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We are reporting on the latest growth and scintillating properties of a recently discovered intrinsic scintillating compound with the K2PtCl6 simple cubic crystal structure: the Cs-based Cs2HfCl6 (CHC) and Cs2HfCl4Br2 (CHCB), both with the density of 3.9 g/cm3, as well as the Tl-based Tl2HfCl6 (THC) and Tl2ZrCl6 (TZC). This article presents a successfully developed process of growing crack-free, single crystals of 16 mm diameter to 1-in-diameter CHC by the Bridgman method. The energy resolution of 2.8% [full-width at half-maximum (FWHM)] at 662 keV has been obtained for small diameters and typical 3.5% (FWHM) at 662 keV has been obtained for 1 in $\times 1$ in CHC. The light yield of 30 000 ph/MeV and the 3.8- $\mu \text{s}$ primary decay time have been measured for CHC. CHC’s excellent linear response to gamma rays compared to those of NaI:Tl and BGO is also reported. The mixed-halides CHC-based compound CHCB performs with a shorter primary decay time of $1.8~\mu \text{s}$ . Introducing Tl, a heavier element than Cs, increases both Zeff and density of THC and TZC, and improves gamma-ray detection efficiency. Primary decay times are also reduced to about $1~\mu \text{s}$ for THC and $2~\mu \text{s}$ for TZC.

We report on the preparation, structure and scintillation properties of single crystal cesium hafnium chloride bromide (Cs2HfCl4Br2 or CHCB). The crystals were grown using a vertical Bridgman technique process. Single crystal X-ray diffraction showed that the as grown CHCB crystal structure was isostructural to Cs2HfCl6 crystals exhibiting the cubic K2PtCl6 –type crystal structure. The Cs2HfCl6−x - Cs2HfBrx system is a solid solution with the lattice parameter of Cs2HfCl6−xBrx increasing linearly with x in the range 0

Professor Jurchescu, Dr. Wolszczak, Professor Burger, Dr. Bourret-Courchesne, and Professor Dorenbos introduce the Journal of Materials Chemistry C–Materials Advances themed collection in memoriam of Prof. Richard T. Williams.

The mid-infrared fluorescence properties of erbium (Er) doped low-phonon ternary chloride-based crystals (KPb2Cl5, Cs2HfCl6, CsPbCl3, CsCdCl3) have been investigated. All crystals were grown by vertical Bridgman technique. Following optical excitations at 805 nm and 660 nm, all Er3+ doped chlorides exhibited infrared emissions at ~2750, ~3500, and ~4500 nm at room temperature. The mid-infrared emission at 4500 nm originating from the 4I9/2 → 4I11/2 transition showed long emission lifetime values of ~7.8 ms and ~11.6 ms for Er3+ doped Cs2HfCl6 and CsCdCl3 crystals, respectively. In comparison, Er3+ doped KPb2Cl5 and CsPbCl3 demonstrated shorter lifetimes of ~3 ms and ~1.8 ms, respectively. The temperature dependence of the 4I9/2 decay times was performed for Er3+ doped CsPbCl3 and CsCdCl3 crystals. We observed that the fluorescence lifetimes were nearly independent of the temperature, indicating a negligibly small non-radiative decay rate through multiphonon relaxation, as predicted by the energy gap law for low phonon energy hosts. The room temperature stimulated emission cross-sections for the 4I9/2 → 4I11/2 transition were determined to be in a range of ~0.14-0.54 x 10-20 cm2 for the studied Er doped chloride crystals.

Research in ceramic scintillators has steadily progressed alongside the research in bulk single crystal scintillator growth. As interest in faster scintillation material production with lower cost increases, more research on scintillating ceramics is needed. Research targeting optimization of optically transparent ceramics that can rival bulk-grown crystals grown may lower cost, increase yield, increase volume, and improve energy resolution in applications and systems currently using sodium iodide and alike. Ceramic scintillators that are dense (>5 g/cm3), have high effective Z (>60), are bright (>40,000 photons/MeV), and are not sensitive to moisture as well as those that can be handled without protection are desired. Ultra-fast ceramic materials are also of interest. This paper presents an equipment design and technique to produce inorganic halide ceramic scintillators Cs2HfCl6 (CHC) and Tl2HfCl6 (THC). Improvements and optimization of CHC and THC ceramic scintillator fabrication are gauged by monitoring the energy resolution and peak position of 137Cs full energy peak at 662 keV. With a 1-inch diameter CHC ceramic scintillator, energy resolution of 5.4% (FWHM) and light yield of 20,700 ph/MeV are achieved, while with a 16-mm diameter THC ceramic scintillator, energy resolution of 5.1% (FWHM) and light yield of 27,800 ph/MeV are achieved. Decay times of 0.6 microseconds (21%) and 3.0 microseconds (79%) are measured for CHC and 0.3 microseconds (13%) and 1.0 microseconds (87%) for THC. Both ceramic CHC and THC scintillators have similarly good proportionality data when compared to their single crystal counterparts.

