Search

Gallium oxide is a newly emerged ultrawide bandgap (4.9 eV) semiconductor that is suitable as a combined electronics and radiation detection platform. We have experimentally demonstrated fast neutron and gamma-ray scintillation from Czochralski-grown β-Ga2O3 in a recent series (October 2023) of experiments at the unmoderated pulsed neutron spallation source located at the Los Alamos Neutron Science Center. Using the neutron time-of-flight (TOF) technique and a fast-gated intensified CCD camera, we observed energy-dependent neutron scintillation for neutron energies ranging from 1 to 400 MeV, including the 14.1 MeV neutron energy relevant to D–T fusion. Neutron flux is quantified and calibrated by cascading the scintillator after the fission chamber, enabling a detailed analysis of temporal and energy-dependent characteristics of the scintillation events. A pronounced scintillation signal from the spallation gamma flash with a temporal full width of half maximum of ∼4 ns is indicative of the material's rapid response. Neutron energy dependent scintillation is observed using the TOF method at a 22.6-m distance from the neutron source. These results highlight the possibility of developing a Ga2O3 based fusion neutron diagnostic platform integrated with both scintillation and electronics functions on the integrated chip scale. [ABSTRACT FROM AUTHOR]

Cloud and bubble chambers have historically been used for particle detection, capitalizing on supersaturation and superheating, respectively. Here, we present new results from a prototype snowball chamber, in which an incoming particle triggers the crystallization of a purified, supercooled liquid. We demonstrate, for the first time, simulation agreement with our first results from 5 years ago: the higher temperature of the freezing of water and significantly shorter time spent supercooled compared to the control in the presence of a Cf-252 fission neutron source. This is accomplished by combining Geant4 modeling of neutron interactions with the Seitz nucleation model used in superheated bubble chambers, including those seeking dark matter. We explore the possible implications of using this new technology for GeV-scale WIMP searches, especially in terms of spin-dependent proton coupling, and report the first supercooling of WbLS (water-based liquid scintillator). [ABSTRACT FROM AUTHOR]

In this advanced instructional laboratory, students explore complex detection systems and nondestructive assay techniques used in the field of nuclear physics. After setting up and calibrating a neutron detection system, students carry out timing and energy deposition analyses of radiation signals. Through the timing of prompt fission neutron signals, multiplicity counting is used to carry out a special nuclear material (SNM) nondestructive assay. Our experimental setup is comprised of eight trans-stilbene organic scintillation detectors in a well-counter configuration, and measurements are taken on a spontaneous fission source as well as two (α,n) sources. By comparing each source's measured multiplicity distribution, the resulting measurements of the (α,n) sources can be distinguished from that of the spontaneous fission source. Such comparisons prevent the spoofing, i.e., intentional imitation, of a fission source by an (α,n) neutron source. This instructional laboratory is designed for nuclear engineering and physics students interested in organic scintillators, neutron sources, and nonproliferation radiation measurement techniques. [ABSTRACT FROM AUTHOR]

Based on the Gravel algorithm and the MLEM algorithm, the neutron energy spectrum unfolding algorithms has been developed by using the SY2001 plastic scintillator detector in its entirety to experimentally measure neutron source characterization of the compact D–D neutron generator. In particular, the degree of optimization of the Mean Relative Error (MRE) is proposed as a determinant of the appropriate termination point for iterations to improve the adaptive nature of the algorithm. The developed neutron energy spectrum unfolding algorithms measure the neutron energy spectra and the neutron angular yields of the compact D–D neutron generator, which are compared with Monte Carlo calculated results. Given the good agreement with the existing results, the developed unfolding algorithms can be used to accurately unfolding neutron energy spectrum, especially, for non-pulsed neutron sources. The measured neutron source characterization results show that the compact D–D neutron generator can produce high yields and quasi-mono-energetic neutrons in the range from 2.2 to 2.8 MeV. The D–D neutron angular yields are anisotropic distributions, particularly, which are relatively higher with neutron emission angles ranging from 40 ∘ to 120 ∘ . This work measure the neutron energy spectra and the neutron angular yields of the compact D–D neutron generator in Lanzhou University, which provide detailed neutron source characterization for using it in neutron physics and neutron application technology. [ABSTRACT FROM AUTHOR]

In nuclear astrophysics, the nuclides 151 Eu and 153 Eu are both in the path of the s-process, and their (n, γ ) cross sections are important input parameters for the calculation of the nuclear astrophysics network. According to the EXFOR database, the neutron capture cross section of natural europium in the resonance region has not been fully measured. The (n, γ ) cross section of nat Eu was measured using the time-of-flight (TOF) technique at the Back-n white neutron source facility of the China Spallation Neutron Source (CSNS) in the 1 eV–to 500 keV range. Four C 6 D 6 liquid scintillator detectors and pulse height weighting techniques were used to measure prompt γ rays and analyze the data. The results of the analysis were compared with the evaluated data of ENDF/B-VIII.0 and JENDL-5.0. It shows that there are some differences between the measurement results and different evaluated data libraries. The resonance parameters of 151 Eu and 153 Eu were extracted in the 1 eV–150 eV region using the R-Matrix code SAMMY. The accurate Maxwellian-averaged capture cross section (MACS) is derived over the temperature range of the s-process nucleosynthesis model. The result shows that at kT=30 keV, the MACS value of 151 Eu is 3417 ± 297 mb and the value of 153 Eu is 2718 ± 237 mb. [ABSTRACT FROM AUTHOR]

Fast and heavy inorganic scintillators with suitable radiation tolerance are required to face the challenges presented at future hadron colliders of high energy and intensity. Up to 5 GGy and 5 × 1018 neq/cm2 of one-MeV-equivalent neutron fluence is expected by the forward calorimeter at the Future Hadron Circular Collider. This paper reports the results of an investigation of proton- and neutron-induced radiation damage in various fast and heavy inorganic scintillators, such as LYSO:Ce crystals, LuAG:Ce ceramics, and BaF2 crystals. The experiments were carried out at the Blue Room with 800 MeV proton fluence up to 3.0 × 1015 p/cm2 and at the East Port with one MeV equivalent neutron fluence up to 9.2 × 1015 neq/cm2, respectively, at the Los Alamos Neutron Science Center. Experiments were also carried out at the CERN PS-IRRAD proton facility with 24 GeV proton fluence up to 8.2 × 1015 p/cm2. Research and development will continue to develop LuAG:Ce ceramics and BaF2:Y crystals with improved optical quality, F/T ratio, and radiation hardness. [ABSTRACT FROM AUTHOR]

