEMMA Quartz & Crystal Company) has been measured at room temperature. Some samples were treated by electrodiffusion (sweeping) in order to change the concentrations of alkali ions, mainly Li + and Na +, which in quartz are known to be linked to Al ions, substitutional for Si ions. The RL emission spectra show evidence of a role of alkali ions in affecting some specific emissions. All the spectra could be analysed as composed of four bands in the blue and UV region. Specifically, the well known blue emission at around 470 nm was seen to be composed by two bands at 430 nm (2.86 eV) and at 485 nm (2.53 eV). Effects of irradiation, during the RL measurements, were clearly seen only in the Li swept in sample, namely an increase in the 485 nm band intensity and a decrease in the 430 nm band one. The previously reported UV emission was detected at 355 nm (3.44 eV) in all the samples, being the most intense band in the swept out sample. A further UV emission was detected at 315 nm (3.94 eV), more intense in untreated samples. Possible assignments of the detected emission bands are discussed in relation to the defects of quartz, specifically focusing on the Al centres that are most affected by sweeping procedures. © 2011 Elsevier B.V. All rights reserved.

Structural and optical properties of solgel silica based glassceramics doped with 0.1 mol% Ce and codoped with Gd at high concentrations, from 5 mol% up to 40 mol%, are investigated and compared to those of analogous samples doped only with Ce. Raman scattering, transmission electron microscopy, and x-ray diffraction reveal the formation of Gd apatite-like silicate (Gd 4.67O(SiO4)3) and of Gd pyrosilicate (Gd 2Si2O7) nanophases whose morphology and crystallinity depend on the Gd concentration and thermal treatments. Optical absorption measurements demonstrate the role of the densification atmosphere in modifying the charge state of Ce ions. The incorporation of Ce3 ions in the nanophases is put in evidence by photo- and radio-luminescence results

We study lutetium hafnate, Lu4Hf3O12, prepared by acetate and citrate combustion in the form of nanometric powders. Optical properties including X-ray excited luminescence, steady-state and time resolved photoluminescence as well as thermally stimulated luminescence are investigated for undoped as well as Eu3+ and Tb3+ doped samples. We identify recombination centers in the host matrix and we tentatively associate the principal emission with a radiative transition of the F + center. We also demonstrate that athermal tunneling of charge carriers between traps and recombination centers is the predominant mechanism of delayed radiative recombination following irradiation by ionizing radiation. © 2011 Elsevier B.V. All rights reserved

We present a systematic study of lead tungstate crystals doped with a small fraction of molybdenum, varying between 0.1% and 5%. These crystals were exposed to a beam of 50 GeV electrons and the signals were unraveled into scintillation and Cherenkov contributions, using the time structure of the signals and/or different types of transmission filters. These studies were carried out in view of the possible application of such crystals in dual-readout calorimeters. (C) 2010 Elsevier B.V. All rights reserved.