Transparent, crack-free single crystal boules of 1-inch diameter Cs2HfCl6 (CHC) and Cs2HfCl4Br2 (CHCB) have been successfully grown using the vertical Bridgman method. Samples sized dia. 23mm×30mm and dia. 23mm×26mm, respectively, are characterized for their optical and scintillation properties. Energy resolutions of 3.5% and 3.7% (FWHM) at 662 keV as well as light yields of 23,000 ph/MeV and 20,000 ph/MeV have been calculated for CHC and CHCB, respectively. Results comparable to previously reported smaller crystals have been obtained. Studies on decay times, non-proportionality, and detector characterization are also reported. (This work was supported in part by U.S. Department of Energy under Grant #DE-SC0015733, U.S. National Science Foundation under Grant #HRD-1547757, and by U.S. National Aeronautics and Space Administration under Grant #NNX16AK42G).

This paper presents the evaluation of an alternative solution for detectors of dual energy x-ray absorptiometry systems. Bone mineral density (BMD) evaluation tools are crucial to the proper diagnosis of osteoporosis. The commercially available DEXA systems utilize CZT as the detector of the small dose of ionizing radiation passing through the area of interest. Our paper presents a novel Strontium Iodide doped with Europium (SrI2:Eu2+) scintillator crystal coupled to a Silicon Photomultiplier (SiPM) array as a less expensive alternative to CZT detector. Dual energy (60 keV and 122 keV) exposure was used for BMD measurements of a bone phantoms containing CaHPO4 to mimic bone and resin to mimic soft tissue. Calibration curves was determined for both BMD and for thickness measurements, validated by “unknown” phantoms. Both calibration curves lead to decreased errors compared to commercially available systems.

A scintillating lithium indium diselenide (LISe) single crystal has recently been found to exhibit an eight-fold increase in its apparent light yield within 80 µm across the surface when excited by cold neutrons. The cause of this observation is currently unknown. In this paper, we report on our investigations to explain the previous observations of nonuniformity in scintillating LISe. Using a two-photon interband excitation instrument, we found that the lower and higher light yield regions “scintillate” at peak emission energies of 1.98 eV and 2.4 eV, respectively, and no region investigated exhibited both. Volumetric evaluation found a relatively uniform scintillation response in each region, verifying that the relatively flat spatial resolution of LISe substrates of varying thickness applied to neutron imaging is not from only near-surface scintillation mechanisms. Raman investigations indicate that the vibrational modes of the scintillating LISe substrate is somewhat different than that reported in literature, but no apparent difference between the two regions was observed. Using ToF-SIMS in each region, we found that the 1.98 eV emission region contains additional lithium, which is consistent with neutron absorption results. We suspect that the sharp transition in peak scintillation emission is due to a change in the charge state of Li-In antisites, but that the observed scintillation light yield and emission energy change is not directly correlated to crystal color. Qualitative comparison between the observed noise in the two-photon “scintillation” spectra indicates that the light yield between each region is not due to the quantum efficiency of the CCD used during cold neutron interrogation experiments, but an actual change in the light yield.

Gamma-ray detection and spectroscopy is the quantitative determination of their energy spectra, and is of critical value and critically important in diverse technological and scientific fields. Here we report an improved melt growth method for cesium lead bromide and a special detector design with asymmetrical metal electrode configuration that leads to a high performance at room temperature. As-grown centimeter-sized crystals possess extremely low impurity levels (below 10 p.p.m. for total 69 elements) and detectors achieve 3.9% energy resolution for 122 keV 57Co gamma-ray and 3.8% for 662 keV 137Cs gamma-ray. Cesium lead bromide is unique among all gamma-ray detection materials in that its hole transport properties are responsible for the high performance. The superior mobility-lifetime product for holes (1.34 × 10−3 cm2 V−1) derives mainly from the record long hole carrier lifetime (over 25 μs). The easily scalable crystal growth and high-energy resolution, highlight cesium lead bromide as an exceptional next generation material for room temperature radiation detection., Detection and spectroscopic measurements of gamma-ray used to rely on expensive materials such as CdZnTe crystals. Here He et al. develop a melt method to grow large size CsPbBr3 perovskite crystals and the devices achieve low cost, high energy resolving capabilities and stability.

