RESUMEN
Fast emitting polymeric scintillators are requested in advanced applications where high speed detectors with a large signal-to-noise ratio are needed. However, their low density implies a weak stopping power of high energy radiation and thus a limited light output and sensitivity. To enhance their performance, polymeric scintillators can be loaded with dense nanoparticles (NPs). We investigate the properties of a series of polymeric scintillators by means of photoluminescence and scintillation spectroscopy, comparing standard scintillators with a composite system loaded with dense hafnium dioxide (HfO2) NPs. The nanocomposite shows a scintillation yield enhancement of +100% with an unchanged time response. We provide for the first time an interpretation of this effect, pointing out the local effect of NPs in the generation of emissive states upon interaction with ionizing radiation. The obtained results indicate that coupling fast conjugated emitters with optically inert dense NPs could lead to surpassing the actual limits of pure polymeric scintillators.
RESUMEN
We report on single crystal growth of laser material Nd:YAG widely used in the applications by the innovative crucible-free floating zone method implemented in an advanced laser optical furnace. We have optimized the parameters for the production of high-quality single crystals of the size typical for laser rods. To reduce the strain and improve machinability, we have developed an afterheater to thermalize the grown part of a single crystal below the hot zone, which is a technique unavailable in common mirror furnaces. The high quality of the single crystals was verified by Laue diffraction, and the internal strain was documented by neutron diffraction. The absorption spectrum corresponds with the parameters of the commercially used material produced by the Czochralski method. The presented methodology for the single crystal growth by the floating zone method with laser heating is applicable for the preparation of other high-quality single crystals of oxide-based materials, particularly in an oxidizing environment unattainable in commonly used crucible methods.
RESUMEN
The crystals of (Lu,Gd)3(Ga,Al)5O12 multicomponent garnets with high density ρ and effective atomic number Zeff are characterized by high scintillation efficiency and a light yield value up to 50,000 ph/MeV. During recent years, single-crystalline films and composite film/crystal scintillators were developed on the basis of these multicomponent garnets. These film/crystal composites are potentially applicable for particle identification by pulse shape discrimination due to the fact that α-particles excite only the film response, γ-radiation excites only the substrate response, and ß-particles excite both to some extent. Here, we present new results regarding scintillating properties of selected (Lu,Gd)3(Ga,Al)5O12:Ce single-crystalline films under excitation by alpha and beta particles and gamma ray photons. We conclude that some of studied compositions are indeed suitable for testing in the proposed application, most notably Lu1.5Gd1.5Al3Ga2O12:Ce film on the GAGG:Ce substrate, exhibiting an α-particle-excited light yield of 1790-2720 ph/MeV and significantly different decay curves excited by α- and γ-radiation.
RESUMEN
A novel all-inorganic CsCu2I3 single-crystalline perovskite as a nonhygroscopic and efficient X-ray and γ-ray scintillator is described herein. It is featured by a one-dimensional (1D) perovskite structure with an orthorhombic system and a space group of Cmcm. The CsCu2I3 crystal emits yellow light peaking at 570 nm originated from strongly localized 1D exciton emission. It appears self-absorption free because of the large Stokes shift of 1.54 eV. The photophysics process of the self-trapped exciton was studied using temperature dependent photoluminescene spectra and decay kinetics measurements. The CsCu2I3 crystal exhibits an extremely low afterglow level of 0.008% at 10 ms under X-ray excitation. Under 137Cs γ-ray irradiation, its light yield is 16â¯000 photons/MeV with an energy resolution of 7.8% at 662 keV.
RESUMEN
Photo-induced synthesis was used for preparation of powder Zn(Cd,Mg)O:Ga scintillating nanocrystals featuring properties of solid solutions. Only ZnO phase was identified without any phase separation up to 10% of Cd after optimization of the preparation. Radioluminescence spectra show the exciton-related emission in UV spectral range with significant blue (ZnMgO:Ga) or red (ZnCdO:Ga) shifts. The emission wavelength is tunable by the Cd/Mg content. Defect-related emission is completely suppressed after treatment in reducing atmosphere. Photoluminescence and cathodoluminescence decays show extremely fast component. Subnanosecond decay together with band gap modulation make Zn(Cd,Mg)O:Ga good candidate for practical applications like X-ray induced photodynamic therapy (PDTX) or those requiring superfast timing.
