BGO Scintillation Crystals Research Articles

Concentration Dependence Orange Light Generation Through Sm3+‐Doped Soda Lime Alumino Borate Glasses for Orange Laser Medium Material

The melt‐quenching technique is used to fabricate calcium sodium aluminum borate glasses (Sm: ANCB) doped with varying concentrations of Sm3+ ions. Characteristics of ANCBSm glasses, including density, molar volume, refractive index, absorption, emission (via visible light, X‐ray, and proton excitation), decay time, and CIE color coordinates, are analyzed. The density, molar volume, and refractive index of ANCBSm glass increased with Sm2O3 concentration. Sm3+ ions enabled photon absorption in both visible and NIR regions, with a strong reddish‐orange emission at 600 nm due to the 6H5/2 → 6P3/2 transition under various excitations. X‐ray excitation is also compared with BGO scintillation crystals. The J–O theory predicted the radiative properties of Sm3+ ion emission levels. Decay curves of the 6H5/2 levels showed a single exponential nature with a millisecond‐order lifetime. CIE chromaticity of ANCBSm glasses is in the reddish‐orange region. ANCBSm glasses have potential applications in orange laser medium material.

An efficient digital pulse processing approach for identification of BGO and LSO scintillator crystals

Identification and discrimination between BGO and LSO scintillators is a fundamental target for handling parallax error within positron emission tomography (PET) applications by depth of interaction. An approach is built for discrimination and identification of BGO and LSO scintillator crystals. This approach is tested using a simulated BGO and LSO pulses. A Matlab Simulink model is implemented for simulation and creation of BGO and LSO scintillation pulses. The simulated pulses depend on 22Na radiation source. The suggested approach has two different algorithms. The first algorithm uses both 1D-Walsh ordered fast Walsh-Hadamard transform (1WFWHT) and fast Chebyshev transform (FCHT) for extracting the features of crystal pulses. The optimum features are selected from 1WFWHT and FCHT using one of three optimization techniques that are binary dragonfly optimization (BDA), binary atom search optimization (BASO) and binary Harris Hawk optimization (BHHO). These optimized features are trained and tested using one of three based classifiers. These classifiers are Naive Bayes classifier (NBC), hierarchical prototype-based (HP) classifier and adaptive neuro-fuzzy inference system (ANFIS) classification. The ANFIS classifier achieves the best accuracy with all optimum (BASO, BDF and BHH) FCHT features. However, the NB classifier introduces the highest accuracy with all optimum (BASO, BDF and BHH) FWHT 1D features. The second algorithm uses the conventional neural network (CNN) for extracting the pulse features. Then, the deep neural network (DNN) is applied for training and testing of the captured pulses. The suggested algorithms are verified and compared in respect of statistical measures. The compared results confirm that the best accuracy and identification rate is accomplished using DNN algorithm. Besides, the DNN has better results compared to conventional classification techniques with optimum feature selection techniques in respect of time consumption. The proposed approach aids in the realisation of overcoming parallax inaccuracy in PET.

Effect of Gd2O3 concentration on photo and X-rays excited luminescence characteristics of Dy3+-Activated Li2O3–SrO–B2O3 glass

Gd3+ and Dy3+-doped borate glasses are considered attractive candidates for white light emission. In this work, the samples, developed by the melt-quenching route, contain a mixture of Gd3+ and Dy3+ with known molar compositions. The determined physical parameters indicate structural changes. Information regarding the Judd-Ofelt (JO) intensity parameters and spectral radiative features, calculated from absorption spectra and emission properties, respectively, are obtained. Excitation and photoluminescence characteristics of the developed samples are found. The energy transfer (ET) efficiency from Gd3+ → Dy3+ is determined by considering their emission intensities and lifetime. The quantum efficiency (QE) of glasses is evaluated. Inokuti –Hirayama (IH) model shows that the Dy3+ → luminescence center ET is dominated by dipole-dipole coulomb interaction. Due to the excitation of more secondary electrons, the X-ray luminescence shows an intense emission pattern. Furthermore, we find the integral scintillation efficiency to be 8.4% of the commercial BGO scintillator crystal for the 10 mol% Gd2O3-doped glass. Commission International deI’Eclairage (CIE) color coordinates and color correlated temperature (CCT) show the suitability of tested samples for white-light applications.

Moh’s hardness Scale and micro vicker’s hardness study of bgo and lyso inorganic scintillators

BGO and LYSO inorganic scintillation crystals were chosen in this paper for density and hardness properties investigation. Moh’s hardness scale was determined by scratching test which of the standard minerals. The micro vicker’s hardness was measured with a diamond indenter and the test load was used at 0.1 kgf. The results show that, the moh’s hardness scale of LYSO crystal are higher than BGO crystal which correspond with micro vicker’s hardness values. The density of scintillation crystals were measured and found to be 7.1 g/cm3 for BGO crystal and 7.15 g/cm3 for LYSO crystal.