Spectroscopic results on the infrared emission properties of trivalent holmium (Ho3+) doped potassium lanthanum chloride (K2LaCl5) are presented. Using ~900 nm excitation, Ho3+ doped K2LaCl5, which has a maximum phonon energy of 235 cm−1, exhibited the infrared emissions at ~1660, ~1995, and ~3900 nm at room temperature. The mid-infrared emission at 3900 nm originated from the 5I5 → 5I6 transition of Ho3+ ions with an exponential decay time of ~7.8 ms at room temperature. The fluorescence lifetimes were almost independent of temperature, indicating a negligibly small non-radiative decay rate for the 5I5 excited state, as predicted by the energy gap law for low phonon energy hosts. The Stark level energies of the lower 5IJ manifolds in Ho:K2LaCl5 were resolved from spectroscopic results performed at cryogenic temperatures. The transition line-strengths, radiative lifetimes, and fluorescence branching ratios were investigated by using the Judd-Ofelt method. In addition, the peak emission cross-section of the 5I5 → 5I6 transition was calculated to be 1.8 × 10–20 cm2 at ~3890 nm.

The crystal growth and behavior of a high-performance, non-hygroscopic scintillator, Cs 2 HfCl 6 (CHC) and its variant, Cs 2 HfCl 4 Br 2 (CHCB) are presented in this work. CHC and CHCB were prepared by melt compounding of sublimed HfCl 4 with CsCl and CsBr to produce material for Bridgman growth. The resulting 1 cm dia. and 1 in. dia. CHC crystals showed in certain parts evidence of CsCl as a secondary phase—a result of a non-stoichiometric (CsCl-rich) melt composition caused by the high vapor pressure of HfCl 4 during compounding. This was verified using micro X-ray fluorescence spectrometry. There is also evidence of a secondary phase in CHCB, which has been presented for the first time. A clear CHC sample had a light yield and energy resolution of 30,000 ph/MeV and 3.3%, respectively, and decay components of 0.39 and 3.9 µs. A sample of CHCB with a secondary phase present in the core had a light yield and energy resolution of 18,600 ph/MeV and 4.4%, and with decay components of 0.38 and 2.0 µs for CHCB. Both crystals showed minimal moisture sensitivity.

This paper describes the synthesis, crystal growth, detector fabrication, radiation hardening studies, MCNP modeling, and characterization of lithium indium diselenide or LiInSe 2 . This newly-developed room-temperature thermal neutron detector has semiconducting and scintillating properties and it is suitable for neutron detection application. LiInSe 2 was synthesized starting from elemental Li, In, Se in two steps due to high reactivity of Li. A single crystal of LiInSe 2 was grown using the Vertical Bridgman method . The room temperature band gap was found to be 2.8 eV using optical absorption measurements. Bulk resistivity was measured at ∼ 5 × 1011 Ω cm. Photoconductivity measurements of LiInSe 2 wafers identified a peak in the photocurrent around 445 nm. Nuclear radiation detectors were fabricated from single crystal wafer and the responses to alpha particles at various biases were measured. The mobility-lifetime product was estimated. Gamma irradiation studies were performed with calculated absorbed doses ranging from 0.2126 to 21,262 Gy. The characterization of the two wafers for their scintillator performance was conducted after each irradiation. The gamma irradiation produced a reduction of the light yield that translated to a lower channel number for the centroid of alpha detection spectra. It also showed a considerable reduction of the decay time after the first irradiation. These are the first studies on gamma radiation hardening with this material.

Nuclear and high energy physics research has a need for new, high performance scintillators with high light yields, high densities, fast decay times, and radiation hardness. In this paper we present crystal growth and results from 16-mm diameter cerium (Ce)-doped Tl2LaCl5 (TLC) and europium (Eu)-doped TlCa2Br5 (TCB) as well as one-inch diameter cerium-doped Tl2GdBr5 (TGB) and europium-doped TlSr2I5 (TSI), each grown in a two-zone vertical furnace by the modified Bridgman method. Samples extracted and processed from the grown boule are characterized for their scintillation properties like energy resolution, light yield, decay time and non-proportionality. Energy resolution (FWHM) at 662 keV of 5.1%, 3.4%, 4.0%, and 3.3% are obtained for samples of TGB, TLC, TCB, and TSI, respectively. Ce-doped TGB and TLC have single decay time components of 26 ns and 48 ns, respectively, while Eu-doped TCB and TSI have long decay times with primary decay constants of 571 ns and 630 ns? These compounds exhibit good proportionality behavior when compared to NaI:Tl and BGO.

