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Liquid scintillators are extensively employed as targets in neutrino experiments and in medical radiography. Perovskite nanocrystals are recognized for their tunable emission spectra and high photoluminescence quantum yields. In this study, we investigated the feasibility of using perovskites as an alternative to fluor, a substance that shifts the wavelengths. The liquid scintillator candidates were synthesized by doping perovskite nanocrystals with emission wavelengths of 450, 480, and 510 nm into fluor PPO with varying nanocrystal concentrations in a toluene solvent. The several properties of the perovskite nanocrystal-doped liquid scintillator were measured and compared with those of a secondary wavelength shifter, bis-MSB. The emission spectra of the perovskite nanocrystal-doped liquid scintillator exhibited a distinct monochromatic wavelength, indicating energy transfer from PPO to the perovskite nanocrystals. Using a 60 Co radioactive source setup with two photomultiplier tubes (PMTs), the light yields, pulse shape, and wavelength shifts of the scintillation events were measured. The light yields were evaluated based on the observed Compton edges from γ -rays, and compared across the synthesized samples. A decrease (or increase) in area-normalized PMT pulse height was observed at higher perovskite nanocrystal (or PPO) concentrations. The results demonstrated the sufficient potential of perovskite nanocrystals as an alternative to traditional wavelength shifters in a liquid scintillator. [ABSTRACT FROM AUTHOR]

The development, preparation, and properties of new plastic scintillators, based on polyvinyl toluene matrix EJ-290 and only one luminophore with a large Stokes shift, are addressed. The primary luminophores tested were 2-(1-naphthyl)-5-phenyloxazole, 1-phenyl-3-mesityl-2-pyrazoline, and 2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene. These were subsequently compared with the commercially used luminophores 2,5-diphenyloxazole and p-terphenyl in combination with wavelength shifters (secondary luminophores) 1,4-bis(2-methylstyryl) benzene and 1,4-bis(5-phenyl-2-oxazolyl)benzene made from the same polyvinyl toluene matrix in the same dimensions. For plastic scintillators produced in this way, their detection properties, such as Compton edge and detection efficiency, were characterized. [ABSTRACT FROM AUTHOR]

POLAR-2, a plastic scintillator based Compton polarimeter, is currently under development and planned for a launch to the China Space Station in 2025. It is intended to shed a new light on our understanding of Gamma-Ray Bursts by performing high precision polarization measurements of their prompt emission. The instrument will be orbiting at an average altitude of 383 km with an inclination of 42° and will be subject to background radiation from cosmic rays and solar events. In this work, we tested the performance of plastic scintillation bars, EJ-200 and EJ-248M from Eljen Technology, under space-like conditions, that were chosen as possible candidates for POLAR-2. Both scintillator types were irradiated with 58 MeV protons at several doses from 1.89 Gy(corresponding to about 13 years in space for POLAR-2) up to 18.7 Gy, that goes far beyond the expected POLAR-2 life time. Their respective properties, expressed in terms of light yield, emission and absorption spectra, and activation analysis due to proton irradiation are discussed. Scintillators activation analyses showed a dominant contribution of β + decay with a typical for this process gamma-ray energy line of 511 keV. [ABSTRACT FROM AUTHOR]

Cerium bromide (CeBr3) scintillation crystal were studied and analyzed from the photon and electron response measurements. For photon response measurements, the radioactive source has been used for the energy range of 0.356 MeV ≤ E ≤ 1.332 MeV. The 137Cs source irradiated with gamma ray energy at 0.662 MeV was used for the electron response measurement using Compton coincidence technique. The variable angles (θ) would generate the gamma energies corresponding to a scattering angle of 30° to 120°. The results of number of photoelectron (Nphe) show responds to linear trends for photon and electron response. The light yield shows increase with increasing the photon and electron energy. The results showed the non-proportionality of photon response and electron response demonstrated good proportional properties of all energy ranges and as the result, the crystal is a promising candidate for gamma or X-rays detection. [ABSTRACT FROM AUTHOR]

Herein, details on the effect of Ce3+ concentration and annealing temperature on luminescence and scintillation properties of Y3Al5O12:Ce3+ (YAG:Ce3+) nanoscintillator powders, prepared by sol–gel method, have been investigated. Despite extensive research on YAG:Ce3+ single crystal, the behavior of this material at the nanoscale is still not fully understood. The photoluminescence spectra of nanoscintillator powders have been measured and analyzed. To properly assess the scintillation properties, the nanoscintillator sample powders are developed for use as a radiation detector and underwent preparation procedures, including surface homogenization and efficient coupling with a photomultiplier tube window. It is shown that even with nanoscintillator powders, pulse height spectra, with well‐resolved photo‐peak from the Compton edge, and scintillation decay curves are obtained. It is found that 0.5 mol% Ce3+ sample annealed at 1000 °C presents the nonradiative quenching concentration with calculated critical distance of 20.21 Å based on the resonance transfer by electric multipole–multipole interaction. Additionally, the sample detector with 0.5 mol% Ce3+ annealed at 1150 °C exhibits the highest light yield (LY) with value 18 900 ph MeV−1 and a better energy resolution value 10% full‐width and half‐maximum under 662 keV γ‐ray from 137Cs source. [ABSTRACT FROM AUTHOR]

