Thermal Neutron Scintillation Research Articles

Transparent Glass Composite Scintillator with High Crystallinity for Efficient Thermal Neutron Detection

AbstractThe sensitive and rapid detection of thermal neutrons holds significant importance in various fields such as energy utilization, medical treatment, and national defense. However, the available thermal neutron scintillator is difficult to reach this target, mainly limited by the optical and scintillating performance. Herein, the in situ crystallization strategy of glass to construct scintillation glass composites for efficient thermal neutron detection is proposed. The congruent crystallization of the hybridized alkali earth silicate glass system may not only achieve high crystallinity, but also will keep the refractive indexing matching between the precipitated crystal and precursor glass phases. The prepared glass composites feature high luminescence efficiency, optical transmission and excellent neutron response properties. These factors collectively contribute to the robust neutron scintillation performance with a light output of ≈36 000 photons/neutron, which represents the highest value among glass‐based scintillators. Moreover, the composite configuration brings about the additional function of thermal neutron and γ‐ray discrimination. By using this composite scintillator, the neutron detector is constructed and demonstrates its application for detecting thermal neutron and distinguishing it from γ‐ray in an online way. The studies prove that glass composites with high crystallinity are expected to be promising candidates for a new generation of multifunctional neutron detectors.

Growth and Scintillation Properties of 6Li Containing Ce:LaCl3-Based Eutectic Scintillator for Neutron Detection

In this study, Ce:6LiCl/LaCl3 with a high 6Li concentration was developed as a novel thermal neutron scintillator, in which Ce3+ serves as an activator for the LaCl3 phase. The Ce:6LiCl/LaCl3 eutectic was grown in a quartz ampoule (inner diameter: 4.0 mm) using the Bridgman–Stockbarger technique. The grown eutectic contained 0.038 mol/cm3 6Li, which is greater than that found in commercially available scintillators such as LiCaAlF6 single crystals and Li glass. The Ce:6LiCl/LaCl3 eutectic has a lamellar eutectic structure and is optically transparent. A 350 nm emission due to Ce3+ 4f-5d transition was observed. The light yield under neutron irradiation was estimated to be 5.0 times higher than that of Li-glass. In this eutectic, the 6Li (n, a) 3H reaction made the 6LiCl phase to act as the neutron capture phase and LaCl3 to act as the scintillator phase.

Tl-Doped CsI/⁶LiBr Scintillator for Thermal Neutron Detection With Ultrahigh Light Yield

In this study, a novel thermal neutron scintillator of Tl:CsI/LiBr was developed. The eutectics were fabricated at the various growth rate and investigated their scintillation properties. As a material design guideline, Tl:CsI, which has an excellent α/γ ratio, was selected as the scintillator phase to realize high light yield at the energy of α-rays and tritons generated by the nuclear transmutation reaction with <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> Li, and LiBr, which has a refractive index close to that of CsI, was selected as the neutron capture phase. Radioluminescence measurement under X-ray irradiation was also performed to obtain the emission spectrum of the eutectics. The light yield and decay time for thermal neutron were measured using <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">252</sup> Cf and were much higher than those of conventional scintillators for thermal neutron. Furthermore, fabricated eutectic can have the higher sensitivity to thermal neutron due to the high <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> Li concentration compared to conventional single crystal scintillators. Therefore, we have succeeded in developing a promising scintillator material.

Large scale BN-perovskite Nanocomposite Aerogel Scintillator for Thermal Neutron Detection.

State-of-the-art thermal neutron scintillation detectors rely on rare isotopes for neutron capture, lack stability and scalability of solid-state scintillation devices, and poorly discriminate between the neutron and gamma rays. Our boron nitride (BN) - CsPbBr3 perovskite nanocomposite aerogel scintillator enables discriminative detection of thermal neutrons, features the largest known size (9cm across), the lowest density (0.17g/cm3 ) among the existing scintillation materials, high BN (50%) perovskite (1%) contents, high optical transparency (85%), and excellent radiation stability. The new detection mechanism relies on thermal neutron capture by 10 B and effective energy transfer from the charged particles to visible-range scintillation photons between the densely packed BN and CsPbBr3 nanocrystals. Low density minimizes the gamma ray response. The neutrons and gamma rays are discriminated by complete decoupling of the respective single pulses in time and intensity. These outcomes open new avenues for neutron detection in resource exploration, clean energy, environmental, aerospace, and homeland security applications. This article is protected by copyright. All rights reserved.

