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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]

This work aims at the investigation of the Pulse Shape Discrimination (PSD) capabilities of two very compact detection systems composed of a 3x3x3 cm3 EJ 276 and a 3x3x3 cm3 EJ 276G (the latter green shifted version) plastic scintillators, both coupled to Silicon Photomultiplier (SiPM). The studied systems are supposed to be the basic elementary cell of a new multi-detector for simultaneous detection of neutrons and light charged particles called NArCoS (Neutron Array for Correlation Studies) having both high angular and energy resolution. In this perspective, the results of the experimental qualification of two prototypes with gamma and alpha radioactive sources and in beam tests are reported, in order to characterize the optimum choice for the new device. [ABSTRACT FROM AUTHOR]

The radiation damage to a silicon photomultiplier (SiPM) set on a satellite orbit increases energy threshold for scintillator detectors. We confirmed that 1 krad of radiation increases the energy threshold by approximately a factor of 10, which is worst for our system. Using one or two SiPMs damaged by proton irradiation and a plastic scintillator, we performed the following three experiments in our attempt to lower the energy threshold of radiation-damaged SiPMs to the greatest extent: (1) measurements using a current waveform amplifier rather than a charge-sensitive amplifier, (2) coincidence measurements with two radiation-damaged SiPMs attached to one scintillator and summing up their signals, and (3) measurements at a low temperature. Our findings confirmed that the use of a current waveform amplifier, as opposed to a charge-sensitive amplifier and a shaping amplifier, could lower the energy threshold to approximately 65% (from 198 keV to 128 keV). Furthermore, if we set the coincidence width appropriately and sum up the signals of the two SiPMs in the coincidence measurement, the energy threshold could be lowered to approximately 70% (from 132 keV to 93 keV) with little loss of the acquired signal, compared to that of use of only one scintillator. Finally, if we perform our measurements at a temperature of −20 °C, we could lower the energy threshold to approximately 34% (from 128 keV to 43 keV) compared to that of at 20 °C. Accordingly, we conclude that the energy threshold can be lowered to approximately 15% by using a combination of these three methods. • Radiation damage increases the energy thresholds of SiPMs. • Using a current waveform amplifier can lower the energy threshold. • Coincidence measurement with two SiPMs and a scintillator can lower the energy threshold. • Measurement at low temperature can lower the energy threshold. [ABSTRACT FROM AUTHOR]

Aimed at beta spectrometry and dosimetry for mixed beta-gamma fields, a Si-plastic scintillator coincidence beta-ray spectrometer has been developed. The spectrometer collects pure beta-ray spectra by rejecting the gamma-ray detection events through coincidence. Both pulse height and arrival time of each detection event were recorded in list mode by a compact digital processing system. Spectral measurements were carried out using mixed beta-gamma fields from 90Sr/90Y and 137Cs sources for various beta and gamma count rates to evaluate the system performance. Coincidence beta spectra were collected for four fixed beta count rates (7.3–241 cps) from 90Sr/90Y while the gamma count rate from 137Cs was varied from 500 to 8000 cps. The coincidence beta spectrum was stable and unperturbed by the gamma detection events for most measurements while notable perturbation was observed in the low energy region when the beta to gamma count ratio is very low. • A beta spectrometer with a silicon detector and a plastic scintillator was developed. • The Coincidence algorithm was designed to reject gamma events. • Measured coincidence spectra were consistent in most count rates. • A distortion in spectrum was observed in the low energy region only at a very low beta to gamma count ratio. [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 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]

Scintillating crystals are used in numerous applications of ionizing radiation detectors. In time of flight positron emission tomography (TOF-PET) for example, both energy and coincidence time resolution (CTR) are important characteristics that could significantly benefit if more light from scintillators, otherwise trapped, could be collected by the photodetector. A novel and promising method to extract more efficiently the light produced in crystal scintillators with high index of refraction is to introduce a thin nanopatterned photonic layer on the readout surface. In this paper, we describe the patterning process of a photonic crystal layer made of TiO 2 with 390 nm diameter "pillars" in a square lattice with a periodicity of 580 nm and a structure thickness of 300 nm on one side of a 10x10x10 mm 3 LYSO cube. The production process used was nanoimprint lithography. A substantial increase in light yield of ≥ 50% has been measured in good agreement with our simulations. An interesting result from these measurements is that the improvement in light output is independent of whether the crystal is read out from its photonically patterned side or from the one opposite to it. For all cases studied, the energy resolution improved by a factor of 1.1. On the other hand, the CTR, being very threshold dependent, is unlike the light yield not subject to a constant improvement. It turns out that, at low thresholds, the gain (improvement) in CTR is limited to 1.2, and then rapidly increases to a value of more than 2 at higher thresholds. This is mainly explained by an additionally induced light transfer time spread of the photonic pattern. Several configurations with and without Teflon wrapping were investigated. [ABSTRACT FROM AUTHOR]

