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Abstract: In this study, the scintillation properties of Eu2+ activated CsBa2Br5 are reported. It is an analog of Eu2+ doped CsBa2I5 scintillator that exhibits excellent scintillation properties. Microcrystalline powder samples of this compound were synthesized by reaction in the molten state of cesium bromide, barium bromide and europium bromide. The concentration of an Eu was varied from 0% to 10%. The luminescence was studied under UV and X-ray excitation. The light output is strongly Eu2+ concentration dependent, reaching an estimated maximum of about 92,000photons/MeV at 2% Eu under X-ray excitation. About 50% of the scintillation light decays in less than 1μs. CsBa2Br5:Eu2+ exhibits a complex concentration dependent emission centered around 435nm. [Copyright &y& Elsevier]

Abstract: It is known that the impurities In in CdS and Ga in ZnO act as donors to generate a population of electrons near the bottom of the conduction band. Fast luminescence is observed from these materials but the intensity of the luminescence is strongly dependent on the method used for dopant incorporation. Therefore, it is suspected that an additional dopant is responsible for trapping ionization holes and promoting rapid radiative recombination and these compete with native non-radiative centers. To verify this conjecture and to optimize the luminosity of this class of scintillators, we have been exploring the possibility of introducing dopants that act as efficient hole traps and radiative centers. In this work, we report on the luminosities and decay times of crystalline powders of ZnO doped with the donor Ga3+ and treated with H, doped with the acceptor N3− and with the isoelectronic hole trap S2−. Co-doped samples exhibit a large increase in luminosity and a fast mono-exponential decay. We also report on PbI2 doped with the donors Bi3+, La3+, and In3+ and co-doped with Ga3+ and P3−. PbI2 is dense (d=6.2g/cm3) and is a candidate material for gamma-ray detection. [Copyright &y& Elsevier]

Abstract: We present the scintillation characteristics of 5% Eu2+-doped BaCl2 single crystals grown by the Bridgman–Stockbarger method. The single crystalline samples show very good scintillation properties compared to the previous reports most likely due to improved purity of the crystals. The light output and the energy resolution values derived from pulse height spectra under γ-ray excitation of a 137Cs source are 52,000ph/MeV and 3.5%, respectively. [Copyright &y& Elsevier]

Abstract: The micro-pulling-down () crystal growth of sapphire fibers, whose steady-state limits were the focus of our prior study [Samanta et al., Journal of Crystal Growth 335 (2011) 148–159], is further examined using a parametric sensitivity computation derived by linearizing the nonlinear model around a quasi-steady-state (QSS). In addition, transient analyses are performed to assess inherent stability and dynamic responses in this system. Information from these two approaches enlarges our understanding of this particular process, and the approaches themselves are put forth as valuable complements to classical QSS analysis. [Copyright &y& Elsevier]

Abstract: At the High-Throughput Discovery of Scintillator Materials Facility at Lawrence Berkeley National Laboratory, scintillators are synthesized by solid-state reaction or melt mixing, forming crystalline powders. These powders are formed in various granularity and the crystal grain size affects the apparent luminosity of the scintillator. To accurately predict a “full-size” scintillator''s crystal luminosity, the crystal luminosity as a function of crystal granularity size has to be known. In this study, we examine Bi4Ge3O12 (BGO), Lu2SiO5:Ce3+ (LSO), YAlO3:Ce3+(YAP:Ce), and CsBa2I5:Eu2+ (CBI) luminosities as a function of crystalline grain size. The highest luminosities were measured for 600- to 1000-μm crystal grain sizes for BGO and LSO, for 310- to 600-μm crystal grain sizes for CBI, and for crystal grains larger than 165μm for YAP:Ce. Crystal grains that were larger than 1mm had a lower packing fraction, and smaller grains were affected by internal scattering. We measured a 34% decrease in luminosity for BGO when decreasing from the 600- to 1000-μm crystal grain size range down to the 20- to 36-μm range. The corresponding luminosity decrease for LSO was 44% for the same grain size decrease. YAP:Ce exhibited a luminosity decrease of 47% when the grain size decreased from the 165- to 310-μm crystal grains to the 20- to 36-μm range, and CBI exhibited a luminosity decrease of 98% when the grain size decreased from the 310- to 600-μm crystal grain range to the 36- to 50-μm range. We were able to very accurately estimate full-size crystal luminosities from crystalline grains that are larger than 90μm. [Copyright &y& Elsevier]

Abstract: We present new results obtained from single crystals of Ba binary halides of BaCl2, BaBr2 and BaI2 activated with Eu2+. While these compounds were known as scintillator materials, due to improvements in the crystal growth process and availability of higher purity compounds, we obtained crystals with better performances than what have been reported before. The luminosities of BaCl2:5%Eu2+, BaBr2:5%Eu2+ and BaI2:5%Eu2+ are about 90%, 70% and 60%, respectively, of their theoretical limit. [Copyright &y& Elsevier]