[en] We study defect states in Eu-doped Y₃Al₅O₁₂ powder by thermally stimulated luminescence (TSL) in the temperature range 77–500 K. We identify the main TSL peaks, analyze them by the initial rise technique and calculate the characteristic parameters of the corresponding traps. Tunneling of charge carriers between traps and recombination centers up to about 265 K is observed and discussed. Recent study established the presence of both Eu²⁺ and Eu³⁺ centers in the studied Y₃Al₅O₁₂ powder. The TSL spectra show that Eu²⁺ and Eu³⁺ centers compete in the charge carrier capture. We show that previously observed Eu²⁺ luminescence quenching is due to both classical thermal quenching and thermal ionization of the Eu²⁺ excited state. We model the temperature dependence of the delayed recombination intensity.

[en] Highlights: •Three stable non-stoichiometric phases in SrO–HfO₂ sintered mixtures determined. •Relation between XRPD analyses and radioluminescence spectra studied. •Highly efficient radioluminescence of Sr_0.98Hf_1.02O_3.02 phase revealed. •Nature of emission centers in non-stoichiometric phases discussed. -- Abstract: Non-stoichiometric strontium hafnate powder samples were prepared by reaction in solid state using the starting SrO–HfO₂ mixture with different ratios of binary constituents. XRD analysis was systematically performed and correlated with the observed radioluminescence characteristics. In the samples with starting surplus of HfO₂ a Sr_0.98Hf_1.02O_3.02 phase was identified which is associated with the 334 nm emission band. Its radioluminescence intensity exceeds more than thirty times that of bismuth germanate (BGO) standard single crystal scintillator. In the samples with initial surplus of SrO, two different Sr-rich phases were identified in the sintered material. Their radioluminescence spectra peak within 420–430 nm and intensities are comparable to that of BGO

[en] Although luminescence properties of Pb²⁺ and Ce³⁺ in SrHfO₃ host (SHO) have been recently studied due to various potential applications, the mechanism of the Pb²⁺ and Ce³⁺ excited states thermal quenching has not been addressed. Both Pb²⁺ and Ce³⁺ doped SHO microcrystalline powders were prepared by multi-step solid state annealing technique. Radioluminescence and photoluminescence (PL) spectra as well as both the prompt and delayed decay kinetics were investigated in the wide temperature range (10 - 500 K) using the time-resolved luminescence spectrocopy techniques. Temperature dependences (TDs) of PL decay time and PL emission intensity of both Pb²⁺ and Ce³⁺ centres were fit by the fenomenological model. Corresponding excited state characteristics were determined. The innovative method of measuring the TD of intensity of the delayed radiative recombination was employed to better understand the origin of temperature quenching of the Pb²⁺ and Ce³⁺ decay times. The method put in evidence the excited state thermal ionization of both activators in the SHO host. The influence of dopant concentration and suitability of both the Pb and Ce-doped SHO for phosphor and scintillator applications are discussed.

[en] Rare-earth (RE = Ce, Pr, Sm, Tb) doped ternary sulfides of the general formula RbLu_0.99RE_0.01S₂ and undoped RbLuS₂ were synthesized in the form of crystalline hexagonal platelets by chemical reaction in the electric resistance furnace under the flow of hydrogen sulfide. Only a single crystalline phase of the rhombohedral lattice system (space group R anti 3 m) was detected by X-ray powder diffraction. Absorption and luminescence characteristics were measured. The band edge of RbLuS₂ is found at 310 nm, and characteristic Pr³⁺, Sm³⁺ and Tb³⁺ 4f-4f emission lines in the visible spectral range are observed. A charge transfer transition in the Pr³⁺ excitation spectrum in the near UV spectral region is revealed and an efficient energy transfer from the host to the emission centers is found. The application potential for white LED or X-ray phosphors is discussed. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

[en] Ternary alkali lead halides doped by rare-earth ions are considered to be suitable materials for solid-state lasers operating in the broad spectral range from ultraviolet to mid-infrared (IR) wavelengths. This contribution is focused mainly on the luminescence study of the low-phonon energy rubidium lead chloride RbPb₂Cl₅ (RPC) materials doped with a low concentration of trivalent neodymium (5 mol%), praseodymium (5 mol%), and dysprosium (0.1 mol%) ions. Broad emission bands with maxima around 4.70 m, 5.25 m, and 5.15 m were observed in Pr:RPC, Nd:RPC, and Dy:RPC samples, respectively, which makes these materials promising for future mid-IR laser development, especially in terms of their broad tunability and/or ultrashort pulse generation. (paper)

