High Light Yield Research Articles

Photonic-crystals-based GAGG:Ce scintillator with high light output and fast decay time for soft X-ray detection

Gd2O2S:Tb (P43) powder was widely used in soft X-ray detection due to its high light yield. Compared with P43, GAGG:Ce scintillator has high light transmittance, fast decay time and strong radiation resistance. Photonic crystals (PhCs) can be used to enhance the light output of scintillator. In this paper, two-dimensional (2D) photonic crystals that consist of square arrays of air holes etched into TiO2 layer were fabricated on the exit surface of GAGG:Ce scintillator to enhance its light output. The luminescence spectra and the light output of GAGG:Ce scintillator with/without PhCs were measured at the BL08U1A beamline of Shanghai Synchrotron Radiation Facility. The results showed that the light output of GAGG:Ce scintillator with PhCs can be enhanced by a factor of 1.43 times compared with the reference GAGG:Ce scintillator, 2.35 times compared with YAG:Ce scintillator, 1.24 times compared with Gd2O2S:Tb scintillation ceramic and 0.76 times compared with P43 powder layer with the mass thickness of about 1.3mg/cm 2 with optical grease coupling. No significant change was observed in luminescence decay time between GAGG:Ce scintillator with and without PhCs. It makes GAGG:Ce scintillator with PhCs a promising material instead of P43 powder and YAG:Ce scintillator in soft X-ray detector.

First operation of undoped CsI directly coupled with SiPMs at 77 K

The light yield of a small undoped cesium iodide (CsI) crystal directly coupled with two silicon photomultipliers (SiPMs) at about 77 Kelvin was measured to be 43.0 pm 1.1 photoelectrons (PE) per keV electron-equivalent (keV_text {ee}) using X and gamma -ray peaks from an ^{241}Am radioactive source from 18 to 60 keV. The high light yield together with some other technical advantages illustrate the great potential of this novel combination for neutrino and low-mass dark matter detection, particularly at accelerator-based neutrino sources, where random background can be highly suppressed by requiring coincident triggers between SiPMs and beam pulse timing signals. Some potential drawbacks of using cryogenic SiPMs instead of photomultiplier tubes (PMTs) were identified, such as worse energy resolution and optical cross-talks between SiPMs. Their influence to rare-event detection was discussed and possible solutions were provided.

Optimized scintillation strip design for the DANSS upgrade

DANSS is a one cubic meter plastic scintillator detector with a primary goal of sterile neutrino searches at a commercial nuclear reactor. Due to its highly advantageous location, fine segmentation and ability to change the distance to the neutrino production origin, DANSS is ahead of many similar experiments around the world in terms of the counting rate, signal to background ratio and sterile neutrino exclusion regions. Yet a moderate energy resolution of the detector prevents further progress in the physics program. The main challenge of the planned upgrade is to achieve an energy resolution of 12% at 1 MeV. The new design of the main sensitive element — the plastic scintillation strip — is the most important step forward. The strip prototypes were manufactured and tested at the pion beam of the PNPI synchrocyclotron. More than twice higher light output together with fairly flat detector response uniformity, longitudinal timing information and other optimizations will help to reach the upgrade goal. This paper discusses the drawbacks of the current strip version, outlines the new features of the proposed upgrade, describes the beam test procedure and presents the test results reflecting the advantages of the new strip design in comparison with the current version.

Effect of Gd3+-Sm3+ Energy Transfer on the Luminescence Properties of Ba-Na-B Glasses

In this work, Sm3+-doped Ba-Na-B glasses with the varying of Gd3+ concentration from 0 to 10 mol% were prepared by melt-quenching technique. The absorption spectra show the highest peak at 402 nm (in UV-Vis region) and at 1227 nm (in NIR region). The emission spectra, excited by 402 nm excitation wavelength, show the emission peaks centered at 563, 600, 646 and 706 nm. The glass sample with 2.5 mol% of Gd3+ ions show the highest light yield. The emission spectra, excited by 275 nm for investigation of Gd3+ to Sm3+ energy transfer, also highest emission peaks observed at 311 and 622 nm for Gd3+ ions. The emission peaks observed at 563, 600, 646 and 706 nm for Sm3+ ions. The glass sample with 7.5 mol% of Gd3+ ions show the highest light yield because of the better energy transfer from Gd3+ to Sm3+ ions. The color of the emission from these glass samples are located in orange emission region when excited with 402 nm and located in reddish-orange emission region when excited with 275 nm.