This paper reports on the performance of the inorganic scintillator caesium hafnium chloride (CHC) under exposure to the mixed radiation field of an AmBe neutron source and coupled to a silicon photomultiplier (SiPM). The neutron response is determined using the pulse shape discrimination charge comparison technique which can clearly identify both the ( n , α ) and (c) reactions in the material. Figures of merit for the pulse shape discrimination are presented and the quenching of the different channels is assessed through comparison to Monte Carlo simulations.

An array of lithium indium diselenide (LISe) scintillators were investigated for application in neutron imaging. The sensors, varying in thickness and surface roughness, were tested using both reflective and anti-reflective mounting to an aluminum window. The spatial resolution of each LISe scintillator was calculated using the knife-edge test and a modulation transfer function analysis. It was found that the anti-reflective backing case yielded higher spatial resolutions by up to a factor of two over the reflective backing case despite a reduction in measured light yield by an average of 1.97. In most cases, the use of an anti-reflective backing resulted in a higher spatial resolution than the 50 μ m -thick ZnS(Cu): 6 LiF comparison scintillation screen. The effect of surface roughness was not directly correlated to measured light yield or observed spatial resolution, but weighting the reflective backing case by the random surface roughness revealed that a linear relationship exists between the fractional change (RB/ARB) of the two. Finally, the LISe scintillator array was used in neutron computed tomography to investigate the features of halyomorpha halys with the reflective and anti-reflective backing.

The internal contamination (radio-purity) of a cesium hafnium chloride (Cs 2 HfCl 6 ) crystal scintillator and its starting material (CsCl, HfCl 4 initial and after 3-fold static sublimation purification) was studied by HR-ICP-MS and with an ultra-low-background high purity germanium (ULB-HPGe) detector deep underground. This study was conducted for the purpose of assessing the feasibility of using CHC as a potential detector to the search for rare α decay occurring in Hafnium isotopes. Despite the low radio-purity of starting material, the resulting analysis concluded that the grown CHC crystal is free of nuclides of the U/Th natural decay chain. Only a limit was set on their activities to a few mBq/kg. However, the crystal was found to contain artificial and cosmogenic radionuclides: 137 Cs at 0.8 Bq/kg, 132 Cs at 25 mBq/kg, 134 Cs at 52 mBq/kg and 181 Hf at 14 mBq/kg.

For radiation detection, sensitivity, response time, and energy resolution are important. Scintillating nanoparticles, in principle, can have enhanced light output in comparison with their bulk materials due to quantum size confinement and increased overlap of electron and hole wave function. However, the aggregation and the loss of transparency at high loading into polymers are the challenging issues for practical applications. Here, for the first time, we report a new method to fabricate the blue-emitting nanocomposites with up to 30 wt% nanoparticle loading. First, the polymerizable surfactant coated La0.6Ce0.4F3 nanoparticles are synthesized, and then, they are loaded up to 30 wt% in a polystyrene matrix. The nanocomposites show an intense luminescence and a good transparency, performing much better than the commercial EJ-200 plastic scintillator. The gamma spectra acquired with the nanocomposite show a photopeak for the Co-57 isotope. The gamma spectra of Cs-137 show a full energy peak at around 622 keV, due to the escape of La and Ce Kα X-rays. The observation of the photopeaks is attributed to the enhanced photoelectric effect as a result of increased effective atomic number (Zeff). All these indicate that the high loaded nanocomposites are promising for radiation detection and nuclear material surveillance for homeland security.

The results of investigation into cesium hafnium chloride (Cs 2 HfCl 6 ) scintillating crystals as a promising detector to search for rare nuclear processes occurring in Hf isotopes is reported. The light output, quenching factor, and pulse-shape characteristics have been investigated at room temperature. The scintillation response of the crystal induced by α -particles and γ -quanta were studied to determine possibility of particle discrimination. Using the optimal filter method we obtained clear separation between signals with a factor of merit (FOM) = 9.3. This indicates that we are able to fully separate signals originating from α -particles and γ -quanta. Similar fruitful discrimination power was obtained by applying the mean time method (FOM = 7) and charge integration method (FOM = 7.5). The quenching factor for collimated 4 MeV α -particles is found to be 0.36, showing that α -particles generate more than a third of the light compared to γ -quanta at the same energy.