Energy transfer from Gd3+ to Sm3+ and luminescence characteristics of CaO–Gd2O3–SiO2–B2O3 scintillating glasses

In this work, density, optical, photoluminescence and x-ray scintillation properties of calcium gadolinium silicoborate glass (CaO:Gd2O3:SiO2:B2O3) have been investigated. Glasses were prepared by the conventional melt quenching technique. The results show that the density of glass increased with increasing of Sm2O3. The optical spectra of glass shows eleven discrete absorption bands at 360, 373, 403, 475, 944, 1077, 1225, 1368, 1468, 1520 and 1586nm which are due to the transitions of 6H5/2 to 4D3/2, 6P7/2, 6P3/2, 4I11/2, 6F11/2, 6F9/2, 6F7/2, 6F5/2, 6F3/2, 6H15/2 and 6F1/2, respectively. The emission spectra were observed and assigned to 312, 563, 600, 646 and 703nm by excitation at 275nm. The emission intensity of Sm3+ increased with increasing of Sm2O3 concentration until 0.25mol%, while decay time decrease with increasing of Sm2O3 content. For results of the radioluminescence (RL), they perform four emission peaks with the strongest emission at 598nm. Glass doped with 0.35mol% Sm2O3 show the highest RL emission. The integral scintillation efficiency of 0.35mol% Sm2O3 doped glass was determined as 25% of commercial BGO scintillator crystal.

Pilot Studies With BGO Scintillators Coupled to Low-Noise, Large-Area, SiPM Arrays

Despite the fact that timing capabilities for devices based on BGO are limited when compared with LYSO or LSO based systems, the cost of BGO is considerably lower and could thus, be an option for devices with high scintillator volumes (as in the case of nuclear medicine scanners), but also in smaller dedicated imagers. Recently, many studies have been carried out in order to determine the potential capabilities of BGO for PET and SPECT applications, where BGO scintillator crystals have been coupled to SiPM photosensor devices. However, so far these studies have only been done on small-size BGO samples. In this work, we have studied three different BGO size configurations, coupled to a ${\hbox {12}} \times {\hbox {12}}$ low-noise SiPM array. Each SiPM has an active area of ${\hbox \times {\hbox {3}} \hbox{mm}^{2}$ with a pixel pitch of 4.2 mm. A special charge division network providing information for each row and column output of the SiPM array has been used. The first tested BGO configuration has 2.5 mm crystal pixel pitch and 10 mm thickness, while the second makes use of smaller 1.5 mm pixels with 1.67 mm pitch but only 3 mm thick. The third evaluated configuration provided limited photon depth of interaction (DOI) information by using two staggered layers of BGO pixels also with 2.5 mm pitch and with a total thickness of 20 mm. Performances of these configurations in terms of spatial and energy resolutions have been determined. Energy resolution as good as 14.2% was obtained. Our results indicate that single layer crystal arrays with pixel values as low as 1.5 mm or two staggered layers with 2.5 mm pitch are well suited for PET applications, such as low-cost and high performance dedicated PET systems or large systems.

Comparative Studies of the Light Yield Non-Proportionality and Energy Resolution of CsI(Tl), LYSO and BGO Scintillation Crystals

This article, for comparison, the non-proportionality of light yield and energy resolution of BGO, LYSO and CsI(Tl) scintillators couple to the R1306 PMT readouts were investigated. At 662 keV from 137Cs source, the good energy resolution of 7.13% for CsI(Tl) superior than LYSO and BGO scintillators. The energy resolution on gamma-ray energy was also evaluated to expose the scintillator intrinsic resolution parameters. For non-proportionality of light yield, the study showed a light yield non-proportionality 0.35% of LYSO, the value is better than 4.82 % for CsI(Tl) and 1.53 % of BGO scintillators.

Calorimetry of the CMD-3 detector

CMD-3 is a general purpose detector designed to study e+e− annihilation into hadrons. It is mounted at VEPP-2000 collider which operates in the wide energy range, Ec.m.s=0.32−2GeV. The calorimetry at the detector is based on three subsystems: closest to the beam pipe barrel Liquid Xenon calorimeter, outer barrel calorimeter based on CsI scintillation crystals and the endcap calorimeter made of BGO scintillation crystals. We describe the structure of the calorimeters, their electronics and the energy calibration procedures.

