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• CeBr 3 and NaI (Tl) scintillators characterized with array of Silicon Photomultipliers. • Energy resolution improves with lower shaping time and higher SiPM over-voltage. • Temperature dependency of gain of SiPM array: ∼−0.81 %/°C for overvoltage of 2.5 Volts. • Temperature dependency of light yield for CeBr 3 : ∼−0.27 %/°C for −31 °C to +26 °C. • Temperature dependency of light yield for NaI (Tl): ∼+0.5 %/°C for −31 °C to +26 °C. Interaction of X-rays with a scintillation detector produces optical photons in the visible range. The spectral and spatial information of the X-ray can be derived by detecting these output photons using a Silicon Photomultiplier (SiPM). Two types of detector modules: CeBr 3 and NaI (Tl), coupled with an array of SiPM are presented here, which are being developed for the future space exploration programs. The development of the front end electronics (FEE) for the charge readout from SiPM for X-ray spectrometer application is presented here which is characterized for SiPM's over-voltages and shaping amplifier's time constant. In this article, both the detector modules are subjected to a wide temperature range to establish a relationship of the SiPM's gain, energy resolution and scintillators' output photon yield with ambient temperature. The test results show that energy resolution improves with higher over-voltage of SiPM and also with lower operating temperature. The gain of the SiPM array shows negative temperature dependence of ∼−0.81 %/°C for an over-voltage of 2.5 Volts. To derive the temperature dependency of scintillators' output photons, gain of the SiPM array was made constant by operating it at a fixed over-voltage for a wide temperature range. With the constant gain of SiPM, CeBr 3 scintillator shows negative temperature coefficient of ∼−0.27 %/°C and NaI (Tl) shows positive temperature coefficient of ∼+0.5 %/°C for the light output in the temperature range of −31 °C to +26 °C. [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]

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]

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]

Activity of 225Ac was measured by the digital anti-coincidence spectroscopy technique using a 4πα–γ detector configuration, composed of a sandwich type 4π plastic scintillator and Ge detectors. Ultrathin plastic scintillators were used for selective detection of α-particles emitted from 225Ac and its progenies, and the α-counting efficiencies of a 4π plastic scintillation detector for individual nuclides in the decay chain were determined as well. A list-mode multichannel analyzer was employed to record coincidence/anti-coincidence events for off-line analyses. The time difference distribution spectra revealed α-particle emission following 213Po decay without β-particle interference from 213Bi. • Selective α-particle detection using ultrathin plastic scintillators for 225Ac. • Individual α-efficiencies determined by 4πα(PS)–γ(Ge) anti-coincidence spectroscopy. • α-particles from short-lived 213Po(T 1/2 = 3.7 μs) detected without interference. • Effect of β-particle from 213Bi confirmed from γ–α/β time difference distribution. • Results were consistent with those obtained using the CN method with LSC. [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]

A color scintillation detector for relative dose distribution measurement was developed at PSI. The system consists of a gadolinium-based scintillating screen mounted perpendicularly to the beam axis and coupled with a color CMOS camera in a light-tight box. The camera is equipped with an iris (aperture) controller to remotely adjust the number of photons reaching the image sensor. To improve the measurement accuracy and decrease the image artifacts, we investigated different methods for spatial calibration and optimized the internal light reflection by adjusting the detector structure. The response dependence on camera working distance, iris setting, and color channels was assessed. The depth-dose curves of the gadolinium-based scintillator in three RGB channels were compared with reference curves measured by an Advanced Markus plane-parallel ion chamber. The quenching effect of the ▪ screen measured with this system amounts to about 10% in the Bragg peak region of a 150 MeV proton beams. The shape of the emission spectrum was observed to be independent of the ionization density. Preliminary investigations showed that it is possible to correlate the ratio of the detector response in different color channels with the proton ionization density. • A color scintillation detector was developed and characterized in clinical proton beams. • Two methods for spatial calibration were evaluated and results benchmarked against a commercial detector. • The developed detector can be used to evaluate the quenching of different scintillating probes in RGB channels. • Preliminary investigation on the possibility to correlate the color response to the residual proton energy. [ABSTRACT FROM AUTHOR]

Dose-rate monitoring instruments measure the ambient dose equivalent and hence are crucial for protecting workers from radiation exposure. Although plastic scintillation detectors (PSDs) are ideal equipment for dosimetry, they are rarely used owing to the lower detection efficiency than other scintillation detectors. In this study, we acquired ten types of G(E) functions to utilize a PSD in spectroscopic dosimetry using the least-square and first-order methods. The energy response of PSD was much improved in terms of dose evaluation. • Measurement of ambient dose equivalent using a plastic scintillation detector. • Detector with an EJ-276G plastic scintillator coupled to a silicon photomultiplier. • G(E) function obtained using the least-square and first-order methods. • Ensemble G(E) function showed the most stable and superior performance. [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]

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]

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]

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]

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]

The NaI(Tl) detector is one of the most used in gamma ray spectrometry because it presents high counting efficiency for gamma rays in a wide energy range. This study presents the modeling of a real 1¼ x ¾" NaI(Tl) scintillation detector + photomultiplier using computational simulations carried out by the MCNP6 code, which considers energy resolution. In the mathematical model, the sensitive volume of the detector was adjusted using 241Am and 137Cs radiation sources by means of the absolute photopeak efficiency. Moreover, the MCNP6 code was used to calculate the effective solid angle of the detector in order to obtain the intrinsic efficiency response function. The mathematical model was experimentally validated using calibrated radioactive sources (241Am, 133Ba, 137Cs and 60Co) and the response functions - efficiency curve and energy resolution - were obtained. In addition, an experimental evaluation of the crystal homogeneity of the detector was made using a137Cs radiation source and a 3D printed device developed without stepper motors. The proposed methodology is able to obtain absolute photopeak efficiency in agreement with experimental data with maximum relative error of 5.64%. The gamma scanning procedure indicated that the crystal of the detector remained homogeneous. • Modeling of a 1¼ x ¾" NaI (Tl) scintillation detector using MCNP6 code. • The model was experimentally validated using 241Am, 133Ba, 137Cs and 60Co sources. • Detector function fit parameters were experimentally obtained using radiation sources. • The effective solid angle and intrinsic efficiency were calculated using MCNP6 code. • Development of an experimental gamma scanning device without step motors. [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]

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]

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]