Seed-Crystal-Induced Cold Sintering Toward Metal Halide Transparent Ceramic Scintillators.

Scintillators with high spatial resolution at a low radiation dose rate are desirable for X-ray medical imaging. To challenge the state-of-art technology, it is necessary to design large-area wafers with high light yield, oriented light transport, and reduced light scattering. Here, a seed-crystal-induced cold sintering is adopted and a <001>-textured TPP2 MnBr4 (TPP: tetraphenylphosphonium) transparent ceramic is fabricated with a large-area wafer of 5cm in diameter, exhibiting high optical transparency of above 68% over the 450-600nm range. The compelling scintillation performance of the TPP2 MnBr4 wafer includes a light yield of ≈78000± 2000 photons per MeV, a low detection limit 8.8 nanograys per second, about 625 times lower than the requirement of X-ray diagnostics (5500 nanograys per second), and an energy resolution of 17% for high-energy γ-rays (662keV). X-ray imaging demonstrates a high spatial resolution of 15.7 lp mm-1 . Moreover, the designed material exhibits good retention of the radioluminescence intensity and light yield. This work presents a paradigm for achieving light-guiding properties with high transparency and large-area fabrication by grain orientation engineering, and the transparent, textured metal halide ceramic scintillator is expected to provide a route for advancement in the X-ray imaging of tomorrow.

In Situ Fabrication of Cs3Cu2I5: Tl Nanocrystal Films for High-Resolution and Ultrastable X-ray Imaging.

Cs3Cu2I5 nanocrystals (NCs) are considered to be promising materials due to their high photoluminescence efficiency and X-ray hardness. However, the present strategy depends on tedious fabrication with excessive chemical waste. The evasive iodide ion dissociation, inadaptable ligand system, low stability, and relatively low light yield severely impede their applications. Herein, we develop an in situ fabrication strategy for a flexible and large-area Tl-doped Cs3Cu2I5 NC-polymer composite scintillation film with a high light yield (∼48800 photons/MeV) and improved stability. Tween 80 and phosphinic acid successfully inhibit the oxidation of iodide ions, and the films can be stored for at least six months. As a result, a high spatial resolution of 16.3 lp mm-1 and a low detection limit of 305 nGyair s-1 were achieved. A radioluminescence intensity of >80% was maintained after a total irradiation dose of 604.8 Gy. These results indicate the promising application of these copper halide NCs in low-cost, flexible, and high-performance medical imaging.

Cerium Bromide Single-Crystal X-Ray Detection and Spectral Compatibility Assessment with Various Optical Sensors

Scintillators with high light yield (LY) values are of interest for medical imaging applications, in harsh environments, nondestructive testing (NDT), etc. CeBr3 has a LY of 60000 photons per MeV, a value much higher than other efficient materials, such as Lu3Al5O12:Ce (25000 photons/MeV); thus, its X-ray detection properties would be of interest to be examined for medical imaging applications. The X-ray detection and absorption properties of a single crystal CeBr3 sample along with the compatibility of its produced light with various optoelectronic sensors were examined. In this study, the quantum detection (QDE) and the energy absorption efficiency (EAE) of CeBr3 were calculated. The findings were compared with data for 10 × 10 × 10 m m 3 Lu3Al5O12:Ce and CaF2:Eu single crystals. The measured optical spectrum produced by CeBr3 was well correlated with the spectral response of commercial optical sensors, yielding spectral matching higher than 93% for various photocathodes, e.g., GaAs (94%), E-S20 (95%), and bialkali and multialkali (95-97%), as well as with flat panel position-sensitive photomultipliers (95-99%). The energy absorption properties of CeBr3 were found higher than those of Lu3Al5O12:Ce and CaF2:Eu for X-ray tube voltages greater than 100 kVp. The quantum detection efficiency was 100% across the examined energy range. Even though CeBr3 is hygroscopic and has a mediocre 5.1 g/cm3 density, the QDE, EAE, and spectral correlation results are promising for medical imaging applications.

