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The response of a gamma-ray spectrometer is generally determined by analyzing full-energy peaks. However, full-energy peaks cannot be measured easily in the case of scintillation detectors that consist of light elements, such as glass scintillators. Only a strong Compton plateau appears in the spectrum of such detectors. Therefore, Compton edgers were used to evaluate the response of these detectors. The response of a low-resolution 6 Li-glass detector to gamma rays was measured for the first time by a coincidence method with a high-resolution LaBr 3 :Ce detector using cascade gamma rays (2.75 and 1.37 MeV) from a 24Na source. Coincidence gates were applied at the peaks of the spectrum of the LaBr 3 :Ce detector at the 0.51 MeV annihilation peak, and the sum peaks of a gamma ray and a backscattered gamma ray. By analyzing the gated spectra of the 6 Li-glass detector, the energy-dependent detector response (i.e., the output strength and its dispersion) was determined. • Evaluation of the response characteristics, including signal output and broadening, of a low-resolution 6Li-glass detector to gamma rays up to approximately 2.5 MeV. • Coincidence measurement of cascade gamma rays emitted from a 24Na source with a high-resolution detector, a LaBr 3 :Ce detector. • Peak analysis of the spectra of the 6Li-glass detector gated at gamma ray peaks of the LaBr3:Ce detector. [ABSTRACT FROM AUTHOR]

Experiments such as mu2e (FNAL, USA) and COMET (KEK, Japan) seek the direct muon-to-electron conversion to study Charged Lepton Flavor Violation processes. A highly efficient (up to 99.99% efficiency) cosmic muon detection system is needed to achieve a single-event sensitivity below 1 0 − 17 . In this article, the possibility of attaining such efficiency in the short and long term is discussed for modules based on 7-mm- or 10-mm-thick and 40-mm-wide plastic scintillation strips with a single 1.2 mm WLS fiber glued into the groove along the strip and using MPPC/SiPM for light detection. A Simplified Light Yield Distribution (SLYD) method to estimate the efficiency of the module is proposed, and the simulation results obtained with GEANT 4 for a system based on a 4-by-4 array of 7x40x3000 mm strips are compared with the experimental data. It is found that for the systems requiring efficiency of 99.99% and higher, it is important to improve the light yield as much as possible and to achieve the smallest possible gap between neighbor scintillation volumes is important. [ABSTRACT FROM AUTHOR]

Signal saturation in the Silicon PhotoMultiplier (SiPM) often causes a serious problem in using a detector equipped with SiPMs for scintillator readout. Conventionally, SiPM signal saturation is measured through direct injection of visible light pulses to the SiPM. However, the method works poorly with the scintillation detector because the effects of the time constant of the emission of scintillation light are not included. Here, we present a novel method to measure the precise degree of SiPM signal saturation in scintillation detectors. The key difference from the conventional method is to use UV light pulses, as opposed to visible light ones, to inject and excite scintillation light in the detector. It allows us to directly measure the degree of saturation in situ taking into account all the major effects in the detector, such as the time constant of the scintillation emission. We also develop a new model for SiPM signal saturation and validate it with the measured degree of saturation with the above-mentioned new method. [ABSTRACT FROM AUTHOR]

This paper aims to demonstrate the feasibility of the proposed compensated neutron logging (CNL) tool for the absolute measurement of the porosity of subsurface formation based on the computational simulation study. Conventional CNL tools use 3He gas detectors, but solid-state scintillation detectors such as stilbene and CLYC are explored in this study. Monte Carlo simulations were conducted to investigate the advantages of the proposed CNL tool and the effects of environmental parameters such as pore fluid, borehole radius, and rock type on the absolute porosity measurement. Comparing simulated responses from the stilbene and CLYC detectors with conventional 3He detector, the stilbene-based logging system was expected to exhibit the highest neutron detection efficiency, while the porosity calibration performance was evaluated to be better with the CLYC-based system. Pore fluid makes differences in porosity calibration curves associated with the hydrogen content. Larger borehole radius deteriorates the porosity calibration performance. The shape of porosity calibration curve was altered for a certain rock type. Neutron-induced gamma spectroscopy may reveal the rock type information based on gammas from certain elements. One can identify the rock type from the CLYC results based on photopeaks from silicon, which may be relatively hard to accomplish with the stilbene-based system. The proposed system is expected to allow absolute porosity measurement in a broader environmental configuration compared to the conventional system. [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]

External optical crosstalk remains a significant source of correlated noise in scintillation detectors optically coupled to silicon photomultiplier (SiPM) arrays and can influence achievable performance by limiting the maximum overvoltage at which a detector can be operated. This study evaluated the potential benefits of incorporating an optical bandpass filter, which is absorptive to optical crosstalk and transmissive for scintillation photons, between the scintillator and SiPM array. Several SiPM and bandpass configurations were characterized, including single-element and SiPM arrays with bare, filter-coupled, crystal-coupled, and crystal-filter-coupled interfaces. Coupling the optical filter between a 4 × 4 array of Broadcom AFBR-S4N44P164 M (NUV-MT) SiPMs and a 12 × 12 × 20 mm3 LYSO crystal decreased the total number of detected optical photon noise by up to 92%. The impact of the filter on crosstalk probability reduction was also characterized by the single-channel measurements with the same SiPM, suppressing external crosstalk up to 64%. With the filter coupled, SiPMs were operable at very high overvoltage. The results of these studies demonstrate that optical filtering is a promising technique to significantly reduce correlated noise in scintillation detectors employing SiPMs. [ABSTRACT FROM AUTHOR]