RESUMEN
We report a broad comparative analysis of the spectroscopic and laser properties of solid solution Lutetium-Yttrium Aluminum Garnet (LuYAG, (LuxY1-x)3Al5O12) ceramics doped with Yb. The investigation was mainly aimed to assess the impact of the Lu/Y ratio on the Yb optical and laser properties. Therefore we analyzed a set of samples with different Y/Lu balance, namely 25/75, 50/50 and 75/25, with 15% Yb doping. We found that the Yb absorption and emission spectra changed from YAG to LuAG when gradually increasing in Lu content. Regarding the laser emission, remarkable results were achieved with all samples. Maximum output power was 8.2 W, 7.3 W and 8.7 W for Y/Lu balance 25/75, 50/50 and 75/25 respectively, at 1030 nm; the slope efficiency and the optical-to-optical efficiencies approached or exceeded 60% and 50% respectively. The tuning range was investigated using an intracavity ZnSe prism. The broadest tuning range (998 nm to 1063 nm) was obtained with Y/Lu balance 75/25, whereas the emission of the other two samples extended from 1000 nm to 1058 nm. To the best of our knowledge, this is the first comparative analysis of Yb:LuYAG ceramics or crystals as laser host across such a broad range of Y/Lu ratios.
RESUMEN
Highly luminescent ZnO:Ga-polystyrene composite (ZnO:Ga-PS) with ultrafast subnanosecond decay was prepared by homogeneous embedding the ZnO:Ga scintillating powder into the scintillating organic matrix. The powder was prepared by photo-induced precipitation with subsequent calcination in air and Ar/H2 atmospheres. The composite was subsequently prepared by mixing the ZnO:Ga powder into the polystyrene (10 wt% fraction of ZnO:Ga) and press compacted to the 1 mm thick pellet. Luminescent spectral and kinetic characteristics of ZnO:Ga were preserved. Radioluminescence spectra corresponded purely to the ZnO:Ga scintillating phase and emission of polystyrene at 300-350 nm was absent. These features suggest the presence of non-radiative energy transfer from polystyrene host towards the ZnO:Ga scintillating phase which is confirmed by the measurement of X-ray excited scintillation decay with picosecond time resolution. It shows an ultrafast rise time below the time resolution of the experiment (18 ps) and a single-exponential decay with the decay time around 500 ps.
RESUMEN
We report the first laser oscillation on Yb0.15:(Lu0.5Y0.5)3Al12 ceramics at room temperature. At 1030 nm we measured a maximum output power of 7.3 W with a corresponding slope efficiency of 55.4% by using an output coupler with a transmission of T = 39.2%. The spectroscopic properties are compared with those of the two parent garnets Yb:YAG and Yb:LuAG. To the best of our knowledge these are the first measurements reported in literature achieved with this new host.
RESUMEN
The laser performance of a 5% Yb doped Lu2SiO5 (Yb:LSO) has been investigated in quasi continuous-wave pumping regime along the three principal dielectric axes of the crystal, to obtain a complete characterization of its laser properties. The comparison among the obtained results for differently polarized lasers, in term of relative slope efficiency and absolute efficiency, allows the exploitability of different orientations of the material in order to be determined to obtain efficient laser sources. The laser slope efficiency and the energy conversion efficiency were similar for emission polarized along the three indicatrix axes, with noticeable maximum values of slope efficiency around 90% for polarization along the Y and Z axes. Tunable laser action has been obtained in the range 990 nm - 1084 nm, with sizeable differences in the shape of the tuning curve for polarization along the X, Y and Z axes. In particular, the tuning for polarization along the Z axis is relatively flat and uniform in the range 1023 nm - 1083 nm.
RESUMEN
We prepare InGaN/GaN multiple quantum well (MQW) structure by metal-organic vapour phase epitaxy and characterize it by fine XRD measurements. We demonstrate its suitability for scintillator application including a unique measurement of wavelength-resolved scintillation response under nanosecond pulse soft x-ray source in extended dynamical and time scales. The photoluminescence and radioluminescence were measured: we have shown that the ratio of the intensity of quantum well (QW) exciton luminescence to the intensity of the yellow luminescence (YL) band IQW/IYL depends strongly on the type and intensity of excitation. Slower scintillation decay measured at YL band maximum confirmed the presence of several radiative recombination centres responsible for wide YL band, which also partially overlap with the QW peak. Further improvements of the structure are suggested, but even the presently reported decay characteristics of the excitonic emission in MQW are better compared to the currently widely used single crystal YAP:Ce or YAG:Ce scintillators. Thus, such a type of a semiconductor scintillator is highly promising for fast detection of soft x-ray and related beam diagnostics.