SU‐C‐201‐01: Investigation of the Effects of Scintillator Surface Treatment On Light Output Measurements with SiPM Detectors

Purpose:To examine the effect of different scintillator surface treatments (BGO crystals) on the fraction of scintillation photons that exit the crystal and reach the photodetector (SiPM).Methods:Positron Emission Tomography is based on the detection of light that exits scintillator crystals, after annihilation photons deposit energy inside these crystals. A considerable fraction of the scintillation light gets trapped or absorbed after going through multiple internal reflections on the interfaces surrounding the crystals. BGO scintillator crystals generate considerably less scintillation light than crystals made of LSO and its variants. Therefore, it is crucial that the small amount of light produced by BGO exits towards the light detector. The surface treatment of scintillator crystals is among the factors affecting the ability of scintillation light to reach the detectors. In this study, we analyze the effect of different crystal surface treatments on the fraction of scintillation light that is detected by the solid state photodetector (SiPM), once energy is deposited inside a BGO crystal. Simulations were performed by a Monte Carlo based software named GATE, and validated by measurements from individual BGO crystals coupled to Philips digital‐SiPM sensor (DPC‐3200).Results:The results showed an increment in light collection of about 4 percent when only the exit face of the BGO crystal, is unpolished; compared to when all the faces are polished. However, leaving several faces unpolished caused a reduction of at least 10 percent of light output when the interaction occurs as far from the exit face of the crystal as possible compared to when it occurs very close to the exit face.Conclusion:This work demonstrates the advantages on light collection from leaving unpolished the exit face of BGO crystals. The configuration with best light output will be used to obtain flood images from BGO crystal arrays coupled to SiPM sensors.

Light Yield Non-Proportionality and Energy Resolution of BGO and CsI(Tl) Scintillation Crystals

This work was investigated on gamma ray scintillation response of inorganic scintillators. BGO and CsI(Tl) was carried out in the energies ranging from 59 keV to 1332 keV. The scintillation responses of the crystals were measured using photomultiplier tube (R1306 PMT) readout. The light yield non-proportionality and energy resolution were analyzed with Gamma Acquisition & Analysis program. The photofraction for both crystals was determined and compared with the cross-section ratio which calculated by WinXCom program.

Electromagnetic calorimeters of the CMD-3 detector

Recently the CMD-3 detector has started to record the experimental information produced at the VEPP-2000 e+e− collider at BINP (Novosibirsk). CMD-3 is a general purpose detector for a study of e+e− annihilation to hadrons in the wide center-of-mass energy range, The calorimetry in the detector is based on three subsystems: closest to the beam pipe barrel liquid xenon calorimeter, outer barrel calorimeter based on CsI scintillation crystals and endcap calorimeter made of BGO scintillation crystals. Construction and tests of the calorimeters are described, first results from the experimental runs are presented.

Radiation sensitivity of GSO and LSO scintillation detectors

Radiation resistance of 4×4×30 mm 3 GSO and LSO imaging scintillation detectors has been studied for low-energy gamma-ray doses of 10 4 Gy (10 6 rad) and 10 5 Gy (10 7 rad). Radiation hardness was determined by the measurement of optical transmission through GSO and LSO scintillation crystals before and after irradiations with 60Co gamma-rays. The results have been analysed in terms of the radiation-induced absorption coefficients and compared with radiation sensitivity measurements of small BGO scintillation crystals. The recovery time of irradiated small GSO and LSO crystals has also been determined.

Radiation resistance of heavy scintillators to low-energy gamma-rays

Radiation resistance of BGO, fluoride (BaF 2, CeF 3) and tungstate (PbWO 4, CdWO 4) heavy scintillation crystals due to low-energy gamma-rays has been studied for doses up to 10 5 Gy. Results are discussed in terms of degradation of transmission and appropriated induced absorption coefficients. The recovery time has been estimated from measurement of transmission spectra during 0.5–15 days after irradiations.

Energy response of a novel compact Ge+BGO spectrometer for 4–20 MeV γ-rays

The energy response of a novel composite Ge+BGO spectrometer has been measured for high-energy (4–20 MeV) photons. The spectrometer consists of a cooled Ge solid state central detector surrounded by a single BGO scintillator crystal without having interfering materials in between. Good energy resolution (≈1.7%) combined with a considerable photopeak efficiency ( ε≈17%) have been obtained at 15.1 MeV in “adding-back” mode. GEANT Monte-Carlo code simulations reproduce the measured response rather well and show a very good suppression factor against neutrons (≥100) and also against cosmic rays (≥3000) for this composite spectrometer.