Scintillation radiation detectors based on silicon photomultipliers (SiPMs) are widely used nowadays both in various medical apparatus and physics experiments, e.g., in PET. At the same time, this technology has great potential in terms of creating X-ray photon counting detectors, which are in demand both in medicine and applied research. In this work, we investigate the influence of main SiPM parameters on the overall system performance, as well as different methods of data readout. It is shown that the use of SiPMs with shorter cell recovery time and larger number of microcells makes it possible to achieve a rate capability of 12 Mcps (mega counts per second) per channel. At the same time, the scintillator decay time is still among the limiting factors for such systems. [ABSTRACT FROM AUTHOR]

This work presents a systematic study of the properties (Light Output Non-Uniformity (LONU) and energy resolution) of two CsI(Tl) scintillation units over a span of almost three years, under adverse conditions of humidity and temperature. These two crystals are part of the CALIFA detector, a highly segmented calorimeter and spectrometer for γ rays and light-charged particles, that is placed surrounding the reaction target at Cave C, the experimental cave of the R 3 B (Reactions with Radioactive Relativistic Beams) collaboration at the GSI-FAIR facilities in Darmstadt, Germany. The findings obtained after the experiment indicate that there was no significant impact on the performance in terms of resolution and LONU. This suggests that the employed wrapping for light collection effectively serves as an excellent barrier against humidity. As a result, the crystal is preserved in a far better condition than initially anticipated. [ABSTRACT FROM AUTHOR]

We successfully developed 20- and 40-wt% HfO 2 -nanoparticle-loaded plastic scintillators (Hf-PLSs), and subsequently, assembled X-ray timing scintillation detectors using the Hf-PLSs and silicon avalanche photodiodes (Si-APDs) as the photodetector. Two types of Si-APDs were examined for two different detectors. A proportional-mode APD (pAPD) exhibited a nanosecond response, but a relatively low internal gain of less than several hundred. By contrast, a Geiger-mode APD exhibited a high gain of 105−6, but its output pulse width was longer than several tens of nanoseconds; the pixelated device is called as SiPM. A pAPD (Hamamatsu Photonics S8664-4433, 3 mm in diameter) was used as the photodetector and was combined with 20 wt% Hf-PLS (∼3 mm cube) as the X-ray scintillation timing detector. A SiPM (Hamamatsu Photonics S13360-3025, 3 mm × 3 mm) was assembled with 40 wt% Hf-PLS (∼3 mm cube). The characteristics of the two types of scintillation timing detectors were evaluated using a 57.61-keV synchrotron X-ray beam to assess their applicability in nuclear resonant scattering experiments. Both the detectors were cooled down to −35 or −20 °C to reduce noise and obtain a higher APD gain. A good time resolution of (0.31 ± 0.04) ns (FWHM) was easily obtained with the SiPM detector using a large APD gain at −20 °C, although the time resolution of the pAPD detector finally reached (0.39 ± 0.04) ns (FWHM) at −35 °C owing to a small gain of 146. However, a maximum count rate of over 1.4 × 107 s−1 was observed owing to the fast response of the pAPD detector, whereas the SiPM detector exhibited a maximum count rate of 5.9 × 106 s−1 because of the long pulse tail of ∼30 ns. [ABSTRACT FROM AUTHOR]

In order to improve the temporal response of SiC-HPMTs, a new SiC detector with a faster time response (leading edge 1.5 ns, FWHM 4 ns) was developed for constructing an improved SiC-HPMT. Then the properties of the improved SiC-HPMT were studied in detail. Compared with those of the previous SiC-HPMT, the temporal response of the improved SiC-HPMT, with a leading edge of about 2 ns and a FWHM of less than 5ns was effectively improved. The maximum linear current that exceeded 630 mA depends on both the accelerating and focusing voltage (V a) and the bias voltage (V SiC) of the SiC detector, but has a strong dependence on V a. The scintillation detector comprised of the improved SiC-HPMT and an EJ228 scintillator can accurately obtain the multiple peaks characteristic of the pulsed X-ray source, which indicates that the improved SiC-HPMT can well satisfy the requirements for measuring the time information of fast pulsed radiation fields. In addition, the SiC-HPMT should be placed at the position that deviates from the radiation beam to avoid the direct irradiation on the SiC detector. The improved SiC-HPMT will further expand its application in pulsed radiation field measurements and become a supplement for existing photoelectric detectors. [ABSTRACT FROM AUTHOR]

We report on a highly selective experimental setup for particle- γ coincidence experiments at the Super-Enge Split-Pole Spectrograph (SE-SPS) of the John D. Fox Superconducting Linear Accelerator Laboratory at Florida State University (FSU) using fast CeBr 3 scintillators for γ -ray detection. Specifically, we report on the results of characterization tests for the first five CeBr 3 scintillation detectors of the CeBr 3 Array (CeBrA) with respect to energy resolution and timing characteristics. We also present results from the first particle- γ coincidence experiments successfully performed with the CeBrA demonstrator and the FSU SE-SPS. We show that with the new setup, γ -decay branching ratios and particle- γ angular correlations can be measured very selectively using narrow excitation energy gates, which are possible thanks to the excellent particle energy resolution of the SE-SPS. In addition, we highlight that nuclear level lifetimes in the nanoseconds regime can be determined by measuring the time difference between particle detection with the SE-SPS focal-plane scintillator and γ -ray detection with the fast CeBrA detectors. Selective excitation energy gates with the SE-SPS exclude any feeding contributions to these lifetimes. [ABSTRACT FROM AUTHOR]

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. • First position sensitive ZnO:Zn neutron detector was developed using orange WLSF. • ZnO:Zn has count rate capabilities 2 times higher than equivalent ZnS:Ag detector. • Gamma sensitivities are ∼10−5 at 74% trigger efficiency. • Neutron detection efficiency of ZnO:Zn at 1 Å was 25% less than the ZnS:Ag detector. • Improvements to light output or collection needed to improve detection efficiency. [ABSTRACT FROM AUTHOR]

