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The aim of this study was to experimentally assess the luminescence efficiency of a cerium fluoride (CeF3) inorganic scintillator in crystal form as a possible alternative to high-luminescence but hygroscopic cerium bromide (CeBr3). The experiments were performed under typical diagnostic radiology X-rays (50–140 kVp). Parameters such as the crystal's absolute luminescence efficiency (AE) and the spectral matching with a series of optical detectors were examined. The replacement of bromine with fluorine appeared to drastically reduce the AE of CeF3 compared to CeBr3 and other commercially available inorganic scintillators such as bismuth germanate (Bi4Ge3O12-BGO). CeF3 reaches a maximum luminescence efficiency value of only 0.8334 efficiency units (EUs) at 140 kVp, whereas the corresponding values for CeBr3 and BGO were 29.49 and 3.41, respectively. Furthermore, the emission maximum (at around 313 nm) moved towards the lower part of the visible spectrum, making CeF3 suitable for spectral coupling with various photocathodes and photomultipliers applied in nuclear medicine detectors, but completely unsuitable for spectral matching with CCDs and CMOS. The obtained luminescence efficiency results denote that CeF3 cannot be applied in medical imaging applications covering the range 50–140 kVp; however, examination of its luminescence output in the nuclear medicine energy range (~70 to 511 keV) could reveal possible applicability in these modalities. [ABSTRACT FROM AUTHOR]

This article briefs the basic characteristics, relative merits, and limitations of inorganic nanoscintillators that based on scintillation mechanism and associative physical phenomena. The structure features of different physical forms of nanoscintillator, as particle, film, ceramic and glass, and the applications of nanotechnology in scintillator are discussed. The critical factors affecting scintillation process under nanoscale are analyzed, and the related behaviors and mechanisms are explained from structure effect, surface effect and confined effect. The development of inorganic nanoscintillator in ionizing radiation detection is reviewed, and the application prospect is forecasted. [ABSTRACT FROM AUTHOR]

Radiodiagnostic technologies are powerful tools for preventing diseases and monitoring the condition of patients. Medicine and sectors such as industry and research all use this inspection methodology. This field demands innovative and more sophisticated systems and materials for improving resolution and sensitivity, leading to a faster, reliable, and safe diagnosis. In this study, a large characterization of gadolinium oxysulfide (Gd2O2S) scintillator screens for imaging applications has been carried out. Seven scintillator samples were doped with praseodymium (Pr3+), terbium (Tb3+) activators and co-doped with praseodymium, cerium, and fluorine (Gd2O2S:Pr,Ce,F). The sample screens were prepared in the laboratory in the form of high packing density screens, following the methodology used in screen sample preparation in infrared spectroscopy and luminescence. Parameters such as quantum detection efficiency (QDE), energy absorption efficiency (EAE), and absolute luminescence efficiency (ALE) were evaluated. In parallel, a structural characterization was performed, via XRD and SEM analysis, for quality control purposes as well as for correlation with optical properties. Spatial resolution properties were experimentally evaluated via the Modulation Transfer Function. Results were compared with published data about Gd2O2S:Pr,Ce,F screens produced with a standard method of a sedimentation technique. In particular, the ALE rose with the X-ray tube voltage up to 100 kVp, while among the different dopants, Gd2O2S:Pr exhibited the highest ALE value. When comparing screens with different thicknesses, a linear trend for the ALE value was not observed; the highest ALE value was measured for the 0.57 mm thick Gd2O2S:Pr,Ce,F sample, while the best MTF values were found in the thinner Gd2O2S:Pr,Ce,F screen with 0.38 mm thickness. [ABSTRACT FROM AUTHOR]

Abstract This article presents a new perspective on the development of inorganic scintillator-based fiber dosimeters (IOSFDs) for medical radiotherapy dosimetry (RTD) focusing on real-time in vivo dosimetry. The scintillator-based optical fiber dosimeters (SFD) are compact, free of electromagnetic interference, radiation-resistant, and robust. They have shown great potential for real-time in vivo RTD. Compared with organic scintillators (OSs), inorganic scintillators (IOSs) have larger X-ray absorption and higher light output. Variable IOSs with maximum emission peaks in the red part of the spectrum offer convenient stem effect removal. This article outlines the main advantages and disadvantages of utilizing IOSs for SFD fabrication. IOSFDs with different configurations are presented, and their use for dosimetry in X-ray RT, brachytherapy (BT), proton therapy (PT), and boron neutron capture therapy (BNCT) is reviewed. Challenges including the percentage depth dose (PDD) deviation from the standard ion chamber (IC) measurement, the angular dependence, and the Cherenkov effect are discussed in detail; methods to overcome these problems are also presented.