A novel non-destructive testing scanning system based on a large-size line array fast neutron detector and compact D-T neutron source has been constructed. The scanning range is up to 1000 mm, and the resolution is better than 1 mm. The fast neutron detection subsystem consists of a polypropylene zinc sulfide scintillator embedded with wavelength-shifting fibers, coupled with a light lens and a scientific CCD camera. With a new rotating tritium target, the lifetime of the compact D-T neutron source could achieve ten hours. The experimental results indicate that the scanning method based on line array fast neutron detector and D-T neutron source is feasible and enables the detection of slits on the order of 0.5 mm in width. Fast neutron tomography has been realized by this detection system too. [ABSTRACT FROM AUTHOR]

The optically segmented single volume scatter camera (OS-SVSC) aims to image neutron sources for nuclear nonproliferation applications using the kinematic reconstruction of elastic double-scatter events. We report on the design, construction, and calibration of one module of a new prototype. The module includes 16 EJ-204 organic plastic scintillating bars individually wrapped in Teflon tape, each measuring $0.5 {\mathrm {cm}}\times 0.5 {\mathrm {cm}}\times 20 {\mathrm {cm}}$. The scintillator array is coupled to two custom silicon photomultiplier (SiPM) boards consisting of a $2\times 8$ array of SensL J-Series-60035 SiPMs, which are read out by a custom 16 channel DRS4 based digitizer board. The electrical crosstalk between SiPMs within the electronics chain is measured as $0.76\% \,\pm \,0.11\%$ among all 16 channels. We report the detector response of one module including interaction position, time, and energy, using two different optical coupling materials: EJ-560 silicone rubber optical coupling pads and EJ-550 optical coupling grease. We present results in terms of the overall mean and standard deviation of the $z$ -position reconstruction and interaction time resolutions for all 16 bars in the module. We observed the $1\sigma z$ -position resolution for gamma interactions in the 0.3–0.4 MeVee range to be 2.24 cm ± 1.10 cm and 1.45 cm ± 0.19 cm for silicone optical coupling pad and optical grease, respectively. The observed $1\sigma $ interaction time resolution is 265 ps ± 29 ps and 235 ps ± 10 ps for silicone optical coupling pad and optical grease, respectively. [ABSTRACT FROM AUTHOR]

A dual-particle imager based on a rotational modulation collimator (RMC) utilizing a Cs2LiYCl6:Ce (CLYC) scintillator was developed and investigated for its dual-particle imaging performance. Design considerations and previous simulation work were verified by conducting experiments, and experimental results showing neutron and gamma-ray imaging capabilities were obtained. The imaging performance of the CLYC-based RMC system was further evaluated by investigating it in a mixed neutron and gamma-ray environment, and dual-particle imaging capability of the RMC system was demonstrated. Signal-to-noise ratio (SNR) values larger than 45 were achieved for reconstructed images of each neutron and gamma-ray source distribution, if modulation patterns were obtained with average fractional counting uncertainty of less than 3%. The structural similarity (SSIM) index of reconstructed images was calculated to be almost unity, indicating an artifact-free image. [ABSTRACT FROM AUTHOR]

Precise measurement under high counting rates has been a major challenge for γ -ray spectroscopy, where signals generally pile up with each other and their characteristic values are deeply coupled. An off-line pile-up pulse recovery algorithm based on template matching is developed for LaBr 3 scintillation detectors and has been applied to data from China Spallation Neutron Source (CSNS) Back-n white neutron beamline. As an improvement to the traditional Template Matching methods, the predetermined template shape is associated with pulse amplitudes, which is found crucial to achieve the best fitting results. Moreover, a universal strategy of setting the initial values of fitting allows to resolve signals that are separated in time by less than the characteristic rise time. Processing of simulated pulses demonstrates that the lower limit of interval to distinguish successive events is 10 ns, which is a significant improvement to the previous works. The algorithm performs well under a counting rate of 6 × 1 0 7 s−1, and is still effective up to 1 0 8 s−1. Analysis of experimental data indicates that this algorithm recovers over 98% count yield under a counting rates of no more than 4 × 1 0 6 s−1 in this work, providing a more reliable approach to deduce neutron-induced reaction cross sections. [ABSTRACT FROM AUTHOR]

Due to the shortage of the 3He gas and its rapidly increasing price, scintillator detectors, the advantages of which are high spatial resolution and capability of detection in real time, become widely used in many neutron instruments. In this work, a position-sensitive neutron detector consisting of a 6LiF/ZnS scintillation screen and a silicon photomultiplier array linked to a capacitive network to detect the positions of incident neutrons, is constructed and tested. To evaluate the detector performance, a series of neutron beam experiments with the detector prototype were performed in the BL20 at the China Spallation Neutron Source. The spatial resolution was measured, and the energy-selective neutron imaging and Bragg edge measurements of a 316L stainless steel sample were performed. A sub-millimeter spatial resolution could be obtained for the detector prototype under study. The detector with such a high spatial resolution is promising for applications in neutron scattering experimental installations, especially for neutron single-crystal diffractometers. [ABSTRACT FROM AUTHOR]

Neutron imaging is a powerful tool for observing the internal structure of an object without destroying the object. Neutron imaging (neutron radiography) is a prominent application of neutrons but still requires significant improvements, for example, in sensitivity, resolution, radiation hardness, and handling of neutron imaging detectors. This paper presents the development and the first neutron imaging results of a neutron flat-panel detector (nFPD) based on an In–Ga–Zn–O (IGZO) thin-film transistor (TFT)/photodiode array coupled with a LiF/ZnS scintillator sheet. Direct photo-coupling to the scintillator increases the light collection efficiency. Moreover, unlike lens-coupled neutron cameras, the proposed detector is compact and easy to handle. Owing to the high off-state resistance of IGZO TFTs, their leakage current is lower than that of conventional TFTs, enabling the IGZO TFTs to hold an accumulated charge for a longer period of time and allowing longer exposure times for imaging. This would be a powerful feature for imaging at compact neutron sources with limited flux. This paper reports on the first neutron imaging results with an IGZO nFPD, its performance evaluation, and a demonstration of three-dimensional computed tomography with neutrons. [ABSTRACT FROM AUTHOR]