Background: The Jagiellonian Positron Emission Tomograph is the 3-layer prototype of the first scanner based on plastic scintillators, consisting of 192 half-metre-long strips with readouts at both ends. Compared to crystal-based detectors, plastic scintillators are several times cheaper and could be considered as a more economical alternative to crystal scintillators in future PETs. JPET is also a first multi-photon PET prototype. For the development of multi-photon detection, with photon characterized by the continuous energy spectrum, it is important to estimate the efficiency of J-PET as a function of energy deposition. The aim of this work is to determine the registration efficiency of the J-PET tomograph as a function of energy deposition by incident photons and the intrinsic efficiency of the J-PET scanner in detecting photons of different incident energies. In this study, 3-hit events are investigated, where 2-hits are caused by 511 keV photons emitted in e + e - annihilations, while the third hit is caused by one of the scattered photons. The scattered photon is used to accurately measure the scattering angle and thus the energy deposition. Two hits by a primary and a scattered photon are sufficient to calculate the scattering angle of a photon, while the third hit ensures the precise labeling of the 511 keV photons. Results: By comparing experimental and simulated energy distribution spectra, the registration efficiency of the J-PET scanner was determined in the energy deposition range of 70–270 keV, where it varies between 20 and 100 % . In addition, the intrinsic efficiency of the J-PET was also determined as a function of the energy of the incident photons. Conclusion: A method for determining registration efficiency as a function of energy deposition and intrinsic efficiency as a function of incident photon energy of the J-PET scanner was demonstrated. This study is crucial for evaluating the performance of the scanner based on plastic scintillators and its applications as a standard and multi-photon PET systems. The method may be also used in the calibration of Compton-cameras developed for the ion−beam therapy monitoring and simultaneous multi-radionuclide imaging in nuclear medicine. [ABSTRACT FROM AUTHOR]

We investigated the scintillation light yields of Tb-doped SiO2 glasses. We prepared 0.05, 0.1, and 0.5% Tb-doped SiO2 glasses by melting and solidifying sintered ceramic rods using an oxygen burner. The obtained samples showed no crystalline phases in X-ray diffraction measurements. Pulse height spectra of the Tb-doped SiO2 samples were measured under γ-ray excitation using a measurement system for slow decay pulses. The number of channels at the Compton edge of the 0.5% Tb-doped sample was the highest and was approximately 50% of that of a commercial lithium glass scintillator (GS20). By considering the light yield of GS20 and the wavelength dependence of the quantum efficiency of the photomultiplier tube, the light yield of the 0.5% Tb-doped SiO2 sample was estimated as 3800 photons/MeV. [ABSTRACT FROM AUTHOR]

(1) Background: Gamma cameras have wide applications in industry, including nuclear power plant monitoring, emergency response, and homeland security. The desirable properties of a gamma camera include small weight, good resolution, large field of view (FOV), and wide imageable source energy range. Compton cameras can have a 4π FOV but have limited sensitivity at low energy. Coded-aperture gamma cameras are operatable at a wide photon energy range but typically have a limited FOV and increased weight due to the thick heavy metal collimators and shielding. In our lab, we previously proposed a 4π-view gamma imaging approach with a 3D position-sensitive detector, with which each detector element acts as the collimator for other detector elements. We presented promising imaging performance for 99mTc, 18F, and 137Cs sources. However, the imaging performance for middle- and high-energy sources requires further improvement. (2) Methods: In this study, we present a new gamma camera design to achieve satisfactory imaging performance in a wide gamma energy range. The proposed gamma camera consists of interspaced bar-shaped GAGG (Ce) crystals and tungsten absorbers. The metal bars enhance collimation for high-energy gamma photons without sacrificing the FOV. We assembled a gamma camera prototype and conducted experiments to evaluate the gamma camera's performance for imaging 57Co, 137Cs, and 60Co point sources. (3) Results: Results show that the proposed gamma camera achieves a positioning accuracy of <3° for all gamma energies. It can clearly resolve two 137Cs point sources with 10° separation, two 57Co and two 60Co point sources with 20° separation, as well as a 2 × 3 137Cs point-source array with 20° separation. (4) Conclusions: We conclude that the proposed gamma camera design has comprehensive merits, including portability, 4π-view FOV, and good angular resolution across a wide energy range. The presented approach has promising potential in nuclear security applications. [ABSTRACT FROM AUTHOR]