A network of specialist laboratories support the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) with re-measurements of radionuclide samples, including xenon gas. The measurement of four xenon fission product radionuclides ( 133 Xe, 135 Xe, 131m Xe and 133m Xe) can be used to detect an underground nuclear explosion. Laboratories use a range of techniques to measure the radionuclides, including beta-gamma (β − γ) coincidence spectrometry. These highly-sensitive measurements are capable of detecting concentrations of down to 500 atoms of 133 Xe in a few cm 3 of xenon. In some detector systems, detection of the metastable isomers ( 131m Xe and 133m Xe) can be more challenging due to interferences between the signatures of different radionuclides. Recent work has shown that using high-purity Germanium (HPGe) high-resolution gamma detectors, these interferences can be reduced, lowering the dependence of the detection limits on radionuclide sample isotopic composition. One downside of these detectors is the reduction in detection efficiency, which impacts the overall detection sensitivity; so assessing different detector systems is a priority for radionuclide laboratories. This work presents a coincidence detector system comprising of a plastic scintillator gas cell and a large-crystal high-purity germanium detector. The energy resolution, coincidence detection efficiency, MDA and interference factors are determined from measurements of synthetic radioxenon gas samples. • A plastic scintillator and HPGe β − γ coincidence system has been configured for the measurement of isotopes of radioxenon • Calculations show that this type of setup can improve the detection limits compared to other systems. • High-resolution γ -detectors can separate Xe and Cs X-rays, decreasing interference. [ABSTRACT FROM AUTHOR]

Neutron spectrometry is important for radiation metrology, radiation protection, accelerator physics etc. The spectral response of a capture-gated detector to mono-energetic neutrons contains a significant peak, making it easy to be analyzed. But this system output not only capture-gated events (CGE) but also chance coincidence events (CCE). It is critical to identify and eliminate CCE. However, chance coincidence has not been analyzed in detail before. This paper aims to find a way to eliminate CCE and get the spectrum of CGE. Thus, categories of CCE were analyzed and their probability equations were established. Then recorded pulses from a composite scintillator measured in mixed radiation fields were used to verify CCE and explore the influence of timing gate. Results show that n/γ discrimination is effective to distinguish CCE caused by γ-rays and calculate the amount of CCE caused by fast neutrons. Timing gate should be determined according to the different distributions of CGE and CCE. Spectrum of CGE can be acquired by subtracting that of fast neutron CCE from the fast neutron spectrum of coincidence events. • Categories and probabilities of chance coincidence events (CCE) are analyzed for capture-gated neutron spectrometry. • Time distributions of capture-gated events (CGE) and CCE are calculated to determine timing gate. • The amount of fast neutron CCE is computed with that of γ-ray CCE identified via n/γ discrimination. • Spectrum of coincidence events is decomposed into spectra of CGE and fast neutron CCE. [ABSTRACT FROM AUTHOR]

Measurement of the four relevant radioxenon isotopes, namely 131m Xe, 133m Xe, 133Xe, and 135Xe, play a key role in underground nuclear explosion monitoring for ensuring compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). A β - γ coincidence system that employs a plastic scintillator detector and a HPGe detector was developed in Beijing Radionuclide Laboratory. The Minimum Detectable Activity (MDA) in a 24-h measurement of the system for 131m Xe, 133m Xe, 133Xe and 135Xe can achieve 1.8 mBq, 1.4 mBq, 3.4 mBq and 4.1 mBq, respectively. [ABSTRACT FROM AUTHOR]