We report the generation of La2Zr2O7:5%Eu3+@Y2O3 (LZO5E@YO) core@shell crystalline inorganic-inorganic heterogeneous nanoparticles (NPs). The Y2O3 (YO) shell coating process based on a chemical sol-gel method led to the growth of a thin YO shell on the ordered pyrochlore La2Zr2O7:5%Eu3+ (LZO5E) core NPs. Photoluminescence (PL) analyses demonstrated a blue shift of 15 nm on charge transfer (CT) excitation band of the core@shell NPs from that of the core NPs. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) along x-ray diffraction (XRD), Fourier-transform Infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS) studies confirmed the formation of the thin YO layer over the LZO5E core NPs. The PL intensity of the LZO5E@YO core@shell NPs was enhanced by three fold compared to that of the LZO5E core NPs, and higher quantum yield (QY) was observed for the former compared to the original NPs by more than 70%. Higher radioluminescence (RL) emission was also observed for the core@shell NPs compared to the core NPs. Our ability of obtaining near-perfect core@shell heterostructure with enhanced luminescence performance opens the door for the development of efficient La2Zr2O7:5%Eu3+@Y2O3 NPs for both optical and x-ray scintillation applications.

Lithium containing chalcogenide single crystals have become very promising materials for photonics and radiation detection. Detection applications include nuclear nonproliferation, neutron science, and stellar investigations for the search of life. Synthesis and single crystal growth methods for lithium containing chalcogenide, specifically LiIn 1− x Ga x Se 2 , single crystals are discussed. This study elucidates the possibility of improving neutron detection by reducing the indium capture contribution; with the incorporation of the lithium-6 isotope, gallium substitution may overcome the neutron detection efficiency limitation of 6 LiInSe 2 due to appreciable neutron capture by the indium-115 isotope. As a figure of merit, the ternary parent compounds 6 LiInSe 2 and 6 LiGaSe 2 were included in this study. Quality crystals can be obtained utilizing the vertical Bridgman method to produce quaternary compounds with tunable optical properties. Quaternary crystals of varying quality depending on the gallium concentration, approximately 5×5×2 mm 3 or larger in volume, were harvested, analyzed and revealed tunable absorption characteristics between 2.8–3.4 eV.

This paper reports on successful growth and performance evaluation of two large diameter Cs2HfCl6 (CHC) and Cs2HfCl4Br2 (CHCB), both recently developed scintillator crystals. The discovery of Cs2HfCl6 (CHC) as a scintillator has lately generated much interest in this material and its family, which belongs to the K2PtCl6 cubic crystal structure. CHC is an intrinsic scintillator that is non-hygroscopic (slightly deliquescent, i.e., slightly moisture sensitive but does not deteriorate much when left in air), has no self-radioactivity, provides excellent energy resolution, and has excellent non-proportionality. CHC has a moderate density of 3.9 g/cm3 and an effective atomic number of 58. Reported in this paper are transparent crack-free single crystal CHC and CHCB boules of one inch in diameter, both grown using the vertical Bridgman method. Samples retrieved from the boules, sized ∅23 mm × 30 mm and ∅23 mm × 26 mm, respectively, are characterized for their optical and scintillation properties. Energy resolutions of 3.5% and 3.7% (FWHM) at 662 keV, respectively, are reported. Light yields of 23,000 ph/MeV and 20,000 ph/MeV have been calculated for the large diameter CHC and CHCB crystals, respectively. Results comparable to previously reported results for smaller crystals have been obtained. Studies on decay time, non-proportionality, as well as detector characterization are also reported.

This study addresses various aspects of diversity in high energy physics through a scientometric analysis of the literature spanning approximately three decades, from the LEP and Tevatron era to the LHC era. It concerns both fundamental physics and technological research related to high energy physics, and compares the evolution of some diversity parameters in this field with that in other research domains, such as nuclear physics and astrophysics. The data are collected from the Web of Science and are analyzed by means of econometric methods and techniques pertaining to statistical ecology.

Osteoporosis is a bone disease characterized by low Bone Mineral Density (BMD) leading to a reduction in bone quality.

In this paper the growth of a 16mm diameter Ce-doped Tl$_2$NaYCl$_6$ and its characterization as a gamma-ray detector are reported. With a 16 mm dia. x 8 mm cylindrical sample, energy resolution of 4.1% (FWHM) at 662 keV and light yield of 27,800ph/MeV are measured. Decay times of 91 ns (34%), 462 ns (52%), and 2.1 microseconds (15%) are calculated. The x-ray excited emission spectrum exhibits bands that are similar to other Tl-based elpasolite scintillators like Tl$_2$NaYCl$_6$:Ce., arXiv admin note: text overlap with arXiv:1911.03611

Lithium based chalcogenides have many uses in the nuclear science field. 6LiInSe2 (or LISe) has been researched extensively because of its ability to operate in both scintillator and semiconductor modes. This makes it useful in applications including nuclear material detection for national security, space applications, and medical imaging. In some applications growth and fabrication costs are of concern, as it takes upwards of 40 days to synthesize a charge, grow a crystal and fabricate a detector. Ceramics are a solution for this long route of preparation. This research shows that using a 6LiInSe2 ceramic instead of a single crystal significantly decreases the time required to make a detector. In the present work, ceramic wafers can be formed using a mechanical press equipped with a heating attachment. The resulting ceramic wafer performs very similar to a slow-growth single crystal when used in the scintillator mode.

