Neutron Scintillation Detectors Research Articles

Demonstration of shape analysis of neutron resonance transmission spectrum measured with a laser-driven neutron source

Laser-driven neutron sources (LDNSs) can generate strong short-pulse neutron beams, which are valuable for scientific studies and engineering applications. Neutron resonance transmission analysis (NRTA) is a nondestructive technique used for determining the areal density of each nuclide in a material sample using pulsed thermal and epithermal neutrons. Herein, we report the first successful NRTA performed using an LDNS driven by the Laser for Fast Ignition Experiment at the Institute of Laser Engineering, Osaka University. The key challenge was achieving a well-resolved resonance transmission spectrum for material analysis using an LDNS with a limited number of laser shots in the presence of strong background noise. We addressed this by employing a time-gated 6Li\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{6}{\ extrm{Li}}$$\\end{document}-glass scintillation neutron detector to measure the transmission spectra, reducing the impact of electromagnetic noise and neutron and gamma-ray flashes. Output waveforms were recorded for each laser shot and analyzed offline using a counting method. This approach yielded a spectrum with distinct resonances, which were attributed to 115In\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{115}\\,{\ extrm{In}}$$\\end{document} and 109Ag\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{109}{\ extrm{Ag}}$$\\end{document}, as confirmed through neutron transmission simulation. The spectrum was analyzed using the least-square nuclear-resonance fitting program, REFIT, demonstrating the possibility of using an LDNS for nondestructive areal-density material characterization.

Scintillation properties of Eu-doped LiBr crystalline scintillators under X-, γ-ray, and neutron irradiation

Scintillators for neutron detection have been required as alternative detectors for 3He gas proportional counters, which are in short supply. Therefore, Eu-doped LiBr single crystals as new scintillators for neutron detection were synthesized by the vertical Bridgman method, and the photoluminescence and scintillation properties were evaluated. Under ultraviolet light and X-ray irradiation, the emission due to 4f65d1–4f7 (8S7/2) transitions of Eu2+ was observed at 440 nm. According to pulse height spectra under 252Cf neutron irradiation, 0.01 % Eu-doped LiBr showed the highest light yield of 4600 ph/n among the prepared samples, and the α/γ ratio of 0.01 % Eu-doped LiBr was 0.37, which was better than that of commercial GS20 scintillator.

Exploring crucial technological advancements in Anger-Camera neutron detectors for single crystal neutron diffraction

In accordance with the second phase construction blueprint for the China Spallation Neutron Source (CSNS-II), the proposal includes the establishment of a single crystal neutron diffractometer. This apparatus necessitates a neutron detector array spanning over 1 m2 and capable of covering neutron diffraction angles from 20° to 160°. Additionally, the detector's position resolution must better than 1 mm × 1 mm. To meet such requirements, a scintillator neutron detector based on the Anger-Camera principle was designed. The detector is composed of a 6LiF/ZnS (Ag) scintillation screen, optical guide, silicon photomultipliers (SiPMs) array and self-design composite compression readout electronic systems. A detector prototype, featuring a detection area of 50 mm × 50 mm, was fabricated and subjected to testing at the BL20 neutron test line in the China Spallation Neutron Source (CSNS). The detector system achieved an optimal position resolution of 0.6 mm, while the maximum count rate was approximately 20 kHz. Moreover, the detector's Bragg edge imaging capability was preliminarily investigated using stainless steel samples, demonstrating its future potential for Bragg edge transmission imaging. The proposed detector demonstrates promising potential as a candidate for the single crystal diffractometer in CSNS-II.

Lithium Tetraborate as a Neutron Scintillation Detector: A Review

The electronic structure and translucent nature of lithium tetraborate (Li2B4O7) render it promising as a scintillator medium for neutron detection applications. The inherently large neutron capture cross-section due to 10B and 6Li isotopes and the ease with which Li2B4O7 can be enriched with these isotopes, combined with the facile inclusion of rare earth dopants (occupying the Li+ sites), are expected to improve the luminescent properties, as well as the neutron detection efficiency, of Li2B4O7. The electronic structure of both doped and undoped Li2B4O7 were explored, using photoemission and inverse photoemission spectroscopies, optical measurements, and theoretical computational studies such as density functional theory. The scintillation properties are further enhanced because of the wide bandgap, making Li2B4O7 extremely translucent, so that capturing the neutron scintillation output is neither hindered nor diminished. Therefore, in this review, demonstrations of the possible amplification of neutron capture efficiencies, courtesy of rare-earth dopants, along with insights into a significantly large charge production (associated with neutron capture), are presented.

