The aim of the present study was to investigate the absolute luminescence efficiency of gadolinium oxysulfide powder scintillators, doped with praseodymium, cerium and fluorine (Gd2O2S:Pr,Ce,F). ...Gd2O2S:Pr,Ce,F is a non-hygroscopic material, emitting green light with short decay time. For the purposes of this study, two scintillating screens with coating thicknesses 35.7 and 71.2 mg/cm2, were prepared in our laboratory from Gd2O2S:Pr,Ce,F powder (Phosphor Technology, Ltd) by sedimentation on silica substrates. The light emitted by the phosphors under investigation was evaluated by performing measurements of the absolute efficiency under X-ray exposure conditions with tube voltages ranging from 50 to 130 kV. Results were compared with previously published data for Gd2O2S:Eu screens. The spectral compatibility of Gd2O2S:Pr,Ce,F with various existing optical detectors, was investigated after emission spectra measurements. Particle size and morphology parameters of the Gd2O2S:Pr,Ce,F powder phosphor were verified via scanning electron microscope (SEM) micrographs. Absolute efficiency was found to maximize at 60 kVp for the 71.2 mg/cm2 and at 90 kVp for the 35.7 mg/cm2 Gd2O2S:Pr,Ce,F screens. Absolute efficiency of the 71.2 mg/cm2 Gd2O2S:Pr,Ce,F screen was higher in the whole X-ray tube voltage range showing potential interest for non-CT medical imaging (i.e. dental radiology) or industrial digital radiography.
•Two Gd2O2S:Pr,Ce,F screens (35.7 & 71.2 mg/cm2) were prepared by sedimentation.•Peak absolute efficiency was obtained for the 71.2 mg/cm2 screen at 60 kVp.•Gd2O2S:Pr,Ce,F showed very good spectral compatibility with CMOS and CCD sensors.
The aim of the present study was to investigate the absolute luminescence efficiency (AE) of mixed oxyorthosilicate (Lu,Gd)2SiO5:Ce (LGSO:Ce) single crystals, under X-ray irradiation. Six ...(Lu,Gd)2SiO5:Ce crystal samples, with dimensions of 3 × 3 × 5, 3 × 3 × 6, 3 × 3 × 10, 3 × 3 × 15, 10 × 10 × 10 and 10 × 10 × 20 mm3 were examined. The light emitted by the crystals, was evaluated by performing measurements of the AE under X-ray exposure conditions, with tube voltages ranging from 50 to 130 kV. Results were compared with previously published data for GSO:Ce and LSO:Ce crystals. The spectral compatibility of the (Lu,Gd)2SiO5:Ce crystal, with various existing optical detectors, was investigated after emission spectra measurements. Absolute efficiency was found maximum at 130 kVp for the 3 × 3 × 15 mm3 (Lu,Gd)2SiO5:Ce crystal (25.40 E.U). AE of the 10 × 10 × 10 mm3 (Lu,Gd)2SiO5:Ce crystal was found higher than both GSO:Ce and LSO:Ce crystals, in the whole X-ray tube range. The emission spectrum of (Lu,Gd)2SiO5:Ce is excellent matched with the spectral sensitivities of photocathodes and silicon photomultipliers often employed in radiation detectors. Considering the high luminescence efficiency values and the spectral compatibility with the various photodetectors, (Lu,Gd)2SiO5:Ce crystal could be considered for use in combined medical imaging detectors i.e. integrated PET/CT detectors.
•Six (Lu,Gd)2SiO5:Ce single crystals were examined under radiographic X-ray energies.•LE was found maximum at 130 kVp for the 3 × 3 × 15 mm3 crystal (25.40 E.U).•The 10 × 10 × 10 mm3 LGSO:Ce was found with higher LE than both GSO:Ce and LSO:Ce.•The emission spectrum is excellent matched with the sensitivities of PMTs and SiPMs.
Inorganic-scintillator development van Eijk, Carel W.E.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2001, Volume:
460, Issue:
1
Journal Article
Peer reviewed
A review is presented of recent inorganic scintillator R&D. Attention is focused on Ce doped gamma-ray and thermal-neutron scintillators for counting applications.
Range verification of particle beams in real time is considered a key for tapping the full potential of radio-oncological particle therapies. The novel technique of prompt gamma-ray timing (PGT), ...recently proposed and explored in first proof-of-principle experiments, promises range assessment at reasonable expense but challenges detectors, electronics, and data acquisition. Energy-selected time distributions have to be measured at very high throughput rates to obtain the statistics necessary for range verification with single pencil beam spots. Clinically applicable systems should provide a time resolution of about 200 ps, to be obtained with large (about 2" diameter) scintillators, detector loads in the few-Mcps range, and data acquisition rates around 1 Mcps, if possible with compact and inexpensive systems. Such requirements can be met best with CeBr 3 scintillators read out with conventional photomultiplier tubes, coupled to commercial but customized electronics featuring high-resolution pulse digitization and fast digital signal processing. The paper deduces design parameters from the constraints given by typical treatment conditions, and presents first results obtained with prototype detectors and electronics developed in accordance with the derived specifications.