[en] Rare-earth (RE = Ce, Pr, Sm, Eu, Tb) doped ternary sulfides having the general formula RbLa_0.99RE_0.01S₂ and undoped RbLaS₂ were synthesized in the form of crystalline hexagonal platelets by a chemical reaction in an electric resistance furnace under the flow of hydrogen sulfide. X-ray powder diffraction confirmed the single crystalline phase of the rhombohedral lattice system (space group R-3 m, α-NaFeO₂ structure type) with hexagonality c/a = 5.34, consistent with the already reported RbLaS₂ structure. Time-resolved luminescence spectroscopy was employed to investigate radioluminescence, photoluminescence, decay kinetics and absorption spectra. An RbLaS₂ band edge at 322 nm was found and characteristic Pr³⁺, Sm³⁺ and Tb³⁺ 4f-4f emission lines in the visible spectral range were observed. The charge transfer transitions in the Pr³⁺- and Sm³⁺-related excitation spectra in the range 330-350 nm are described and the efficient energy transfer from the host to the emission centers is revealed. We discuss the potential for application of these materials in field emission displays, white LED solid-state lighting and X-ray phosphors.

[en] In the presented review paper, new potentially interesting material family, RE-doped ternary sulfides ALnS₂ (RE=Ce, Pr, Sm, Eu, Tb, Tm; A=Rb, K; Ln=La, Gd, Lu, Y) is discussed. Their synthesis is described and the structural and optical properties, characterized by methods of X-ray diffraction, time-resolved luminescence spectroscopy and electron paramagnetic resonance, are summarized and reviewed especially with respect to the influence of their composition. All samples discussed were synthesized in the form of transparent crystalline hexagonal platelets by chemical reaction under the flow of hydrogen sulfide. Their luminescence characteristics, including absorption, radioluminescence, photoluminescence excitation and emission spectra and decay kinetics, were measured and evaluated in a broad temperature (8–800 K) and concentration (0.002–20% of dopants) range. The application potential of mentioned compounds in the field of white LED solid state lightings or X-ray phosphors is thoroughly discussed. - Highlights: • RE-doped ALnS₂ (A=K, Rb; Ln=La, Gd, Lu, Y) were synthesized. • Their optical characteristics are summarized. • Concentration and temperature dependences of luminescence features investigated. • EPR technique is employed to explain Eu²⁺ incorporation into KLuS₂ host. • The application potential in white LED and X-ray phosphors is discussed.

[en] The modern market offers low cost high performance FPGA integrated circuits equipped with dozens of multi gigabit serial links making them ideal devices for data transmission and data sorting applications. Therefore we have designed the new DAQ system that would perform the detector readout and event building in a custom made FPGA based hardware. The software part will provide the control and monitoring function. Currently, the prototypes of the new FPGA card are being tested and the control and monitoring software is being prepared for the tests with the real hardware.

[en] Luminescence of the Bi³⁺ single and dimer centers in UV and visible ranges is studied in YAG:Bi (0.13 and 0.27 at% of Bi, respectively) single crystalline films (SCFs), grown by liquid phase epitaxy from a Bi₂O₃ flux. The cathodoluminescence spectra, photoluminescence decays, and time-resolved spectra are measured under the excitation by accelerated electrons and synchrotron radiation with energies of 3.7 and 12 eV, respectively. The energy level structure of the Bi³⁺ single and dimer centers was determined. The UV luminescence of YAG:Bi SCF in the bands that peaked at 4.045 and 3.995 eV at 300 K is caused by radiative transitions of Bi³⁺ single and dimer centers, respectively. The excitation spectra of UV luminescence of Bi³⁺ single and dimer centers consist of two dominant bands, peaked at 4.7/4.315 and 5.7/6.15 eV, related to the ¹S₀→³P₁ (A band) and ¹S₀→ ¹P₁ (C-band) transitions of Bi³⁺ ions, respectively. The excitation bands that peaked at 7.0 and 7.09 eV are ascribed to excitons bound with the Bi³⁺ single and dimer centers, respectively. The visible luminescence of YAG:Bi SCF presents superposition of several wide emission bands peaking within the 3.125-2.57 eV range and is ascribed to different types of excitons localized around the Bi³⁺ single and dimer centers. Apart from the above mentioned A and C bands the excitation spectra of visible luminescence contain wide bands at 5.25, 5.93, and 6.85 eV ascribed to the O^2-→Bi³⁺ and Bi³⁺→Bi⁴⁺ + e charge transfer transition (CTT) in Bi³⁺ single and dimer centers. The observed significant differences in the decay kinetics of visible luminescence under excitation in A and C bands of Bi³⁺ ions, CTT bands, and in the exciton and interband transitions confirm the radiative decay of different types of excitons localized around Bi³⁺ ions in the single and dimer centers.

[en] This paper presents the current data acquisition system (DAQ) of the COMPASS experiment at CERN and discusses development of a new DAQ. The aim of the new DAQ is to substitute software event building by structure composed of special FPGA cards that will do the event building. The software part of the new DAQ is robust multinode system with high emphasis on reliability. It is based on state machines and implemented in C++ with usage of the QT framework, the DIM library, and the IPBus technology. A prototype of the system has been developed and tested. The new DAQ software fulfills given requirements.