In this paper we are reporting on the progress and scale up of the Cerium-doped Tl 2 LiYCl 6 (TLYC) scintillator. The boules up to 2-inch in diameter were grown by the Bridgman method at Fisk University. The lapped and polished samples were characterized for their scintillation properties including gamma-neutron dual mode detection. The 1.5-inch diameter samples demonstrated the energy resolution as good as 4.5% (FWHM) at 662 keV. The neutron peak due to 6Li(n, α) reaction was observed at 1.8 MeV gamma equivalent energy. Gamma-neutron pulse shape discrimination (PSD) was demonstrated with the Figure-of-Merit (FOM) of 1.8. The hermetically encapsulated samples were also evaluated for their radiation hardness with irradiation up to 1 Mrad. [ABSTRACT FROM AUTHOR]

Positron annihilation lifetime (PAL) spectroscopy has long been considered as a powerful approach to characterize atomic-scale vacancy-type defects and supermicropores, which affect the macroscopic properties of materials. In standard PAL measurements, several million annihilation events are required to achieve accuracy. For a conventional PAL spectrometer which consists of two scintillation detectors and analytical electronics, the two detectors are usually perpendicularly positioned to diminish spectra distortions (caused by backscattering and pileup). The perpendicular placement of detectors leads to a counting rate of 100 – 300 counts/second (cps) while using a 30 μ Ci 22Na source (3.3 – 10 cps/ μ Ci). Consequently, collecting one PAL spectrum with total counts of one million takes several hours. The long time limits its potential to observe changes in the microstructure. To increase the counting rate of PAL measurements, we propose a novel multi-detector PAL spectrometer, which includes three or four detectors, a digital oscilloscope, and an algorithm for any detector to record both start and stop signals. The spectrometer achieves a high counting rate of around 2144 cps (71.5 cps/ μ Ci) with four detectors, which is about ten times that of a conventional one with two detectors perpendicularly positioned. This work enables us to perform in-situ PAL measurements to disclose the minute-scale evolution of microstructure more precisely during fast physical and chemical processes in the future. • A better spectrum unfolding accuracy can be achieved with a larger total count. • The scintillator size and geometry was optimized using Geant4. • A reversible start/stop data acquisition algorithm was developed to double the counting rate. • The novel spectrometer is highly extendable to 3, 4 and more detectors. • The counting rate of ten times higher than the conventional spectrometer was obtained. [ABSTRACT FROM AUTHOR]

We have combined two low-threshold detector technologies to develop a large-mass, low-threshold detector system that simultaneously measures the athermal phonons in a sapphire detector while an adjacent silicon high-voltage detector detects the scintillation light from the sapphire detector. This detector system could provide event-by-event discrimination between electron and nuclear events due to the difference in their scintillation light yield. While such systems with simultaneous phonon and light detection have been demonstrated earlier with smaller detectors, our system is designed to provide a large detector mass with high amplification for the limited scintillation light. Future work will focus on at least an order of magnitude improvement in the light collection efficiency by having a highly reflective detector housing and custom phonon mask design to maximize light collection by the silicon high-voltage detector. [ABSTRACT FROM AUTHOR]

Organic scintillators exhibit fast timing, high detection efficiency for fast neutrons and pulse shape discrimination (PSD) capability. PSD is essential in mixed radiation fields, where different types of radiation need to be detected and discriminated. In neutron measurements for nuclear security and non proliferation effective PSD is crucial, because a weak neutron signature needs to be detected in the presence of a strong gamma-ray background. The most commonly used deterministic PSD technique is charge integration (CI). This method requires the optimization of specific parameters to obtain the best gamma-neutron separation. These parameters depend on the scintillating material and light readout device and typically require a lengthy optimization process and a calibration reference measurement with a mixed source. In this paper, we propose a new method based on the scintillation fluorescence physics that enables to find the optimum PSD integration gates using only a gamma-ray emitter. We demonstrate our method using three organic scintillation detectors: deuterated trans-stilbene, small-molecule organic glass, and EJ-309. In all the investigated cases, our method allowed finding the optimum PSD CI parameters without the need of iterative optimization. [ABSTRACT FROM AUTHOR]

Gamma-ray astronomy in the MeV energy range shows a lack of sensitivity compared to other gamma-ray energy bands. Several space observatory projects are proposed to space agencies to fill this gap. The COMCUBE CubeSat project will focus on the measurement of the polarization of the prompt emission of gamma-ray bursts (GRBs) which can provide an understanding of the physics of ultra-relativistic jets. Furthermore, the linear polarization of distant gamma-ray sources could be a probe to study the fundamental physics related to the Lorentz invariance violation. A Compton telescope is particularly well-suited for that purpose. We develop an instrument including double-sided silicon strip detectors and scintillation crystals coupled to a pixelated photodetector. The incoming photon undergoes an inelastic scattering in one or several layers of a position-sensitive silicon strip detector before being absorbed in a position-sensitive calorimeter based on inorganic scintillators. The measurement of both positions and energy deposits enables the determination of the photon's source direction. It also enables measurement of the linear polarization of the incident gamma-rays. In this contribution, we present the results of the extensive work we have carried out to develop the calorimeter and its integration into a Compton telescope prototype. We conclude by showing the first image and polarization measurements. [ABSTRACT FROM AUTHOR]