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 aim of the present work was to investigate the absolute luminescence efficiency (AE) of a lutetium aluminum Lu3Al5O12:Ce (LuAG:Ce) garnet, doped with cerium, combined with various microelectronic ...optical sensors. Two LuAG:Ce samples, with dimensions of 5 × 5 × 10 and 10 × 10 × 10 mm3 were examined. The light emitted by the crystals, was evaluated by performing measurements of the AE using X-rays from 50 to 130 kV. The spectral compatibility of the LuAG:Ce crystal, with various existing optical detectors, was investigated after emission spectra measurements. Results were compared with previously published data for commercially available lutetium based and cerium doped crystals, such as, (Lu,Gd)2SiO5:Ce and Lu2SiO5:Ce, frequently used in medical imaging applications. Absolute efficiency was found maximum at 130 kVp for the 5 × 5 × 10 mm3 LuAG:Ce crystal (31.86 efficiency units-E.U). AE of the 10 × 10 × 10 mm3 LuAG:Ce crystal was found higher than both LGSO:Ce and LSO:Ce crystals (of equal dimensions). The emission spectrum of LuAG:Ce is excellent matched with the spectral sensitivities of photocathodes, charge coupled devices (CCD), non-passivated amorphous hydrogenated silicon photodiodes (a-Si:H) and complementary metal-oxide semiconductors (CMOS) microelectronic devices employed in radiation detection. Considering the higher luminescence efficiency values than currently used crystals and the spectral compatibility with the various photodetectors, LuAG:Ce single crystal could be considered for use in imaging detectors, such as, PET/CT scanners.
•Two LuAG:Ce single crystals were examined under radiographic X-ray energies.•Comparisons with LGSO:Ce and LSO:Ce crystals were performed.•AE was found maximum at 130 kVp for the 5 × 5 × 10 LuAG:Ce crystal (31.86 EU).•LuAG:Ce single crystal could be considered for use in combined medical imaging detectors.
GEANT4-based Monte Carlo simulation has been performed for a <inline-formula> <tex-math notation="LaTeX">2''\phi \times 2'' </tex-math></inline-formula> 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 <inline-formula> <tex-math notation="LaTeX">2''\phi \times 2'' </tex-math></inline-formula> 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.
Nonlinear quenching of electron–hole pairs in the denser regions of ionization tracks created by γ‐ray and high‐energy electrons is a likely cause of the light yield non‐proportionality of many ...inorganic scintillators. Therefore, kinetic Monte Carlo (KMC) simulations were carried out to investigate the scintillation properties of pure and thallium‐doped CsI as a function of electron–hole pair density. The availability of recent experimental data on the excitation density dependence of the light yield of CsI following ultraviolet excitation allowed for an improved parameterization of the interactions between self‐trapped excitons (STE) in the KMC model via dipole–dipole Förster transfer. The KMC simulations reveal that nonlinear quenching occurs very rapidly (within a few picoseconds) in the early stages of the scintillation process. In addition, the simulations predict that the concentration of thallium activators can affect the extent of nonlinear quenching as it has a direct influence on the STE density through STE dissociation and electron scavenging. This improved model will enable more realistic simulations of the non‐proportional γ‐ray and electron response of inorganic scintillators.
Estimation of Fano factor in inorganic scintillators Bora, Vaibhav; Barrett, Harrison H.; Fastje, David ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2016, Volume:
805
Journal Article
Peer reviewed
Open access
The Fano factor of an integer-valued random variable is defined as the ratio of its variance to its mean. Correlation between the outputs of two photomultiplier tubes on opposite faces of a ...scintillation crystal was used to estimate the Fano factor of photoelectrons and scintillation photons.
Correlations between the integrals of the detector outputs were used to estimate the photoelectron and photon Fano factor for YAP:Ce, SrI2:Eu and CsI:Na scintillator crystals. At 662keV, SrI2:Eu was found to be sub-Poisson, while CsI:Na and YAP:Ce were found to be super-Poisson.
An experiment setup inspired from the Hanbury Brown and Twiss experiment was used to measure the correlations as a function of time between the outputs of two photomultiplier tubes looking at the same scintillation event. A model of the scintillation and the detection processes was used to generate simulated detector outputs as a function of time for different values of Fano factor. The simulated outputs from the model for different Fano factors was compared to the experimentally measured detector outputs to estimate the Fano factor of the scintillation photons for YAP:Ce, LaBr3:Ce scintillator crystals. At 662keV, LaBr3:Ce was found to be sub-Poisson, while YAP:Ce was found to be close to Poisson.
The paper presents a comparison of three neutrons identifying methods in scintillators based on ZnS with
6
Li and
10
B: 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.
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