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Pr3+ doped high density germanate glasses were prepared by the melt-quenching method. The physical and luminescent properties were investigated. The glass containing BaF 2 represented maximum phonon energy of 810 cm−1, and the glass density was greater than 6 g/cm3. The glass exhibited good radiation resistance under 2 h of X-ray irradiation. Intense blue, green emissions and weak red emissions were observed when the glass was excited by X-ray, and the blue fluorescence lifetimes were in the range of 9.15–12.59 μs The results show that Pr3+ doped germanate glass could be a potential scintillating material in the field of X-ray detection for fast events. [ABSTRACT FROM AUTHOR]

Ce3+-doped dense glasses with high light yield (LY) are promising scintillators for use in high-energy particle physics research and radiation sensors for high-energy X- and γ- ray detection. In this work, Ce3+-doped (60-x)SiO 2 -xBaF 2 -20Al 2 O 3 -20Gd 2 O 3 oxyfluoride glasses have been prepared under a CO reducing atmosphere. Substitution of SiO 2 by BaF 2 has been made to increase the density, and the effects on luminescence and scintillation properties have been investigated. The amorphous nature of the prepared glass is confirmed by the XRD profile showing an absence of any diffraction peaks. The broad photoluminescence (PL) emission band of the Ce3+ 5d–4f transition in the 330–580 nm range is observed peaking around 385 nm and the PL decay is governed in the range of 46–53 ns decay time. The 10 mol% BaF 2 glass with density of 4.54 g/cm3 shows the highest LY value of 1590 photons/MeV and energy resolution of 16.5% in the pulse height spectrum of 662 keV γ rays, and the LY of 141 photons/MeV and energy resolution of 21.7% in the pulse height spectrum of 5.5 MeV α particles. • Ce3+-doped (60-x)SiO 2 -xBaF 2 -20Al 2 O 3 -20Gd 2 O 3 (x = 0–20) glasses were prepared under CO atmosphere. • XRD pattern confirms an amorphous nature of the prepared glass. • Gd3+ to Ce3+ energy transfer was observed in the prepared glasses. • Light yield of 1590 photons/MeV at 662 keV γ rays was obtained for 10 mol% BaF 2 containing glass. • Energy transport efficiency in scintillation process increases with increasing BaF 2 content. [ABSTRACT FROM AUTHOR]

The physical, electronic and optical properties of Barium halides have been investigated by both experimental and theoretical approaches. The First Principle electronic structure and optical properties were calculated by DFT formalism using Full Potential Linearized Augmented Plane Wave plus local orbitals (FP-LAPW + lo) implementing different appropriate exchange-correlation functionals in WIEN2k code at various applied volumetric pressure up to 50 GPa. All the properties of these halides were analyzed and compared using their cation-anion radii ratio and ionicity. Except BaF 2 , the other three halides show ionic to covalent transformation at 50 GPa applied pressure. Both experimental and theoretical results compare reasonably well. The scintillation efficiency of these three halides was found to be directly proportional to their ionicity or band gap. • Study of physical, electronic and optical properties of Barium halides by experimental and theoretical approaches. • All the properties of the halides were analyzed and compared using their cation-anion radii ratio and ionicity. • The direct type band gap of the three halides decrease with pressure at least till 50 GPa. • Observed ionic to covalent transformation at 50 GPa applied pressure. • Experimental and theoretical results match reasonably well. [ABSTRACT FROM AUTHOR]

A systematic study is conducted to understand the digital time of flight (TOF) response for a pair of fast scintillator detectors; BaF 2 –LaBr 3 , BaF 2 -BC501A, and LaBr 3 -BC501A respectively. Coincidence signals from each detector pair, irradiated by 22Na source, are acquired by LeCroy HDO5000A digital oscilloscope. While operating the oscilloscope at 2.5 giga samples per second (GSPS) and 500 mega samples per second (MSPS) of sampling rates, over 10 k coincidence signals were collected for each pair of detectors. Data at different sampling rates; 1.66 GSPS, 1.25 GSPS, 833 MSPS, 625 MSPS, 333 MSPS, and 250 MSPS were generated by down-sampling method. Using anode signal, the photon arrival time marker is determined by digital constant fraction (DCF) algorithm for each detector pair on event-by-event basis. For a given rate, the algorithm is optimized at various delay and fraction values to get the minimum TOF dispersion. Mentioned pairs reveals the TOF resolution (FWHM) as; 0.58 ns, 0.79 ns, 0.907 ns and 0.53 ns, 0.94 ns, 1.08 ns at 250 MSPS and 2.5 GSPS respectively. While analysing the events, a saturation in the TOF width is observed from 500 MSPS onward. The saturated dispersion values for the aforementioned pairs are found to be 0.53 ns, 0.94 ns, and 1 ns respectively. Effect is being understood by calculating the optimum DCF transition region distribution for BC501A and LaBr 3 detectors, reveals a constant curvature profile at different rates. To further explain the saturation effect on computational ground, a simple pulse fitting approach is adopted using Landau distribution. Event-by-Event processing of fitted pulses followed by TOF resolution calculation reproduces the experimental numbers. [ABSTRACT FROM AUTHOR]

