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Portable neutron/gamma scintillation detector for status monitoring of accelerator-driven neutron source IREN (Archive)

Accelerator-driven system (ADS) facilities world-wide opens new opportunities for nuclear physics investigations, so that a high flux of neutrons through spallation reactions can be produced at these facilities. It is known that the measurement, continuous monitoring and optimization of the particle accelerator beam intensity are among the most important actions in the operation of such facilities. Considering this point of view, this paper presents a neutron/gamma counter based on a micropixel avalanche photodiode (MAPD) and a plastic scintillator that monitors the status of the accelerator-driven intense resonance neutron source (IREN) facility by measuring the neutron-gamma intensity in the target hall. The electronics of the modular neutron counter has been designed and developed, including a bias voltage source (up to 130 V), a preamplifier (36 gain) and discriminator (>10 mV) circuit. The last product of MAPD (operation voltage- 55 V, PDE- 33 %, total number of pixels- 136900) was used as a photon readout from a plastic scintillator. The sensitive area of MAPD was 3.7*3.7 mm2 and the size of the plastic scintillator 3.7*3.7*30 mm3. The measurement was carried out in the IREN target hall, where it was necessary to monitor not only high neutron fluxes, but also gamma quanta. The experimental results demonstrated a dependence between the count rate of the detector and the frequency of the accelerator, which ranges from 2 to 50 Hz.

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Investigation of the possibility of a new detector based on SiPM in nuclear forensics

The development of nuclear technologies, the production and active use of radioisotopes, and the production of radiopharmaceuticals, medical isotopes and other radioactive materials are increasing every year. Therefore, the importance of ensuring the safety of highly active isotopes, as well as providing the necessary instruments for measuring and identifying radioactive materials, must be taken into account. Modern equipment such as high purity germanium detectors (HPGe) is costly and requires specialized staff skills as well as special operating conditions such as low temperatures and high voltages. It is proposed to explore the possibilities of using a silicon photomultiplier (SiPM) with a deep pixel structure in nuclear gamma spectrometry, which will make it possible to increase the efficiency of scintillation detectors. The paper presents the results of a study of the newest silicon photomultipliers MAPD-3NM II assembled in a 16-element matrix, which was the detector part of the proposed LaBr3(Ce) scintillation spectrometer. The study was carried out using radioisotopes of uranium. The aim of the research is to reveal the possibility of differentiating depleted and natural uranium materials from each other without using special software by means of the proposed set of equipment.

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The angular distributions of prompt-fission γ-rays with respect to the direction of fission fragments in the monochromatic “warm” neutron induced fission of 235U have been studied. The fragments were detected with low-pressure position sensitive multi-wire proportional counter and the gamma-rays with a plastic scintillators. The time-of-flight method is used to discriminate prompt neutrons and prompt γ-rays of fission. From the measured angular distributions with respect to the direction of the selected fragments, the value of the laboratory anisotropy has been found to be 15% in comparison to the value obtained in the perpendicular direction. The measurements indicate the existence of a significant anisotropy of emission of the γ-rays in the emitting-fragment system, suggesting the presence of significant angular momenta of the fragments correlated with the fission axis, which also lead to an enhanced emission of the γ-rays. Moreover, the article includes a new technique for measuring and correcting the obtained angular distribution, in the case of when plastic scintillators have different threshold levels for detection of γ-rays.

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Ternary particles of Z= 1 to 4 emitted in spontaneous fission of 252Cf

This paper presents the results of ternary light charged particles from 252Cf spontenous fission source. The method DeltaE – E was applied to identify the particle by a position sensitive DeltaE – E telescope.The specific energy loss (DeltaE) was measured using the transmission type DeltaE detector (thicknesses of 150 μm ) ordered from the company Micron Semiconductors, while the residual energy (E) was measured by a Timepix detector with thicknesses of 600 μm . It was possible to measure partial-energy spectra of the various ternary particle types due to the thicknesses of Al foil (31 μm) and DeltaE detector (150 μm) placed before E detector. The energy spectrum of protons was qualitatively different from the spectra of the other particles since protons from Al(n,p) and Si (n,p) reactions could contribute to the spectra.