Inverted N-polar blue and blue-green light emitting diodes with high power grown by metalorganic chemical vapor deposition

The N-polar orientation of GaN may be an option for the development of longer wavelength visible optoelectronics because of its higher indium uptake. N-polar InGaN LEDs with an inverted p-side down configuration and buried tunnel junctions were grown by metalorganic chemical vapor deposition. Fabricated devices in the wavelength range of 450–509 nm showed record high light output power for N-polar LEDs, up to 0.21 mW on-wafer at 20 A/cm2 with an emission wavelength of 470 nm. These results represent an improvement in performance of more than one order of magnitude over previously reported N-polar LEDs, demonstrating potential for the N-polar orientation in the nitride optoelectronics space.

Correlated and integrated directionality for sub-MeV solar neutrinos in Borexino

Liquid scintillator detectors play a central role in the detection of neutrinos from various sources. In particular, it is the only technique used so far for the precision spectroscopy of sub-MeV solar neutrinos, as demonstrated by the Borexino experiment at the Gran Sasso National Laboratory in Italy. The benefit of a high light yield, and thus a low energy threshold and a good energy resolution, comes at the cost of the directional information featured by water Cherenkov detectors, measuring B8 solar neutrinos above a few MeV. In this paper we provide the first directionality measurement of sub-MeV solar neutrinos which exploits the correlation between the first few detected photons in each event and the known position of the Sun for each event. This is also the first signature of directionality in neutrinos elastically scattering off electrons in a liquid scintillator target. This measurement exploits the subdominant, fast Cherenkov light emission that precedes the dominant yet slower scintillation light signal. Through this measurement, we have also been able to extract the rate of Be7 solar neutrinos in Borexino. The demonstration of directional sensitivity in a traditional liquid scintillator target paves the way for the possible exploitation of the Cherenkov light signal in future kton-scale experiments using liquid scintillator targets. Directionality is important for background suppression as well as the disentanglement of signals from various sources.8 MoreReceived 10 September 2021Accepted 24 January 2022DOI:https://doi.org/10.1103/PhysRevD.105.052002Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Physical SystemsNeutrinosTechniquesCherenkov detectorsNeutrino detectorsParticle data analysisScintillatorsParticles & Fields

First Directional Measurement of Sub-MeV Solar Neutrinos with Borexino.

We report the measurement of sub-MeV solar neutrinos through the use of their associated Cherenkov radiation, performed with the Borexino detector at the Laboratori Nazionali del Gran Sasso. The measurement is achieved using a novel technique that correlates individual photon hits of events to the known position of the Sun. In an energy window between 0.54 to 0.74MeV, selected using the dominant scintillation light, we have measured 10 887_{-2103}^{+2386}(stat)±947(syst) (68%confidence interval) solar neutrinos out of 19 904 total events. This corresponds to a ^{7}Be neutrino interaction rate of 51.6_{-12.5}^{+13.9} counts/(day·100 ton), which is in agreement with the standard solar model predictions and the previous spectroscopic results of Borexino. The no-neutrino hypothesis can be excluded with >5σ confidence level. For the first time, we have demonstrated the possibility of utilizing the directional Cherenkov information for sub-MeV solar neutrinos, in a large-scale, high light yield liquid scintillator detector. This measurement provides an experimental proof of principle for future hybrid event reconstruction using both Cherenkov and scintillation signatures simultaneously.