Mesoporous crystalline BaF 2 nanopowder with a specific surface area of up to 34.8 m2/g was produced by a pulsed electron beam through the evaporation of targets of micro-sized BaF 2 powder with optical purity (S red = 0.38 m2/g). The texture and thermal features of the BaF 2 nanopowder (before and after annealing in air at a temperature of 200 °C) and some properties of compacts made of the BaF 2 nanopowder by magnetic-pulse compaction and static pressing were studied. Glassy, opaque, and black compacts, which are promising materials for use as scintillators and dosimeters, were produced by magnetic-pulse compaction in a vacuum at a temperature of about 425 °C. It was found that heating up to 425 °C is sufficient for removing defects in nanopowders. The effect of pressing methods on the pulsed cathodoluminescence and photoluminescence spectra of the compacts was studied. Luminescent properties were found to depend on pressing technology. It was also determined that surface color centers, the number of which decreases during heating, are responsible for the pulsed cathodoluminescence band near ∼560 nm. [ABSTRACT FROM AUTHOR]

The short-wavelength sub-nanosecond luminescence in BaF 2 material, discovered in the early 80s, gave a new direction to research into fast scintillators and phosphors. In contrast to 'typical' luminescence occurring within the forbidden band gap, the new type of emission was due to transitions between the upper core and valence bands. Thus it was named core-valence luminescence (CVL); the terms cross-luminescence and Auger-free luminescence have also been used. Given its unusual nature, this new luminescence process has attracted considerable interest in the field of condensed matter physics. During the sequent decades (till the end of the previous century) CVL has been experimentally observed in several dozen compounds and the conditions for detecting CVL have been established. Interest in this kind of luminescence increased in recent years due to the emergence of new methods of crystal synthesis, the development of high-speed solid-state photodetectors, and the construction of unique modern set-ups using synchrotron radiation. This paper analyzes the numerous studies of CVL, obtained mainly over the past decade. Experimental and theoretical data on this topic are considered in detail. Special attention is given to new results on scintillation characteristics of BaF 2 in the form of single crystals, ceramics, nanoparticles, and composites. The features of CVL in binary and ternary compounds are discussed. Some Cs- and Ba-based ternary halides show relatively high light yields and represent promising fast scintillators. The prospects of using materials with CVL as fast scintillators for time-of-flight positron emission tomography and other applications are deliberated. • Overview of recent theoretical and experimental findings on Core Valence luminescence. • Most attractive CVL crystals for ultrafast scintillator applications analyzed. • Prospects for future studies and underexplored CVL materials listed. [ABSTRACT FROM AUTHOR]

Due to their reported fast decay times, Cs 2 ZnCl 4 and Cs 3 ZnCl 5 are promising candidates for detection of gamma rays and X-rays in high count rate and fast timing applications. In this work, we show that single crystals with better optical quality than previously demonstrated – and larger in size – can be grown via the vertical Bridgman method. Highly transparent Ø7 mm crystals of undoped Cs 2 ZnCl 4 and Cs 3 ZnCl 5 are grown and measured to have light yields surpassing those previously reported, achieving 1980 ± 100 ph/MeV and 1460 ± 70 ph/MeV at 662 keV – a 55% and 232% improvement, respectively. We observe single-component scintillation decay times for both Cs 2 ZnCl 4 (1.66 ns) and Cs 3 ZnCl 5 (0.82 ns) and radioluminescence emission with maximum intensity at ∼290 nm. Scalability of these materials is also evaluated based on growth of Ø22 mm crystals. Minimal cracking is observed, and the fast decay times are maintained at this size. Coincidence time resolution of 3 × 3 × 5 mm3 and 7 × 7 × 10 mm3 pixels cut from Ø22 mm Cs 2 ZnCl 4 are measured to be 148 ± 1 ps FWHM and 175 ± 1 ps FWHM, respectively. The improved performance and ability to be fabricated in large sizes now place Cs 2 ZnCl 4 and Cs 3 ZnCl 5 on the map as potential contenders for radiation detection applications where BaF 2 – the most commonly used ultrafast inorganic scintillator – is typically considered. • Single crystals of Cs 2 ZnCl 4 and Cs 3 ZnCl 5 were grown by the vertical Bridgman method. • Cs 2 ZnCl 4 had a scintillation decay time of 1.66 ns and light yield of 1980 ph/MeV at 662 keV. • Cs 3 ZnCl 5 had a scintillation decay time of 0.82 ns and light yield of 1460 ph/MeV at 662 keV. • The coincidence time resolution of Cs 2 ZnCl 4 was measured to be as good as 136 ± 2 ps FWHM. [ABSTRACT FROM AUTHOR]