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Gamma ray detection performance of newly developed MAPD-3NM-II photosensor with LaBr3 (Ce) crystal

This paper presents the gamma-ray detection performance of the newly developed MAPD-3NM-II type SiPM sensor array (4 ×


4) with LaBr3


(Ce) scintillator. The gamma-ray spectra of various sources have been measured in the energy range from 26 keV up to 1332 keV. The newly developed array based on MAPD-3NM-II sensors proved


22% enhancement in energy resolution in comparison to the former MAPD-3NM-I based array. The energy resolution of 662 keV gamma-rays measured by MAPD-3NM-II was 3.3% while clearly surpassing 4.25% resolution of MAPD-3NM-I predecessor. The enhancement is related to the high PDE of the new MAPD-3NM-II. Obtained results show that the new MAPD-3NM-II demonstrated good energy resolution and linearity in the studied energy region. The energy resolution of the new detector developed based on MAPD-3NM-II was better than all previous products of MAPD.

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Magnetic system for controlling the spin of polarized neutronsf

A spin control magnetic system was developed and assembled at the JINR Laboratory of Neutron Physics (Dubna, Russia) and was tested with a beam of polarized neutrons at the POLI instrument of the FRM II reactor in Garching (Germany). This paper presents the principle of operation and a method for compensating the influence of external magnetic fields on polarization using this device. The system consists of three precession coils in a magnetic screen. The first coil allows, by changing the current in it, to ensure the rotation of the neutron spin by an arbitrary angle relative to the magnetic field inside the coil. The remaining two coils are designed to compensate for the effect of scattered magnetic fields on the beam polarization, and to preserve the polarization vector direction.

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Innovative photodetector for LIDAR systems. (Archive)

Optical imaging systems are widely used in the drone industry (optical navigation, terrain scanners), industry (distance measurement, 3D visualization), security (optical scanners and motion sensors), robotics (motion sensors, terrain or field scanning), etc. Lidar (Light Detection and Ranging) systems have a different structure depending on their purpose, and the principle of operation is based on measuring the time difference between the emission time of a laser or other light source and the time of its reflection from the object, where the reflected photons fall on the photodetector. This time interval is about hundreds of ps. Accuracy, photography speed and system efficiency depend on the performance of the photodetector module. Modern development of high technologies; the new efficiency of detecting a large photon flux makes it possible to develop photodetectors with a nanolayer micropixel structure. The paper presents the development of a modern and highly sensitive micropixel avalanche photodetector. The developed photodetector have high speed, low noise and high resolution. The improvement of these parameters allows the developed photodetectors to become an indispensable component of lidar systems.

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Improvement of parameters of micro-pixel avalanche photodiodes

The paper is concerned with the parameter study of a new generation of micro-pixel avalanche photodiodes (MAPD) with deeply buried pixel structure, also named silicon photomultipliers (SiPM) or multi-pixel photon counter (MPPC). The new MAPD of type MAPD-3NM was manufactured in the frame of collaboration with Zecotek Company. Measurements were carried out and discussed in terms of the important parameters such as the current-voltage and capacitance-voltage characteristic, gain, the temperature coefficient of breakdown voltage, breakdown voltage, and gamma-ray detection performance using an LFS scintillator. The obtained results showed that the newly developed MAPD-3NM photodiode outperformed the previous generation in most parameters and can be successfully applied in space application, medicine, high-energy physics, and security. New proposals are also discussed, for further improvement of the parameters of the MAPD photodiodes that will be produced in the coming years.

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Investigation of parameters of new MAPD-3NM silicon photomultipliers

In the presented work, the parameters of a new MAPD-3NM-II photodiode with buried pixel structure manufactured in cooperation with Zecotek Company are investigated. The photon detection efficiency, gain, capacitance and gamma-ray detection performance of photodiodes are studied. The SPECTRIG MAPD is used to measure the parameters of the MAPD-3NM-II and scintillation detector based on it. The obtained results show that the newly developed MAPD-3NM-II photodiode outperforms its counterparts in most parameters and it can be successfully applied in space application, medicine, high-energy physics and security.

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