A 128-channel positron detection system will be constructed at Experimental Muon Source (EMuS) of China Spallation Neutron Source (CSNS) to conduct muon spin rotation/relaxation/resonance ($\mu $ SR) measurements. Each detector channel consists of a scintillator, a light guide, and a photomultiplier tube (PMT). The long light guide is bent to an “L” shape to propagate optical photons from the scintillator to the PMT. A series of Geant4 simulations and experiments has been performed to optimize the light collection performance of the L-bent detector. Geometry deformation induced by the bending process has been well modeled. Simulation results agree with the experimental tests. Accordingly, a novel hybrid wrapping method (scintillator with polytetrafluoroethylene (PTFE) and light guide with aluminum tape) has been developed to improve the amplitude of detector signals greatly. Compared to wrapping the detector with merely PTFE tapes or aluminum tapes, this method leads to an enhancement in light collection efficiency of 73% or 14%, respectively. Two optimally manufactured prototype detectors using the novel wrapping method have been tested at the ISIS Muon Facility. The beam tests demonstrated that the L-bent detectors can precisely measure the behavior of muon spins inside samples. Therefore, the L-bent detector design is competent for $\mu $ SR applications at CSNS/EMuS. [ABSTRACT FROM AUTHOR]

Two organic scintillators (EJ309 and stilbene) with their different detection chains and elaborate software were used to measure neutron spectra of AmBe and PuC sources. Method of shadow cone ensures minimization of scattered neutron influence. To separate neutrons and γ, a modern method of pulse shape discrimination was employed using fast digitizers. Calibration was performed by γ sources and three different methods for the identification of the Compton edge. Spectrometric systems also used different light output functions and unfolding methods. The same spectra were calculated using the MCNP6 code and the JENDL-5 library. The measured and calculated results were mutually compared, and also with the published results available in the literature. Generally, the results agree on the main peaks of neutron spectra but differ in their abundance. The lower limit for the ability to distinguish between neutrons and γ in spectrometry with organic scintillators was found at about 1.5 MeV. • Neutron spectra of AmBe and PuC sources were measured and calculated. • The measured/unfolded spectra and calculated ones agree in shape. • Methods of energy calibration and neutron/gamma separation are described. [ABSTRACT FROM AUTHOR]

Gd 3 Al 2 Ga 3 O 12 :Ce (GAGG) scintillators with different readout photo-sensors, a 2 × 2 matrix of four SensL ARRAY J-60035-4P-BGA silicon photomultipliers (SiPMs), and a HAMAMATSU R5505-70 photomultiplier (PMT) have been tested for neutrons obtained from neutron generators exploiting d-d and d-t reactions. It was demonstrated that neutrons having energy 2.8 MeV produce in the detector materials the spectrum of secondary particles, which is identical to the spectrum measured under thermal neutrons of the isotope sources. The pulse height spectra detected under 14.6 MeV neutrons were found to be quite different. Pulse shape discrimination (PSD) data processing technique was applied to separate neutron and γ-ray signals. The signals of secondary particles, protons, and α-particles were confidently distinguished at the strong background of the γ-rays. The results gathered open up the prospects of using the GAGG scintillator to identify neutrons generated in d-t reactions against a strong background of γ-rays. [ABSTRACT FROM AUTHOR]

Dynamic Light Scattering (DLS) and Small-Angle Neutron Scattering (SANS) are two key tools to probe the dynamic and static structure factors, respectively, in soft matter. Usually, DLS and SANS measurements are performed separately, in different laboratories, on different samples, and at different times. However, this methodology has particular disadvantages for a large variety of soft materials, which exhibit a high sensitivity to small changes in fundamental parameters, such as waiting times, concentration, pH, and ionic strength. Here, we report on a new portable DLS-SANS apparatus that allows one to simultaneously measure both the microscopic dynamics (through DLS) and the static structure (through SANS) on the same sample. The apparatus has been constructed as a collaboration between two laboratories, each an expert in one of the scattering methods, and was commissioned on the LOQ and ZOOM SANS instruments at the ISIS Pulsed Neutron and Muon Source, U.K. [ABSTRACT FROM AUTHOR]

Investigated in this work were sensitivities of a prototype detector for the detection of low-mass dark matter particles produced at the Spallation Neutron Source at the Oak Ridge National Laboratory in 2 years of data taking. The presumed prototype consisted of 10 kg undoped CsI or NaI scintillation crystals directly coupled with SiPM arrays operated at 77 K. Compared to the COHERENT CsI(Na) detector, a much higher light yield was assumed for the prototype. An experiment with a cylindrical 1 kg undoped CsI crystal coupled directly to two photomultiplier tubes at about 77 K was conducted as the first step to verify the idea. A light yield of 26.0 ± 0.4 photoelectrons per keV electron-equivalent was achieved. This eliminated the concern of self light absorption in large crystals raised in some of the early studies. [ABSTRACT FROM AUTHOR]

This paper describes the design and operation of the Polaris time-of-flight powder neutron diffractometer at the ISIS pulsed spallation neutron source, Rutherford Appleton Laboratory, UK. Following a major upgrade to the diffractometer in 2010–2011, its detector provision now comprises five large ZnS scintillator-based banks, covering an angular range of 6° ≤ 2θ ≤ 168°, with only minimal gaps between each bank. These detectors have a substantially increased solid angle coverage (Ω ∼ 5.67 sr) compared to the previous instrument (Ω ∼ 0.82 sr), resulting in increases in count rate of between 2× and 10×, depending on 2θ angle. The benefits arising from the high count rates achieved are illustrated using selected examples of experiments studying small sample volumes and performing rapid, time-resolved investigations. In addition, the enhanced capabilities of the diffractometer in the areas of in situ studies (which are facilitated by the installation of a novel design of radial collimator around the sample position and by a complementary programme of advanced sample environment developments) and in total scattering studies (to probe the nature of short-range atomic correlations within disordered crystalline solids) are demonstrated. [ABSTRACT FROM AUTHOR]