The paper presents a comparison of three neutrons identifying methods in scintillators based on ZnS with 6Li and 10B: charge integration method, pulse gradient analysis, and simplified digital charge collection. A quality factor is used for comparison. It is calculated by the distribution of distances from the event position to the discrimination curve. It is shown that the charge integration method is observed to provide the best discrimination performance in this research. [ABSTRACT FROM AUTHOR]

Purpose: High‐dose rate (HDR) and pulsed‐dose rate (PDR) brachytherapy would benefit from an independent treatment verification system to monitor treatment delivery and to detect errors in real time. This paper characterizes and provides an uncertainty budget for a detector based on a fiber‐coupled high‐Z inorganic scintillator capable of performing time‐resolved in vivo dosimetry during HDR and PDR brachytherapy. Method: The detector was composed of a detector probe and an optical reader. The detector probe consisted of either a 0.5 × 0.4 × 0.4 mm3 (HDR) or a 1.0 × 0.4 × 0.4 mm3 (PDR) cuboid ZnSe:O crystal glued onto an optical‐fiber cable. The outer diameter of the detector probes was 1 mm, and fit inside standard brachytherapy catheters. The signal from the detector probe was read out at 20 Hz by a photodiode and a data acquisition device inside the optical reader. In order to construct an uncertainty budget for the detector, six characteristics were determined: (1) temperature dependence of the detector probe, (2) energy dependence as a function of the probe‐to‐source position in 2D (determined with 2 mm resolution using a robotic arm), (3) the signal‐to‐noise ratio (SNR), (4) short‐term stability over 8 h, and (5) long‐term stability of three optical readers and four probes used for in vivo monitoring in HDR and PDR treatments over 21 months (196 treatments and 189 detector calibrations, and (6) dose‐rate dependence. Results: The total uncertainty of the detector at a 20 mm probe‐to‐source distance was < 5.1% and < 5.8% for the HDR and PDR versions, respectively. Regarding the above characteristics, (1) the sensitivity of the detector decreased by an average of 1.4%/°C for detector probe temperatures varying from 22 to 37°C; (2) the energy dependence of the detector was nonlinear and depended on both probe‐to‐source distance and the angle between the probe and the brachytherapy source; (3) the median SNRs were 187 and 34 at a 20 mm probe‐to‐source distance for the HDR and PDR versions, respectively (corresponding median source activities of 4.8 and 0.56 Ci, respectively); (4) the detector response varied by 0.6% in 11 identical irradiations over 8 h; (5) the sensitivity of the four detector probes decreased systematically by 0–1.2%/100 Gy of dose delivered to the probes, and random fluctuations of 4.8% in the sensitivity were observed for the three probes used in PDR and 1.9% for the probe used in HDR; and (6) the detector response was linear with dose rate. Conclusion: ZnSe:O detectors can be used effectively for in vivo dosimetry and with high accuracy for HDR and PDR brachytherapy applications. [ABSTRACT FROM AUTHOR]

Scintillation-based fiber dosimeters are a powerful tool for minimally invasive localized real-time monitoring of the dose rate during Low Dose Rate (LDR) and High Dose Rate (HDR) brachytherapy (BT). This paper presents the design, fabrication, and characterization of such dosimeters, consisting of scintillating sensor tips attached to polymer optical fiber (POF). The sensor tips consist of inorganic scintillators, i.e. Gd 2 O 2 S:Tb for LDR-BT, and Y 2 O 3 :Eu+4YVO 4 :Eu for HDR-BT, dispersed in a polymer host. The shape and size of the tips are optimized using non-sequential ray tracing simulations towards maximizing the collection and coupling of the scintillation signal into the POF. They are then manufactured by means of a custom moulding process implemented on a commercial hot embossing machine, paving the way towards series production. Dosimetry experiments in water phantoms show that both the HDR-BT and LDR-BT sensors feature good consistency in the magnitude of the average photon count rate and that the photon count rate signal is not significantly affected by variations in sensor tip composition and geometry. Whilst individual calibration remains necessary, the proposed dosimeters show great potential for in-vivo dosimetry for brachytherapy. [ABSTRACT FROM AUTHOR]