Novel flexible and conformable composite neutron scintillator based on fully enriched lithium tetraborate

Thermal neutron detection is a key subject for nuclear physics research and also in a wide variety of applications from homeland security to nuclear medicine. In this work, it is proposed a novel flexible and conformable composite thermal neutron scintillator based on a fully enriched Lithium Tetraborate preparation (^{6}Li_2^{10}B_4O_7) combined with a phosphorescent inorganic scintillator powder (ZnS:Ag), and is then distributed into a polydimethylsiloxane matrix. The proposed scintillator shows a good neutron detection efficiency (max. sim 57% with respect to the commercial EJ-420), an average light output of sim 9000 ph/neutron-capture, a remarkable insensitivity to gamma-rays (Gamma Rejection Ratio <10^{-11}), and an extraordinary flexibility, so as to reach extremely small curvature radii, down to 1.5 mm, with no signs of cracking or tearing. Its characteristics make it suitable to be employed in scenarios where non-standard geometries are needed, for example, to optimize the detector performance and/or maximize the detection efficiency. Finally, the response of a hybrid detector made of a plastic scintillator, wrapped with the proposed scintillator, coupled to a silicon photomultiplier array is described, and the excellent discrimination between gamma-rays, fast and thermal neutrons resulting from data processing is demonstrated.

Thermal neutron scintillation improvement in Ce:Li6Y(BO3)3 single crystals by thermal treatment

The development of efficient, low-cost, and stable solid-state materials for portable thermal neutron detection is highly expected in order to substitute the currently used 3He and BF3 tank detectors. A few Li-based glasses and halide compounds have emerged as candidates, however, all of them present critical drawbacks for their practical implementations. Ce:Li6Y(BO3)3 is a priori a very promising oxide candidate that however has been disregarded so far due to its negligibly low light yield, caused by a poor crystalline and optical quality. In this study, we demonstrate that a post-growth thermal treatment is the key parameter to drastically reduce the concentration of intrinsic defects and scattering centers that lead to severe non-radiative recombination of excited electrons. Even though this annealing step also involves the oxidation of activator Ce3+ ions to Ce4+, a drastic enhancement of the light yield by ∼600% is achieved independently of the Ce3+ concentration within the considered range. The obtained light yield of 4650 ph n−1 is already close to that of reference Li-glass (commercial GS20 with 6000 ph n−1). An additional improvement can be envisaged upon further optimization of the Ce3+ concentration and the annealing time, so that Ce:Li6Y(BO3)3 reaches a light yield comparable to the state-of-the-art one for thermal neutron detection.

Transparent Microcomposite Films Based on a Ce-Doped Li6Gd(BO3)3 Scintillator for Radiation Detection.

Scintillators are widely used for high-energy radiation detection. Hybrid inorganic–organic composite scintillators with high light yields, high light decay rates, excellent stability, and low costs are in great demand. Here, we report a novel scintillator composed of Ce-doped Li6Gd(BO3)3 (LGBO) microphosphors (MPs) and polymethyl methacrylate for X-ray and thermal neutron detection. The Ce-doped LGBO MPs, fabricated using a facile high-temperature solid-state reaction method, exhibit intense blue light at 416 nm under X-ray and UV excitation and have a high photoluminescence quantum yield of ∼63%. More importantly, the composite scintillator based on these MPs has excellent transparency and luminescence intensity. The luminescence integral intensity of composite scintillators is superior to that of commercial CsI:Na under X-ray excitation, and the light yield under thermal neutron irradiation is 21,000 photons/thermal neutron. The scintillation decay time is found to be below 600 ns. The neutron−gamma signal discrimination and neutron detection efficiency of the composite scintillators are acceptable for practical application. There is an excellent separation between neutron and background events. It represents significant improvements in scintillator performances, especially for reliable thermal neutron scintillators that are likely to improve the data qualities of scientific instruments, including charge-coupled device-based imagers and Anger logic-based position-sensitive detectors in neutron user facilities.

