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Lithium iodides are very efficient single‐crystal scintillators for thermal neutron detection. Doping with silver, as activator ions, has shown to improve its limitation of discriminating gamma background by introducing pulse shape discrimination ability. To improve the scintillation performance, single crystals of LiI:Ag, codoped with different concentration of Sr ions, are grown and characterized in details. A systematic investigation of radioluminescence, thermoluminescence, and scintillation properties along with the decay kinetics provides better understanding about the role of defect structure in scintillation mechanism. The extra charge, provided by Sr2+ ions, is found to alter the defect structure with relative reduction of the contribution from the deeper trap centers in comparison with the shallow traps. Consequently, it leads to a significant improvement of light yield quenching under higher excitation density of charged particle irradiation. The 0.1% Sr codoped crystals provide a better discrimination ability of neutron and gamma radiations for simultaneous detection. [ABSTRACT FROM AUTHOR]

The <100> plane of trans-Stilbene (TSB) crystal has been grown using the low-temperature modified vertical Bridgman method with slight modification in the growth setup. The design of a reformed vertical Bridgman method attached with a gear mechanism was used successfully for the growth of good optical quality TSB crystal. The grown single crystal possesses higher transparency, which proves the crystal's suitability for scintillator and optical applications. Several growth conditions were scientifically optimized to attain improved transmittance. The thermogravimetric analysis confirms that the material is steady up to 125 °C without any phase change. The ordinary (no) and also extraordinary refractive index (ne) was evaluated by utilizing the prism coupling technique at various wavelengths in the range from 407 to 1551 nm. The neutron and gamma-ray discrimination capabilities were measured by pulse shape discrimination (PSD method) through using standard 137Cs (gamma rays) and Am–Be (neutron) radioactive sources with excellent performance. Hirshfeld surface analysis was carried out to explore the various intermolecular interactions in the TSB crystal. The maximum interaction is H...H (51.4%), which is confirmed by the abundance of hydrogen on the molecule. Results are discussed in relation to optical, structural, and scintillation properties of the grown TSB crystal. Due to its PSD ability, this crystal scintillator could be used for numerous utilizations in the division of radiation detection. [ABSTRACT FROM AUTHOR]

A phoswich detector was fabricated using a combination of single-crystal scintillators of CsI:Tl and Gd3Ga3Al2O12:Ce,B. The performance characteristics of this novel phoswich detector were investigated for thermal neutron detection in the presence of different gamma backgrounds using an Am–Be source and in a research reactor beam line. High atomic density and excellent thermal neutron capture cross section of Gd leads to the high detection efficiency for thermal neutrons in a 1-mm thin disk of Gd3Ga3Al2O12 crystal. The high figure of merit of ~6.5 obtained for thermal neutron detection ensures the detector’s excellent discrimination property in the presence of high gamma background. [ABSTRACT FROM AUTHOR]

In this article, single crystals of a new nonhygroscopic scintillating material of tetrafluoroaluminate (TlAlF4) were grown using the Bridgman–Stockbarger technique. The diffraction pattern obtained from powder X-ray diffraction was found to be in good agreement with the reference data. The X-ray-induced luminescence measurements of the grown crystal sample exhibit a very strong intrinsic emission band in the wavelength range from 300 to 450 nm, with a peak maximum at 390 nm. Scintillation properties, such as pulse height spectra and decay time of the grown crystals, were investigated using γ-rays from the 137Cs radiation source. The scintillation light yield was found to be ~11 800 ph/MeV. At room temperature, the measured decay time profile was fitted with three exponential functions; the result showed a fast component of 194 ns (13.1%), a medium component of 992 ns (84.6%), and a slow component of 3.5 μs (2.3%). Trap centers were studied using the results obtained from thermally stimulated luminescence. The temperature dependence of the scintillation light yield and decay time was also studied. The results showed that TlAlF4 is a promising scintillator crystal, and thus, a potential candidate for X-ray and γ-ray detection. [ABSTRACT FROM AUTHOR]

In this article, we have extended our study on the effect of codopants on the scintillation properties of Ce-doped Gd3Ga3 Al2O12(GGAG:Ce) single crystals by investigating their pulse-shape discrimination (PSD) abilities. The GGAG:Ce crystals were grown with boron and calcium codopants using the Czochralski technique. The codoping was found to have substantial effects on the PSD ability of these scintillators. Observable difference in the pulse shapes for alpha and gamma radiations in the B-codoped GGAG:Ce scintillators exhibited the highest PSD, while those with Ca codoping showed no discrimination among the studied samples despite having a significant effect on the scintillation kinetics and a strong quenching of the light yield by alpha radiations that resulted in a minimum α/γ ratio. A correlation of the PSD properties with the defect structure of these single crystals has been made by using optically stimulated luminescence (OSL) for the first time. OSL studies with infrared, blue, and green light provided an insight into the role of defect centers in the relaxation mechanism of the scintillation kinetics of the GGAG:Ce crystals, which subsequently affects their ability to discriminate different kinds of radiation. [ABSTRACT FROM AUTHOR]