Intrinsic background of EJ-309 liquid scintillator detectors

In deep-underground experiments, intrinsic detector background can exceed the external one, limiting the detection sensitivity. Intrinsic background in liquid scintillator neutron detectors consists of α particles emitted from radioactive impurities in the detector housing (and possibly in the liquid). We present the results of long background measurements of 12 EJ-309 liquid organic scintillators detectors in the deep-underground Gran Sasso National Laboratory of the Italian Institute of Nuclear Physics. These detectors are a part of the detection array for the SHADES ERC project that aims to measure the very low cross section (down to picobarn) of the astrophysically important reaction 22Ne(α,n)25Mg. With an exposure of ∼35 days we identify an actinide concentration in the detector housing of 8.4(1.8)sta(1.4)sys×10−2ppm and 1.62(0.57)sta(0.03)sys×10−1ppm of 238U and 232Th, resulting in 64 α particle counts per hour. The half-life of 214Po was also determined as 163.7(11)μs.

Development of a high-speed digital pulse signal acquisition and processing system based on MTCA for liquid scintillator neutron detector on EAST

Development of a high-speed digital pulse signal acquisition and processing system based on MTCA for liquid scintillator neutron detector on EAST

Position sensitive ZnO:Zn neutron detector – A high count rate alternative to ZnS:Ag scintillation detectors

ZnO:Zn is a low afterglow scintillator that is investigated here as a possible higher count rate alternative to ZnS:Ag for scintillation neutron detectors at scattering facilities. In the present work the first position sensitive neutron detector using ZnO:Zn has been produced and its detector performance is evaluated in comparison to a typical ZnS:Ag detector. The detection efficiency of the ZnO:Zn detector at 1 Å was measured to be 74% that of the ZnS:Ag detector, due to lower light output and collection in the ZnO:Zn detector. The trigger efficiency of the ZnO:Zn detector was 61% with gamma sensitivities on the order of 10−5; in comparison, the ZnS:Ag detector was able to achieve trigger efficiencies of 94% at gamma sensitivities ∼10−6. Areas of development to improve these limitations will be discussed. Most importantly, the rate capability of the ZnO:Zn detector was demonstrated to be approximately two times higher than the current standard ZnS:Ag scintillation detectors. With optimisation of signal processing parameters a factor of six times improvement in rate capability may be possible, indicating potential for the use of ZnO:Zn detectors in higher count rate applications.

Silicon photomultiplier based scintillator thermal neutron detector for China Spallation Neutron Source (CSNS)

The energy-resolved neutron imaging spectrometer (ERNI) will be installed in 2022 according to the spectrometer construction plan of the China Spallation Neutron Source (CSNS). The instrument requires neutron detectors with the coverage area of approximately 4 m2 in 5°–170° neutron diffraction angle. The neutron detection efficiency needs to be better than 40% at 1 Å neutron wavelength. The spatial resolution should be better than 3 mm × 50 mm in the horizontal and vertical directions respectively. We develop a one-dimensional scintillator neutron detector which is composed of the 6LiF/ZnS (Ag) scintillation screens, the wavelength-shifting fiber (WLSF) array, the silicon photomultipliers (SiPMs), and the self-designed application-specific integrated circuit (ASIC) readout electronics. The pixel size of the detector is designed as 3 mm × 50 mm, and the neutron-sensitive area is 50 mm × 200 mm. The performance of the detector prototype is measured using neutron beam 20# of the CSNS. The maximum counting rate of 247 kHz, and the detection efficiency of 63% at 1.59 Å are obtained. The test results show that the performance of the detector fulfills the physical requirements of the ERNI under construction at the CSNS.