Growth of 6Li-enriched LiCl/BaCl2 eutectic as a novel neutron scintillator

In this study, Eu:6LiCl/BaCl2 with a high Li concentration was developed as a novel thermal neutron scintillator. Eu ions were doped as activators for the BaCl2 phase, and Eu:6LiCl/BaCl2 eutectics were grown via the vertical Bridgman–Stockbarger method in quartz ampoules (inner diameter = 4 mm). The Eu:6LiCl/BaCl2 eutectic exhibited a lamellar eutectic structure and optical transparency. The 400 nm emission due to the Eu2+ 4f–5d transition was observed in the BaCl2 phase by a cathode luminescence measurement. The light yield under neutrons was estimated to be over 20 200 photons MeV−1. A PSD study was also performed using gamma and alpha-rays. The Eu:6LiCl/BaCl2 eutectic scintillator showed good potential for PSD.

Growth and scintillation properties of LiBr/CeBr3 eutectic scintillator for neutron detection

A 6LiBr/CeBr3 eutectic thermal-neutron scintillator, with a high 6Li concentration, was developed using the vertical Bridgman method. The grown eutectic contained an 6Li molar ratio of 35%, which is higher than those of the commercial neutron scintillators such as Ce:LiCaAlF6 and Ce:Cs2LiYCl6. Furthermore, it showed optical transparency and a lamellar eutectic structure elongating along the growth direction. The synthesized eutectic showed emission peaks at 360 and 380 nm, originating from the Ce3+ 5d-4f transition in the CeBr3 scintillation phase. The scintillation performance of 6LiBr/CeBr3 was evaluated under X-ray, γ-ray, and neutron irradiation to corroborate its neutron detection potential.

Growth and scintillation properties of Ce doped [formula omitted]LiBr/LaBr[formula omitted] eutectic scintillator for neutron detection

In this study, Ce:6LiBr/LaBr3 eutectic with a high Li concentration was developed as a novel thermal neutron scintillator. Ce served as an activator for the LaBr3 phase, and Ce:6LiBr/LaBr3 eutectics were grown via the vertical Bridgman method in quartz ampoules (inner diameter = 4 mm). In the eutectic, the 6LiBr phase worked as the neutron capture phase by the 6Li (n, a) 3H reaction, and Ce:LaBr3 worked as the scintillator phase. The Ce:6LiBr/LaBr3 eutectic exhibited a lamellar eutectic structure and optical transparency, as well as 350 and 380 nm emission due to Ce3+ 5d-4f transition. The light yield under neutrons excitation was estimated to be 74000 photons/neutron. The scintillation decay time was 18.7 ns.

Basic study of ceramic lithium strontium borates as thermal neutron scintillators

AbstractA special group of luminescence materials are scintillators for thermal neutron detection. Due to the properties of neutrons (contrary to e.g. electrons or gamma photons), a different approach has to be utilized—the high content of atoms with the sufficient absorption cross‐section toward neutrons and lower material density are needed. This work pursues a basic study of LiSrBO3 and LiSr4(BO3)3 doped with cerium or europium—materials promising as thermal neutron scintillators. These borates exhibit promising properties such as the high content of lithium and boron, suitable density, and proper environment for luminescent ions. Radioluminescence of these ceramic borates doped with cerium and europium was examined and promising samples were further characterized by photoluminescence spectroscopy and radioluminescence and photoluminescence kinetics measurement. The radioluminescence study of these borates is published for the first time. Cerium‐doped borates, in particular, exhibit a very promising response to an X‐ray excitation.

Growth and scintillation properties of Eu doped Li2SrCl4/LiSr2Cl5 eutectic

In this study, a Eu-doped Li2SrCl4/LiSr2Cl5 eutectic with a high 6Li concentration was developed as a novel thermal neutron scintillator. The doped Eu served as an activator in the Li2SrCl4 and LiSr2Cl5 phases. The Eu-doped Li2SrCl4/LiSr2Cl5 eutectic was grown using the vertical Bridgman method in a sealed quartz ampoule. The eutectic exhibited a lamellar eutectic structure elongated along the pulling direction, and was optically transparent. The emissions at 401 and 412 nm were attributed to the Eu2+ 4f-5d transition in the Li2SrCl4 and LiSr2Cl5 phases, respectively. The light yield under 5.5 MeV α -rays was estimated to be 5,600 photons/5.5 MeV α -rays. The scintillation decay time was 312 ns. In the eutectic, the Li2SrCl4 and LiSr2Cl5 phases contributed to scintillation and neutron capture by the 6Li (n, a) 3H reaction.