The anti-Compton phoswich (ACP) detector, which is composed of multiple scintillators with one photomultiplier tube, takes into account the Compton suppression function and portability, and therefore, a discussion on how to design its shape to improve the performance of the detector has become necessary. Based on an ACP detector using a well-typed LaBr3:Ce/NaI:Tl composite scintillator that has been developed in the laboratory in early work, this study uses GEANT4 to simulate and study the influence of the change in the shape and size of the secondary scintillator on the performance of the detector, such as the Compton suppression ratio, the energy resolution, and the full-energy peak (FEP) loss. In the course of the study, we mainly investigate the variation of the performance of the detector in two ways. First, the inclination angle of the truncated cone is gradually changed to compare its FEP address and Compton suppression ratio. Second, the case of the well-shaped and annular-shaped secondary scintillators is compared, respectively, to find out their impact on energy resolution and FEP address. The final results show that, compared with the ACP detector using a φ75 × 90 mm2 LaBr3:Ce/NaI:Tl cylindrical composite scintillator, a truncated cone-shaped composite scintillator of 0.8 inclination may have an equivalent 137% light yield (137% signal-to-noise ratio), a Compton suppression ratio of 89.62% (at 662 keV), 89.98% FWHM energy resolution, and a volume reduction of 36.74%, which means that the weight of the detector is reduced by 2.107 kg. [ABSTRACT FROM AUTHOR]

A new broad-energy, high-resolution gamma ray spectrometer (GRS) with Compton suppression function has been developed recently in the HL-2A tokamak to obtain the gamma ray information in the energy range of 0.1–10 MeV. This is the first time to develop an anti-Compton GRS for a magnetic confinement fusion device. The anticoincidence detector consists of a large-volume high purity germanium (HPGe) crystal (Φ63 × 63 mm2) as the primary detector and eight trapezoidal bismuth germinate (BGO) scintillators (trapezoid crystal with 30 mm thickness) as the secondary detector. The anti-coincidence data processing is implemented by a digital-based data acquisition system with fast digitization and software signal processing technology. Using radioisotope gamma ray sources and Monte Carlo N-Particle code, the energy and efficiency of the spectrometer have been calibrated and quantitatively tested. The Compton continuum suppression factor reaches 4.2, and the energy resolution (Full Width at Half Maximum) of the 1.332 MeV full energy peak for 60Co is 2.1 keV. Measurements of gamma ray spectra with Compton suppression using the spectrometer have been successfully performed during HL-2A discharges with different conditions. The performance of the spectrometer and the first experimental results are presented in this paper. [ABSTRACT FROM AUTHOR]

In this study, we propose a hybrid coded-aperture and Compton camera based on cerium-doped Gd3Al2Ga3O12 (GAGG:Ce) scintillator arrays coupled with Multi-Pixel Photon Counter (MPPC) arrays. The sensitive detector of the gamma camera consists of a single GAGG:Ce crystal coupled with a single-chip MPPC unit module. An impedance bridge circuit and a 64-channel data acquisition system were employed to record the code-aperture events and Compton coincidence events. After the calibration of position and energy, the total energy resolution for 662 keV gamma-rays from 137Cs was 6.6%. The hybrid camera had the characteristics of mechanical collimation and electronic collimation at the same time. In the code aperture mode, the reconstructed images were obtained by direct deconvolution and maximum likelihood expectation maximization (MLEM) methods. In the Compton imaging mode, the energy-dependent method was applied to order the sequence of Compton scatter events. The simple back-projection algorithm and list-mode MLEM algorithm were adopted for image reconstruction. Practical performances demonstrated that the angular resolutions in two modes were measured as 5.2° and 11.4°, respectively. In addition, the hybrid camera had a desirable imaging capability in a wide energy range (32 keV–2.6 MeV) and a wide field of view (∼210° in the horizontal direction). As for the sensitivity, the camera had a commercially available sensitivity level of localizing a 137Cs point source, producing ∼0.026 µSv/h in 5 min. Furthermore, the function of distinction for different radiation sources was preliminarily realized. [ABSTRACT FROM AUTHOR]

In this study, we demonstrated the process of an integrated apparatus for decay time analysis and gamma radiation measurement with a liquid-scintillator-based cadmium-doped zinc oxide (CZO) nanomaterial. Generally, time-resolved photon counting is an essential analysis method in the field of precision measurement in the quantum domain. Such photon counting equipment requires a pulse laser that can be repeated quickly while having a sharp pulse width of picoseconds or femtoseconds as a light source. Time-correlated single photon counting (TCSPC) equipment, which is currently a commercial product, is inconvenient for recent development research because the scintillator size and shape are limited. Here, neodymium-doped yttrium aluminum garnet (Nd/YAG) laser TCSPC equipment was constructed to analyze the fluorescence characteristics of scintillators having various sizes and shapes. Then, a liquid scintillator added with CZO nanomaterial was prepared and the Nd/YAG laser TCSPC equipment test was performed. As a result of measuring the scintillator using the manufactured Nd/YAG laser TCSPC equipment, the non-CZO liquid scintillator was analyzed at 2.30 ns and the liquid scintillator equipped with CZO-loaded nanomaterial was analyzed at 11.95 ns. It showed an error within 5% when compared with the result of commercial TCSPC equipment. In addition, it was verified that the Nd/YAG laser TCSPC system can sufficiently measure the decay time in nanoseconds (ns). Moreover, it was presented that the Compton edge energy of Cs−137 is 477.3 keV, which hardly generates a photoelectric effect, and Compton scattering mainly occurs. [ABSTRACT FROM AUTHOR]