Zero‐Dimensional Luminescent Metal Halide Hybrids Enabling Bulk Transparent Medium as Large‐Area X‐Ray Scintillators

AbstractScintillators are critical in medical imaging, non‐destructive security screening, and space exploration applications. However, it still remains a challenge to achieve large‐area and high‐transparency scintillators by a low‐cost and easy‐to‐implement way. Herein, a large transparent medium with a diameter over 10 cm is prepared via a facile melt‐quenching strategy using a stoichiometric mixture of ethyltriphenylphosphonium bromide (ETPBr) and MnBr2 as raw materials. Benefiting from the crystallization behavior of high‐efficiency green‐emitting (ETP)2MnBr4 nanocrystals hybridized with amorphous phase in the transparent wafer, the (ETP)2MnBr4‐based transparent medium as a scintillator evidences a high transparency (over 80%, ranging from 500 to 800 nm), a high light yield of ≈35 000 ± 2000 photon per MeV, a low detection limit of 103 nGy S–1, and a competitive spatial resolution of 13.4 lp mm–1 for X‐ray imaging. This work offers a distinctive simple and fast melt‐quenching methodology to fabricate (ETP)2MnBr4 metal halide X‐ray scintillator wafer with large‐area and shape flexibility, excellent transparency, and high scintillation performance for the medical or industrial X‐ray imaging application.

Photoluminescence and X-ray excited scintillating properties of Tb3+-doped borosilicate aluminate glass scintillators

lthough single crystal scintillators have excellent performance, they have some drawbacks such as high cost, complicated elaboration method and difficulty of growth on large-scale. Glass scintillators are widely investigated to replace single crystal scintillators because of their simple fabrication method and low cost. In this paper, a series of transparent borosilicate aluminate glass scintillators doped with Tb3+ were successfully prepared by traditional melt-quenching method. The structural, luminescent, and X-ray excited scintillating properties were investigated. These glass samples show high stability and high transparency, and present good luminescent and scintillating properties. Sample with Tb3+ doping concentration of 10% has the best scintillating performance. The integrated intensity of X-ray excited luminescence is 66.6% of that of commercial Bi4Ge3O12 single crystal scintillator, and the quantum efficiency (under 378 nm excitation) is 70.3%. Our findings suggest that Tb3+-doped borosilicate aluminate glasses with high light yield might be used as potential scintillators.

Neutron transmission imaging with a portable D-T neutron generator

A portable fast-neutron imaging system is being developed to provide complementary information to field X-ray imaging. Applications include inspection of vehicles and infrastructure for corrosion, measurement of material levels in containers, and inspection of munitions and suspicious packages. While fast-neuron imaging generally provides lower imaging resolution compared to X-rays, fast-neutron interaction cross-sections have a weak dependence on material Z. This enables imaging of low-Z materials inside high-Z materials. Here, we discuss the limitations and current improvements in fast-neuron imaging. Limitations in portable fast-neutron imaging systems include low D-T neutron generator output, low light production in ZnS(Cu) imaging scintillators, low resolution due to scintillator thickness and D-T spot size, and digital-panel darknoise that varies in time and position and that can be 100× larger than the neutron signal. We have made improvements in these areas through development of a segmented high light yield scintillator, panel noise mitigation techniques, and testing of new high-output, small spot size D-T neutron generators. The segmented high light yield fast-neutron scintillator demonstrated 5× increase in light compared to ZnS(Cu). An additional 2× improvement in signal-to-noise was demonstrated with panel-noise mitigation techniques. Our MCNP calculations also show good agreement with neutron imaging results We have demonstrated improvements in fast-neutron imaging through development of a segmented high light yield neutron scintillator, mitigation of digital panel noise, and preliminary testing with new high-output, small spot size D-T neutron generators. We have also demonstrated good results modeling fast-neutron images and scatter effects using MCNP.

Cesium Lead Halide Nanocrystals based Flexible X‐Ray Imaging Screen and Visible Dose Rate Indication on Paper Substrate