The Wolsung Nuclear Power Plant in Korea is under IAEA safeguards. During IAEA physical inventory verifications, the Optical Fiber radiation Probe System has been used since 2007 as the official instrument for verification of spent fuel. Its low sensitivity requires excessive time and labor to perform the IAEA safeguard activities and increases the operator load for preparing a dangerous and time-consuming secondary inspection. The objective of this paper is to develop a superior new optical fiber-based scintillation detector to deal with such issues. To increase the sensitivity of the instrument, a new optical fiber-based scintillation detector was developed by combining a p-terphenyl scintillator with a new type of optical fiber. A field test was carried out in the CANDU Wolsung Unit 1 to characterize the performance of the new detector. The field test showed that the OFPS using the new optical fiber-based scintillation detector has at least 100-times higher sensitivity and can also measure even very weak signals not measurable by the existing detector. From the experimental results, we can conclude that the newly developed OFPS detector would increase the effectiveness and efficiency of nuclear safeguards for verification of spent fuel in wet storage pools of CANDU reactors. • A new optical fiber-based scintillation detector has been assessed for spent-fuel safeguards. • The detector is made of a p-terphenyl organic scintillator to enhance the light yield and response time. • The signals of spent-fuel bundles with low activity were observed with the new detector. [ABSTRACT FROM AUTHOR]

Coincidence measurements between cosmic ray detectors placed some distance apart are the standard way to detect the arrival of extensive air showers created in the Earth atmosphere by the interaction of a high energy primary particle. In this project we tried to exploit the potential of a detector array based on the use of several small area individual detectors, which could be easily re-configured in different detection geometries and employed in basic and applied physics investigations. Such low-cost facility is also intended as an educational tool for master and Ph.D. students in a cosmic ray physics laboratory. Each module is based on a small size scintillator tile, with a Wavelength Shifter bar and a Silicon photomultiplier for light collection and readout. Individual signals from SiPMs are sent to an Arduino MEGA board for trigger, data acquisition, GPS time stamping and storage. This paper will report the design of the project and a few physics cases, resulting from the outcome of several measurements campaigns carried out with different geometrical configurations. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Additive manufacturing techniques have advanced significantly and get more and more interesting also for the development of active parts of particle detectors. The main advantages are the flexibility in building 3D-forms, as well as fast prototyping cycles. For many detector applications it is crucial to use well-tested materials to avoid aging problems. Printers working with granulates allow the direct printing of original materials, including the usage of several different materials at the same time. This is very attractive, for example, for segmented and 3D-integrated detectors like calorimeters or trigger veto systems based on plastic scintillators coupled to photodetectors. In this work, we focus on the printing of transparent plastic granulates. We compare different thermoplastics as base material, particularly polymethylmethacrylate (PMMA) and polystyrene (PS). The printing process is ARBURG Plastic Freeforming featuring in-line drying, plasticizing with melting points up to 350 °C and high-frequency droplet discharging. The main challenges are the transparency of the printed parts and their surface quality. The former is investigated using a UV/Vis spectrometer, the latter using a confocal 3D-microscope. We present a comparison to reference samples and discuss potential future applications of this technology. • Examination of transparent samples produced from original granulate materials using additive manufacturing. • Up to 91% transmittance achieved for 3D-printed polymethylmethacrylate samples. • Comparison of different thermoplastics including polystyrene. [ABSTRACT FROM AUTHOR]

This work presents a novel optical method for selecting new liquid compounds for scintillation detectors. This method consists in the evaluation of the optical properties of the compounds and the definition of parameters quantifying their emission yield, based on the study of the scintillation spectra. It is a comparative method as it allows the choice of the best liquid scintillator among many through a step-by-step selection based on: (1) the fluorescence spectra of the matrix, (2) the fluorescence spectra of the matrix with a dye, (3) the Ion Beam Induced Luminescence spectra of the matrix with different dye percentages. We used the proposed method to identify new liquids which may be suitable for neutron detection. This work shows the results of this application: a new organic non-toxic and non-flammable liquid scintillator has been identified. [ABSTRACT FROM AUTHOR]

Recently, various neutron detectors, such as scintillation detectors, are being developed as alternatives to 3He proportional counters. Here we focus on the thickness and property controls of inorganic scintillators used for thermal neutron detection in intense γ -ray fields without considering pulse shape discrimination (PSD) techniques. GS20 TM (a lithium glass) and LiCaAlF 6 crystals activated with Ce (LiCAF:Ce) scintillators with thicknesses of 0.5 and 1.0 mm, respectively, have been employed because they have faster decay times than other inorganic scintillators. Pulse signals generated by photomultiplier tubes, to which the scintillators were coupled, were inserted into a digital pulse processing unit with a sampling rate of 1 GHz, and the areas of waveforms were integrated for 360 ns. Neutron/ γ -ray detections and discriminations were performed via pulse integrations without using PSD techniques. For GS20 TM , the relative energy resolution values of the thermal neutron peaks were 11% and 12% in 0.5 mm and 1.0 mm thicknesses, respectively, and those for LiCAF:Ce were 18% and 36% in 0.5 mm and 1.0 mm thicknesses, respectively. In a 60Co γ -ray field, the neutron detection for GS20 TM in a 0.5 mm thickness was possible at dose rates of up to 0.919 Gy/h; however, for LiCAF:Ce, neutron detection was possible at 0.473 Gy/h, and it failed at 0.709 Gy/h. The neutron/ γ -ray discrimination of GS20 TM was better than that of LiCAF:Ce due to its better energy resolution and higher detection efficiency (6Li content). • We focus on the property controls of scintillators for neutron/ γ -ray discrimination. • Neutron detection using GS20TM and LiCAF:Ce is performed in a γ -ray field. • GS20TM exhibits better neutron/ γ -ray discrimination than LiCAF:Ce in a γ -ray field. [ABSTRACT FROM AUTHOR]