Waseda University and Tokyo Tech are developing a 50 kg-class small satellite, tentatively named INnovative Space Probe for Imaging R-process Emission (I N S P I R E), which is scheduled for launch in 2027. The primary detector of the satellite is a BOX-type Compton Camera (CC-Box) that enables to observe low energy gamma rays (30 keV − 200 keV) in pinhole mode and high energy gamma rays (150 keV − 3 MeV) in Compton mode. The CC-Box consists of a pixelized Ce:GAGG scintillator array using a depth-of-interaction (DOI) structure, which is optically coupled to an MPPC array. The Ce:GAGG arrays are also positioned on the side of detector to enhance its sensitivity. Herein, we describe the detailed design of the CC-Box, its data processing flow, and its weight and power specifications. We then assess the anticipated performance of the detector in terms of continuum and line sensitivities, together with a simulation of the Crab nebula observation. Finally, a brief review of the experimental results is performed using hands-on devices already implemented in nuclear medicine and atmospheric observations, such as gamma-ray imaging of thunderclouds. [ABSTRACT FROM AUTHOR]

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]

Obtaining directional information is required in many applications such as nuclear homeland security, contamination mapping after a nuclear incident and radiological events, or during the decontamination work. However, many directional radiation detectors are based on directional shielding, made of lead or tungsten collimators, introducing two main drawbacks. The first is the size and weight, making those detectors too heavy and irrelevant for utilization in handheld devices, drone mapping, or space applications. The second drawback is the limited field of view (FOV), which requires multiple detectors to cover the whole required FOV or machinery to rotate the detector’s narrow FOV detector. We propose a novel $4\pi $ directional detector based on a segmented hollow cubic detector, which uses the Compton effect interactions with no heavy collimators. The symmetrical cubical design provides both higher efficiency and $4\pi $ detection ability. Instead of the traditional two types of detectors (scatterer and absorber) structure, we use the same type of detector, based on Gd3Al2Ga3O12 (GAGG) (Ce) scintillator coupled to silicon photomultiplier. An additional advantage of the proposed detector is obtained by locating the photon sensors inside the detector, behind the scintillators, which improves the radiation hardness required for space applications. Furthermore, such an arrangement flattens the temperature variation across the detector, providing better gain stability. The main advantage of the proposed detector is an efficient $4\pi $ radiation detection for high-energy gamma rays without the use of heavy collimators. [ABSTRACT FROM AUTHOR]

Since the beginning of using liquid scintillators for gamma–neutron separation, there have been many articles dealing with long-term degradation, especially due to oxygen dissolved in the cocktail or presented during scintillator encapsulation. Oxygen is a well-known quenching agent causing a significant reduction of light yield. The effect of aging of liquid organic scintillators, namely EJ301, EJ309 (both Eljen Technology), and new custom-made cocktails based on 1-Phenyl-3-(2,4,6-trimethylphenyl)-2-pyrazoline and 2,5-Bis (5-tert-butyl-benzoxazol-2-yl)thiophene luminophores, were investigated for more than half a year. The research was focused on the Compton edge shifting of gamma particles since the position is proportional to the light yield of the selected scintillator. It was proven that all investigated cocktails suffered from different deterioration of the light yield in the investigated period, especially those containing a low concentration of luminophore. On the other hand, the gamma–neutron separation was improving up to the 100th day of measurement. Furthermore, the gamma–neutron separation was observed and quantified using figure of merit (FoM) for samples prepared and filled under normal and nitrogen atmosphere during the mentioned period. All stated parameters of liquid scintillator NE213 manufactured by Nuclear Enterprises Ltd. opened more than three decades ago were measured and used for comparison. It was observed that even after 30 years, this cocktail was still able to discriminate gammas from neutrons. [ABSTRACT FROM AUTHOR]

Neutron and gamma-ray imaging systems are deployed within the field of nuclear safeguards for the detection and localization of special nuclear materials and other materials of interest. 237Np is one of these materials of interest due its presence in spent nuclear fuel and potential for use in nuclear weapons when purified. Here, for the first time, a 6 kg neptunium sphere (98.8 wt% 237Np) was measured using a dual-particle imager, from the University of Michigan, consisting of organic glass and inorganic scintillators. The novel composition of organic glass scintillator was recently developed at Sandia National Labs and has been used in particle imaging systems due to its time resolution and particle discrimination capabilities. Gamma-ray energy spectra from single and coincident events were extracted and the sequencing of Compton scatter and photoelectric absorption gamma-ray events was used to generate images using simple backprojection. The emissions of interest in this work are the 312 keV and 416 keV gamma rays from 233Pa, a daughter isotope from the neptunium decay series. The results of this work show that there is close agreement between the true source location in angular space and the converged location from the gamma ray images created using the system. The gamma spectroscopy from single and coincident events also identified the characteristic emission from the daughter isotope and could be used to assist with the identification of 237Np. Furthermore, successful localization of the source with 5 s of data demonstrates the practical application of the imaging system for imaging and detection of material in weapons-useable quantities. [ABSTRACT FROM AUTHOR]