AbstractMetal halide semiconductors have huge potential on X‐ray detection, due to their high atomic number, adjustable photoluminescence wavelength, superior stability, and simple fabrication process. Here, cesium lead halide nanocrystals (CsPbX3 NCs) are fabricated on paper substrate as scintillator screen for the first time. By means of all‐solution processed spray‐coating method with optimization of polymethyl methacrylate, large‐area (&gt;600 cm2) and low‐cost (0.0975 dollar cm−2) flexible scintillator screens are obtained with high resolution (≈5 lp mm−1), low detection limit (2.97 μGy s−1), high light yield (≈30000 photons/MeV), and fast response speed (&lt;15 ms). The screen can achieve high‐resolution X‐ray non‐distortion imaging for non‐planar objects and realize battery check and safety monitoring at a broad range of photon energy (10–160 keV). In addition, real‐time dose rates can be easily estimated through counting the luminous arcs of the designed visible indicator. More important, the screen shows remarkable tolerance to high‐dose X‐ray radiation (tolerance over 60 Gyair continuous radiation with only 3% performance degradation), water soaking (2000 h), and conventional storage (over 300 days without apparent deterioration under ambient conditions). Hence, this work may provide huge potential in the field of medical diagnosis, non‐planar detection, and safety monitoring in the future.

Evaluation of photoluminescence and scintillation properties of Yb2+-doped CsMX3 (M = Ca, Sr; X = Cl, Br) crystals

The photoluminescence (PL) and scintillation properties of CsMX3:Yb2+ (M = Ca, Sr; X = Cl, Br) crystals grown using a self-seeding solidification method were demonstrated. During PL and scintillation, spin-allowed and spin-forbidden Yb2+ 4f14–4f135d transitions were observed for CsCaBr3:Yb2+ and CsSrBr3:Yb2+, whereas only spin-forbidden transitions were observed for CsCaCl3:Yb2+ and CsSrCl3:Yb2+. The scintillation decay time constants of the spin-allowed transitions for CsCaBr3:Yb2+ and CsSrBr3:Yb2+ were 210 and 64 ns, respectively, while those for the spin-forbidden transitions of CsMX3:Yb2+ (M = Ca, Sr; X = Cl, Br) were between 57 and 390 μs? Based on the pulse height spectra, light yields of CsMX3:Yb2+ (M = Ca, Sr; X = Cl, Br) were estimated to be between 2700 and 5500 photons/MeV. When the slow components were considered, the estimated range increased to 16,000–120,000 photons/MeV. CsCaCl3:Yb2+ and CsCaBr3:Yb2+ showed high total light yields of 48,000 and 120,000 photons/MeV, respectively, when compared to CsSrCl3:Yb2+ and CsSrBr3:Yb2+, for which the obtained yields were 16,000 and 23,000 photons/MeV, respectively. Owing to their high light yields, CsMX3:Yb2+ (M = Ca, Sr; X = Cl, Br) crystals, including the slow components, therefore have the potential to replace conventional scintillators in current-mode detectors.

(Gd,Ce)2O3-Al2O3-SiO2 scintillation glass

Heavy scintillation glass of Gd2O3-Al2O3-SiO2 composition doped with Ce, combining high light yield and fast scintillation kinetics, was developed. The glass samples were prepared at 1500 °C by a melt-quench technique; the resulting glass was colorless and satisfactorily homogeneous. A photoluminescence study showed that a variety of sites for the Ce3+ ion stabilization exists in the glass, but the phenomenon was found less pronounced compared to BaO-Gd2O3-SiO2 glass. The glass has demonstrated ∼4 times faster scintillation kinetics and a minor drop of the light yield related to barium-gadolinium-silica glass, which makes this material of particular interest for large volume detectors in high energy physics, medical imaging, and other applications due to a low-cost production capability.

Bounce back with triplet excitons for efficient X-ray scintillation

Efficient harvesting of triplet excitons in organic molecules is crucial for developing high-performance X-ray scintillators and X-ray imagers. High-performance organic scintillators based on thermally activated delayed fluorescence (TADF) have been recently demonstrated, allowing the triplet excitons to generate a high light yield under X-ray illumination. These TADF organic molecules outperformed the benchmark anthracene-based scintillators.