There is a global trend to increase the light yield of CsI scintillators used in neutrino and dark matter detection by operating undoped crystals at cryogenic temperatures. However, high light yield alone is not sufficient to guarantee a low-energy threshold. The response of undoped crystals to nuclear recoils at cryogenic temperatures is equally important. A liquid nitrogen-based cryostat was developed to measure the nuclear quenching factor of a small undoped CsI crystal using monoenergetic neutron beams at the Triangle Universities Nuclear Laboratory (TUNL). To minimize neutron scattering, high-Z materials were reduced around the crystal. The structure and performance of the cryostat are described in detail. Using this cryostat, a system light yield of 33. 4 ± 2. 0 photoelectrons per keV electron-equivalent (PE/keV ee) was observed at 5.9 keV ee , enabling the measurement of nuclear quenching factors at very low energies. The results of the quenching factor measurement will be reported in a subsequent paper. Non-negligible negative overshoot was observed in the tails of the observed light pulses. The origin of this issue and the correction procedure are described in detail. This information may be useful for others who encounter similar technical challenges. [ABSTRACT FROM AUTHOR]

Crystal scintillators and in particular inorganic scintillators play an important role in the investigation of Dark Matter (DM) and other rare processes. The investigation of a DM signature, as the annual modulation, or the directionality technique requires the use of highly radiopure detectors able to explore the very low energy region maintaining a high stability of the running conditions. In this paper, the cases of NaI(Tl), ZnWO4 and SrI2(Eu) crystal scintillators are described in the framework of our activities at the Gran Sasso National Laboratory of the INFN. Their role, the obtained results in DM investigation, as well as their potential and perspectives for the future are reviewed. [ABSTRACT FROM AUTHOR]

Radiodiagnostic technologies are powerful tools for preventing diseases and monitoring the condition of patients. Medicine and sectors such as industry and research all use this inspection methodology. This field demands innovative and more sophisticated systems and materials for improving resolution and sensitivity, leading to a faster, reliable, and safe diagnosis. In this study, a large characterization of gadolinium oxysulfide (Gd2O2S) scintillator screens for imaging applications has been carried out. Seven scintillator samples were doped with praseodymium (Pr3+), terbium (Tb3+) activators and co-doped with praseodymium, cerium, and fluorine (Gd2O2S:Pr,Ce,F). The sample screens were prepared in the laboratory in the form of high packing density screens, following the methodology used in screen sample preparation in infrared spectroscopy and luminescence. Parameters such as quantum detection efficiency (QDE), energy absorption efficiency (EAE), and absolute luminescence efficiency (ALE) were evaluated. In parallel, a structural characterization was performed, via XRD and SEM analysis, for quality control purposes as well as for correlation with optical properties. Spatial resolution properties were experimentally evaluated via the Modulation Transfer Function. Results were compared with published data about Gd2O2S:Pr,Ce,F screens produced with a standard method of a sedimentation technique. In particular, the ALE rose with the X-ray tube voltage up to 100 kVp, while among the different dopants, Gd2O2S:Pr exhibited the highest ALE value. When comparing screens with different thicknesses, a linear trend for the ALE value was not observed; the highest ALE value was measured for the 0.57 mm thick Gd2O2S:Pr,Ce,F sample, while the best MTF values were found in the thinner Gd2O2S:Pr,Ce,F screen with 0.38 mm thickness.

To probe the nature of the physical processes responsible for the nonlinear scintillation light yield of inorganic scintillators, we have combined an ab initio based Monte Carlo code for calculating the microscopic spatial distributions of electron-hole pairs with an atomistic kinetic Monte Carlo (KMC) model of energy-transfer processes. In the present study, we focus on evaluating the contribution of an annihilation mechanism between self-trapped excitons (STE) to the scintillation response of pure CsI and Ce-doped LaBr3. A KMC model of scintillation mechanisms in pure CsI was developed previously and we introduce in this publication a similar model for Ce-doped LaBr3. We show that the KMC scintillation model is able to reproduce both the kinetics and efficiency of the scintillation process in Ce-doped LaBr3. Relative light output curves were generated at several temperatures for both scintillators from simulations carried out at incident γ-ray energies of 2, 5, 10, 20, 100, and 400 keV. These simulations suggest that STE-STE annihilation can account for the initial rise in relative light yield with increasing incident energy for both types of materials. This is due to the fact that the proportion of high-density regions decreases as the incident energy increases, thus reducing the likelihood for STE-STE encounter. In addition, the simulations clearly show a lack of temperature dependence of the relative light output, in agreement with a majority of experimental work on the temperature dependence of nonlinearity in inorganic scintillators. The collective modeling tool is a fundamental advance over phenomenological modeling approaches because it has its foundation in first-principles physics of scintillation. While the KMC simulations here are parametrized largely by empirically derived rate constants, this study suggests that combining ab initio based electron-hole pair distributions with ab initio derived rate constants for a select set of energy transfer processes is in principle sufficient to detach this tool from experiment entirely, yielding a holistic predictive simulation framework useful for exploring a wide range of scintillator performance characteristics. [ABSTRACT FROM AUTHOR]