Strontium iodide (SrI 2 ), an important new scintillator crystal having a high light yield and excellent energy resolution, was grown for the first time by the edge-defined film-fed (EFG) growth method. Using high purity starting materials and floating dies made of graphite, fused quartz or AlN, large cylindrical, planar or square cross-section single crystals (12–15 mm across and >7 cm long) were produced at growth rates up to 15 mm/h, significantly faster than the current Bridgman growth technology. Details on the equipment used to grow this deliquescent material and on its growth behavior are given along with some discussion of crystalline quality.

Strontium iodide doped with europium (SrI 2:Eu2+ ) is a new scintillator being developed for use in high-energy astrophysical detectors with excellent energy resolution. Nonproportionality is the primary limiting factor to improving its energy resolution, although the physics of nonproportionality is not yet fully understood. In the past few years, co-dopants have been used to alter nonproportionality. By irradiating a SrI 2:Eu2+ sample with a 2255 Ci 137Cs source, we explore both the crystal's potential for space-based applications in a radiation environment and this new method of altering nonproportionality. At ~6200 Gy irradiation, a drop of 7.8% at 700 nm and a drop of 14.1% at 450 nm were seen in the transmission spectrum. Nonproportionality was also reduced after irradiation, shifting from 87% to 101% of the theoretical light yield at 32.1 keV, while the 4.7 keV peak decreased 40% closer to its theoretical value. We propose a novel method of altering the nonproportionality of scintillators, using radiation-induced F-centers in place of co-dopants.

Semiconducting lithium indium diselenide, 6 LiInSe 2 or LISe, has promising characteristics for neutron detection applications. The 95% isotopic enrichment of 6 Li results in a highly efficient thermal neutron-sensitive material. In this study, we report on a proof-of-principle investigation of a semiconducting LISe pixel detector to demonstrate its potential as an efficient neutron imager. The LISe pixel detector had a 4×4 of pixels with a 550 µm pitch on a 5×5×0.56 mm 3 LISe substrate. An experimentally verified spatial resolution of 300 µm was observed utilizing a super-sampling technique.

Cerium-doped lutetium aluminum garnet (LuAG:Ce) and yttrium aluminum garnet (YAG:Ce) transparent ceramics of same dimension were fabricated and their optical and scintillation properties were studied. LuAG:Ce transparent ceramic showed higher light yield under UV and X-ray excitation with respect to YAG:Ce transparent ceramic. YAG:Ce transparent ceramic showed higher light yield under gamma excitation and better energy resolution, which could be due to the considerable amount of slower emission (38.5%) in LuAG:Ce as well as lower optical transparency with respect to YAG:Ce ceramic.

Lithium indium diselenide, 6 LiInSe 2 or LISe, is a newly developed neutron detection material that shows both semiconducting and scintillating properties. This paper reports on the performance of scintillating LISe crystals for its potential use as a converter screen for cold neutron imaging. The spatial resolution of LISe, determined using a 10% threshold of the Modulation Transfer Function (MTF), was found to not scale linearly with thickness. Crystals having a thickness of 450 µm or larger resulted in an average spatial resolution of 67 µm, and the thinner crystals exhibited an increase in spatial resolution down to the Nyquist frequency of the CCD. The highest measured spatial resolution of 198 µm thick LISe (27 µm) outperforms a commercial 50 µm thick ZnS(Cu): 6 LiF scintillation screen by more than a factor of three. For the LISe dimensions considered in this study, it was found that the light yield of LISe did not scale with its thickness. However, absorption measurements indicate that the 6 Li concentration is uniform and the neutron absorption efficiency of LISe as a function of thickness follows general nuclear theory. This suggests that the differences in apparent brightness observed for the LISe samples investigated may be due to a combination of secondary charged particle escape, scintillation light transport in the bulk and across the LISe-air interface, and variations in the activation of the scintillation mechanism. Finally, it was found that the presence of 115 In and its long-lived 116 In activation product did not result in ghosting (memory of past neutron exposure), demonstrating potential of LISe for imaging transient systems.

