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Abstract KCaI 3 :Eu is a scintillator composition that is promising for national security applications, with a high light yield and good energy resolution (∼ 70,000 ph/MeV and ∼ 3% E.R. at 662 keV, respectively). In addition to its high performance, we have been successful at growing KCaI 3 :Eu at larger sizes (38 mm diameter) without cracking. In this work we utilized a multi ampoule growth station to grow four 38 mm diameter crystals simultaneously. Three of these crystals achieved an energy resolution of ∼ 4% at 662 keV. The three crystals were hermetically packaged and a collimation study was carried out. This study revealed that light yield at a given irradiation location is dominated by photon path lengths and self-absorption, while the energy resolution dependence is affected heavily by local crystal quality. A 50 mm diameter KCaI 3 :Eu crystal was grown that achieved an energy resolution of 4.6% at 662 keV. GEANT4 was used to model a gap-style package that results in reduced photon path lengths, and therefore reduced self-absorption probability. [ABSTRACT FROM AUTHOR]

Inch-sized scintillating crystals are required for practical radiation detectors such as hand-held radio-isotope identification devices. In this work, a transparent and colorless 2-inch diameter KCa 0 . 8 Sr 0 . 2 I 3 : 0 . 5 mo % E u 2 + single crystal was grown by the vertical Bridgman method, and the scintillation properties of a ∅ 50 mm × 45 mm long sample were evaluated. The Eu 2 + 5 d 1 - 4 f emission under X-ray excitation is centered at 472 nm. Its scintillation decay time under 137 Cs source irradiation is 2 . 37 μ s , and the absolute light output is 51,000 ± 3000 photons/MeV. The energy resolution at 662 keV was evaluated for different orientations of the crystals with respect to the PMT, and the effect of 40 K background subtraction on energy resolution was evaluated. The performance of the packaged crystal was also investigated. [ABSTRACT FROM AUTHOR]

The presented study reports on the spectroscopic characteristics of a new high performance scintillation material KCaI 3 :Eu. The growth of ∅ 17 mm boules using the Bridgman–Stockbarger method in fused silica ampoules is demonstrated to produce yellow tinted, yet transparent single crystals suitable for use in spectroscopic applications due to very promising performance. Scintillation light yield of 72,000 ± 3000 ph/MeV and energy resolution of 3% (FWHM) at 662 keV and 6.1% at 122 keV was obtained from small single crystals of approximately 15 mm 3 . For a much larger 3.8 cm 3 detector, 4.4% and 7.3% for the same energy. Proportionality of the scintillation response to the energy of ionizing radiation is within 96% of the ideal response over an energy range of 14–662 keV. The high light yield and energy resolution of KCaI 3 :Eu make it suitable for potential use in domestic security applications requiring radionuclide identification. [ABSTRACT FROM AUTHOR]

We report here the effect of Eu 2+ concentration in KCa 0.8 Sr 0.2 I 3 :Eu 2+ single crystal scintillators. KCa 0.8 Sr 0.2 I 3 :Eu 2+ single crystals doped with 0.5, 1, 3, 5, and 7 mol% Eu 2+ were grown by the Bridgman method. The effects of varying Eu 2+ concentration and crystal volume on the scintillation properties, including light yield, energy resolution, nonproportionality, scintillation decay time and afterglow level, were systematically investigated. For 5 mm×5 mm×5 mm samples, the best light yield of 86,000±4000 photons/MeV was achieved with a content of 5 mol% Eu 2+ ; its energy resolution of 2.5% at 662 keV was comparable to that of LaBr 3 :Ce 3+ and SrI 2 :Eu 2+ . With larger samples of about 2.2 cm 3 , the best performances achieved were for 3 mol% Eu 2+ concentration, i.e. a light yield of 76,000±4000 photons/MeV and an energy resolution of 3% at 662 keV. A direct correlation between nonproportionality and Eu 2+ concentration was found. A continuous lengthening of scintillation decay time and x-ray induced afterglow level with increasing Eu 2+ concentration was observed. The self-absorption effect was evaluated by using the Stokes shift and the temperature dependence of the photoluminescence decay (PL) of the Eu 2+ centers. The sample with the highest dopant concentration had more severe temperature quenching of the Eu 2+ 5d-4f emission than the sample with the lowest dopant concentration, which could be ascribed to the thermally activated concentration quenching. [ABSTRACT FROM AUTHOR]

We present a study of mixed halide single crystal scintillators with the general formula CeBr 3− x Cl x , where 0≤ x ≤3. Single crystals with various bromine–chlorine ratios were grown by the Bridgman method, and their scintillation properties were investigated. Under X-ray irradiation, the peak emission ranged between 350 and 450 nm. The absolute light yield ranged between 44,000 and 60,000 photons/MeV under 137 Cs gamma-ray irradiation. The energy resolution at 662 keV was between 4.6% and 5.0%. The major scintillation decay time was less than 17 ns, and slightly increased with higher chlorine to bromide ratio. The X-ray diffraction indicated that the lattice constants decreased with higher chlorine content. A moisture absorption study showed that higher chlorine content can greatly decrease the hygroscopicity. [ABSTRACT FROM AUTHOR]

A nat LiCl–BaCl 2 :Eu 2+ eutectic scintillator was synthesized by the vertical Bridgman method aiming at the application of thermal neutron detection. The molar ratio of LiCl and BaCl 2 was 75.1/24.9, which corresponds to the eutectic composition in the LiCl–BaCl 2 system. The grown eutectic showed a periodic microstructure of BaCl 2 :Eu 2+ and LiCl phases with 2–3 μm thickness. The α-particle induced radioluminescence spectrum of the scintillator showed an intense emission peak at 406 nm due to the Eu 2+ 5d 1 → 4f emission from the BaCl 2 :Eu 2+ phase and an additional weak emission peak at 526 nm. The scintillation decay time was 412 ns. LiCl–BaCl 2 :Eu 2+ eutectic samples exhibited non-correlated neutron detection efficiency and light yield as a function of crystal length, suggesting material non-uniformities within the boule. The relative light yield was equal to or greater than that of Nucsafe lithium glass. Gamma-ray exposures indicate that gamma/neutron threshold discrimination for higher energy gamma-rays will be limited. [ABSTRACT FROM AUTHOR]