Recent theoretical and experimental results have brought renewed interest and focus on the topic of fission fragment angular momentum. Measurements of neutrons and γ rays in coincidence with fission fragments remain the most valuable tool in the exploration of fission physics. To achieve these scientific goals, we have developed a system that combines a state-of-the-art fission fragment detector and n − γ radiation detectors. A new twin Frisch-gridded ionization chamber has been designed and constructed for use with a spontaneous fission source and an array of forty trans -stilbene organic scintillators (FS-3) at Argonne National Laboratory. The new ionization chamber design we present in this work aims at minimizing particle attenuation in the chamber walls, and provides a compact apparatus that can be fit inside existing experimental systems. The ionization chamber is capable of measuring fission fragment masses and kinetic energies, whereas the FS-3 provides neutron and γ -ray multiplicities and spectra. The details of both detector assemblies are presented along with the first experimental results of this setup. Planned event-by-event analysis and future experiments are briefly discussed. [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 this article, Iranian Noble Gas Analyzing System ( INGAS ) will be introduced. This system is based on beta–gamma coincidence technique and consists of a well-type NaI(Tl) as gamma or X radiation detector and a cylindrical plastic scintillator to detect beta or conversion electron. Standard NIM modules were utilized to detect coincidence events of detectors. Both the beta and gamma detectors were appropriately calibrated. The efficiency curve of gamma detector for volume geometry was obtained by comparing the results of gamma point sources measurements and simulations of GATE V7.0 Monte Carlo code. The performance of detection system was checked by injection of 222 Rn and 131m Xe gaseous source in the detection cell. The minimum detectable activity of the system for 133 Xe is 1.240±0.024 mBq for 24 h measurement time. [ABSTRACT FROM AUTHOR]

The POLAR experiment is a joint Chinese-European project conceived for a precise measurement of gamma ray polarization and optimized for the detection of the prompt emission of Gamma-Ray Bursts (GRBs) in the energy range 50–500 keV. POLAR is a novel compact space-borne Compton polarimeter consisting of 1600 low- Z plastic scintillator bars (EJ-248M), read out by 25 flat-panel multi-anode photomultiplier tubes. In the paper, we first present a dedicated experiment to study the non-linear energy response of EJ-248M plastic scintillator bars to electrons and the detailed data analysis. Second we obtained the Birks’ constant of EJ-248M plastic scintillator as kB = 0.143 mm / MeV by least squares fitting. Finally we used Geant4 simulation to study the influence of non-linear energy response on the performance of POLAR, through which it was found that non-linear energy response will lead to a significant decrease in statistics and result in larger uncertainty in polarization measurement. The paper presents a general solution to the study of non-linear energy response of plastic scintillators to electrons. [ABSTRACT FROM AUTHOR]

We describe a technique, applicable to liquid-argon-based dark matter detectors, allowing for discrimination of alpha-decays in detector regions with incomplete light collection from nuclear-recoil-like events. Nuclear recoils and alpha events preferentially excite the liquid argon (LAr) singlet state, which has a decay time of ∼ 6 ns. The wavelength-shifter TPB, which is typically applied to the inside of the active detector volume to make the LAr scintillation photons visible, has a short re-emission time that preserves the LAr scintillation timing. We describe the production method and characterization of a wavelength-shifting polymeric film – pyrene-doped polystyrene – which we developed for the DEAP-3600 detector. At liquid argon temperature, the film's re-emission timing is dominated by a modified exponential decay with a time constant of 279(14) ns, and has a wavelength-shifting efficiency of 46.4(2.9)% relative to TPB, measured at room temperature. By coating the detector neck (a region outside the active volume where the scintillation light collection efficiency is low) with this film, the visible energy and the scintillation pulse shape of alpha events in the neck region are modified, and we predict that through pulse shape discrimination, the coating will afford a suppression factor of O (1 0 5 ) against these events. [Display omitted] • Wavelength shifter characterization. • Background rejection techniques for liquid argon detectors. • Cryogenic detector technologies. [ABSTRACT FROM AUTHOR]