Single crystals of a new promising material Tl2HfCl6 were successfully grown by using a modified vertical Bridgman furnace. Various growth conditions were systematically optimized to achieve improved scintillation characteristics. For the first time, the crystalline phase and structure were analyzed using the Rietveld refinement method. The emission and scintillation properties were investigated in detail. The emission peak under X-ray excitation was centered at 398 nm, which was compatible with the quantum efficiency of the conventional photosensors. The scintillation decay time under γ-ray excitation exhibited a major component of 1 μs with the light yield of 32 000 photon per MeV. The improved energy resolution of the grown crystal was measured to be 4.0% at 662 keV. The significant improvement in decay time, light yield and energy resolution over previously reported results was mainly achieved by adopting a systematic approach of material purification. The applicability of this material in various fields was also investigated for the first time by recording the combined radiation of α-particles and γ-rays. These different types of radiations could be sufficiently separated by employing the charge comparison method with a promising figure-of-merit of 2.6. A simulation using Geant4 was also performed for comparing the detection efficiency of Tl2HfCl6 with those of the conventional halide crystal scintillators. Due to its good scintillation performance and pulse shape discrimination capability, this scintillator may be reasonably considered for various applications in the field of radiation detection. [ABSTRACT FROM AUTHOR]

Single crystals of Gd3Ga3Al2O12:Ce were grown successfully and a slice having thickness lesser than 1 mm was processed from the grown crystals to setup a portable thermal neutron detector. The presence of Gd isotopes having very high thermal neutron capture cross section ensures almost 100% stopping efficiency in such a low thickness. On the other hand, a lower thickness provided a better discrimination from gamma background. In addition to the continuum gamma, Gd isotopes also produce low-energy conversion electrons and X-rays which could be successfully observed in the form of well discriminated photopeaks at 34 and 74 keV. These photopeaks could also be measured in nuclear reactor beam lines with high gamma background. [ABSTRACT FROM AUTHOR]

Single crystals of Ce doped Li6Gd(BO3)3 (LGBO:Ce), Li6Lu(BO3)3 (LLBO:Ce), and Li6Y(BO3)3 (LYBO:Ce) are grown using the Czochralski technique. A comparison of the challenges faced in the growth of these materials in single crystalline form is discussed. The grown crystals are characterized for their thermal, structural, optical, and scintillation characteristics to explore their potential as thermal neutron detectors. Scintillator detectors based on LRBO:Ce (R = Gd, Lu, Y) crystals are used successfully to record the pulse‐height spectra from various gamma energies and thermal neutron sources in the flux range from 10 to 107 n (cm2 s)–1. [ABSTRACT FROM AUTHOR]

Single crystals of Gd 3 Ga 3 Al 2 O 12 :Ce,B and CsI:Tl were grown by Czochralski and Bridgman techniques, respectively. While both the crystals exhibited similar emission at about 550 nm, their scintillation decay times showed significantly different characteristics. The average scintillation decay time of Gd 3 Ga 3 Al 2 O 12 :Ce,B crystal was found to be about 284 ns for alpha excitation compared to 108 ns measured for a gamma source. On the other hand in CsI:Tl crystals, the alpha excitation resulted in a lower average decay time of 600 ns compared to 1200 ns with gamma excitation. Their pulse shape discrimination (PSD) for gamma and alpha radiations were studied by coupling the scintillators with photomultiplier tube or SiPM and employing an advanced digitizer as well as a conventional zero-crossing setup. In spite of having a poor α/γ light yield ratio, the PSD figure of merit and the difference of zero-crossing time in Gd 3 Ga 3 Al 2 O 12 :Ce,B crystals were found to be superior in comparison to CsI:Tl crystals. [ABSTRACT FROM AUTHOR]

Abstract: UV excited photo luminescence from Li2B4O7:Cu and Li2B4O7:Cu, Ag single crystals has been investigated in the temperature range from 77K to 300K. An excitation band having a doublet structure at 240nm and 262nm was observed for the emission at 370nm that corresponds to 1A1g→1Eg and 1A1g→1T2g crystal field components of the 3d10→3d94s1 transition of Cu+. The relative intensity of these components and their temperature dependence provide a measure of the off-center displacement of the Cu+ ground state in the crystal lattice site. The co-doped Ag plays a role of a sensitizer when doped with Cu and increases the overall emission as the emission between Ag states lies in the excitation region of Cu states. The 370nm emission in both the crystals slightly decreases with temperature; however a sudden increase in the intensity around 264K was observed. [Copyright &y& Elsevier]

