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KCaI 3 :Eu single crystals exhibit favorable scintillation properties and have potential for use in domestic security applications requiring radioisotope identification. The anisotropic thermal expansion of the orthorhombic unit cell of this perovskite-type scintillator has been investigated using in-situ high temperature X-ray diffraction on powdered samples. Samples from single crystals of both pure and Eu-doped KCaI 3 grown by the Bridgman method were used for comparison. Expansion with temperature along the b -axis is greatest with an average linear coefficient of thermal expansion of ≈ (41–46) x 10 −6  K −1 resulting from the weaker bonding between alternating layers of K and Ca parallel to the b -axis. Thermal expansion in each of the KCaI 3 samples has the highest degree of anisotropy with respect to the b and c axis with ratio ᾱ b /ᾱ c of 1.4–1.5. Additionally, we identify the predominant cleavage plane in KCaI 3 as (0 -3 -1) based upon Laue reflection imaging. [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]

We investigate the multi-ampoule growth at 25 mm diameter of ternary iodide single crystal scintillator KCaI 3 :Eu using the randomly oriented self-seeded Bridgman method. We compare scintillation performance between cubic inch scale crystals containing small variations of low nominal europium concentrations previously shown to balance light yield with self-absorption in the host crystal. Growth conditions were optimized in the developmental furnace and four 2 in 3 KCaI 3 :Eu crystals were grown simultaneously producing a total of six 25 mm × 25 mm cylinders. Small variations in activator concentration did not result in significant performance differences among the six measured crystals. A range of energy resolutions of 3.5–4.7% at 662 keV was achieved, surpassing that of NaI:Tl crystals commonly used in spectroscopic detection applications. The function and basic design of the multi-ampoule furnace as well as the process of growing single crystals of KCaI 3 is included here. [ABSTRACT FROM AUTHOR]

A quaternary iodide KCa0.8Sr0.2I3:Eu2+ scintillator with 2.5% energy resolution at 662 keV in a 5 mm3 sample shows great potential for use in gamma-ray spectroscopy applications. In this work, we report the state-of-the-art growth of high quality 25, 38, and 50 mm diameter KCa0.8Sr0.2I3:Eu2+ single crystals by the vertical self-seeding Bridgman method. KCa0.8Sr0.2I3:Eu2+ with a size of ∅25 mm × 25 mm can achieve excellent energy resolutions of 3.15% at 662 keV and 6.8% at 122 keV irradiation, which are superior to that of a commercial NaI:Tl+ of the same size. The nonuniformity of light collection and production in ∅25 mm × 25 mm and ∅38 mm × 38 mm KCa0.8Sr0.2I3:Eu2+ crystals was evaluated by using a technique based on a collimated 137Cs source and coupling the crystal to a photomultiplier tube (PMT) in different directions. The performances of the packaged crystals for practical use were also measured. [ABSTRACT FROM AUTHOR]

KCaI 3 :Eu crystals have been identified as very promising for use in spectroscopic detector applications related to nuclear nonproliferation and domestic security efforts. Initial studies have shown for small crystals a few mm 3 in size with 3% europium dopant concentration, a high light yield of >70,000 ph/MeV and energy resolution of ≈3% at 662 keV is attainable which is comparable with the highest performance scintillators discovered. In this work, single crystals of KCaI 3 with a range of Eu 2+ doping between 0 and 5 at% substituting for Ca 2+ were grown at 22 mm diameter and their performance for gamma-ray spectroscopy studied. Comparisons among crystals approximately Ø22 mm×22 mm (8.4 cm 3 or ≈0.5 in 3 ) provide a more accurate understanding of how scintillation performance changes with Eu doping and increased crystal size. KCaI 3 in the undoped form is shown to be a highly efficient intrinsic scintillator with a defect-related emission at 404 nm which coexists with the Eu 2+ 5d–4f emission in low dopant concentrations and is completely re-absorbed in more heavily doped crystals. For larger crystals, effects from self-absorption due to Eu activation become more evident by a near doubling of decay time for 0.5 in 3 crystals as the activator is increased from 0.5 to 5.0 at% Eu. Comparisons of pulse-height spectra obtained for Ø22 mm×22 mm cylinders with varying Eu concentration suggests best performance is achieved using lower Eu additions closer to 0.5–1.0 at%. Using a modified crystal packaging featuring an offset reflector geometry, 0.5 in 3 crystals of KCaI 3 :Eu can attain under 4% energy resolution at 662 keV. [ABSTRACT FROM AUTHOR]

The newly developed KCa0.8Sr0.2I3:Eu2+ scintillator with 2.5% energy resolution at 662 keV shows great potential for use in gamma-ray spectroscopy applications, but progress toward large-size crystal growth has been hindered by cracking and inclusion problems. In this paper, we report a detailed study on the role of process variables of Bridgman growth, including grain selector designs, ampule surface treatments, and temperature gradients. It was found that crystal cracking can be effectively prevented by using a carbon-coated quartz ampule with a bent capillary. A high temperature gradient of 45 °C/cm at the solid-liquid interface can positively contribute to the suppression of the formation of visible inclusions caused by constitutional supercooling. By using optimized growth parameters, high quality 22 mm diameter KCa0.8Sr0.2I3 single crystals doped with 0.5, 1, and 3 mol % Eu2+ and 38 mm diameter KCa0.8Sr0.2I3 single crystals doped with 0.5 mol % Eu2+ were grown by the Bridgman method. The scintillation properties, including radioluminescence, light yield, energy resolution, and scintillation decay, of Φ22 mm x 22 mm and Φ38 mm x 35 mm samples were 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]

CsSrI3/Eu2+ has very promising scintillation properties for gamma-ray spectroscopy applications, but it has proven difficult to grow high quality single crystals in large sizes. This paper reports a composition-engineering strategy, in this case a combination of off-stoichiometric melts and Eu2+ concentration optimization, to obtain large-size CsSrI3/Eu2+ crystals with excellent energy resolution. Crystals of a series of off-stoichiometric compositions, Cs(1+x)(Sr,Eu)(1-x)I(3-x) (x = 0, 0.05, 0.06, and 0.1), were grown by the Bridgman method. The Cs1.06Sr0.94I2.94/Eu2+ single crystal has the highest optical transmittance between 450 and 800 nm. Cs1.06Sr0.94I2.94 single crystals doped with 0.5, 1, 3, 5, and 7 mol % Eu2+ ions were also grown by the Bridgman method. The effects of Eu2+ concentration on the phase purity and optical and scintillation properties were studied. X-ray diffraction patterns confirmed the phase purity of all samples with the exception of a hydrate phase formed during measurement. Increasing Eu2+ concentration leads to longer decay components due to the effect of self-absorption. An unexpected relationship was found between the Eu2+ concentration and the appearance of two photopeaks in a pulse height spectrum acquired under a single gamma-ray energy of 662 keV irradiation. The origins of this phenomenon are proposed from experimental insights. The optimal composition we developed achieved an excellent energy resolution of 3.4% for ϕ22 mm × 2 mm, 3.9% for ϕ22 mm × 15 mm, and 4.1% for ϕ22 mm × 19 mm at 662 keV. The results of this paper lead to a better understanding of the effects of composition-engineering in optimization of nonstoichiometric scintillator compounds. [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]

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]