Growth and scintillation properties of Eu-doped LiCl/Li2SrCl4 eutectic scintillator for neutron detection

A 6LiCl/6Li2SrCl4 eutectic scintillator with a high Li concentration was developed as a novel thermal neutron scintillator. Eu2+ served as an activator for the 6Li2SrCl4 phase, and Eu-doped 6LiCl/6Li2SrCl4 eutectics were grown via the Bridgman Stockbarger method in quartz ampoules (inner diameter = 4 mm). The Eu-doped 6LiCl/6Li2SrCl4 eutectics exhibited a lamellar-type eutectic structure and optical transparency, as well as 400 nm emission due to Eu2+ 5d-4f transition. The scintillation properties of the eutectics were evaluated under gamma- and alpha-ray irradiation to demonstrate its potential as a thermal neutron scintillator.

Flux-growth of Ce:LiY6O5(BO3)3 single crystals during the Czochralski pulling from nearly congruent Ce:Li6Y(BO3)3 and their optical properties

Ce:Li6Y(BO3)3 (LYBO) is a promising thermal neutron scintillator that can be grown into bulk single crystals by the Czochralski method although it melts incongruently. This study achieves 1-inch Ce:LYBO, and demonstrates the collateral flux-growth of LiY6O5(BO3)3 (LYOB) single crystals at the bottom of the crucible during the pulling of LYBO from a stoichiometric melt. Both LYBO and LYOB belong to monoclinic crystal system with the same space group. Thermal analysis shows that LYOB itself is more incongruent than LYBO, decomposing mainly into Y16.86B8O38 phase when heated up to 1500 ​°C. In contrast to the typical bluish emission of Ce-doped scintillators, like the case of Ce:LYBO, Ce:LYOB crystals exhibit a broad emission peaking in the orange wavelength region, as a result from an extraordinarily large Stokes shift. The ultrafast photoluminescence (PL) decay of Ce:LYOB is due to dominant non-radiative processes that also cause obvious luminescence quenching. This study reports for the first time high-quality Ce:LYOB single crystals, which are characterized in terms of single crystal diffraction, thermal analysis, optical transmittance, excitation and PL at room temperature, PL decay and Raman spectroscopy.

A Monte Carlo Model of the Neutron Detector Based on Lithium-Glass Scintillator

A Monte Carlo model of the thermal-neutron scintillation detector based on NE 912 lithium glass has been created and verified. The simulation was validated by comparing its result to experimental data from a prototype detector exposed to thermal-neutron and γ-ray beams. The light yield in the scintillator for a captured thermal neutron, the quenching factor, and the decay times of the scintillator were determined. The accuracy in reproducing the pulse shapes obtained in the experiment is sufficient to allow analysis of experimental data and estimation of the efficiency of n/γ discrimination techniques. Based on the simulation, it is possible to develop detector models with a low γ-ray sensitivity using heterogeneous composite scintillators with various geometries.

Synthesis and characterization of borate glasses for thermal neutron scintillation and imaging

With the aim of finding promising neutron scintillators, different compositions have been synthesized in the glassy phase and subsequently characterized for their performance as the scintillation screen of thermal neutron imaging systems. Three new compositions having Li, B, and Gd as principal constituents, doped with Eu have been synthesized by the melt quenching method and investigated the first time for neutron imaging in the present study. The concentration of luminescent activator, Eu3+ has been optimized by performing X-ray induced emission of these glass samples. Beam purity investigation along with the luminescence ability of the commercial screen have been also performed prior to the thorough evaluation of the thermal neutron scintillation characteristics of the compositions. The glass samples have been exposed to thermal neutrons for 5 and 10 min separately at the beam port of the research reactor for their performances in conventional direct film neutron radiography technique. The glasses containing Gd have been found to have higher light yield due to energy transfer from Gd ions to Eu activators. However, the composition of 60Li2O3:10Y2O3:28.5B2O3:1.5Eu2O3 (mol%) has been observed to have low light but good thermal neutron discrimination property from the gamma background despite having lesser X-ray luminescence among all three.