Positron annihilation lifetime (PAL) spectrometer is an effective tool to investigate material microstructures. Commonly used PAL spectrometers are conventional PAL spectrometer based on nuclear instrument modules (NIMs) and digital PAL spectrometer based on ultra-high-speed digitizer. Limited by the detection efficiency of the detectors, the coincidence count rate of the PAL spectrometer is always low, causing long time consumption of measurement. To solve this problem, a multi-channel coincidence method based on the ultra-high-speed digitizer was proposed. However, the ultra-high-speed digitizer is usually excessively expensive for research institutes. In this paper, we introduce a four-channel coincidence digital PAL spectrometer. Through the improvement of the timing and trigger circuit, all channels can act as start and stop channels during one measurement. Hence the coincidence count rate can be increased by an order of magnitude. The time measurement shows good linearity and high resolution with a full width half maximum (FWHM) at a level of several tens picoseconds. The effective number of bits (ENOB) of the analog-to-digital converter (ADC) reaches 10.72 bits. The energy resolution of the 511 keV photopeak reaches 4.16% when using LaBr 3 : 5% Ce 3 + scintillator, better than 4.62% of the conventional spectrometer. The time resolution of our PAL spectra when one channel receives start signals and one channel receives stop signals reaches 193.7 ps, better than that of the conventional spectrometer (212.8 ps). The FWHMs of the lifetime spectra of the two and four channel coincidence measurements are 205.8 ps and 212.4 ps respectively. Moreover, the coincidence count rate of our system increases significantly by using the four-channel coincidence method, which can be 10 times higher than the conventional spectrometer. [ABSTRACT FROM AUTHOR]

Abstract: A new setup for photon tagged nuclear reaction analysis pNRA is being developed at Lund’s ion beam analysis facility LIBAF. Particle induced gamma ray emission PIGE and nuclear reaction analysis NRA are two methods that have been extensively used for light isotope measurement in ion beam analysis IBA. There is an abundance of nuclear reactions between light elements and MeV protons, deuterons and alpha particles. This means that in principle all elements from lithium all the way up to chlorine can be analyzed using those techniques. Detection limits can be improved for some elements, if those two methods are fused together into pNRA. The new setup for pNRA will benefit from advances in detector technology that occurred during the last 20years. A LaBr3 scintillator detector and an annular double sided silicon strip detector DSSSD are used in coincidence to detect a gamma and a charged particle respectively. Both detectors are connected to a VME based data acquisition system. Of primary interest in this work is the analysis of isotopic ratios of light elements in geological samples, which are usually thick with a complex matrix. This setup can be for instance used to measure isotopic fractionation of oxygen and boron. We will present the setup and discuss its capabilities. [Copyright &y& Elsevier]

Abstract: This study presents a simple experimental setup for precise inspection of scintillation decay characteristics as a function of the energy deposited in scintillators. The results are discussed for NaI:Tl, LSO:Ce and CeBr3 crystals. The tested samples were coupled to a fast response R5320 photomultiplier from Hamamatsu. The decay time constants were measured by fitting the anode pulses of the PMT registered directly with a TDS5054B digital oscilloscope from Tektronix. Simple analog electronics composed of timing single channel analyzers, gate generators and coincidence/logic unit was used for selection of the deposited energy converted into light within the scintillator, and for triggering the scope to register relevant scintillation pulses. High precision of the experimental setup allowed for registration of non-proportionality curves for all samples. Moreover, non-proportionality was measured for fast and slow decay mode of NaI:Tl separately. The measurement was also used for inspection of possible differences in the pulse shapes originating from Compton scattering events and photoabsorption. [Copyright &y& Elsevier]

Organic glass scintillator (OGS) bars (6 × 6 × 50 mm 3) were melt-cast and characterized with dual-ended readout by silicon photomultiplier arrays. The results were compared to trans -stilbene bars of the same size. Energy resolution was measured via a 137Cs Compton-coincidence experiment. Time resolution was determined via a 22Na coincidence-timing experiment. Depth-of-interaction resolution was measured by moving a gamma-ray fan beam along the major axis of the bars. Pulse shape discrimination capability and neutron light output were determined via a time-of-flight measurement of a 252Cf source. The OGS bars exhibited better energy resolution at 478 keV (10. 3 ± 0. 5 % vs. 11. 2 ± 0. 5 %), better time resolution from 200–341 keVee (270 ps vs. 340 ps FWHM), slightly poorer depth-of-interaction resolution, poorer PSD performance, and higher neutron light output than the stilbene bars. The low cost, ease of manufacturing, brightness, and excellent time resolution make OGS a strong candidate for use in compact radiation imaging systems. [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]