We propose a hierarchical Bayesian model and a state-of-the-art Monte Carlo sampling method to solve the unfolding problem, i.e., to estimate the spectrum of an unknown neutron source from the data detected by an organic scintillator. Inferring neutron spectra is important for several applications, including nonproliferation and nuclear security, as it allows the discrimination of fission sources in special nuclear material (SNM) from other types of neutron sources based on the differences of the emitted neutron spectra. Organic scintillators interact with neutrons mostly via elastic scattering on hydrogen nuclei and therefore partially retain neutron energy information. Consequently, the neutron spectrum can be derived through deconvolution of the measured light-output spectrum and the response functions of the scintillator to monoenergetic neutrons. The proposed approach is compared to three existing methods using the simulated data to enable controlled benchmarks. We consider three sets of detector responses. One set corresponds to a 2.5-MeV monoenergetic neutron source and two sets are associated with (energywise) continuous neutron sources (252Cf and 241AmBe). Our results show that the proposed method has similar or better unfolding performance compared with other iterative or Tikhonov regularization-based approaches in terms of accuracy and robustness against limited detection events while requiring less user supervision. The proposed method also provides a posteriori confidence measures, which offers additional information regarding the uncertainty of the measurements and the extracted information. [ABSTRACT FROM AUTHOR]

We present new results on the neutron detection efficiency of detection systems based on He-3 proportional counters compared to organic liquid scintillators. The experiments were conducted using a well-characterized Cf-252 neutron source, measured bare, and shielded with slabs of polyethylene. The results show that the intrinsic neutron detection efficiency for the bare source is approximately 25% for the He-3 system, and 67% for the liquid scintillator system. When polyethylene sheets were used to shield the source in 2.54 cm increments, the neutron detection efficiency of both systems decreased exponentially to approximately 10% for the case of 25.4 cm. Experimental results were simulated using MCNPX-PoliMi and good agreement was found between measurement and simulation results for all the cases considered here. [ABSTRACT FROM AUTHOR]

In this study, the digital neutron–gamma discrimination (DNGD) has been undertaken based on the pulse-shape discrimination on the anode pulse of a 2" by 2" right cylinder BC501A liquid scintillator with a fast data acquisition card (14-bit resolution, 500 MS/s). Seven different features of the anode pulse have been extracted and the discrimination based on quantum clustering (DBQC) has been studied. The influence of three different parameters (i.e. , η , σ and K) on the discrimination figure-of-merit (FoM) has been investigated. In addition, the FoM dependencies on different choices of DBQC features have been determined. A 100 mCi 241Am-Be neutron source has been used for the DNGD and the calibration has been made with a 1.1 μ Ci 22Na gamma-ray source. The results show that the FoM value is around 1 at 100 keVee bias energy, whilst this value can be improved up to 50% by choosing and setting appropriate features. [ABSTRACT FROM AUTHOR]

We present Monte Carlo (MC) simulation results from a study of a compact plastic-scintillator detector suitable for imaging fast neutrons in the 1 – 10 MeV energy range: the miniTimeCube (mTC). Originally designed for antineutrino detection, the mTC consists of 24 MultiChannel Plate (MCP) photodetectors surrounding a 13 cm cube of boron-doped plastic scintillator. Our simulation results show that waveform digitization of 1536 optically sensitive channels surrounding the scintillator should allow for spatiotemporal determination of individual neutron-proton scatters in the detector volume to ∼ 100 picoseconds and ∼5 mm. A Bayesian estimation framework is presented for multiple-scatter reconstruction, and is used to estimate the incoming direction and energy of simulated individual neutrons. Finally, we show how populations of reconstructed neutrons can be used to estimate the direction and energy spectrum of nearby simulated neutron sources. [ABSTRACT FROM AUTHOR]

A real-time $n/\gamma $ discrimination prototype system based on high-speed waveform sampling and high-performance field-programmable gate array (FPGA) is presented in this paper. In order to accurately record detector signals, a high-speed sampling board with a 14-bit analog-to-digital converter (AD9680) is designed. The BC501A liquid scintillator is employed as the neutron detector, and a discrimination algorithm is implemented in the FPGA of the sampling board. The system is calibrated by 22Na, 137Cs, and 60Co $\gamma $ -sources. A PuC neutron source is used to evaluate the discrimination ability. The figure-of-merit of PuC neutron source is determined to be about 1.005 over an energy range of 0–4000 keVee, which is consistent with the test results of the commercial digitizer, and the false alarm rate of 60Co is 0.19%. This system has been successfully applied for the environmental neutron monitoring experiment during the first commissioning of white neutron source tunnel of China spallation neutron source. [ABSTRACT FROM AUTHOR]

We measure the distribution of energy deposited in a 40 × 88 mm plastic scintillator by e + e − pair production of 4.44 MeV γ -rays. We observe the double-escape peak of 3.42 MeV from pair production by tagging 511 keV annihilation radiation in two high-Z scintillators. The source is a standard commercial neutron source using α -emitting 241Am encapsulated with 9Be, which has a reaction branch feeding the first I π = 2 + state of 12C making the 4.44 MeV γ -rays. We demonstrate the extraction of the double-escape peak from the large neutron-produced backgound, and explore some of the features and difficulties of this technique with our apparatus. [Display omitted] [ABSTRACT FROM AUTHOR]

A Bonner Sphere spectrometer employing a large, 11 mm diameter × 3 mm thickness, 6 LiI(Eu) scintillator (LL-BSS), was assembled. The purpose was to produce a BSS similar in sensitivity to those based on 3 He sensors, but using alternative sensors. With respect to the traditional BSS based on the 4 mm (diameter) × 4 mm (height) 6 LiI(Eu), this new BSS is a factor of 3 more sensitive. LL-BSS response matrix, determined with MCNPX, was experimentally evaluated with monoenergetic reference neutron fields of 144 keV, 565 keV and 1.2 MeV available at NPL (Teddington, UK). The results of the experiment confirmed the correctness of the response matrix within an overall uncertainty lower than ±2%. [ABSTRACT FROM AUTHOR]