Cerium doped Barium Fluoride (BaF 2 Ce) transparent ceramic was fabricated and its luminescence and scintillation properties were studied. The photoluminescence shows the emission peaks at 310 nm and 323 nm and is related to the 5d-4f transitions in Ce 3+ ion. Photo peak at 511 keV and 1274 keV were obtained with BaF 2 Ce transparent ceramic for Na-22 radioisotopes. Energy resolution of 13.5% at 662 keV is calculated for the BaF 2 Ce transparent ceramic. Light yield of 5100 photons/MeV was recorded for BaF 2 Ce(0.2%) ceramic and is comparable to its single crystal counterpart. Scintillation decay time measurements shows fast component of 58 ns and a relatively slow component of 434 ns under 662 keV gamma excitation. The slower component in BaF 2 Ce(0.2%) ceramic is about 200 ns faster than the STE emission in BaF 2 host and is associated with the dipole-dipole energy transfer from the host matrix to Ce 3+ luminescence center.

The electronic structure and optical properties of the LiIn1–xGaxSe2 (x = 0, 0.25, 0.5, 0.75, 1) solid solution were studied by density functional theory (DFT) with pure functionals. The exchange-correlation is treated within the local density approximation (LDA) and generalized-gradient approximation (GGA). The electronic structures for each respective compound are discussed in detail. Calculations reveal that gallium incorporation can be used to tune the optical-electrical properties of the solid solution and correlates with the lattice parameter. The band gap trend of the LiIn1–xGaxSe2 system follows a nonlinear behavior between the LiInSe2 and LiGaSe2 ternary boundaries. The bowing parameter is estimated to be on the order of 0.1–0.3 eV at the Γ-point. Low-temperature optical absorption revealed a 30% change in the temperature dependence of the band gap for the intermediate compound LiIn0.6Ga0.4Se2 compared to ternary boundaries and suggests the heat capacity to be another control element through strain.

La 0.2 Y 1.8 O 3 is a new and promising scintillator which is based on the host material without doping. Here the time gated X-ray excited optical luminescence is measured by using the excitation energy below, above and at the La L 3 -edge. A relatively slow and broad emission with peak at 415 nm has been observed as the dominant emission. Also, a weak emission at 360 nm is observed at the fast window, associated with the recombination of trapped excitons in Y 2 O 3 host. The observations show that the broad emission at 415 nm is most likely due to the recombination of trapped excitons associated with the La 3+ doping into Y 2 O 3 sites.

Fast neutron imaging is a powerful tool to investigate elemental/isotopic compositions of objects, supporting both scientific studies as well as cargo scanning. Current neutron imaging systems are faced with challenges associated with timing, detection efficiency, and/or spatial resolution. Here, we report on the use of a semiconducting lithium indium diselenide neutron sensor coupled to a Timepix ASIC for fast neutron imaging. Using a 15 cm thick copper knife edge, the spatial resolution of the neutron imager was found to be 1.55 mm for 9 MeV neutrons. The experimental detection efficiency at 9 MeV was in general agreement with calculations.

Europium-doped TlSr2I5 (TSI), a new high light yield scintillator for gamma-ray detection, has been grown by the vertical Bridgman method. A 12mm and 16mm diameter boules of TSI is grown in a two-zone vertical furnaces. Samples extracted from the grown boule have been characterized for their scintillation properties. Energy resolution of < 3% (FWHM) at 662 keV and a gamma-ray light yield of approximately 54,000 Ph/MeV have been obtained. Decay times of 395 ns (89%) and 2.0 microseconds (11%) have been measured.

The re-discovery of Cs2HfCl6 (CHC) as a scintillator has lately generated much interest in this material and its family, which belongs to the K2PtCl6 cubic crystal structure [1] . CHC is an intrinsic scintillator that is non-hygroscopic, has no self-radioactivity, provides good energy resolution, and has good non-proportionality. In this paper we are reporting growth and scintillation properties of two new and Tl-, Hf- and Zr-based compounds of Tl2HfCl6 and Tl2ZrCl6, with physical densities of 5.1 g/cm3 and 4.5 g/cm3, respectively and effective atomic numbers (Zeff) of 71 and 69, respectively. Samples from successfully grown 16 mm diameter boules were cut, processed, and characterized for their scintillation and radiometric properties. Energy resolutions of 3.7% (FWHM) for THC and 3.4% for TZC (FWHM) at 662 keV are measured. Primary luminescence decay times of 1.1 μs and 2.3 μs, for Tl2HfCl6 and Tl2ZrCl6, respectively, as well as good proportionality for both materials have been observed.

This study addresses various characteristics of computing and nuclear technology research through a scientometric analysis of the literature related to the IEEE Nuclear Science Symposium, spanning approximately three decades from the LEP and Tevatron era to the LHC era. It analyzes technological research pertaining to computing and instrumentation in nuclear and particle physics, astrophysics and medical physics, and compares the evolution of some diversity parameters within intechnological and fundamental physics research in these fields.