The goal of the present work is to develop a time-of-flight positron emission tomography (TOF-PET) detector system with 100 picosecond (ps) coincidence time resolution (CTR) using arrays of 20 mm length scintillator crystal elements. If successful, this would yield a 1.5-fold better reconstructed image signal to noise ratio (SNR) compared to state-of-the-art clinical TOF-PET systems. The proposed detector configuration comprises LGSO scintillation crystal elements optically coupled to silicon photomultipliers (SiPMs) which are read out by a fast, high precision, multi-channel amplifier/comparator integrated circuit (IC). Results obtained with that IC were compared with those achieved using a high-frequency (HF) readout, comprising discrete element readout for each detector channel. CTR values of 89.6 ± 0.8 ps and 105.1 ± 0.9 ps FWHM were achieved with the HF readout for 3 × 3 × 3 mm3 and 3 × 3 × 10 mm3 LGSO crystals, respectively, and 92.8 ± 0.9 ps and 114.1 ± 1.1 ps FWHM were achieved using the IC board for the same crystal elements. These results demonstrate the capabilities of a scalable IC readout solution for a 100 ps CTR TOF-PET design. [ABSTRACT FROM AUTHOR]

In applications of transmission muography for large objects, plastic scintillator strips with triangular or rectangular cross-sections are frequently selected to construct imaging detectors. Triangular scintillator strips have a better position resolution over those of rectangular ones by a factor of ∼ 3.5 with the same width. The big difference has been carefully studied using Geant4. Simulations show a good agreement with those of existing muography instruments. The position resolution is influenced by the geometry (the size and base angle of triangular strips) and the energy resolution of scintillators, and angles of incoming muons. Two empirical formulas have been proposed to quantitatively estimate the position resolution with respect to the abovementioned influential factors. Perpendicularly and randomly (real angular distribution) incoming muons are considered separately in them. A more widely spread angular distribution of muons can make the position resolution worse. For commonly used triangular scintillator strips with a base angle of 45 ∘ , the ratio of the triangle base length to the position resolution is almost fixed to ∼ 12 varying the base length or energy resolution if an uncorrected Centre of Gravity (CoG) method is used. Such a ratio has a potential to be increased by a factor of ∼ 2 if the CoG method is corrected with the muon incoming angle. The influence of the energy resolution on the position resolution can be ignored. • Two empirical formulas proposed to describe the position resolution of triangular scintillators. • More widely distributed emission angles of muons lead to worse position resolution. • The ratio of triangular scintillator base length to position resolution is almost unchangeable. • The position resolution can be improved by a factor of 2 with muon emission angle corrections. • The influence of energy resolution of scintillators on the position resolution can be ignored. [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]

Muography has a wide range of applications especially in the cross-disciplinary area. It is a powerful tool to probe the internal composition of objects in a non-destructive way. To achieve the goal of muography, it is essential to track muons as precisely as possible. We designed a cosmic muon tracking detector MuGrid using plastic scintillators. In this work, we present the preliminary progress of the MuGrid detector and its demonstrator, including the data acquisition system, characterization of plastic scintillators and Monte Carlo modeling of MuGrid. We also analyzed its detection efficiency, angular resolution, and provided a comparison of back-projection images of simulation and observation in an open environment. A case study is conducted in a tunnel as a validation of the whole system. [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]

A large area plastic scintillator detector system with SiPM read out has been prepared in order to improve the trigger selectivity for reaction studies induced by an intense proton beam with a beam momentum of several GeV/c. The system consists of six trapezoidal modules, each with three plastic scintillator elements that are each equipped with 12 SiPMs. The detection of a charged particle is based on registering coincident signals in several SiPMs. By requiring a signal on at least two of the SiPMs, the noise rate is negligible and a detection efficiency close to 100% is achieved. [ABSTRACT FROM AUTHOR]

We report the experimental validation of a detection module based on a LaBr 3 (Ce＋Sr) scintillator crystal, read by a matrix of Silicon Photomultipliers (SiPMs), for the development of a SPECT system for dose monitoring in Boron Neutron Capture Therapy (BNCT). The goal of the system is to detect the gamma rays at 478 keV emitted by the excited 7Li produced in the 10B(n, α)7Li reaction, to have a real-time localization and quantification of the local dose released to a patient during BNCT treatment. The good energy resolution of the detector (< 3 % at 662 keV) allows to resolve the photopeak at 478 keV from the adjacent annihilation photons photopeak at 511 keV, originated from pair production of high energy gamma rays, such as the hydrogen neutron capture gamma rays at 2.2 MeV. The results shown in this article demonstrate the suitability of our detector in view of future application in BNCT real-time dose monitoring. Good linearity (RMSE < 2.5 cps) between the number of events detected at 478 keV and the boron concentration of the 10B-loaded samples has been achieved, down to a boron concentration of 62 ppm with a neutron flux of approximately 1 × 105 n/cm2/s. [ABSTRACT FROM AUTHOR]

A beam position detector was developed that is based on a thin octagonal-shaped scintillator which is read out by silicon photomultipliers on its eight lateral sides. Its main application is beam diagnostics and triggering for sensitive detector setups using extremely low beam intensities. In-beam tests at the Mainz Microtron have demonstrated that the position of single electrons can be obtained with a precision of below 1 mm when adding systematic and statistical uncertainties. Measurements have been complemented by a simulation with Geant4 to optimize the detector geometry. [ABSTRACT FROM AUTHOR]

A SiPM-based gamma-ray detection module for substituting bulky Photomultiplier Tubes in the readout of large scintillation crystals is presented. The system can be coupled to scintillators up to 3 inches in diameter, with state-of-the-art energy resolution (2.6% at 662 keV) and 80 keV - 20 MeV energy Dynamic Range, simultaneously achieved for the first time. Position sensitivity can also be achieved. Measurements show that a complete replacement of PMTs with SiPMs is already possible thanks to enhancements in silicon technology and lowering costs, making SiPMs a severe contender in many fields now dominated by vacuum-tubes technology. [ABSTRACT FROM AUTHOR]