Abstract: A modified version of a Monte Carlo code called Esquema, developed at the Nuclear Metrology Laboratory in IPEN, São Paulo, Brazil, has been applied for simulating a 4πβ(PS)–γ coincidence system designed for primary radionuclide standardisation. This system consists of a plastic scintillator in 4π geometry, for alpha or electron detection, coupled to a NaI(Tl) counter for gamma-ray detection. The response curves for monoenergetic electrons and photons have been calculated previously by Penelope code and applied as input data to code Esquema. The latter code simulates all the disintegration processes, from the precursor nucleus to the ground state of the daughter radionuclide. As a result, the curve between the observed disintegration rate as a function of the beta efficiency parameter can be simulated. A least-squares fit between the experimental activity values and the Monte Carlo calculation provided the actual radioactive source activity, without need of conventional extrapolation procedures. Application of this methodology to 60Co and 133Ba radioactive sources is presented and showed results in good agreement with a conventional proportional counter 4πβ(PC)–γ coincidence system. [Copyright &y& Elsevier]

A coincidence system using a plastic scintillator detector in 4π geometry has been developed and applied for the standardization of radionuclides. The scintillator shape and dimensions have been optimized for maximum charge particle detection efficiency, while keeping background low and a nearly constant gamma-ray efficiency for different points from the radioactive source. The gamma-ray events were measured with a NaI(Tl) scintillation counter. The electronic system for processing pulses consisted of logic gates and delay modules feeding a time-to-amplitude converter with output to a multichannel analyzer. The alpha detection efficiency measured with 241Am was around 95% and the beta detection efficiency for 60Co was around 67%. Activity measurements of 241Am and 60Co were performed and the results showed good agreement when compared with a conventional coincidence system employing a 4π proportional counter. [Copyright &y& Elsevier]

We have developed a two-dimensional neutron imaging method using rectangular scintillators with wavelength shifting (WLS) fibers for neutron scattering experiments using a next-generation high-intense pulsed-neutron source. In the method, rectangular scintillators are arranged at longitudinal direction and transverse direction and WLS fibers are arranged on the four sides of these scintillators. Luminescences generated in the scintillator are absorbed by the four fibers and wavelength-shifted luminescences are detected by multi-anode photomultipliers. The position of incident neutron is decided by coincidence of the four signals. By preliminary experiments using 5 mm×5 mm×2 mmt 6Li glass scintillators and 0.5 mm∅ WLS fibers, it was concluded that detection efficiency for thermal neutron was 13%. By scanning experiment using a 4×4 6Li glass scintillator array neutron detection system, we obtained the clear spot of incident neutron beam that the cross talk was <10%. [Copyright &y& Elsevier]

133Ba has been standardised by direct measurements for the first time in the laboratory using two counting systems: (i) the 4πβ (plastic scintillator) -γ coincidence, (ii) the 4πβ (proportional counter) -γ coincidence. Furthermore, this standardisation experiment demonstrates the performance and applicability of the recently developed 4πβ (plastic scintillator)-γ coincidence system for radionuclides decaying with complex decay schemes as well as for e, X -γ emitters. Additionally, 133Ba solution standards were prepared to calibrate the pressurized 4π γ ionisation chamber and determination of the calibration coefficient. The E n score is a statistical indicator of the agreement between two independent estimations. Thus, the performance of the PS system was compared to the result obtained with the PC system using the E n score as specified in the ISO13528:2015. The results of measurements are acceptable if E n ≦ 1.0. An E n score of 0.2 was obtained which indicates that, the 133Ba activity concentration obtained by the 4πβ (plastic scintillator) -γ coincidence and 4πβ (proportional counter) -γ coincidence systems are in agreement. This paper presents the standardisation procedure, the results obtained by the measurements and their comparison. • Standardisation of 133Ba. • Efficiency extrapolation technique in variant of e, X -γ coincidence. • Plastic scintillator (PS) is used as beta detector. • Performance demonstration of PS based 4πβ-γ coincidence system for e, X -γ emitters. • Performance of PS system was evaluated with E n score. [ABSTRACT FROM AUTHOR]

Two neutron spectrometers based on a BC-501A liquid organic scintillator were calibrated. The calibration procedure included obtaining the spectrometers' response functions to monoenergetic neutron emissions and estimating the detectors' efficiency and is described in this paper. A 9Be(α , n γ)12C nuclear reaction was used as the neutron source. Simultaneous registration of neutrons and gamma quanta with 4.44 MeV energy enabled the extraction of monoenergetic neutrons corresponding to the first excited state of a 12C nucleus. This process is the basis of the neutron–gamma coincidence method, which was applied in the present experiments. The experiments were conducted using the cyclotron at Ioffe Institute, where α particles were accelerated to energies of 2.06, 5.35, 6.05, and 10.08 MeV. The angular dependence of the energy of produced neutrons provided a wide energy range of monoenergetic neutron emission at the same energy of the incident α particle. The response functions of the BC-501A spectrometers on the monoenergetic neutrons were obtained at energies of 1.9 to 10.4 MeV. The neutron registration efficiency of both detectors was estimated in the same energy range as the responses. [ABSTRACT FROM AUTHOR]