Although the MeV gamma-ray band is a promising energy-band window in astrophysics, the current situation of MeV gamma-ray astronomy significantly lags behind those of the other energy bands in angular resolution and sensitivity. An electron-tracking Compton camera (ETCC), a next-generation MeV detector, is expected to revolutionize the situation. An ETCC tracks each Compton-recoil electron with a gaseous electron tracker and determines the incoming direction of each gamma-ray photon; thus, it has a strong background rejection power and yields a better angular resolution than classical Compton cameras. Here, we study ETCC events in which the Compton-recoil electrons do not deposit all energies to the electron tracker but escape and hit the surrounding pixel scintillator array (PSA). The PSA provides additional information on the electron-recoil direction, which enables us to improve significantly the angular resolution. We developed an analysis method for this untapped class of events and applied it to laboratory and simulation data. We found that the energy spectrum obtained from the simulation agreed with that of the actual data within a factor of 1.2. We then evaluated the detector performance using the simulation data. The angular resolution for the new-class events was found to be twice as good as in the previous study at the energy range 1.0–2.0 MeV, where both analyses overlap. We also found that the total effective area is dominated by the contribution of the double-hit events above an energy of 1.5 MeV. Notably, applying this new method extends the sensitive energy range with the ETCC from 0.2–2.1 MeV in the previous studies to up to 3.5 MeV. Adjusting the PSA dynamic range should improve the sensitivity in even higher energy gamma-rays. The development of this new analysis method would pave the way for future observations by ETCC to fill the MeV-band sensitivity gap in astronomy. [ABSTRACT FROM AUTHOR]

Knowledge of the neutron light-yield response is crucial to the understanding of scintillator-based neutron detectors. In this work, neutrons from 2–6 MeV have been used to study the scintillation light-yield response of the liquid scintillators NE 213A, EJ 305, EJ 331 and EJ 321P using event-by-event waveform digitization. Energy calibration was performed using a GEANT4 model to locate the edge positions of the Compton distributions produced by gamma-ray sources. The simulated light yield for neutrons from a PuBe source was compared to measured recoil proton distributions, where neutron energy was selected by time-of-flight. This resulted in an energy-dependent Birks parameterization to characterize the non-linear response to the lower energy neutrons. The NE 213A and EJ 305 results agree very well with existing data and are reproduced nicely by the simulation. New results for EJ 331 and EJ 321P, where the simulation also reproduces the data well, are presented. [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]

The applicability extent of hadron therapy for tumor treatment is currently limited by the lack of reliable online monitoring techniques. An active topic of investigation is the research of monitoring systems based on the detection of secondary radiation produced during treatment. MACACO, a multi-layer Compton camera based on LaBr3 scintillator crystals and SiPMs, is being developed at IFIC-Valencia for this purpose. This work reports the results obtained from measurements of a 150 MeV proton beam impinging on a PMMA target. A neural network trained on Monte Carlo simulations is used for event selection, increasing the signal to background ratio before image reconstruction. Images of the measured prompt gamma distributions are reconstructed by means of a spectral reconstruction code, through which the 4.439 MeV spectral line is resolved. Images of the emission distribution at this energy are reconstructed, allowing calculation of the distal fall-off and identification of target displacements of 3 mm. [ABSTRACT FROM AUTHOR]

Cerium doped Lanthanum halide scintillators are useful in γ-ray spectroscopy due to their excellent energy resolution and high stopping power. The response of Compton electrons in 1″ × 1″ cylindrical LaCl3:Ce scintillator was recorded using a PIXIE-4 digital data acquisition system having no requirement of any external pulse-processing unit and coincidence unit, which makes the whole measurement setup very compact. The intrinsic energy resolution of Compton electrons in LaCl3:Ce was measured employing the Wide Angle Compton Coincidence Technique (WACCT) for energies ranging from 100 keV to 1 MeV by using 137Cs, 60Co and 22Na γ-ray sources. The effect of coincidence energy gating window was also studied. A good agreement between the present results obtained using a digital method and the results reported in the literature with the analogue method has been observed. [ABSTRACT FROM AUTHOR]