The paper describes the effect of high effective atomic number (Z eff) materials loading in polystyrene based thin-film Plastic Scintillators (PS). Thin plastic scintillator sheets have been loaded with high Z materials such as BaFBr:Eu, Gd 2 O 2 S:Tb, Gd 2 O 3 , BaF 2 , CeO 2 and Bi 2 O 3. Polystyrene based PS sheets of 250 ± 50 μ m thickness have been prepared by dissolving predetermined quantities of polystyrene, 2,5-Diphenyloxazole (PPO) and 1,4-bis(5-phenyl-2-oxazolyl) benzene (POPOP) in the p-xylene solvent. High Z eff material powders of 23 μ m size are mixed in the plastic scintillator solution and coated over the cellulose acetate-based transparency sheets. The dried films are peeled off, and their photoluminescence, radioluminescence, pulse height spectrum and response to alpha, beta, gamma and neutron radiations are studied by adopting suitable methods. The high Z eff materials for loading in PS are selected based on their physical properties like refractive index, bandgap, Z eff , Photoluminescence (PL) properties. While the composite scintillator loaded with 14.3 wt% of BaFBr:Eu2+ showed significant increase compare to other high Z materials. The loading concentration has been optimized as 14.3 wt% from the BaFBr:Eu2+ studies. Most of the composite scintillators showed improvement in radioluminescence and pulse height spectra for different radiations. • Polystyrene based thin plastic scintillator have been prepared by solvent-based fabrication method. • Thin composite plastic scintillator are studied with high Z eff material loading. • High Z eff material loaded composite scintillators showed enhanced response to radiation. • BaFBr:Eu loaded composite PS has shown the best promising result. [ABSTRACT FROM AUTHOR]

We describe here an efficient machine-learning based approach for the optimization of parameters used for extracting the arrival time of waveforms, in particular those generated by the detection of 511 keV annihilation γ -rays by a 60 cm3 coaxial high purity germanium detector (HPGe). The method utilizes a type of artificial neural network (ANN) called a self-organizing map (SOM) to cluster the HPGe waveforms based on the shape of their rising edges. The optimal timing parameters for HPGe waveforms belonging to a particular cluster are found by minimizing the time difference between the HPGe signal and a signal produced by a BaF 2 scintillation detector. Upon applying these variable timing parameters to the HPGe signals, we achieved a γ – γ coincidence timing resolution of ∼ 4.3 ns at the 511 keV photopeak (defined as 511 ± 50 keV) and a timing resolution of ∼ 6.5 ns for the entire γ -ray spectrum—without rejecting any valid pulses. This timing resolution approaches the best obtained by analog nuclear electronics, without the corresponding complexities of analog optimization procedures. We further demonstrate the universality and efficacy of the machine learning approach by applying the method to the generation of secondary electron time-of-flight spectra following the implantation of energetic positrons on a sample. [ABSTRACT FROM AUTHOR]

Fast scintillation materials based on ternary halide mixed crystals, Cs(Ca 1−x Mg x)Cl 3 , were synthesized. The luminescence at the defects or impurity sites within the band-gap excitation were observed. Upon X-ray excitation, bands corresponding to the intrinsic Auger-free luminescence (AFL) for CsCaCl 3 and CsMgCl 3 were observed, and the wavelength of the mixed crystals bands was similar to that of CsCaCl 3. Cs(Ca 1−x Mg x)Cl 3 exhibited a short decay time, which is typical for AFL in CsCl-based compounds, and CsMgCl 3 exhibited the shortest decay time of 1.1 ns and the smallest proportion of the first component (65%). On the other hand, CsCaCl 3 exhibited the longest decay time constant of 2.0 ns and the largest proportion of the first component (92%). The light yields of the fast components for CsCaCl 3 were larger than that of BaF 2 , whereas the light yields of the mixed crystals were lower than those of CsCaCl 3 and CsMgCl 3. The proportion of Cs/Mg in the mixed crystals was expected to affect the decay time constants and light yields, but changes in these properties did not vary much with Cs/Mg ratio. • Auger-free luminescence band was clearly observed under X-ray excitation for Cs(Ca 1−x Mg x)Cl 3. • Cs(Ca 1−x Mg x)Cl 3 exhibited short scintillation decay time constants of less than 2.0 ns. • The fast component light yields of CsCaCl 3 was larger than that of BaF 2 [ABSTRACT FROM AUTHOR]

Scintillators form the chief device for radiation detection, and the study of their characteristics and their related theories is very significant. Specifically, the nonlinear behavior of scintillators under high excitation density has been closely studied owing to its direct influence on the measurements of radiation. We propose a new method to calibrate the nonlinearity of scintillators based on the electron pulse generated by a linear electron accelerator. The nonlinear light yield of several commonly used scintillators versus fluence of 70 MeV electrons in a 10 ps pulse has been measured by adjusting the charge of electron pulses, and the deposition energy threshold is also simulated and calculated. The results show that the deposition energy threshold for the occurrence of 5% nonlinearity is highest for two types of oxide scintillators, viz. LSO and PbWO 4 , followed by fluoride scintillators, viz. BaF 2 and CeF 3 , and the threshold for a plastic scintillator EJ232 is lowest. • The nonlinear light yield of several common scintillators versus fluence of 70 MeV electrons has been first measured. • The deposition energy threshold of several common scintillators excited by 70 MeV electron pulses has been calculated. • We explained our results with known physical mechanism, which can be a reference and comparison for related research. [ABSTRACT FROM AUTHOR]