A highly segmented muon spin rotation/relaxation/resonance (μ SR) spectrometer with over 2500 channels has been proposed in the construction of Phase II of the China Spallation Neutron Source (CSNS). Plastic scintillators are chosen as the detector material due to their high sensitivity to charged particles and good flexibility to various geometries. Gamma-ray sources are commonly used to calibrate the light yield of plastic scintillators. Accordingly, a derivative method has been developed to efficiently locate the Compton edge in gamma-ray spectra. In this method, the minimum and width of the derivative data are regarded as the position of the Compton edge and an estimation of energy resolution, respectively. Both experiments and simulations demonstrate the good reliability of this method for Compton edge positioning and energy resolution characterization. The derived Compton edge shows a systematic shift to the right of its real location. The relative shift is proportional to the energy resolution with a factor of ∼ 0.13. The assumed energy resolution should be corrected by a factor of ∼ 1.19 which is confirmed by inorganic scintillator measurements. In the measurement of plastic scintillators, the assumed Compton edge and energy resolution can well reproduce the energy response spectra for different types of gamma-ray sources. [ABSTRACT FROM AUTHOR]

This paper introduces a novel and extremely simple—and therefore, easily implemented in a field-programmable gate array—method of neutron/gamma pulse discrimination called the histogram-difference method (HDM). Crucially, this method relies on the use of a “reference set” of \gamma -only pulses from 22Na, 137Cs, and 60Co sources and on features extracted from the pulses. The pulses from this reference set are compared to a set of an identical number of n+\gamma pulses from a 252Cf source. Not only can HDM determine the presence of neutrons in the 252Cf source, but it can also estimate the approximate percentage of neutron pulses from that source. The results reported in this paper are based on data from different radioactive sources and a standard scintillator for this type of research, namely, BC-501A. These results were confirmed using three other scintillators, one made in-house and two others that are commercially available, EJ-299–33 and EJ-200. Pulses were encoded using Q values, which are features extracted from the pulses, that is, ( , Q_{\mathrm{ tail}} ) pairs in \text{S}\mathbb {R}^{2}$ . As control, we also encoded pulses as the root-mean-square (RMS) distances from the average pulse of all known $\gamma $ -only pulses and ran HDM using these pulse representations. The results are very similar to those obtained using a $Q$ -value encoding of the pulses. [ABSTRACT FROM PUBLISHER]

This work summarizes a fast neutron detection performance of two different silicon photomultipliers from two manufacturers. The first SiPM (MAPD-3NK) from Zecotek Photonics consists of deeply buried cells with the active area 3. 7 × 3. 7 mm2. The second one (MPPC-S12572-010P) from Hamamatsu, however, consists of surface cell structure which the active area is 3 × 3 mm2. Both SiPMs have the same pixel density of 10 000 mm−2. Both SiPMs coupled to Stilbene (5 ∗ 5 ∗ 5 mm3) and p-terphenyl (5 ∗ 5 ∗ 5 mm3) plastic scintillators were evaluated for detection ability of fast neutrons using a PuBe neutron source. Charge comparison and zero crossing neutron/gamma discrimination techniques were performed for these detectors and the results were compared. The obtained results prove a good fast neutron detection performance of the SiPMs which makes it possible to use these types of neutron detectors in fast neutron detection applications. [ABSTRACT FROM AUTHOR]

Abstract A telescope proton recoil spectrometer consisting of a 500 μ m thick silicon detector and a 2.54 cm × 2.54 cm YAP:Ce inorganic scintillator has been developed to measure the neutron spectrum at ChipIr, a fast neutron beam line that has recently started operations at the ISIS neutron source in the UK. The spectrometer has been tested with protons in the range 5–80 MeV at the INFN-LNS cyclotron accelerator. The light yield of the YAP scintillator to protons has been characterized relative to gamma-rays of same energies and found to scale linearly with the proton energy in the whole range. Background rejection using a Δ E-E technique by combining data from the silicon and YAP:Ce detectors has also been tested successfully. Highlights • A telescope proton recoil neutron spectrometer consisting of a silicon detector and a YAP:Ce scintillator has been designed to measure the neutron spectrum at ChipIr. • We characterized the response of the YAP:Ce scintillator to protons in energy range 5–80 MeV at the INFN-LNS. • The light yield of the YAP:Ce scintillator to protons has been found to scale linearly with the proton energy in the whole range. • Background rejection using a Δ E-E technique by combining data from the silicon and YAP:Ce detectors has been tested successfully. [ABSTRACT FROM AUTHOR]

Neutron–gamma discrimination plays a fundamental role in the fields of radiation protection and nuclide identification. The pulse-shape discrimination (PSD) of liquid scintillators has been widely used as an effective neutron–gamma detection method. In this paper, the KPCA-GMM-ANN combined algorithm is studied for neutron–gamma discrimination. Two radioisotope neutron sources (252Cf and 241Am–Be) were used. The EJ309 liquid scintillator detector was used to output the neutron and gamma pulse signals. The kernel principal component analysis (KPCA) was used to reduce the dimension of the characteristic value of the pulse signal, the gaussian mixture model (GMM) was used to cluster the dimensionality reduction results, and the artificial neural network (ANN) was trained to identify the particle categories and output the clustering results. The KPCA-GMM was compared with the KPCA-GMM-ANN using F1 score(F 1). The discrimination error ratio (DER) was used to compare the KPCA-GMM-ANN with others' ANN. In all datasets, the KPCA-GMM-ANN's F 1 were higher than 0.97, and its DER were lower than 0.035. The results show that the KPCA-GMM-ANN has good discrimination effect, can handle high-dimensional data, and has good generalization ability. • KPCA was used to reduce data dimensionality. • GMM and ANN were used for clustering and identification. • The EJ309 liquid scintillator detector was used to detect the neutron sources. • Two radionuclide neutron sources (252Cf and 241Am–Be) were detected. • F1 score and DER were used as indicators for neutron-gamma discrimination. [ABSTRACT FROM AUTHOR]