CLLBC(Ce) and TLYC(Ce) are novel scintillation materials capable of measuring mixed gamma ray and neutron radiation fields that have gained significant interest in the areas of space and nuclear safety/security science. To date Geant4, the world's most popular Monte Carlo radiation modelling toolkit, has yet to be effectively used to simulate the full response of these materials when coupled to near ultra-violet Silicon PhotoMultipliers (SiPMs). In this work an experimentally validated Geant4 application has been developed with optimised material composition, optical data tables, and physics transport settings that is able to accurately simulate the response of CLLBC(Ce) and TLYC(Ce) SiPM-based radiation detectors under both gamma ray and neutron irradiation. Experimental benchmarking for five different radioactive sources (Co-60, Cs-137, Eu-152, Am-241, and Cf-252) illustrated that this developed Geant4 application was able to reproduce the position and structure of all major spectral features (full energy gamma ray photo-/neutron capture peaks, X-ray escape photopeaks, Compton edge, Compton backscatter peaks, and Compton plateau) to high level of accuracy. [ABSTRACT FROM AUTHOR]

A bismuth-germanate (BGO) anti-Compton shield (ACS) for Compex germanium detector modules was designed, built, and characterised. BGO performance was evaluated for light output and energy resolution. The response of the ACS shield and its impact on germanium detector spectra was measured for standard 60Co, 133Ba, and 137Cs sources. The results were compared to comprehensive Geant4 simulations. The ∼ 70 % improvement of the peak-to-total ratio for the 137Cs 662-keV γ -ray peak is in good agreement with expectations from the simulations. A 133Ba source exemplifies decay schemes of odd- A superheavy nuclei. Congruence between measured and simulated spectra indicates that the Compex plus ACS multi-detector module is well understood. [ABSTRACT FROM AUTHOR]

An entrance window surrounded phoswich design of GAGG:Ce/CsI:Tl has been implemented for a low-background and Compton-suppressed detector. Not as the common phoswich detector does, the GAGG:Ce scintillator with the well-type CsI:Tl scintillator entrance window surrounded makes the efficient large-angle Compton suppression. This design also makes results measured by the phoswich detector have no degradation compared with the single GAGG:Ce detector. The Compton continuum and other backgrounds are reduced by identifying the gamma-ray energy depositions in different scintillators using the real-time rise time discrimination (RTD) method. The background rate is suppressed approximately 74%. The peak-to-total (P/T) ratio at 137Cs and 60Co point sources are 0.769 and 0.561, respectively. The Compton suppression is highly efficient at all the energy range of Compton continuums. The reduction of the Compton continuum and other backgrounds and the improvement of the P/T ratio will greatly expand the application range of the GAGG:Ce detector in low-intensity measurements. [ABSTRACT FROM AUTHOR]

For simultaneous detection of fast and thermal neutrons, a composite scintillator consisting of stilbene crystal and 6Li glass was designed. Energy calibration was finished with a 152Eu γ source through Compton coincidence measurement. A 241Am-Be neutron source with polyethylene moderator was used to test it. The detection efficiency was examined through Monte Carlo simulation. The measured results show that the composite scintillator has excellent triple pulse shape discrimination performance. With the threshold of 100 keV ee , figure of merits for γ -fast neutron and fast neutron-thermal neutron are 1.571 ± 0.009 and 2.376 ± 0.010 respectively. Two thermal neutron peaks emerge at 0.245 MeV ee and 0.291 MeV ee in the energy spectra. 79.24% of the incident thermal neutrons can be detected by 6Li glass. 39.56% of 1 MeV neutrons can be detected by stilbene. • A composite scintillator consisting of stilbene crystal and 6Li glass is designed. • The composite scintillator has excellent triple pulse shape discrimination performance. • 79.24% of the incident thermal neutrons can be detected. [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]

As one of the detectors with superior performances, the Compton continuum in the spectra of the Cerium-doped Lanthanum 3-Bromide (LaBr 3 :Ce) detector should be suppressed for better performances. A compacted LaBr 3 :Ce/NaI:Tl phoswich detector has been designed to reduce the Compton continuum and improve the peak-to-total (P/T) ratio of the photopeaks. The LaBr 3 :Ce scintillator is surrounded by a well-type NaI:Tl scintillator and is coupled to a single photomultiplier tube (PMT). The Compton continuum is reduced by identifying the gamma-ray energy depositions in different scintillators using the real-time rise time discrimination (RTD) method. A Geant4 code with actual geometry was performed to simulate the suppressed and unsuppressed spectra. The peak efficiency of total energy at 1332 keV and 662 keV is 1.58% and 2.75%, the peak to total ratio at 137Cs point source and 60Co point source are 0.545 and 0.367, respectively. The reduction of the Compton continuum and the improvement of the P/T ratio will greatly expand the application range of the LaBr 3 : Ce detector in low-intensity measurements. [ABSTRACT FROM AUTHOR]

We designed a novel, compact, single-plane Compton gamma camera based on GAGG:Ce scintillators read out by silicon photomultipliers. The Compton gamma camera comprises the scatterer and the absorber layers consisting of 8x8 arrays of 3 mm × 3 mm × 3 mm GAGG:Ce pixels. The individual pixels in the scatterer layer are optically coupled to the corresponding pixels in the absorber by the matching 3 mm × 3 mm × 20 mm plexiglass lightguides, and hence both the scatterer and the absorber pixel in one column are readout by the same SiPM. We present the first results of the measured characteristics of the detector. The average energy resolution at 662 keV of the front and the back GAGG:Ce layer is found to be 8.9% ± 1.9% and 10.8% ± 1.6%, respectively. The Compton events are reconstructed based on kinematic conditions and detector geometry and the first image of a 662 keV gamma source is reconstructed using a simple back projection algorithm. [ABSTRACT FROM AUTHOR]