The pulse shape discrimination (PSD) performance of EJ-276 and EJ-301 scintillator readout with silicon photomultiplier (SiPM) was evaluated. Scintillator with 1-inch and 2-inch size was coupled to an 8 × 8 SiPM array, consisting of 3 mm and 6 mm SiPM respectively. The SiPM array was divided into four groups, each amplified with a transimpedance circuit (TIA) and then summed to form a single output. The pulse waveforms were collected with a 500 MHz/12 bit digitizer and analyzed off-line. The PSD performance was evaluated based on the charge comparison method. The 1-inch EJ-276 scintillator combined with SiPM array exhibited a figure of merit (FOM) of 1.41 for an energy threshold of 250 keVee (electron equivalent). The FOM of 2-inch EJ-276 and 1-inch EJ-301 scintillator were 1.15 and 2.15 respectively with the same condition. The experimental results demonstrated the feasibility of a compact fast neutron detector using EJ-276 or EJ-301 scintillator readout by SiPM array with reasonable n / γ discrimination capability. [ABSTRACT FROM AUTHOR]

Monte Carlo radiation transport modeling studies were performed for a compact, and high-resolution gamma-ray computed tomography system designed for imaging irradiated nuclear fuel. The system comprises a 60Co source – chosen for its highly penetrating 1173 keV and 1332 keV gamma rays – a pair of high-aspect-ratio pencil beam collimators, and an inorganic scintillator detector. Two acceleration methods are proposed to rapidly model a transmission type gamma-ray tomography system. The first, a variance reduction technique, is based on performing Monte Carlo simulations with a monodirectionally-biased source, sampled from a characteristic sub-volume of the full source volume. The second acceleration method is based on the deterministic calculations using the Beer–Lambert law and detector response characteristics. Comparison of simulations using acceleration approaches with analog simulations of the fully isotropic, full-volume equivalent, show that the Monte Carlo variance reduction technique gives quantitatively accurate predictions for large collimator aspect ratios while the deterministic calculations are semi-quantitative but converge close to the correct result as the collimator aspect ratio increases. As such, these techniques can be used to reduce the computational cost in generating simulated radiographs and tomographs by several orders of magnitude. Experimental validation efforts are currently underway and will be demonstrated in future work. [ABSTRACT FROM AUTHOR]

Scintillation detectors are widely used in gamma-ray spectrum measurement because of their beneficial characteristics. However, scintillators and photoelectric conversion devices are sensitive to temperature changes, which leads to a drift in the energy spectrum. This paper presents a new method for calibrating a scintillation detector that uses a pulse from an ultraviolet light-emitting diode (UV-LED) to excite a BGO scintillator to generate fluorescence, and to control the drive voltage of the UV-LED to obtain different fluorescence peaks for energy spectrum calibration. Temperature experiments were carried out to obtain the curves of the energy spectrum drift and the 137Cs source for temperature changes in the range from −10 °C to ＋30 °C. With the UV-LED peak position at 10 °C selected as the standard peak, the relative deviation in the energy spectrum drift due to temperature changes was up to 24.41% without calibration, but this was reduced to 6.18% after using the UV-LED reference peak to calibrate. To optimize the calibration method, the pulse energy was calculated by integrating the falling edge of the waveform rather than the whole waveform, and this reduced the maximum relative deviation to 1.45%. Overall, this UV-LED calibration method effectively modifies the scintillation detector's energy spectrum drift and provides a new reference scheme for the online calibration of scintillation detectors. [ABSTRACT FROM AUTHOR]

The high scintillation luminosity of n -type GaAs at 10 °K is surprising because (1) with a refractive index of 3.5, escape is inhibited by total internal reflection and (2) narrow-beam experiments at 90 °K report infrared absorption coefficients of several per cm. This paper presents Monte Carlo calculations showing that the high luminosity at 10 °K can be explained if (1) the narrow-beam absorption is almost all optical scattering and (2) the absolute absorption coefficient is below 0.1 per cm. Sixteen surface reflector configurations are simulated for a range of internal scattering and absolute absorption coefficients, and these can guide the design of cryogenic scintillating GaAs targets for the direct detection of dark matter. The discussion section presents a possible infrared scattering mechanism based on the metallic nature of n -type GaAs. A supplement file describes (1) the Monte Carlo program steps in detail and (2) how narrow-beam and integrating sphere experiments can measure the cryogenic optical scattering and absolute absorption coefficients. [ABSTRACT FROM AUTHOR]

The development of lead tungstate scintillator with the scintillation decay decreased down to the subnanosecond domain is reported. The material exhibits a scintillation decay with a time constant of 640 ps at a light yield of 7 phe/MeV and a high radiation tolerance to the electromagnetic component of ionizing radiation. It is shown to be an outstanding candidate for dual readout of scintillation and Cherenkov photons in electromagnetic calorimetry at future collider experiments. [ABSTRACT FROM AUTHOR]

We have been developing a plastic scintillation counter for the WASA detector. The performance of a plastic scintillation counter with Multi-Pixel Photon Counter (MPPC) readout has been systematically investigated for minimum ionizing particles in terms of the time resolution and the signal amplitude stability. The performance was evaluated under various incident conditions of 2.5 GeV/ c proton beams and with different MPPC settings. A plastic scintillator with a size of 550 × 38 × 8 mm 3 was optically coupled with multiple MPPCs at each plane with a size of 38 × 8 mm 2 for detecting the scintillation photons. The observed time resolution ranges in 37–80 ps (σ) depending on the incident positions and angles for the case of three MPPCs attached to each end. We found the time resolution and the signal amplitude fairly consistent up to the counting rate of 0.2 MHz. [ABSTRACT FROM AUTHOR]