Two inorganic scintillator detectors consisting of Yb:YAG scintillators and photomultiplier tubes, and an oscilloscope were used to studied the neutron sensitivities of Yb:YAG scintillators at the China Spallation Neutron Source (CSNS) Back-n white neutron source. The relative neutron sensitivity curves of two Yb:YAG scintillators in the energy region between 0.5 and 20 MeV were obtained for the first time. As the measured relative neutron sensitivity curves of Yb:YAG scintillators cannot be verified by the Monte Carlo method and there was no referable data, the neutron sensitivity curve of a ST401 scintillator was also studied in the same method and a Geant4 simulation of ST401 scintillator was conducted to verify the experiment method in this paper. The result showed that the experimental and simulation results were approximately consistent between 17–20 MeV, and agreed well between 1–17 MeV. A comparison between the experimental result and references of ST401 scintillator was also applied and the result showed that the curve tendency of the experimental result and references was matched. The above results imply that the measured relative neutron sensitivity curves and the experimental method used herein were reliable. It also demonstrated the feasibility of studying the neutron sensitivity of inorganic scintillator based on the white neutron source. [ABSTRACT FROM AUTHOR]

For the first time we report the ability of the CLLB scintillator to detect and discriminate fast neutrons (2–10 MeV energy range) from gamma-rays and thermal neutrons, using a digital pulse shape discrimination technique. Firstly, we conducted measurements in single mode with an Am–Be source, unshielded and shielded, and we tagged a new cluster of events as the fast neutron-induced zone. The Figure of Merit obtained for the fast neutron/gamma discrimination was 1.1. Then, in order to better characterize these new cluster of events induced by fast neutrons, we conducted measurements in coincidence mode. We used a mono-energetic pulsed neutron source, at the Van de Graaff accelerator facility at the Legnaro National Laboratories (INFN-LNL, Legnaro-Italy), and also, a continuous neutron spectrum (using a 252Cf source). Combining all experimental results with a Monte Carlo model of the CLLB detector, built using the GEANT4 tool kit, it was possible to obtain the light output function of 7Li ions in the CLLB crystal (dL/dE = κ ; κ = 0.36 ± 0.02). Moreover, the intrinsic fast neutron efficiency was modeled by Monte Carlo, obtaining similar values 1.5%–2% for neutrons between 2 MeV and 10 MeV. Finally, an application of this new feature, in the field of nuclear security and nuclear safeguards, is given. • Fast neutron detection with a CLLB scintillation detector. • Fast neutron/gamma-rays/thermal neutrons discrimination by applying digital pulse shape discrimination technique. • Light output of Li ions in the CLLB scintillator. • Recognition of neutron sources. [ABSTRACT FROM AUTHOR]

The LaBr 3 :Ce scintillator has been widely studied for nuclear spectroscopy because of its optimal energy resolution (<3%@ 662 keV) and time resolution (~300 ps). Despite these promising properties, the intrinsic radiation background of LaBr 3 :Ce is a critical issue, and pulse shape discrimination (PSD) has been shown to be an efficient potential method to suppress the alpha background from the 227 Ac. In this paper, the charge comparison method (CCM) for alpha and gamma discrimination in LaBr 3 :Ce is quantitatively analysed and compared with two other typical PSD methods using digital pulse processing. The algorithm parameters and discrimination efficiency are calculated for each method. Moreover, for the CCM, the correlation between the CCM feature value distribution and the total charge (energy) is studied, and a fitting equation for the correlation is inferred and experimentally verified. Using the equations, an energy-dependent threshold can be chosen to optimize the discrimination efficiency. Additionally, the experimental results show a potential application in low-activity high-energy γ measurement by suppressing the alpha background. [ABSTRACT FROM AUTHOR]

A fast neutron detector system that can figure out neutron source direction is developed. The system consists of two rod-shaped fast neutron detectors and one polyethylene moderator. Pulse shape discrimination plastic scintillators are applied for reduced gamma-ray background and improved system sensitivity for fast neutron detection. The neutron detectors are placed on the back and front sides of the moderator facing a neutron source. Experiments are conducted for a single rod-shaped detector and the system changing the PuBe neutron source direction. Simulation-based studies are also performed using the Monte Carlo simulation code, PHITS (Particle and Heavy ion Transport code System). Taking the ratio of counts of the front and back system detectors, linear change with an increased detector angle is observed, except for near 0° and 90°. This enables us to deduce neutron source direction from several measurements. The method is probably useful for a quick and efficient survey of neutron sources or special nuclear materials. [ABSTRACT FROM AUTHOR]

We simulated a 2 ′ ′ × 2 ′ ′ EJ-301 organic liquid scintillation detector in the GEANT4 framework to obtain its response to standard gamma and neutron sources. The resolution scale and Birks' constant for the EJ-301 scintillator have been estimated by comparing the simulation with experimental data. We calibrated the detector for fast neutron measurements with the help of an Am–Be source using two unfolding methods: RooUnfold and Gravel unfold. The neutron spectra obtained from both unfolding methods are similar to the Am–Be ISO (International Organization for Standardization) spectrum. The calibrated detector can be used in an underground site to understand the neutron background in rare event search experiments. [ABSTRACT FROM AUTHOR]

In this paper imaging of neutron sources and identification and separation of a neutron source from another neutron source is described. The system is based upon organic liquid scintillator detector, tungsten collimator, bespoke fast digitiser and adjustable equatorial mount. Three environments have been investigated with this setup corresponding to an AmBe neutron source, a 252 Cf neutron source and both sources together separated in space. In each case, events are detected, digitised, discriminated and radiation images plotted corresponding to the area investigated. The visualised neutron count distributions clearly locate the neutron source and, relative gamma to neutron (or neutron to gamma) fraction images aid in discriminating AmBe sources from 252 Cf source. The measurements were performed in the low scatter facility of the National Physical Laboratory, Teddington, UK. [ABSTRACT FROM AUTHOR]