In the study of this paper, based on the symmetry of regular icosahedron, a spherical detector system for 4 π field-of-view (FOV) gamma imaging was proposed based on 80 GAGG (Ce:GAGG, Gd3Al2Ga3O12) scintillator pixels. The spherical detector system combines both coded aperture (CA) and Compton imaging (CI) modalities. The detector system was simulated precisely with an experimental test of one representative GAGG pixel. Several radionuclides with characteristic energy ranging from 59.5 keV to 1.33 MeV were imaged under the far-field situation. Both imaging modes realize the 4 π view while the coded aperture method achieves a higher image quality for radioactive sources with lower energy and the Compton method performs conversely. The imaging system can localize a 10 mCi 137Cs point source at 10 m within 1 s in the two modes and the Compton imaging mode reaches a high detection efficiency of up to 200 cps/ μ Sv/h for 137Cs. And the angular estimation full-width-at-half-maximum (FWHM) was approximately 5.2°for coded aperture mode and 14°for Compton mode. The angular resolution was evaluated to be better than 30°. The high intrinsic imaging sensitivity and reasonable imaging quality make this detector system design attractive for far-field radiation imaging. [ABSTRACT FROM AUTHOR]

After the nuclear accident at the Fukushima Daiichi Nuclear Power Plant, researchers focused on the accident and studied the effects of leaked radiation based on radiation detection and measurement. Many methods can be used for monitoring and mapping natural and leaked radionuclides; however, portable detectors installed in unmanned ground or aerial vehicles (UAVs) can measure radioactivity near the target point, preventing damage to the human body from radiation in highly contaminated areas. Compton cameras have a wider field-of-view (FOV) and less weight than a detector system that uses a mechanical collimator. In a previous study, a position-sensitive 4 π Compton camera based on a lutetium–yttrium oxyorthosilicate (LYSO) scintillator attached to silicon photomultipliers (SiPMs) was developed. Compared with a semiconductor-based Compton camera operating with a power device supplying more than a thousand volts, our system requires a maximum of approximately several tens of volts. In addition, our Compton camera has a single-crystal structure; hence, it has advantages in terms of FOV and efficiency over a Compton camera that utilizes separate detectors. In this study, a modified scintillator-based Compton camera was created using an advanced SiPM model and a gadolinium aluminum gallium garnet (GAGG) scintillator. In the experiment, 133Ba, 22Na, and 137Cs radionuclides were used for data acquisition, and simple back-projection and list-mode maximum likelihood expectation maximization algorithms were used to reconstruct the Compton images. The 4 π FOV coverage was evaluated using Compton imaging and angular resolution measure (ARM), and the results indicated that FOV coverage was degraded when the angle between the radiation source and the perpendicular axis of the detector was near 45°. The degradation of the ARM reflected as the bimodal distribution became more severe for the Compton camera based on the LYSO scintillator than that based on the GAGG scintillator, which was attributed to the intrinsic radiation of LYSO from 176Lu considered as background noise. In the evaluation of intrinsic efficiency, the influence of intrinsic radiation was significantly large. Without background noise rejection, the intrinsic efficiencies for 356, 511, and 662 keV radiation were 0.66%–1.28%, and 1.50%–3.05% for the detection system based on the GAGG and LYSO scintillators, respectively. After background noise rejection, the intrinsic efficiencies were re-calculated as 0.64%–1.27% and 1.39%–1.72% for the detection system based on the GAGG and LYSO scintillator, respectively. [ABSTRACT FROM AUTHOR]

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) is mainly designed to detect Gamma-Ray Bursts associated with gravitational wave events. The lanthanum bromide (LaBr 3) scintillator with two types of doping (5% Ce 3 + only, 5% Ce 3 + co-doped with 1.5% Sr 2 +) are used in the Gamma-Ray Detectors (GRDs) of GECAM. Here, by analyzing the on-ground calibration data, we find different characteristics of these two doping types of LaBr 3 scintillator, including the Energy-Channel (E-C) relation, photon non-proportional response, energy resolution, as well as the electron non-proportional response which is derived from photon response and Monte Carlo simulation with Bayesian inference method. The results also show that the photon scintillation light yield and energy resolution can be improved by co-doping Sr 2 + in LaBr 3 :Ce 3 + scintillator, owing to a direct inhibitory effect on the electron non-proportional response. By taking the electron non-proportional response into account, we find that the simulated spectrum is in good agreement with the measured one, including Compton structure, escape peak of Lanthanum and Bromine as well as full energy peak, indicating that the electron non-proportional response is an essential factor in the energy response of scintillator detector thus should be considered in the data analysis. [ABSTRACT FROM AUTHOR]