The development of new solid-state laser materials for mid-infrared (mid-IR) laser sources continues to be interest for potential applications in remote sensing of bio-chemical agents, IR countermeasures, and IR spectroscopy. Fluorescent materials based on Ho3+ doped crystals and glasses with narrow phonon spectra cover a wide wavelength range between ~1-4 µm. In this work, spectroscopic characterization on infrared emission properties of trivalent holmium (Ho3+) doped potassium lanthanum chloride (K2LaCl5) were explored. K2LaCl5 is slightly hygroscopic but possesses a maximum phonon energy of 235 cm-1. The low maximum phonon energy of K2LaCl5 leads to low non-radiative decay rates and efficient IR fluorescence. The studied Ho3+ doped K2LaCl5 material was grown by Bridgman technique. Using ~900 nm excitation, IR emissions centered at ~1.66, ~1.995, and ~3.90 µm were observed from Ho:K2LaCl5 corresponding to the 5I5-->5I7, 5I7-->5I8, and 5I5-->5I6 transitions of Ho3+ ions. Spectroscopic results and data modeling including the Stark level energies, Judd-Ofelt analysis, transitions cross-sections, and fluorescence dynamics will be presented at the conference.

6LiInSe2 has gained attention recently as a semiconducting thermal neutron detector. As presented herein, the chalcogenide compound semiconductor also detects incident neutrons via scintillation, making 6LiInSe2 the only lithium containing semiconductor to respond to neutrons via both detection mechanisms. Both yellow and red crystals, which appear in the literature, were investigated. Only the yellow crystal responded favorably to ionizing radiation, similar to the semiconducting operation utilizing electrodes. The obtained light yield for yellow crystals is 4400 photons/MeV, referenced to Bi4Ge3O12 (BGO).The estimated thermal neutron light yield was 21,000 photons/thermal neutron. The two measured decay time components were found to be 31±1 ns (49%) and 143±9 ns (51%).This crystal provides efficient, robust detection of neutrons via scintillation with respectable light yield and rapid response, enabling its use for a broad array of neutron detection applications.

The performance of Cd1−x Zn x Te (CZT) materials for room-temperature gamma/x-ray radiation detection continues to improve in terms of material quality and detector design. In our prior publications, we investigated the use of multiple wavelengths of light (in the visible and infrared) to target charge carriers at various trap energies and physical positions throughout crystals. Light exposure significantly alters the charge mobility and improves carrier collection at the anode contact. This study presents an investigation of material performance as a radiation detector during such illumination. The decrease in charge trapping and increase in charge collection due to a higher probability of free electron release from traps contributed to an increase in the resolution-based performance of the detector through controlled illumination. We investigated the performance improvement of CZT crystals with previously known levels of intrinsic defects and secondary phases, at various voltages, light-emitting diode (LED) light wavelengths, and shaping times. Although our setup was clearly not optimized for radiation detector performance, it demonstrated substantial resolution improvements (based on full-width at half-maximum using 662-keV gamma rays from 137Cs upon illumination with 950-nm light) of 16% to 38% in comparison with unilluminated CZT under similar conditions. This manuscript includes discussion of the electrooptic behavior and its effect on performance. Additional testing and fabrication of a detector that incorporates such LED light optimization could lead to improved performance with existing detector-grade materials.

We grew CdTe x Se 1− x crystals with nominal Se concentrations of 5%, 7%, and 10% by the vertical Bridgman technique, and evaluated their compositional homogeneity and structural quality at the NSLS’ X-ray fluorescence and white beam X-ray topography beam lines. Both X-ray fluorescence and photoluminescence mapping revealed very high compositional homogeneity of the CdTe x Se 1− x crystals. We noted that those crystals with higher concentrations of Se were more prone to twinning than those with a lower content. The crystals were fairly free from strains and contained low concentrations of sub-grain boundaries and their networks.

Intrinsic materials can offer advantages over doped materials for some important applications. The doped material might suffer from non-uniform distribution of the dopant, such as fine-scale striations and larger scale segregation, which might affect the overall device response, especially for large-volume detectors such as those in demand for homeland security applications for gamma spectroscopy. Cs2LiCeCl6 (CLCC), being an intrinsic scintillator, can be grown in large volume to produce large detectors with good performance, provided the crystals are free from unwanted scattering centers. CLCC belongs to the elpasolite family and the structure is cubic, so large-volume ingots can be grown without the strains resulting from anisotropic thermal expansion coefficients. In this presentation, we will discuss extensive material characterization and device response of CLCC for gamma and thermal neutron detector applications.