Compositionally Disordered Doped with Cerium Crystalline Garnet Type Materials for Brighter and Faster Scintillations

Ce-doped tetracationic garnets (Gd, M)3Al2Ga3O12(M = Y, Lu) form a family of new multipurpose promising scintillation materials. The aim of this work was to evaluate the scintillation yield in the materials of quaternary garnets activated by cerium ions with partial isovalent substitution of the matrix-forming gadolinium ions by yttrium or lutetium ions.Materials were obtained in the form of polycrystalline ceramic samples, and the best results were shown by samples obtained from the raw materials produced by the coprecipitation method. It was found that ceramics obtained from coprecipitated raw materials ensure a uniform distribution of activator ions in the multi-cationic matrices, which enables the high light yield and fast scintillation kinetics of the scintillation. It was demonstrated that the superstoichiometric content of lutetium/gadolinium in the material is an effective method to suppress phosphorescence accompanied scintillation. For ceramics with the composition (Gd, Lu)3Al2Ga3O12 , a scintillation yield of more than 50.000 ph/MeV was achieved. The scintillation kinetics was measured to be close to the kinetics with a decay constant of 50 ns.In terms of the set of the parameters, the developed scintillation materials are close to the recently developed alkali halide materials LaBr3:Ce, GdBr3:Ce. Moreover, they have high mechanical hardness, are characterized by the absence of hygroscopicity, and are better adapted to the manufacture of pixel detectors used in modern devices for medical diagnostics.

Stable and Bright Commercial CsPbBr3 Quantum Dot-Resin Layers for Apparent X-ray Imaging Screen.

CsPbBr3 quantum dots (QDs) have recently gained much interest due to their excellent optical and scintillation properties and their potential for X-ray imaging applications. In this study, we blended CsPbBr3 QDs with resin at different QD concentrations to achieve thick films and to protect the CsPbBr3 QDs from environmental moisture. Then, their scintillation properties are investigated and compared to the traditional commercial scintillators, CsI:Tl microcolumns, and Gadox layers. The CsPbBr3 QD-resin sheets show a high light yield of up to 21 500 photons/MeV at room temperature and a relatively small variation in light yield across a wide temperature range. In addition, the CsPbBr3 QD-resin sheets feature a small scintillation afterglow. The CsPbBr3 QD-resin sheets show a negligible trap density for the concentration below 50% weight, indicating that traps might arise from the aggregation of the QDs. The CsPbBr3 QD-resin sheets are also very stable at low irradiation intensities and relatively stable at higher intensities, with higher CsPbBr3 QD concentrations being more stable. Gamma-ray-excited-time-resolved emission measurements at 662 keV showed that the CsPbBr3 QD-resin sheets have an average scintillation decay time between 108 and 176 ns, which are still 10 000 and 6000 times faster than CsI:Tl and Gadox, respectively. Imaging tests show that the CsPbBr3 QD-resin sheets have a mean transfer function of 50% at 2 lp/mm and 20% at 4 lp/mm, comparable to that of commercial Gadox layers. This feature makes CsPbBr3 QD-resin sheets a good candidate for the low-cost, flexible X-ray imaging screens and γ-ray applications.

First Cherenkov directional detection of sub-MeV solar neutrinos in Borexino

Borexino is a 280t liquid scintillator detector at the Laboratori Nazionali del Gran Sasso (LNGS), Italy. Its main goal is the precision spectroscopy of solar neutrinos down to energies of 0.19 MeV and for this task it features an unprecedented radio-purity and a high scintillation light yield. The solar neutrinos are measured by the elastic scattering off electrons which induce isotropically emitted scintillation photons as well as a sub-dominant number of Cherenkov photons that are detected by photomulitplier tubes. Here we present the first detection of sub-MeV solar neutrinos using their associated Cherenkov photons in a high light yield liquid scintillator detector. In Borexino electrons with E>0.16MeV produce Cherenkov photons, where the ratio of Cherenkov photons from the neutrino scattered electrons is estimated to be < 1% for all PMT hits, so a typical event by event direction reconstruction is not possible. Instead this analysis looks at the integrated signal of the PMT hits of all detected events by correlating the position of each hit PMT relative to the reconstructed position of the event and the well known position of the Sun. In this way it is possible to measure an angular distribution that shows the statistical contribution of Cherenkov photons from the solar neutrino recoil electrons. Using the Geant4-based Borexino Monte Carlo to produce the expected angular distribution for solar neutrinos and background we have measured neutrino events out of 19904 total events for an energy region around the 7Be edge between 0.53 MeV and 0.74 MeV.