Performance optimization of the scintillator neutron detectors for EMD in CSNS

Abstract Chinese Spallation Neutron Source (CSNS) has successfully produced its first neutron beam in 28th August 2017. It has been running steadily from March, 2018. According to the construction plan, the Engineering Materials diffractometer (EMD) will be installed between 2019- 2023. This instrument requires the neutron detectors with the cover area near 3m2 in two 90° neutron diffraction angle position, the neutron detect efficiency better than 40%@1Å, and the spatial resolution better than 4mm×200mm in horizontal and vertical directions respectively. We have developed an one-dimensional position sensitive neutron detector based on the oblique 6LiF/ZnS(Ag) scintillators, wavelength shifting fibers and SiPMs (Silicon Photomultipliers) readout. The inhomogeneity of the neutron detection efficiency between each pixel and each detector module, which caused by the inconsistency of the wave-length shifting fibers in collecting scintillation photons, need to be mitigated before the installation. A performance optimization experiment of the detector modules was carried out on the BL20 (Beam Line 20) of CSNS. Using water sample, the neutron beam with Φ5mm exit hole was dispersed relate evenly into the forward space. According to the neutron counts of each pixel of the detector module, the readout electronics threshold of each pixel is adjusted. Compared with the unadjusted detector module, the inhomogeneity of the detection efficiency for the adjusted one is improved from 69% to 90%. The test result of the diffraction peak of the standard sample Si showed that the adjusted detector module works well.

Determination of energy-dependent neutron backgrounds using shadow bars

Understanding the neutron background is essential for determining the neutron yield from nuclear reactions. The neutron backgrounds were determined for heavy-ion collision experiment using the shadow-bar method, where beams of 40,48Ca at 56, 140 MeV/u impinged on targets of 58,64Ni and 112,124Sn. In the analysis presented here, brass shadow bars are placed in front of organic liquid scintillator neutron detectors to determine the energy-dependent neutron background fractions. The measurement of neutron spectra with and without shadow bars is important to determine the neutron background more accurately. The neutron background, along with its sources and systematic uncertainties, are explored with a focus on the impact of background models and their dependence on neutron energy.

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.

Study of a possible silicon photomultiplier based readout of the large plastic scintillator neutron detector NeuLAND

The NeuLAND (New Large-Area Neutron Detector) plastic-scintillator-based time-of-flight detector for 0.1–1.6GeV neutrons is currently under construction at the Facility for Antiproton and Ion Research (FAIR), Darmstadt, Germany. In its final configuration, NeuLAND will consist of 3,000 2.7m × 5 cm × 5 cm big plastic scintillator bars that are read out on each end by fast timing photomultipliers.Here, data from a comprehensive study of an alternative light readout scheme using silicon photomultipliers (SiPM) are reported. For this purpose, a NeuLAND bar was instrumented on each end with a SiPM-based prototype of the same geometry as a 1” photomultiplier tube, including four 6 × 6mm2 SiPMs, amplifiers, high voltage supply, and microcontroller.Tests were carried out using the 35MeV electron beam from the superconducting Electron Linac for beams with high Brilliance and low Emittance (ELBE) with its picosecond-level time jitter in two different modes of operation, namely parasitic mode with one electron per bunch and single-user mode with 1–60 electrons per bunch. Acqiris fast digitisers were used for data acquisition. In addition, off-beam tests using cosmic rays and the NeuLAND data acquisition scheme have been carried out.Typical time resolutions of σ≤ 120ps were found for ≥95% efficiency for minimum ionising particles, improving on previous work at ELBE and exceeding the NeuLAND timing goal of σ< 150ps. Over a range of 10–300MeV deposited energy in the NeuLAND bar, the gain was found to deviate by ≤10% (≤20%) from linearity for 35μm (75μm) SiPM pitch, respectively, satisfactory for calorimetric use of the full NeuLAND detector. The dark rate of the prototype studied was found to be lower than the expected cosmic-ray induced background in NeuLAND.

Performance test of different silicon photomultipliers for the 6LiF:ZnS(Ag) based neutron detectors of CSNS

The China Spallation Neutron Source (CSNS) is a large scientific facility whose main aim is to support multidisciplinary research on material characterization using neutron scattering. Twenty neutron spectrometers will be built as multidisciplinary platforms for scientific research by national institutions, universities, and industry. Scintillator neutron detectors for the spectrometers under construction have recently been developed using silicon photomultipliers (SiPMs) for the readout. This paper studies the characteristics of three candidate SiPMs, including the breakdown voltage, gain, temperature coefficient, dark count rate, and radiation tolerance. Two measurement platforms were built to evaluate each SiPM. We summarize the results from our analysis of laboratory tests and beam test data to characterize the performance of the SiPMs. The MicroFJ-30035-TSV SiPM manufactured by the SensL Corporation is chosen as the best SiPM for the scintillator detectors at CSNS.