This article presents the measurements of the luminescence and scintillation under X-ray of undoped, Si-doped, and Si, B codoped gallium-arsenide (GaAs) samples at cryogenic temperature over a wide infrared (IR) region using Si and InGaAs photodetectors. The undoped GaAs has a narrow emission band at 838 nm (1.48 eV) and a low light output of about 2 ph/keV. The GaAs:Si has three broad luminescence bands at 830 nm (1.49 eV), 1070 nm (1.16 eV), and 1335 nm (0.93 eV) and a light output of about 67 ph/keV. GaAs:(Si, B) has four luminescence bands at 860 nm (1.44 eV), 930 nm (1.33 eV), 1070 nm (1.16 eV), and 1335 nm (0.93 eV) with a light yield of approximately 119 ph/keV. With advances in photodetection, GaAs promises to be a useful cryogenic scintillator for the detection of electron recoils from MeV/c2 dark matter. [ABSTRACT FROM AUTHOR]

GEANT4-based Monte Carlo simulation has been performed for a $2''\phi \times 2''$ L cylindrical CsI(Tl) single-crystal scintillator. The simulation includes transport of incident gamma photons as well as generation and transport of optical photons in the crystal up to the coupled photodetector. An optical photon detection spectrum was generated from the number of optical photons detected at the photodetector surface per incident primary gamma photon. This spectrum is equivalent to a conventional pulse-height spectrum, apart from the fact that its abscissa is only proportional, but not equal, to the actual pulse height (volts). This has an energy resolution of about 6.5% at 662 keV arising from the light generation and transport statistics. This spectrum was compared with an experimentally recorded pulse-height spectrum (after the abscissa of both the spectra were converted to energy scale) from a gamma spectrometer based on an in-house grown $2''\phi \times 2''$ L cylindrical CsI(Tl) crystal, thereby validating the simulation code. The effects of variation of scintillation and optical properties as well as physical and surface parameters on the simulated spectrum were subsequently studied in order to identify the important parameters. The quantum efficiency of the photodetector and the matching of its spectral response with the emission spectrum of the scintillator, reflectivity of the scintillator coating material, and the absolute light yield of the scintillator were identified as the parameters that influence the pulse-height spectrum in the most dominant way. Results of simulation presented in this paper are likely to facilitate the optimization of future detector setups. [ABSTRACT FROM AUTHOR]

Lead Tungstate (PbWO4, PWO) has become presently the most commonly used scintillator material for electromagnetic calorimetry in medium and high-energy physics. There exists substantial demand for future calorimeters such as the completion of the PANDA electromagnetic compatibility (EMC) as well as various detector projects under discussion at Jefferson Lab or Brookhaven National Laboratory in the United States. Nearly, 6700 crystals are missing for the barrel section of the PANDA-EMC since the successful mass production of PWO using the Czochralski method was stopped after bankruptcy of the Bogoroditsk Technical Chemical Plant (BTCP) in Russia. Intermediate research and development efforts with the Shanghai Institute of Ceramics, Chinese Academy of Science, Shanghai, China, as an existing producer exploiting the modified Bridgman method could not reach the required quality in a consistent manner. End of 2014, the CRYTUR (Turnov, Czech Republic) has restarted the development of lead tungstate based again on the Czochralski method with impressive progress. The modified and optimized technology has already produced full size samples of PWO-II quality. This paper will present a detailed status report on a first preproduction run of 89 crystals focusing on the achieved optical performance, light yield, kinetics, and temperature dependence and radiation hardness. [ABSTRACT FROM AUTHOR]

The emergence of new solid-state avalanche photodetectors, e.g. SiPMs, with unprecedented timing capabilities opens new ways to profit from ultrafast and prompt photon emission in scintillators. In time of flight positron emission tomography (TOF-PET) and high energy timing detectors based on scintillators the ultimate coincidence time resolution (CTR) achievable is proportional to the square root of the scintillation rise time, decay time and the reciprocal light yield, C T R ∝ τ r τ d ∕ L Y . Hence, the precise study of light emission in the very first tens of picoseconds is indispensable to understand time resolution limitations imposed by the scintillator. We developed a time correlated single photon counting setup having a Gaussian impulse response function (IRF) of 63ps sigma, allowing to precisely measure the scintillation rise time of various materials with 511keV excitation. In L(Y)SO:Ce we found two rise time components, the first below the resolution of our setup < 10 ps and a second component being ∼ 380 ps. Co-doping with Ca 2 + completely suppresses the slow rise component leading to a very fast initial scintillation emission with a rise time of < 10ps. A very similar behavior is observed in LGSO:Ce crystals. The results are further confirmed by complementary measurements using a streak-camera system with pulsed X-ray excitation and additional 511 keV excited measurements of Mg 2 + co-doped LuAG:Ce, YAG:Ce and GAGG:Ce samples. [ABSTRACT FROM AUTHOR]