The design and performance of a new Compton-suppressed HPGe and charged-particle array, CLARION2-TRINITY, are described. The TRINITY charged-particle array is comprised of 64 Cerium-doped Gadolinium Aluminum Gallium Garnet (GAGG:Ce) crystals configured into five rings spanning 7–54 degrees, and two annular silicon detectors that can shadow or extend the angular coverage to backward angles with minimal γ -ray attenuation. GAGG:Ce is a non-hygroscopic, bright, and relatively fast scintillator with a light distribution well matched to SiPMs. Count rates up to 40 kHz per crystal are sustainable. Fundamental characteristics of GAGG:Ce are measured and presented, including light- and heavy-ion particle identification (PID) capability, pulse-height defects, radiation hardness, and emission spectra. The CLARION2 array consists of up to 16 Compton-suppressed HPGe Clover detectors (≈ 4 % efficiency at 1 MeV) configured into four rings (eight HPGe crystal rings) using a non-Archimedean geometry that suppresses back-to-back coincident 511-keV gamma rays. The entire array is instrumented with 100- and 500-MHz (14 bit) waveform digitizers which enable triggerless operation, pulse-shape discrimination, fast timing, and pileup correction. Finally, two examples of experimental data taken during the commissioning of the CLARION2-TRINITY system are given: a PID spectrum from 16O + 18O fusion-evaporation, and PID and Doppler-corrected γ -ray spectra from 48Ti + 12C Coulomb excitation. [ABSTRACT FROM AUTHOR]

The intermediate phases between the initial interaction of ionizing radiation in scintillators and the production of scintillation light have been extensively studied over the years. Observable features of scintillators such as energy and time resolution have been in part explained through pre-scintillation mechanisms. Whereas the early energy transfer processes following the photoelectric (or Compton) interaction of an energetic photon with an atomic electron in scintillator materials were fully described, their spatio-temporal characteristics have had limited quantification. For 511 keV photon interaction in (TOF-)PET detectors, the production of a primary electron carrying most of the energy leads to non-localized energy deposit distribution having some temporal extent. Here, we characterize the spatial, temporal and energy evolution of the primary electron generated by 511 keV photons in different scintillators using Monte Carlo simulations. We aim to provide a general quantitative description detailing the dynamics of energy transfer, such as the electron ejection angle, track length and tortuosity, time course and remaining energy as a function of the initial interaction point. Simulation results show that the electron track is tortuous with a short extent and a rapid energy transfer within 100 μ m in high-Z (e.g., BGO) or high density (e.g., LuAP:Ce) materials while the extent nearly doubles in lighter materials like Ba F 2 in which the track tortuosity is 10%–50% lower. The time fluctuations of the photoelectron full energy deposit remain below 1 ps FWHM, therefore adding negligible jitter to the time resolution of coincident detectors. These simulations provide a better understanding of the main carrier dynamics from simple characteristics as some detector concepts require low-range, contained energy deposit (e.g., pixelated crystal arrays) whereas others benefit from a greater extent of energy deposition (e.g., structures designed for energy sharing). [ABSTRACT FROM AUTHOR]

A new segmented plastic scintillator detector Tuike has been developed for recoil-beta tagging experiments at the Accelerator Laboratory of the University of Jyväskylä. The detector consists of individual plastic scintillator bars arranged in two orthogonal layers, and the scintillation light is detected using silicon photomultipliers. Performance of the new detector was tested using fusion-evaporation reaction 40Ca(36Ar, pn)74Rb, and the results are discussed here. It was found that for beta particles seen in the main silicon detector, Tuike can tag high-energy beta particles with a 48(10)% efficiency. An energy calibration method using Compton edges of gamma ray transitions is described in the present work. Tuike was demonstrated to improve the sensitivity to identify weak fusion-evaporation channels associated with beta decays having high beta end-point energy, enabling nuclear structure studies along the N = Z line. [ABSTRACT FROM AUTHOR]

In this study, the photon interaction and the electron nonproportional response of Cs 2 LiYCl 6 :Ce (CLYC) scintillation were studied. The radioactive source of 137Cs that irradiated gamma rays with an energy of 662 keV were used in this experiment. For photon interaction, the mass attenuation coefficient (μ / ρ), the effective atomic number (Z e f f ) and the electron density (N e l ) were measured with eight different gamma ray energies using Compton scattering technique. For nonproportional response, the coincidence electron energy spectra were recorded at seven scattering angles of 30°–120° using Compton coincidence technique. The values of μ / ρ , Z e f f and N e l show decrease with the increasing of gamma ray energies. The nonproportional show that the CLYC demonstrated good proportional property all in the electron energy range of 99.24–450.59 keV. • CCT of CLYC crystal was studied for electron respond. • Zeff of CLYC has higher than of GAGG and CMO crystals. • Result show good proportionality from 200 keV up to 450.59 keV. [ABSTRACT FROM AUTHOR]