Исследование и подавление чувствительности нейтронных сцинтилляционных детекторов к гамма-излучению

The article continues the consideration of the main problems arising in the development of a real-time multi-detector neutron spectrometer. In previous articles [1,2], possible ways of forming the spectral characteristics of polystyrene scintillation neutron detectors and the results of their calculation using the GEANT-4 modeling software library [1] and restoring the absolute values of the spectral components of the measured neutron flux from their normalized values determined with using a pretrained neural network based on the responses of detectors used in the spectrometer with different spectral characteristics [2]. This article presents the results of studying the processes of scintillation initiation in organic scintillators under the influence of neutron and gamma radiation and considers possible methods for suppressing the sensitivity of a multi-detector neutron spectrometer to accompanying gamma radiation.

Digital pulse analysis for fast neutron recoil spectroscopy with a 4He scintillation detector

Helium-4-based fast neutron scintillation detectors are an attractive alternative to pulse-shape discrimination-capable organic scintillators for fast neutron detection and spectroscopy, as the response of the detectors to gamma rays is intrinsically limited to low energy deposition. Consequently, the neutron recoil distribution can be measured with these detectors without the need for pulse shape analysis. In this work, the response of an Arktis S670 4He scintillation detector to D-D, D-T, and 252Cf neutrons was measured. The detector has a unique construction and readout mechanism, with multiple output channels observing the same scintillation event, and an analysis method was developed to aggregate the outputs from all channels into a single list. The D-D and D-T neutron responses were used to perform a two-point energy calibration, which yielded a near-zero intercept, suggesting that the 4He scintillation medium behaves linearly to a higher energy than previously reported, and that a two-point calibration is sufficient for nuclear recoil energies below 9 MeV. Furthermore, the detector was measured to have 16.7-ns FWHM time resolution when using the developed custom analysis, a reduction of 4.9 ns when compared to the conventional pulse analysis.

DM-like anomalies in neutron multiplicity spectra

A new experiment collects data, since November 2019, at a depth of 210 m.w.e. in the Callio Lab in the Pyhasalmi mine in Finland. The setup, called NEMESIS (New Emma MEasurementS Including neutronS), incorporates infrastructure from the EMMA experiment with neutron and large-area plastic scintillator detectors. The experiment’s primary aim is to combine muon tracking with position-sensitive neutron detection to measure precision yields, multiplicities, and lateral distributions of high-multiplicity neutron events induced by cosmic muons in various materials. The data are relevant for background evaluation of the deep-underground searches for Dark Matter (DM), neutrino-less double beta decay, etc. Preliminary analysis revealed anomalies in muon-suppressed neutron multiplicity spectra collected during a 344-day run (live time) with a 565 kg Pb target. The spectra, otherwise well described by an exponential fit, show three peaks at high multiplicities. Although still at a low statistical significance, these small excesses match the outcome of an earlier measurement. The nature of the anomalies remains unclear, but, in principle, they may be a signature of self-annihilation of a WIMP with a mass close to 13 GeV/c2. With that assumption, the expected cross-section would be around 10−42 cm2 for Spin-Dependent or 10−46 cm2 for Spin Independent interactions. We propose verifying this hypothesis with an upgraded NEMESIS experiment, able to collect an order of magnitude more data than this measurement. Based on the statistical uncertainty, analysis of the event rate indicates that cross-section limits for DM mass range of approximately 3-40 GeV/c2 can be investigated with such a setup.

A prototype of the SiPM readout scintillator neutron detector for the engineering material diffractometer of CSNS

A high detection efficiency thermal neutron detector based on the 6LiF/ZnS(Ag) scintillation screens, wavelength-shifting fibers (WLSF) and Silicon photomultiplier (SiPM) readout is under development at China Spallation Neutron Source (CSNS) for the Engineering Material Diffractometer (EMD).A prototype with a sensitive volume of 180mm×192mm has been built. Signals from SiPMs are processed by the self-design Application Specific Integrated Circuit (ASIC).The performances of this detector prototype are as follows: neutron detection efficiency could reach 50.5% at 1 Å, position resolution of 3, the dark count rate <0.1Hz, the maximum count rate >200KHz. Such detector prototype could be an elementary unit for applications in the EMD detector arrays.