In this work the predictions of the background spectra of ten scintillating crystals with lutetium for 1 cm3 cubes are presented. These spectra were obtained by performing Monte Carlo simulations of the 176Lu decay, and the radiation interaction mechanisms in the crystal materials, using PENELOPE and GATE, and by using an analytic model based on the 176Lu decay radiation emission and absorption probabilities. To properly simulate these materials, the mass density and elemental composition were investigated from various references, from which other important properties were derived, such as the expected count rate due to their intrinsic radiation and the intrinsic quantum efficiency for a continuous range of crystal thickness and photon energies, presented as two-dimensional maps. Additionally, other physical properties important for radiation detection of the lutetium-based scintillators are also compared to those of lutetium oxyorthosilicate, the most prevailing material in current detector technology for various imaging applications. [ABSTRACT FROM AUTHOR]

The absolute luminescence efficiency (AE) of a calcium fluoride (CaF2:Eu) single crystal doped with europium was studied using X-ray energies met in general radiography. A CaF2:Eu single crystal with dimensions of 10 × 10 × 10 mm3 was irradiated by X-rays. The emission light photon intensity of the CaF2:Eu sample was evaluated by measuring AE within the X-ray range from 50 to 130 kV. The results of this work were compared with data obtained under similar conditions for the commercially employed medical imaging modalities, Bi4Ge3O12 and Lu2SiO5:Ce single crystals. The compatibility of the light emitted by the CaF2:Eu crystal, with the sensitivity of optical sensors, was also examined. The AE of the 10 × 10 × 10 mm3 CaF2:Eu crystal peaked in the range from 70 to 90 kV (22.22 efficiency units; E.U). The light emitted from CaF2:Eu is compatible with photocathodes, charge coupled devices (CCD), and silicon photomultipliers, which are used as radiation sensors in medical imaging systems. Considering the AE results in the examined energies, as well as the spectral compatibility with various photodetectors, a CaF2:Eu single crystal could be considered for radiographic applications, including the detection of charged particles and soft gamma rays.

In this study, a conventional Bonner sphere spectrometer, together with 6 LiI(Eu) inorganic scintillator used as the central detector, was used to obtain the neutron energy spectrum of an 241 Am–Be source. To achieve this, we calculated the response matrices corresponding to eight different sizes of polyethylene spheres for the neutron energies ranging from about 10 −7 to 15 MeV in 54 energy groups by using the MCNPX2.6 code, and the 241 Am–Be neutron spectrum was obtained using a modified version of the neutron spectrum unfolding code, AFITBUNKI. In a feasibility study, similar calculations were performed with different sizes of polyethylene cylinders. A comparison between the unfolded spectra of a typical 241 Am–Be neutron source with those of Bonner spheres, cylinders of similar sizes, and standard 241 Am–Be neutron energy spectra shows that the spectrometer with polyethylene cylinders can be used as a potential alternative for conventional Bonner spheres. [ABSTRACT FROM AUTHOR]

The results from ab initio quantum chemical calculations for inorganic scintillators BaBrI:Eu and BaСlI:Eu are presented. The calculations were performed using the density functional theory and the VASP software package. Estimates are made for the band-gap width of the crystals, and for the locations of 4 f- and 5 d-levels of Eu ions with respect to the valence and conduction bands, respectively, and the possibility of using a new material based on BaСlI:Eu as a scintillator is evaluated. [ABSTRACT FROM AUTHOR]

Gamma radiation detection in the range of 662 keV, the reference for environmental protection, is done through extrinsic optical fiber sensors. The fluorescence rendered by an inorganic scintillator when irradiated with such gamma rays is gathered by a modified polymer optical fiber tip. This modification increases the recorded signal when compared with plain unaltered fiber. Two fiber tip modification are then compared in terms of light gathering capability. A chemically etched fiber, in which the cladding and part of the core are removed, and a tapered fiber in which the core-cladding structure is kept. Both structures are comparable in length and final diameter, and show linear response in the tested range up to 2 Gy/h air Kerma rate. The etched fiber shows a higher slope than the tapered one, although both improve the signal gathered by a plain fiber tip. The easy fabrication and handling of the reported transducers, together with the improved signal gathering, allow to reduce the overall system budget with the use of low-cost optoelectronics in the detection stage. This offers a significant improvement for surveillance systems in radioprotection applications, in which presence of gamma radiation coming out accidental leakage or spurious sources activity is the main target. [ABSTRACT FROM AUTHOR]