Single crystal of Ce doped Gd 3 Ga 3 Al 2 O 12 is one of the most studied advanced scintillators currently. The scintillation kinetics has been investigated with different excitations. The higher excitation density of alpha particles quenches the scintillation light yield but on the contrary the decay curve gets accelerated with gamma rays unlike that have been typically observed for conventionally used halide scintillators. In view of resolving this unusual behavior, a thorough investigation has been first time performed by carrying out systematic experiments on temperature dependent scintillation properties with gamma and alpha irradiation. The dependence of light yield for both radiations behaves differently with temperature with a notable early onset of quenching for charged particles. All three decay components also behave differently with temperature to indicate the various mechanisms governing the relaxation of excited charged carriers. At some temperatures the decay time components indeed behave in the similar manner as measured for halide crystals. The maximum difference in decay components carrying major amplitude occurs close to room temperatures leading to better discrimination ability. A strong correlation with thermo-luminescence properties has been observed to investigate the role of defect structure. A comprehensive model based on the prominent role of charged carriers released from trap centers along with the energy transfer and migration via Gd sub-lattice in governing the scintillation properties has been convincingly presented. It has demonstrated precisely the unusual behavior of this material but can be extended more considerably to describe various properties of other scintillators as well. • Single crystals of Ce doped Gd 3 Ga 3 Al 2 O 12 were grown by Czochralski method. • The light yield quenches under massive particle radiations but the decay time slows down. • A model is proposed to explain this strike difference from halide scintillator. • Temperature dependent kinetics studied under different radiations. • The role of defect structure and host energy transfer with excitation kinetics for alpha and gamma. [ABSTRACT FROM AUTHOR]

The discrimination of different types of radiations like gamma, charged particles, neutrons etc., is required in various applications in Academic, the Nuclear industry, homeland security, medical diagnostics, etc. For these versatile uses, we have developed a novel phoswich detector consisting of two promising single crystal scintillators to discriminate various kinds of radiation with a promising figure-of-merit (FOM) along with advantages over other single crystal scintillators reported so far. The high pulse-shape discrimination (PSD) for different radiations has been achieved by a novel combination of a Boron co-doped Gd 3 Ga 3 Al 2 O 12 :Ce (GGAG) crystal coupled to a CsI:Tl (CsI) single crystal in a phoswich detector design. This combination was optically coupled to a single photomultiplier tube and a desktop digitizer to build a compact detector setup. The FOM for discriminating alpha and gamma radiations was observed to be better than twice that of the FOM obtained using individual crystals. The gamma interacting in the front GGAG crystal and the back CsI crystal could also be discriminated with a distinguishing FOM that may lead to notable improvement of spatial resolution in the medical imaging applications. The gamma–gamma discrimination and the presence of Gd in GGAG makes it a suitable candidate for the detection of thermal neutrons in mixed fields. Overall, the observed significant improvement in the discrimination ability along with the remarkable versatility opens a vast scope for using this combination in various applications. [ABSTRACT FROM AUTHOR]

A compact gamma spectrometer was developed by employing an in-house grown single crystal of Gd 3 Ga 3 Al 2 O 12 :Ce,B scintillator optically coupled with a silicon photodiode. The performance of the detector was characterized in detail. The detector setup works with a low bias voltage of 9 V, drawn from a single battery. Power to the electronic components of the entire system is derived from a single universal serial bus port by employing required DC–DC converters. In addition to the low voltage operation, this developed spectrometer is very compact in size compared to the one developed by employing photo-multiplier tubes. The system offers excellent linearity over the gamma energy range of 344–1408 keV and an optimum energy resolution of about 13% at 662 keV. [ABSTRACT FROM AUTHOR]

Thallium doped Cesium Iodide (CsI:Tl) radioluminescent microcrystals are promising candidate for scintillation applications that include medical imaging, nuclear safety and high energy particle detection applications. This paper introduces, for the very first time, an antisolvent recrystallization method to synthesize microcrystals of CsI:Tl. The antisolvent recrystallization method is useful for synthesizing microcrystals at room temperature under atmospheric pressure and humidity conditions with high product yield approaching ∼90 %. The polycrystalline nature of the CsI:Tl microcrystals is confirmed from the X-ray diffraction analysis, wherein the crystallite size is found to be in the range of 20–25 nm. The scanning electron microscopy revealed the size of microcrystals in the range of 1–13 μm. The doping concentration of thallium (with 0.06, 0.10, 0.20, 0.50 and 1.00 mol%) strongly affects the luminescence yield. At higher concentration of doping, a shift towards long wavelength is observed. The strongest luminescence yield is observed in the sample of 0.2 mol% Thallium doping, which is around 76 % of luminescence compared to single crystal of CsI:Tl. This work provides a low-cost alternative to the growth of radioluminescent microcrystals in comparison with the existing single crystal growth approaches. CsI (0.2 mol% Tl) microcrystals (A) Normal light (B) Under the exposure of UV light. [Display omitted] • Novel method for CsI:Tl microcrystals synthesis in ambient conditions. • CsI:Tl (0.2 mol% Tl) yields maximum luminescence efficiency. • Achieves 76 % luminescence of CsI:Tl single crystals. • Cost-effective alternative for radioluminescent microcrystal growth compared to single crystals. [ABSTRACT FROM AUTHOR]