Evaluation of detection efficiency and neutron scattering in NAND detector array: FLUKA simulation and experimental validation

The light output response and efficiency of 5”×5” BC501A liquid scintillator neutron detectors composing the NAND detector array have been measured by time of flight technique using 252Cf source. Energy dependent detection efficiency was calculated using FLUKA Monte Carlo code and validated by experimental measurement. FLUKA simulation incorporated fission neutron correlation and kinematics of neutron emission from fission source determining the energy distribution of neutrons in the laboratory frame. The intrinsic features of the scintillator were studied by including particle dependent quenching and light output resolution. Comparison of FLUKA simulation of scintillation light produced by neutrons and gamma rays with measurements provided realistic results. The calculated neutron detection efficiency at ∼0.5 MeV threshold reproduces the experimental data reasonably well in the studied energy range, 0.5<En<12MeV. Neutron scattering from target chamber material in NAND was investigated using FLUKA concluding that the loss in neutron flux due to scattering from the chamber wall is ∼ 12%. The scattering amounts to background neutron counts in neighbouring detectors comparable to cross-talk events. The absolute efficiency of the NAND array was estimated to be ∼1.40% after taking into consideration the intrinsic efficiency of liquid cells, geometrical efficiency and flux loss due to scattering.

Strong emission from Ce3+ doped gadolinium oxyfluoroborate scintillation glasses matrix

The gadolinium oxide and oxyfluoride borate glasses doped with cerium ion (Ce3+) were studied comparatively in the physical, glass network, optical, luminescence and scintillation properties. The average values of glass density and molar volume represent that oxide glass is heavier and possesses larger molar-size than oxyfluoride glass. FTIR measurement confirms the main glass network of both glass series are based on BO4 unit, and the OH group amount in oxide glass is higher than in oxyfluoride glass. Oxide and oxyfluoride glasses in this work absorb the photons in ultraviolet and initial visible light region proved by the absorption spectra. The ultraviolet, with 275 and 310 nm wavelengths, and X-ray radiation were used to excite the glass samples to investigate the luminescence spectra. The emission broad bands around 300 – 500 nm (excited by ultraviolet) and 350 – 650 nm (excited by X-ray) exhibit the luminescence under electronic transition of Ce3+. The emission intensity of oxyfluoride glass is beyond intensity of oxide glass due to less amount of OH group vibration. The X-ray integral-scintillation efficiency of CeF3 doped oxide and oxyfluoride glass is 8.98% and 45.89%, respectively, compared to BGO crystal. The oxyfluoride borate glasses doped with Ce3+ performs the high potential for using as a glass scintillator in the X-ray and possibly in the neutron scintillation detector.

Adaptability of n–$$\upgamma$$ discrimination and filtering methods based on plastic scintillation

Neutrons have been extensively used in many fields, such as nuclear physics, biology, geology, medical science, and national defense, owing to their unique penetration characteristics. Gamma rays are usually accompanied by the detection of neutrons. The capability to discriminate neutrons from gamma rays is important for evaluating plastic scintillator neutron detectors because similar pulse shapes are generated from both forms of radiation in the detection system. The pulse signals measured by plastic scintillators contain noise, which decreases the accuracy of n– $$\upgamma$$ discrimination. To improve the performance of n– $$\upgamma$$ discrimination, the noise of the pulse signals should be filtered before the n– $$\upgamma$$ discrimination process. In this study, the influences of the Fourier transform, wavelet transform, moving-average filter, and Kalman algorithm on the charge comparison method, fractal spectrum method, and back-propagation neural network methods were studied. It was found that the Fourier transform filtering algorithm exhibits better adaptability to the charge comparison method than others, with an increasing accuracy of 6.87% compared to that without the filtering process. Meanwhile, the Kalman filter offers an improvement of 3.04% over the fractal spectrum method, and the adaptability of the moving-average filter in back-propagation neural network discrimination is better than that in other methods, with an increase in 8.48%. The Kalman filtering algorithm has a significant impact on the peak value of the pulse, reaching 4.49%, and it has an insignificant impact on the energy resolution of the spectrum measurement after discrimination.