The temperature dependence of four inorganic scintillation detectors was examined spectrally using the HYPERSCINT Research Platform 200. The detectors were subject to 6 MV photon irradiations from a linear accelerator, varying only the temperature of the detectors. Optical fibre connectorisation was characterised and found to be essential to the repeatability of measurements. The magnitude of the temperature effect on each detector was evaluated by calculating the percentage change in total photon counts for a range of temperatures. Gd 2 O 2 S:Tb and Gd 2 O 2 S:Eu exhibited the lowest change in counts with temperature, 0.12%/°C and −0.10%/°C, respectively, with ZnS:Ag showing the highest change in counts of −0.55%/°C. Gd 2 O 2 S:Pr photon counts changed by −0.25%/°C. All the scintillators demonstrated linearity when the change in photon counts with temperature in the full-width at half maximum of their spectrum are integrated. Establishing the magnitude of the temperature dependence of the materials is critical to decide whether correction factors are required. This is especially true in applications such as brachytherapy, where detectors equilibrise to body temperature. • Temperature effect on scintillators established in a clinical temperature range. • HYPERSCINT RP-200 used with inorganic scintillators using 6 MV photon beam. • Change in photon output up to 0.55%/°C demonstrating scintillator choice is key. • Linearity of effect demonstrated permitting a range correction methods. [ABSTRACT FROM AUTHOR]

We use the phenomenological continuum model for inorganic scintillators proposed by the author to give decay time estimates for four scintillators previously studied, namely NaI:Tl, CaF2, Gd2SiO5Ce (GSO:Ce), and LaCl3:Ce. We show that, in order to obtain a good estimate of the decay time, we need to know (besides other well-known parameters) either the excitation carriers’ mobility or the structure and the parameters of the recombination mechanism. For these four materials, we know the data for the recombination term, whereas we have very scarce information about mobilities. However, we show that also in absence of experimentally-measured mobilities, with reasonable assumptions about them, we can obtain a good estimate for the slow component of the decay time. We show also when it is appropriate to model scintillation with one of the two most-used phenomenological models, the kinetic and the diffusive. The main point of the present approach is that it requires a limited set of experimentally-measured data and can be hopefully used in conjunction with more sophisticated and detailed models to design faster inorganic scintillators.

We propose a time-of-flight (TOF) technique using plastic scintillators which have fast decay time of a few ns for positron emission tomography (PET). While the photoelectric absorption probability of the plastic for 511 keV gamma rays are extremely low due to its small density and effective atomic number, the cross section of Compton scattering is comparable to that of absorption by conventional inorganic scintillators. We thus propose TOF-PET using Compton scattering with plastic scintillators (Compton-PET), and performed fundamental experiments towards exploration of the Compton-PET capability. We demonstrated that the plastic scintillators achieved the better time resolution in comparison to LYSO(Ce) and GAGG(Ce) scintillators. In addition we evaluated the depth-of-interaction resolving capability with the plastic scintillators. [ABSTRACT FROM AUTHOR]

CeBr 3 crystals meet many of the demands of high performance scintillators, due to their excellent timing properties, good effective Z and high photon yield. It is important to characterize their efficiency and to verify whether modern Monte Carlo codes are reliable enough to reproduced the observed values. We report here on the measurement of both total and photopeak efficiency of a 1” diameter×1” height CeBr 3 crystal for gamma-ray energies up to 1.4 MeV at several distances, using a variety of low energy gamma rays sources. The measured experimental efficiencies are compared with simulations developed in the framework of PENELOPE and GEANT4. [ABSTRACT FROM AUTHOR]

Inorganic scintillators, composed of high-atomic-number materials such as the CsI(Tl) scintillator, are commonly used in commercially available a silicon diode and a scintillator embedded indirect-type electronic personal dosemeters because the light yield of the inorganic scintillator is higher than that of an organic scintillator. However, when it comes to tissue-equivalent dose measurements, a plastic scintillator such as polyvinyl toluene (PVT) is a more appropriate material than an inorganic scintillator because of the mass energy absorption coefficient. To verify the difference in the absorbed doses for each scintillator, absorbed doses from the energy spectrum and the calculated absorbed dose were compared. From the results, the absorbed dose of the plastic scintillator was almost the same as that of the tissue for the overall photon energy. However, in the case of CsI, it was similar to that of the tissue only for a photon energy from 500 to 4000 keV. Thus, the values and tendency of the mass energy absorption coefficient of the PVTare much more similar to those of human tissue than those of the CsI. [ABSTRACT FROM AUTHOR]