The CdZnTe detector, a room-temperature semiconductor detector, has many applications for nuclear safety and nuclear medicine because of its high energy resolution and small size when compared with scintillator detector and high purity Germanium detector respectively. Radionuclide imaging is one of the most important applications that requires adequate three-dimensional position resolution. In this work, we used a CdZnTe crystal from eV Products with a pixelated anode to achieve approximately 1.0 mm position resolution on an electrode plane and 0.9 mm position resolution in depth when the CdZnTe detector's pixel pitch is 2 mm and thickness is 5 mm. We also improved the energy resolution of a 662 keV full-energy peak in a 137Cs energy spectrum to 1.27% after running a selection of full-energy deposited events based on depth, compared with 4.06% without this operation. [ABSTRACT FROM AUTHOR]

A new pulse-processing electronics architecture for photomultipliers coupled to fast scintillators used in nuclear physics experiments is described. The system comprises a field programmable gate array (FPGA) based time-to-digital converter (TDC), as well as custom analog electronics for amplification and efficient analog signal processing. These electronics include separate fast and slow discrete amplifiers to extract the timing and energy information of the incident radiation on cerium doped lanthanum bromide scintillators. With the slow amplifier, a novel circuit that is able to convert energy information directly into pulse width with a linear dependence is introduced. Advanced and highly demanded features such as low-processing time, high data rate handling capabilities and long collection windows have been tested with radioactive ion-beams. These characteristics of pulse-processing modules will further push the boundaries of experimental freedom. [ABSTRACT FROM AUTHOR]

A High Efficiency fast-Response GAmma detector (HERGA) for the identification of radionuclides and for gamma-ray imaging is presented. The detector is compact, ideal for real-time analysis, with low power consumption, suitable for industrial process control, environmental monitoring and localization of nuclear wastes. A prototype consisting of 16 Cs I (Tl) scintillators coupled to photomultiplier tubes (PMTs) with a digital readout was built. The scintillators are arranged in a 4 × 4 matrix; a 7 × 7 mask composed by plastic and tungsten tiles has been used to validate the imaging figures of merit according to coded mask principle. A 2D Kolmogorov–Smirnov pattern recognition statistical method has been developed, allowing to achieve a point spread function (PSF) of a few mrad for pointlike sources. The Minimum Detectable Activity (MDA) was also determined in the case of pointlike radioactive sources. [ABSTRACT FROM AUTHOR]

In a neutron-diagnosed subcritical experiment, a highly sensitive and fast detector is required to accurately determine the true fission γ -ray emission rate from an object composed of special nuclear material under interrogation, in addition to a proper detector response model for use in forward modeling. We present the development of a detector response model that is based in GEANT4 and uses post-processing techniques to include photomultiplier tube time and pulse height response effects. We also define a set of detector performance evaluation metrics that emphasized our experimental objectives. A suite of time and pulse height response measurements for several diverse detector assemblies are described. These assemblies were simulated with this response model and benchmarked against the laboratory measurements. This response model reproduces the pulse height curve shapes and performance hierarchy of the measured detectors well. Additionally, the simulated time response curves exhibit reasonable agreement with counterpart measurements. These measurements and simulation results together suggest that a large volume EJ-299-49 plastic scintillator that is mated to an ultraviolet transmitting plastic light guide and relies on total internal reflection for light transport to the photocathode will provide significantly faster timing, increase pulse height by a factor of 3, and require 25% less γ rays to meet experimental needs, compared to the candidate detector design developed prior to the availability of this response model. Application of this response model and associated performance metrics in the context of large-scale design sensitivity studies is also discussed. [ABSTRACT FROM AUTHOR]

The present work reports the performance of 1.5 ′ ′ x 1.5 ′ ′ CeBr 3 cylindrical fast scintillator detectors, coupled to the Photomultiplier Tube (PMT) Hamamatsu R13089-100. The detectors are characterized with respect to the energy linearity response, energy resolution, absolute photopeak efficiency and time resolution, using standard radioactive sources. The energy spectra recorded for different radioactive sources and the absolute photopeak efficiency at different source-to-detector distances are compared with the GEANT4 Monte Carlo simulation. The best time resolution of 141 (1) ps, measured for the 1173–1332 keV prompt γ -ray cascade for a single 1.5 ′ ′ x 1.5 ′ ′ CeBr 3 detector, is reported from the present work. The results are compared with the values reported for similar detectors of different sizes. [ABSTRACT FROM AUTHOR]

This paper describes an experimental setup developed to measure the beta-ray energy spectrum as well as a Geant4 simulation study conducted to characterize the properties of a beta-spectrometer. The beta-spectrometer comprises a multi-wire chamber to generate signals to indicate the incidence of beta rays and a plastic scintillation detector to measure its energy. The coincidence method of the detector signals was used to remove high gamma-ray interference. To evaluate the performance of the developed spectrometer, the energy spectra were measured with the radionuclide sources (137Cs and 207Bi) emitting internal conversion electrons and gamma rays. The gamma-ray interference removal rate of the spectrometer using the coincidence method was 99.12 ± 0.09%. To reconstruct the beta spectrum from the measured spectrum, Monte Carlo simulations using the Geant4 toolkit were performed to calculate the coefficient related to the effect of gamma rays. The obtained spectrum confirmed that the energy resolution and intrinsic internal conversion peak detection efficiency of the beta-spectrometer were 10.2% at 1 MeV and 91.6%, respectively. [ABSTRACT FROM AUTHOR]

