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In this work the Bridgman crystal growth and scintillation properties of both undoped and Tl-doped Cs 3 Cu 2 I 5 are presented. This material is very attractive for gamma and X-ray detection applications, with a density of 4.53 g/cm3 and effective atomic number of 51.9. Undoped Cs 3 Cu 2 I 5 had a light yield of 41,500 photons/MeV, with an energy resolution of 4.4% at 662 keV. Thallium doping at 0.5 mol % resulted in a much-improved scintillation response, in which light yield increased to 98,200 photons/MeV and energy resolution reduced to 3.3% at 662 keV. The X-ray excited emission is centered at 442 nm for the undoped and 500 nm for the Tl-doped crystals. The undoped emission is broad, typical of excitonic emission, while thallium doping results in an even broader band with features of both the undoped and thallium defect-mediated emissions. • Transparent single crystals of undoped Cs 3 Cu 2 I 5 and Cs 3 Cu 2 I 5 (Tl) were grown via the Bridgman technique. • Phase purity was established via powder XRD analysis. • Undoped Cs 3 Cu 2 I 5 has 41,500 photons/MeV and 4.4% energy resolution at 662 keV. • Tl doping at 0.5 mol% improves light yield to 98,200 photons/MeV and energy resolution to 3.3%. [ABSTRACT FROM AUTHOR]

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]

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]

Europium doped strontium iodide (SrI 2 :Eu 2 +) is one of the cutting-edge halide scintillators for gamma-ray spectroscopy applications due to its low radioactive background, ultrahigh light yield (70,000–100,000 photons/MeV), and excellent gamma-ray energy resolution (2.6%–3% at 662 keV). In this work, we report an improvement in the scintillation characteristics of SrI 2 :Eu 2 + single crystals via tetravalent ion codoping, namely Zr 4 +. High quality SrI 2 :Eu 2 + single crystals codoped with 0, 0.05, 0.1, and 0.2 at.% Zr 4 + were grown by the Multi-ampoule Bridgman method. All of the as-grown crystals are transparent, crack-and inclusion-free. They have high optical quality with a transmittance of over 70%. The effects of Zr 4 + codoping on spectral properties and decay kinetics of SrI 2 :Eu 2 + under optical, and x- and gamma-ray excitation are studied. An enhancement of gamma-ray spectroscopic resolution from 2.8 to 2.5% at 662 keV and 5.4 to 5% at 122 keV is achieved upon Zr 4 + codoping with a slightly enhanced light yield of 95,000 photons/MeV. [ABSTRACT FROM AUTHOR]