For safety reasons, it is desirable to measure radiation as remotely as possible. For remote measurement of gamma radiation, the fiber-optic sensor (FOS) was developed in this study by combining a plastic optical fiber and an inorganic scintillator. To identify the best shape of the sensing probe of the FOS in terms of its detection efficiency, three different shapes of probe were fabricated using an inorganic scintillator: a cylinder and two bundles of different lengths (30 and 10 mm). To identify the best reflector for the sensing probe, the side of each probe was wrapped with one of three different reflectors: Teflon tape, TYVEK 1056D, and aluminum foil. In this study, a total of twelve different sensing probes were prepared: three different shapes of sensing probes with three different reflectors, and three different shapes of the sensing probes without reflectors. To measure gamma radiation, a cesium-137 source (1 μCi) in a disk shape, 26 mm in diameter, was attached to the end of the sensing probes. The measurements showed that bundle shape II (a bundle of 26 inorganic scintialltors, 1 mm in diameter and 10 mm in length) was the best shape for the sensing probe, and aluminum foil was the best reflector. [ABSTRACT FROM AUTHOR]

Inorganic scintillators play an important role in the detection and spectroscopy of gamma and X-rays, as well as in neutrons and charged particles. For a variety of applications, new inorganic scintillation materials are being studied. New scintillation detector applications arise continuously and, consequently, the interest in the introduction of new fast scintillators becomes relevant. Scintillation crystals based on cesium iodide (CsI) have relatively low hygroscope, are of easy handling and low cost, features that favor their use as radiation detectors. In this work, lithium and bromine doped CsI crystals were grown using the vertical Bridgman technique. In this technique, the charge is maintained at high temperature for 10 h for the material melting and complete reaction. The temperature gradient 21 °C/cm and 1 mm/h descending velocity are chosen as technique parameters. After growth is finished, the furnace is cooled at a rate of 20 °C/h to room temperature. The concentration of the lithium doping element (Li) studied was 10 ^-3 ~\mathrm M and the concentration of the bromine was 10 ^-2 ~\mathrm M . Analyses were carried out to evaluate the scintillators developed concerning the neutron from the AmBe source with energy range of 1 MeV to 12 MeV [1]. Lithium can capture neutrons without gamma-ray emission, thus, reducing the back-ground. The neutron detection reaction is ^6\mathrm Li(\mathrm n,\alpha ) ^3 \mathrm H with a thermal neutron cross section of 940 barns. In this paper, the feasibility of the CsI:Li and CsI:Br crystals as neutron detectors for monitoring was investigated, due to the fact that in our work environment there are two nuclear research reactors and calibration systems. [ABSTRACT FROM PUBLISHER]

The light response of two thin inorganic scintillators based on YAP:Ce and LaBr 3 :Ce crystals has been measured with protons in the 4–8 MeV energy range at the Uppsala tandem accelerator and in the 8–26 MeV energy range at the Legnaro tandem accelerator. The crystals have been calibrated in situ with 137 Cs and 60 Co γ-ray sources. The relative light yields of protons with respect to gammas have been measured and are here reported to be (96±2)% and (80±2)% for YAP:Ce and LaBr 3 :Ce, respectively. The results open up to the development of a Telescope Proton Recoil spectrometer based on either of the two crystals as alternative to a silicon based spectrometer for applications to high neutron fluxes. [ABSTRACT FROM AUTHOR]

Inorganic scintillators with high density and high light yield are of major interest for applications in medical imaging and high energy physics detectors. In this work, the optical and scintillation properties of Mg co-doped Ce:Gd 3 Al 2 Ga 3 O 12 crystals, grown using Czochralski technique, have been investigated and compared with Ce:Gd 3 Al 2 Ga 3 O 12 ones prepared with identical technology. Improvements in the timing performance of the Mg co-doped samples with respect to Ce:Gd 3 Al 2 Ga 3 O 12 ones have been measured, namely a substantial shortening of the rise time and scintillation decay components and lower afterglow were achieved. In particular, a significantly better coincidence time resolution of 233 ps FWHM, being a fundamental parameter for TOF-PET devices, has been observed in Mg co-doped crystals. The samples have also shown a good radiation tolerance under high doses of γ-rays, making them suitable candidates for applications in harsh radiation environments, such as detectors at future collider experiments. [ABSTRACT FROM AUTHOR]