In this study, a high-spatial-resolution scintillator-type X-ray detection system with a silicon separator was developed. The image characteristics are evaluated, and the approaches required for the practical application of the proposed system were discussed. X-ray inspection is an indispensable benefit in various fields; however, the spatial resolution of a scintillation-type X-ray detector is not as high as that of a direct-conversion X-ray imaging detector due to the scattering of the scintillator emissions. Therefore, the purpose of this study was to suppress such diffusion and improve the resolution to achieve a high-spatial-resolution scintillator-type X-ray imaging detector. Silicon wafers were processed to create small square holes in pixel patterns, and these holes were filled with the scintillator. The spatial resolution of the sample was then measured to confirm its improvement. The high-spatial-resolution of the scintillator-type detector was achieved using silicon separators. Moreover, appropriate noise characteristics and detection efficiency must be ensured to achieve good detection capability. Based on X-ray irradiation experiments and image quality evaluations, indicators were obtained for improving the image detection performance of the silicon separator in terms of noise and detection efficiency. Thus, the scintillator-type imaging detector with the high-spatial-resolution could be of practical use. • Spatial resolution of a scintillator-type X-ray image detector is improved. • Silicon wafer is processed to make small holes in a pixel pattern as a collimator. • Scintillator is separated by 400 μ m -thick silicon walls. • Significant results were obtained for scintillator-type imaging detectors. • Scintillation light intensity was successfully reduced by the silicon separator. [ABSTRACT FROM AUTHOR]

Plastic scintillators are characterized with high detection efficiency, high response speeds, uneven optical efficiency distributions, and poor energy resolution. In this work, we developed a new discrimination algorithm, namely, the average energy (AE) algorithm, for artificial γ radiation sources and implemented it in a hand-held plastic scintillator detector. The algorithm provided excellent discrimination capability of naturally occurring radiation materials (NORM) and artificial radiation Sources. The energy deposited by all radiation sources in small plastic scintillators, was simulated and analyzed using the Monte Carlo method. And all those radiation sources are categorized by the International Atomic Energy Agency. A plastic scintillator detector system was then constructed for proof of concept using 241Am, 137Cs, 60Co, radium-bearing ore, and thorium ore. A large-sized plastic scintillator detector was used for comparison, and the correctness of the AE algorithm was verified. The AEs of the NORM region ranged from 631.5 ± 13.3 keV to 783.6 ± 17.2 keV and 1173.6 keV or more, and the collection time of a single measurement was less than 3 s (5214 photons). Results showed that the AE algorithm could quickly and accurately identify γ artificial radiation sources from the background and NORM. The AE algorithm should always be used in conjunction with the energy window algorithm to avoid misjudgments. [ABSTRACT FROM AUTHOR]

A 1-inch stilbene and EJ-276 (plastic) organic scintillators were characterized in view of their use in a portable survey meter for fast neutron detection and dose rate measurements in radiation protection. They were coupled with a large area Silicon Photomultiplier (SiPM) array and characterized in terms of neutron/ γ –ray (n/ γ) discrimination capability, count rate linearity, count rate saturation effects, temperature stability and neutron detection efficiency. A Pile-Up Rejection (PUR) algorithm was developed and tested to increase their count rate linearity with increasing dose rate. Results show that the stilbene exhibits better performance compared to the plastic in terms of: Pulse Shape Discrimination (PSD) with a Figure Of Merit (FOM) of 1.5 vs. 1.1, energy resolution (15% vs 20% at 662 keV) and fast neutron efficiency (12% vs. 9% with an AmBe source). For both scintillators, the dose rate response is linear up to 1 mSv/h with a 137Cs γ -ray source. With a neutron source, the response is linear, and the FOM is almost constant for dose rates up to 1.5 mSv/h. The PUR reduces the false neutron events by one order of magnitude when the detectors are irradiated with a γ -ray source up to 10 mSv/h, and it correctly works when irradiated with an AmBe source at 1.5 mSv/h together with a 137Cs source up to 60 μ Sv/h. The proposed PUR algorithm is promising but needs to be tested with a higher intensity mixed n/ γ field. The temperature stability of both detectors was also studied in the temperature range from −10 °C to ＋40 °C. The light yield increases by around 25% for both detectors when reducing the temperature. The variation of the neutron count rate is around 10% in the same temperature range. This work provides a complete overview of the performance of these detectors and a coherent comparison between the two types of scintillators with the same experimental setup. [ABSTRACT FROM AUTHOR]

Machine learning is a powerful tool used in many different areas, from image processing to space navigation and high-energy physics. In this paper we present a configuration of different artificial intelligent tools aimed at the extraction of features from data registered in the SciBar Cosmic Ray Telescope (SciCRT). The SciCRT is an array of plastic scintillator bars that work nearly independently as particle detectors. When a particle crosses inside the telescope, scintillation photons are emitted by the plastics. The intensity of photons is directly proportional to the energy deposited in each bar. Taking advantage of the construction of the telescope, the small transverse area of the scintillator bars, it is possible to do particle tracking and analysis. The main purpose of SciCRT is the detection of solar neutrons originated in the violent phenomena taking place at the surface of the Sun. Nonetheless, the SciCRT is capable of detecting different kinds of secondary particles produced by the interactions of primary cosmic rays with the atmospheric nuclei. For this reason, the task of signal classification is essential. Our final goal will be the classification of detected cosmic ray particles, as well as, the unfolding of the neutron energy spectrum and the estimation of the angular distribution. To achieve this our methodology relies of pattern recognition, artificial neural networks, k -means clustering and k -Nearest Neighbors. In addition, our paper presents a Monte Carlo simulation of the SciCRT for the training and evaluation of the machine learning algorithms. [ABSTRACT FROM AUTHOR]