Neutron detection performance of gallium nitride based semiconductors

Neutron detection is crucial for particle physics experiments, nuclear power, space and international security. Solid state neutron detectors are of great interest due to their superior mechanical robustness, smaller size and lower voltage operation compared to gas detectors. Gallium nitride (GaN), a mature wide bandgap optoelectronic and electronic semiconductor, is attracting research interest for neutron detection due to its radiation hardness and thermal stability. This work investigated thermal neutron scintillation detectors composed of GaN thin films with and without conversion layers or rare-earth doping. Intrinsic GaN-based neutron scintillators are demonstrated via the intrinsic 14N(n, p) reaction, which has a small thermal neutron cross-section at low neutron energies, but is comparable to other reactions at high neutron energies (>1 MeV). Gamma discrimination is shown to be possible with pulse-height in intrinsic GaN-based scintillation detectors. Additionally, GaN-based scintillation detector with a 6LiF neutron conversion layer and Gd-doped GaN detector are compared with intrinsic GaN detectors. These results indicate GaN scintillator is a suitable candidate neutron detector in high-flux applications.

Flexible scintillation sensors for the detection of thermal neutrons based on siloxane 6LiF containing composites: Role of 6LiF crystals size and dispersion

The detection of thermal neutrons is increasingly important for several fields of interest, so new versatile, manageable and adaptable detectors are needed for applications in different environments and situations. To date, scintillators for thermal neutrons available on the market are fragile and with low adaptability. In this work, flexible and robust thermal neutron scintillators with improved properties as compared to commercial ZnS:Ag based phosphors are produced. The scintillators are produced by mixing ZnS:Ag powder and 6LiF nano-crystals in polysiloxane binders. 6LiF nano-crystals are synthesized by co-precipitation method, and the detection efficiency is optimized by tuning the crystal size through different solvent/co-solvent ratios. Then, the detection yield to thermal neutrons is investigated as related both to the crystal size and to the binder. Two different siloxanes, either with pendant phenyl groups or with aliphatic groups are used, the former being intrinsically fluorescent and with higher polarizability than the latter. The response to γ-rays is also evaluated. Lastly, the right combination of base resin and 6LiF crystals size allows to produce flexible scintillators for thermal neutrons with performances comparable to the commercial standard and with higher mechanical robustness and stability.

Optical Observation of Single Neutron Detection

The feasibility of using highly pixelated light sensors as neutron detectors is the subject of a collaboration between ILL and ESS Bilbao. The fast paced development of camera sensors can meet the future challenges of neutron detection if an optical coupling able to increase the signal to noise ratio and enlarge the detection area is identified. Fiber optics tapers seem the best candidates, but issues about their radiation resistance and price make photographic objectives a more sensible choice. The performances of photographic optics have been tested as well as the light output of several thermal neutron scintillators. Thanks to the use of a highly transmissive optics, single neutrons could be observed in 6LiF/ZnS(Ag) for the first time.

Bright [formula omitted]-activated polycrystalline ceramic neutron scintillators

Scintillation properties of Eu2+-doped CaF2-AlF3-6LiF (Eu:CALF) polycrystalline ceramic thermal-neutron scintillators as a function of AlF3 concentration have been studied. The emission band peaked at a wavelength of 425–431 nm is due to the presence of Eu:CaF2 micro-crystallites. The highest light output from these samples is approximately 20,000 photons per thermal neutron, which is 3 times that of a GS20 6Li-glass scintillator. The pulse-decay lifetime and light output vs. AlF3 concentration may be understood using a radiation trapping model and the formation of a Li3AlF6 phase. At lower AlF3 concentration, Al3+ ions in Eu:CaF2 passivate the hole-trapping defects and enhance the light output; whereas at higher AlF3 concentration, Al3+ ions lead to the formation of electron trapping centers in Eu:CaF2 and the Li3AlF6 phase is formed, which reduces the light output. A neutron–gamma-discrimination (NGD) ratio of 9×108 was obtained from Principal Component Analysis (PCA) of digital waveforms, while Fisher Linear Discriminant Analysis (FLDA) can completely separate the thermal neutrons from 60Co gamma rays within the limit of gamma event statistics used in this work. Our results suggest that Eu:CALF scintillators can potentially replace the GS20 scintillator used for thermal and cold neutron detection systems.