Five types of scintillators for parallel detection of neutrons and γ were tested for their pulse shape discrimination ability. All detectors are based on 6Li (n,alpha)3H reaction. LiI, ZnS and polystyrene were used as scintillators. Tests were performed at different neutron and γ mixed fields (AmBe, Cf) using a small Hamamatsu photomultiplier and a Picoscope digitizer. A polystyrene-based ZnS + LiF detector was proven to be the most suitable for neutron-γ separation and similar sensitivity for both types of radiation to construct a single device to measure integral quantities neutrons and γ (fluence, ambient dose equivalent) in parallel. The ZnS + LiF detector based on plexiglass, is in principle useable also, but has low sensitivity to γ radiation. The tested Li glass or LiI crystal does not have the ability to separate neutron and γ. With amplitude discrimination it can be used as a neutron detector for a much simpler probe for a Bonner spectrometer. • Pulse shape discrimination of neutrons and γ can be performed with affordable digitizer. • A polystyrene-based ZnS + LiF detector is the most suitable for neutron-γ separation and sensitivity for both types of radiation. • Measurement of (fluence, ambient dose equivalent of neutrons and γ in parallel is possible -based ZnS + LiF detector. • Used Li glass or LiI crystal does not have the ability to separate neutron-γ. [ABSTRACT FROM AUTHOR]

The paper describes the preparation and characterization methodology of thermal neutron sensitive inorganic compound loaded polystyrene based thin-film Plastic Scintillators (PS). Inorganic compounds with thermal neutron sensitive elements such as B 2 O 3 , LiF, Gd 2 O 2 S:Tb, Gd 2 O 3 , Gd(BO 2) 3 :Tb is loaded in plastic scintillators, at predetermined weight percentage in a solvent-based fabrication method. The PS base solution is prepared by dissolving required quantities of polystyrene, 2,5-Diphenyloxazole (PPO), 1,4-bis(5-Phenyloxazol-2-yl) Benzene (POPOP) in the p- xylene solvent. The loading material is mixed with the scintillator solution and coated over cellulose acetate-based transparency sheet. Thin sheets of 200 × 150 mm size and 250 ± 50 μm thickness PS are prepared through multiple coating. Photoluminescence (PL), Radioluminescence (RL) and pulse height spectra (PHS) of α, β, γ and neutron sources of the composite scintillators are studied. The selection of loading compounds is decided on their physical properties such as refractive index, the atomic percentage of neutron sensitive elements in the inorganic compound, band gap, and cost and availability of material. Gadolinium based compounds as a thermal neutron absorber showed higher detection capability for low-energy neutrons. Among the gadolinium loaded PS, Gd(BO 2) 3 :Tb (14.3 wt%) composite scintillator showed the highest RL. A comprehensive analysis of PL, RL, PHS of α, pure β and γ sources, un-moderated and moderated Am–Be neutron source is discussed in the paper. • Polystyrene based thin composite scintillators loaded with high neutron absorbent inorganic compound. • Increased luminescence emissions except B 2 O 3 loaded composite scintillators. • Enhanced radiation response in micro particle loaded composite scintillators. • Comparatively higher neutron and gamma photon sensitivity to Gd-compound loaded PS. [ABSTRACT FROM AUTHOR]

In this paper, simulations were carried out using Monte-Carlo N-Particle MCNP-4C code to determine the energy dependence of the response of a highly sensitive silver-activation detector used for fast-neutron detection after moderated to thermal neutrons. The detector consists of sandwiched alternating thin-sheets of silver and crystal scintillator Anthracene. The simulations also had considered different materials and designs to get the most efficient design for detecting signals from fast-neutrons interactions with the active materials (silver) and the scintillator. The energy and charge depositions of photons and electrons created by fast-neutron interactions with detector within the detection-cell were simulated for different scenarios. Owing on the simulations, a method to maximize the response by modifying the design was identified. The optimal configurations are suitable for a wide range of monitoring and detecting neutron sources especially for big detectors implemented for security purposes, where the costs and weighs can be reduced significantly. • Monte-Carlo simulations carried out to optimize activation neutron detectors. • Obtained results lead specialties to design the most effective neutron detector. • Optimized designs can significantly decrease weight and size of big detectors. • Optimized designs can significantly decrease the costs of big neutron detectors. [ABSTRACT FROM AUTHOR]

Monte Carlo methods, with the MCNP5 code, were used to estimate the pulse-height spectra of γ-rays induced in three hydrogen-rich moderators modeled as 20.32 cm-diameter spheres made of water, polyethylene and gasoline. The source-term was a point-like 241AmBe neutron source. The pulse-height spectra were estimated as measured with a NaI(Tl) scintillator and as measured by a detector without the low-resolution limitation. In the moderators the induced γ-rays are produced in 1H(n, γ)2H reactions; also another two gamma rays are scarcely produced in 12C(n, n'γ)12C and 16O(n, n'γ)16O inelastic scattering reactions. For the case of polyethylene moderator the pulse-height spectrum was measured with a gamma-rays spectrometer with a 3" Ø × 3" NaI(Tl) scintillator and compared with the calculated spectrum, where is shown that the 4.44 MeV photon is produced by the neutron source. • The PHS of neutron-induced γ-rays were calculated using MC methods. • Moderators are water, polyethylene and gasoline. • The poor-resolution spectra show the 2.22 MeV due the 1H(n, γ)2H reaction. • The spectra show the induced γ-rays due to inelastic scattering in 12C and 16O. • Experimental validation was carried out for polyethylene. [ABSTRACT FROM AUTHOR]

It is shown that the use of the standard constant fraction timing method for obtaining timestamps of signals from an organic stilbene scintillator leads to a systematic difference in timestamps when detecting neutrons and γ -rays. A detailed study of this effect was carried out using a digital time-of-flight spectrometer based on a stilbene detector and a pulsed source of quasi-monoenergetic neutrons based on the 2H(d,n)3He reaction. It is shown that this effect is present for the entire range of crystal light output values and is related to the difference in the rise time of signals induced by neutrons and γ -rays. It is demonstrated that this effect can lead to a systematic error in absolute measurements of the prompt fission neutron spectra using the time-of-flight method with conventional analog constant fraction timing. A method for compensating this systematic shift based on the analysis of the timestamps position for the digital signals at the different values of the constant fraction is suggested. [ABSTRACT FROM AUTHOR]