Investigation of a new readout scheme for high resolution scintillation crystal arrays using photodiodes

We are exploring the possibility of using PIN photodiodes to readout the scintillation crystals used in positron emission tomography (PET) detector designs. Semiconductor photodetectors typically have a lower signal to noise ratio than photomultiplier tubes (PMTs). However, they have the advantage of compactness, and, thus, scintillation crystal readout schemes not available to PMTs because of their size and geometry limitations, are readily available to photodiodes. With current PET detector designs, only a small fraction of the available scintillation light, created from 511 keV gamma ray interactions within the crystal, is collected. Scintillation light collection studies were performed for several crystal geometries and surface treatments using both simulations and measurements. In this report, we present a feasible photodiode readout scheme that allows greater than 90% of the available scintillation light created in either BGO or LSO scintillation crystals to be collected by the photodetector. This improvement in light collection with the photodiode readout somewhat compensates for its lower inherent signal to noise ratios and makes it feasible for use in PET detectors. A coincident timing spectrum resolution of 9.4 ns FWHM was measured for 511 keV interactions with one LSO crystal coupled to a photodiode, the other to a PMT.

An analog decoding BGO block detector using circular photomultipliers

This is a positron camera detector design study using quadrant sharing of circular phototubes and optically cross-coupled BGO scintillation crystals. The goal is to design a very high spatial resolution detector using the larger and less expensive circular phototubes, so that the high production cost of high spatial resolution, multi-slice positron cameras may be lowered. Theoretical calculations and experimental studies have been performed using 19 mm diameter phototubes. The study shows that (a) BGO detector-pitch in the range of 2.2/spl times/2.2 mm to 3.0/spl times/3.0 mm (transaxial x axial) can be decoded with these 19 mm diameter phototubes, and (b) it is possible to achieve very uniform signal pulse-height for all the BGO crystals in the block with this design, even though there are relatively large air-gaps between circular phototubes. This study shows that very high spatial resolution, approaching the theoretical resolution of PET imaging, can be achieved using the cheaper 19 mm circular phototubes.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A 2-dimensional detector decoding study on BGO arrays with quadrant sharing photomultipliers

This is a theoretical estimation and experimental study of the positron camera detector design using quadrant sharing of phototubes and optically cross-coupled BGO scintillation crystals. This study estimates the maximum number of BGO crystals which can be coupled to a photomultiplier and be decoded with this design, based on the number of photoelectrons generated and the optical efficiency of the crystal-phototube combination. From photoelectron statistics, a 10/spl times/10 BGO array can be coupled to a single square phototube (Hamamatsu R-2497) and have each crystal clearly decoded. Simulation of 1-dimensional and 2-dimensional statistical photoelectron distribution verifies the estimations. The simulation also yields the optimal distribution of light to the decoding phototubes. This theoretically optimal light distribution is used to guide the development of an 8/spl times/8 array of 3.2/spl times/3.2 mm BGO crystals (10 mm deep) using Hamamatsu R-2497 phototubes. All 64 crystals in the array can be clearly identified. The reconstructed image resolution is further estimated for the 8/spl times/8 and 10/spl times/10 arrays. These resolution results are also compared to discrete detectors which do not use analog decoding. The comparison shows that the analog decoding process degrades the image resolution by 7 to 9%. >

High energy electron fluxmeter

An instrument for measurement of high energy electrons (1-10 MeV) in the Earth's radiation belts has been designed, calibrated and flown on-board the CRRES spacecraft. The instrument uses a triple coincidence arrangement with two solid state detectors and a BGO scintillator crystal to identify electrons and discriminate against energetic protons. A thorough description of the construction and calibration is presented along with an example of on-orbit data.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Ultrafine electromagnetic calorimetry: The Y(4s) case

The role played by electromagnetic calorimetry in the reconstruction of beauty mesons produced in e +e − annihilation by the Y resonances decays at rest is recognized to be fundamental. In this paper we discuss the requests dictated by physics to the calorimeter performances; we briefly review existing detectors and we look for options offered by new available materials. Different choices are evaluated assuming as figure of merit the capability in reconstructing the highest number of π 0 still keeping a good signal-to-noise ratio. The option of using BGO scintillator crystals is finally described in some detail.

Performance Study of the Whole-Body, Multilayer Positron Computed Tomograph. - PCTW-II -

A whole body Positron CT has been developed. The system has a gantry consisting of 4 detector-rings and provides 7 slice-images simultaneously. The continuously rotating scan method is employed in this system. Each detector-ring consists of 192 gamma-ray detectors using BGO scintillation crystals (12×24×24 mm). A dual rectangular photomultiplier tube has been developed to increase the detector packing factor and to improve detector performance. Spatial resolution for reconstructed image is equal to 7.6 mm FWHM at the center of FOV. In a 20 cm-dia. cylindrical phantom, sensitivities are 33.9 kcps/(?Ci/cc) and 52.0 kcps/(?Ci/cc) in the in-plane and cross-plane, respectively. These include scattered coincidence events. By using the projection background cutting method, scatter coincidence counts are estimated as 21.6 % and 23.3 % of the total coincidence counts in the in-plane and cross-plane, respectively.