The work is devoted to a quantitative comparison of different inorganic scintillators to be used in neutron-radiation inspection systems. Such systems can be based on the tagged neutron (TN) method and have a significant potential in different applications such as detection of explosives, drugs, mines, identification of chemical warfare agents, assay of nuclear materials and human body composition [1]–[3]. The elemental composition of an inspected object is determined via spectrometry of gammas from the object bombarded by neutrons which are tagged by an alpha-detector built inside a neutron generator. This creates a task to find a quantitative indicator of the object identification quality (via elemental composition) as a function of basic parameters of the $\gamma$-detectors, such as their efficiency, energy and time resolutions, which in turn are generally defined by a scintillator of the detector. We have tried to solve the task for a set of four scintillators which are often used in the study of TN method, namely BGO, {\rm LaBr}_{3}, LYSO, NaI(Tl), whose basic parameters are well known [4]–[7]. [ABSTRACT FROM AUTHOR]

Heavy inorganic scintillator based detectors are used in various applications. You can find them in high energy physics as well as in nuclear medical imaging systems but also in homeland security radiation monitoring devices. In all these different detectors, light is produced in the scintillator and has to be transported towards a photodetector. The standard optical coupling of such a detector suffers from an inefficient light extraction towards the photodetector due to the high index of refraction of the scintillator and the accompanying total internal reflections. With the means of photonic nanostructuring of the different surfaces of the scintillator, the light transport can be optimized, which has a direct impact on the timing and light yield performance of the detector. Previous work from our group has already shown that photonic crystals (PhCs) can be used as diffraction gratings to improve the light coupling between a photodetector and a scintillator. Moreover, nanoscale surface structuring techniques could also be extended to the sidewalls, the wrapping, or the detector itself, which would open up a number of new possibilities for optimization of the light transport of scintillation based detectors. To show that PhCs can also be produced on a large industrial scale, we started to investigate different methods for cheap and large area PhC structuring. In this work, the current results on our efforts on PhC scintillator production will be described. The different projects include nanoimprint technologies, interference lithography and colloidal lithography. To conclude, we will summarize the different efforts of our group and collaborators and show up-to-date results of PhC improved scintillators. [ABSTRACT FROM AUTHOR]

This report gives a review of the radiation damages induced by gammas and energetic hadrons in inorganic scintillating materials. We discuss the creation and recovery of color centers in scintillating materials under gamma and high energy proton irradiation, the two main causes of irradiation in High Luminosity LHC. The induced phosphorescence and the production of radioisotopes in heavy and light inorganic scintillators and in surrounding construction materials, as well as their influence on the possible design of the detector working in a high dose rate environment, are also described. [ABSTRACT FROM AUTHOR]

It is important to optimize the crystal-photodetector coupling for gamma detection since it improves the light extraction and is directly linked to the achieved time resolution. In this paper we present our work on altering the geometry of the crystal coupling face to enhance the light output. Simulations compare the light output of alternative geometries of the crystal extraction face with respect to that of the regular cuboid geometry. We machined two different crystal shapes from 2 \times 2 \times 15\ \mm^3 LSO crystals and measured the light output for different wrapping and coupling conditions. We also measured the coincidence time resolution (CTR) of the shaped crystals to compare the effect of timing on shaped crystals with respect to the reference samples. Simulations predicted an increase of up to 35% in light transfer efficiency for certain geometries of the exit face with respect to that of a regular cuboid geometry. Experimental measurements performed on shaped LSO crystals (2 \times 2 \times 15\ \mm^3) show that an increase in light output of up to 40% and a systematic improvement in CTR of at least 5% is possible for one of the tested geometries. This opens new windows for preparing crystals used in TOF-PET scanners and high energy physics experiments. [ABSTRACT FROM AUTHOR]

This review covers direct searches for dark matter, and the role inorganic scintillators have to play in them. Particle dark matter may make up most of the matter in the universe. Direct searches for dark matter are progressing thanks to improvements in detector technology. The phase space predicted by various theories is vast. Noble-element based detectors, soon weighing one ton, seem best-placed to search for relatively heavy ( \gtrsim 20~\GeV) particles, and have already probed dark matter-nucleon cross sections as small as 7 \times 10^-46~\cm^2. A variety of other technologies, including cryogenic detectors, gaseous ones and CCDs, will cover lower masses (down to 1 GeV or less), where recent hints for a discovery have been seriously undermined. Background rejection is essential in this field. Inorganic scintillators have roles to play at cryogenic temperatures, where the scintillation signal can be coupled to a measurement of phonons, providing particle identification. Future experiments with highly radiopure and high light yield NaI(Tl) can contribute to direct investigation of the longstanding detection claim from DAMA/LIBRA. [ABSTRACT FROM AUTHOR]