Determination of the neutron response function is essential for measuring the energy of neutrons emitted from natural and artificial neutron sources and nuclear reactions. This paper presents the calculation procedure of generating a neutron analytical response function for NE213 scintillation detectors in the energy range of 0.2–148 MeV. To obtain the analytical response function, the available neutron experimental response functions were grouped according to their behavior in different energy ranges. Different analytical functions were fitted to the experimental data of the detector response function for each neutron energy range. The function which best fits the experimental data was selected. Then a computer program was written for calculating the parameters of the analytical function by using the fitting functions and their parameters for each desired energy, and generating the analytical response functions. A comparison of the results shows that the analytical response functions are much faster and more consistent with the experimental response functions than the generated response functions of stand-alone codes and general-purpose Monte Carlo codes. • The analytical neutron response function of NE213 scintillator has been calculated. • A very user-friendly program was developed to calculate the analytical response. • The results of the analytical model are consistent with the experimental results. [ABSTRACT FROM AUTHOR]

Fast neutron time-of-flight (ToF) has been used to characterise the location of a source of a mixed radiation field. Two EJ-309 organic scintillators and a fast, digital, data acquisition system have been used in a variety of positions to identify the location of a 252Cf neutron source inside a steel, water-filled tank. A methodology for extracting the distance between the neutron source and the neutron detector has been developed and verified with MCNP simulations. A reconstruction algorithm using the ToF data has been developed. The location of the neutron source has been estimated on this basis to be within 20 cm of its known location with a spatial resolution of ± 7.8 cm. p-values extracted from the null test hypothesis have been estimated to be 0.975 and 0.996 for experimental and simulation data, respectively. By correctly identifying the location of the source, the potential for the system to discern between scattered and unscattered neutrons is demonstrated. • Fast neutron time-of-flight data, derived from the separation of γ rays and neutrons emitted in spontaneous fission in 252Cf, have been used to identify the position of a 252Cf source. • Experimental data, derived with two organic scintillation detectors, have been compared with data from a parallel simulation-based study and are observed to converge with one another. • The technique appears to be resistant to perturbations by neutrons scattered by the surroundings. • The position of the source determined by time-of-flight agrees within uncertainties with the known source location. [ABSTRACT FROM AUTHOR]

A radiation detection system consisting of an array of three Cs 2 LiYCl 6 :Ce 3 + elpasolite cells was studied for simultaneous, directional neutron and gamma-ray measurements. Utilizing a neutron source and gamma-ray sources, measurements were carried out while rotating the three-cell array 360°. The measurement data was processed using a maximum likelihood estimation technique to determine the most probable angle pointing to the radioactive source. The detection system enables measuring gamma rays and neutrons simultaneously and estimating locations of radioactive sources within 23°. • Detection system based on elpasolite CLYC scintillators was studied for directional detection of neutrons and gamma rays. • Experimental study of the scintillator responses was carried out using a three-cell array. • Maximum likelihood estimation technique was used to localize a radiation source. • Three-cell array is feasible to ascertain the direction to a neutron source and a gamma-ray source. [ABSTRACT FROM AUTHOR]

In this article, we present a measurement of flow rate, yield and effusion time of a 23Ne production and transport system. We used an accelerator-driven Li(d,n) neutron source to produce neutrons up to 20 MeV. The radioactive atoms were produced by a 23Na(n,p) reaction at a NaCl target. Later, the atoms were diffused out from the NaCl crystals and effused from the production chamber via a 10 m hose to a measurement cell and their decay products were detected using High Purity Germanium (HPGe) and plastic scintillator detectors. The resulting flow rate was 6. 9 ± 0. 7 ⋅ 1 0 4 a t o m s s e c and the total yield was 3. 2 ± 0. 6 ⋅ 1 0 − 9 a t o m s d e u t e r o n . We summarize our methods and estimates of efficiencies, rates of production and effusion. [ABSTRACT FROM AUTHOR]

Terbium doped gadolinium oxysulfide (GOS:Tb) ceramics were successfully fabricated by pre-sintering in vacuum and HIP post-treatment in Ar atmosphere. Ceramic densification in vacuum and HIP was discussed in the detail mainly by relative density and FESEM characterizations. The fabricated GOS:Tb ceramics were translucent with 0.5 mm thickness after HIP post-treatment. Optical and scintillation properties of GOS:Tb ceramics were also investigated. Temperature-dependent X-ray excited spectra were recorded using a homemade XEL spectrometer. Neutron scintillation light output was also measured in China Spallation Neutron Source (CSNS). The light output was measured to be about 284 photons per neutron with different thicknesses of GOS:Tb ceramics. • Highly dense GOS:Tb ceramics were prepared by vacuum sintering combined with HIP post-treatment. • The light output of GOS:Tb ceramic scintillator screen is increased by 23% compared with powder form. • The fabricated GOS:Tb ceramic is very promising for using as scintillator in neutron imaging technology. [ABSTRACT FROM AUTHOR]

Liquid organic scintillators are widely used in radiation measurements. NE213 (or its equivalent, BC-501A) in neutron-gamma discrimination (NGD) and two new scintillators, UGLLT and UGAB, in alpha-beta discrimination are two common examples. In this paper, the NGD capabilities of these three scintillators were studied and their figure-of-merits (FoMs) were measured for comparison. The three different NGD methods used in this study were zero-cross method (ZCM), charge integration method (CIM) and filtered charge integration method (FCIM), where ZCM was analog and the two other methods were digital. A 1.1 μCi point 22Na gamma ray source and 100 mCi cylindrical 241Am–Be neutron source (3.5 cm diameter by 5 cm length) were used for the energy calibration and the NGD, respectively. The FoM values for NE213, UGLLT and UGAB at 100 keVee discrimination bias (i.e. , the preset threshold voltage, generally expressed in keVee unit, upon which the generated pulse-heights are recorded) using ZCM, CIM and FCIM methods were (1.060 ± 0.037, 1.430 ± 0.040, 1.70 ± 0.054), (0.910 ± 0.029, 1.270 ± 0.018, 1.460 ± 0.027) and (0.890 ± 0.027, 1.200 ± 0.020, 1.460 ± 0.026), respectively. Although UGAB scintillator exhibits the least discrimination quality, one can choose an appropriate neutron-gamma discrimination method to improve its FoM. The low-temperature flammability, toxicity and high-evaporation properties of NE213 scintillator may motivate some researchers to use UGLLT and UGAB scintillators as alternatives to NE213, however, by selecting the most efficient discrimination method. [ABSTRACT FROM AUTHOR]