161Tb, which emits low-energy β−- and γ-particles in addition to conversion and Auger electrons, has aroused increased interest for medical imaging and therapy. To support the use of this radionuclide, a161Tb solution was standardised using the β-γ coincidence technique, as well as the TDCR method. The solution had 4.5·10−3% of 160Tb impurities. Primary coincidence measurements, with plastic or liquid scintillators for beta detection, were carried out using both analogue and digital electronics. TDCR measurements using defocusing, grey filtering and quenching for varying the efficiency were also made. Monte Carlo calculations were used to compute the detection efficiency. The coincidence measurements with analogue electronics and the TDCR show a good consistency, and are compatible with the digital coincidence results within uncertainties. An ampoule of this solution was submitted to the BIPM as a contribution to the international reference system. • 161Tb has aroused increased interest recently for medical imaging and therapy. • 161Tb was standardised using the β(PS,LS)-γ(CeBr 3) coincidence techniques. • 161Tb was also standardised with the TDCR method using MC electron spectra. • Coincidence results are consistent with TDCR measurements. • An ampoule of the solution was submitted to the International Reference System. [ABSTRACT FROM AUTHOR]

Abstract: In this work we report on the coincidence resolving time performance of SiPMs with different sizes, produced at FBK, coupled to the same LYSO scintillators. The measurements are performed both with and without the differential leading edge discriminator at three different temperatures, 20°C, 0°C and −20°C. The photo-detectors feature an active area of 2×2mm2 and 4×4mm2. The scintillators have a cross-section of 1.8×1.8mm2 and height of 10mm. The measurements show that, once we eliminate the effect of noise on the timing measurements, we obtain similar coincidence resolving times for the two SiPM sizes considered. This means that the SiPM capacitance, at least up to 4×4mm2, is not a limiting factor. [Copyright &y& Elsevier]

Charge sensitive type preamplifiers are usually used in scintillators, such as NaI (TI) and BGO, to preprocess the current pulse output of detectors. Under high-intensity gamma radioactive field, the wide falling edge of a charge sensitive preamplifier signal will cause a serious pulse pile-up, and the pile-up pulse will be discarded. Consequently, the pulse throughput rate declines significantly. Meanwhile, the charge sensitive amplifier can easily integrate two pulses with an approximate time of arrival into a single pulse to generate an accidental coincidence effect. After using a current-sensitive amplifier on the current pulse output from the detector in the system designed in this work, such output is digitalized by using a waveform digitizer with 125MHz sampling rate. The baseline is estimated statistically via a histogram, a real-time fitting and peeling algorithm is designed for the falling edge pile-up of the current pulse signal to recover the pile-up signal, and the digital charge of the current pulse signal is integrated to obtain particle energy. A 4L NaI(TI) scintillator detector is used in the experiment to measure the 137Cs γ radioactive source. Under a 165kcps counting rate, the pulse throughput rate is up to 99 %, the accidental coincidence probability is 0.387%, and the energy resolution reaches 7.54%, Even under a 3Mcps counting rate, the pulse throughput rate is still 85.43%. Therefore, the overall performance is superior to conventional voltage-type digital spectrometers under high counting rate application. [ABSTRACT FROM AUTHOR]

Compton imaging is a promising gamma-ray imaging method based on the Compton scattering kinematics due to high Compton scattering probability for sub-MeV to MeV gamma-rays. A conventional Compton camera has a disadvantage of low signal-to-background ratio (SBR), which is caused by drawing of multiple Compton cones. A method to solve this fundamental problem is the double-photon emission computed tomography (DPECT), which uses the coincidence detection for cascade gamma-rays and significantly increases the SBR using intersections of two Compton cones. In this study, we demonstrated the DPECT method by using 134Cs radio isotope, which is one of important radioisotopes for the imaging of fuel debris, with two Ce:Gd 3 (Al,Ga) 5 O 12 (GAGG) scintillator Compton cameras. [ABSTRACT FROM AUTHOR]