The article describes the method for modifying the scintillation calorimeter detectors
3 (
) and
4 (
) of the GAMMA-400 space complex in order to obtain the possibility of detecting neutrons produced ...in the process of passing electrons (positrons) and high-energy protons through detector matter. The presented method will allow to increase the rejection factor of background radiation without degrading the basic capabilities of the detectors
and
.
Calibration of the scintillator detector based on a plastic scintillator EJ-276 for neutron–gamma pulse shape discrimination (PSD) experiments was carried out. Optical characteristics of electrons as ...the function of their deposited energy were experimentally studied. The calibration was implemented by comparing the experimental response from gamma sources with that obtained by means of GEANT4 simulation. It is shown that a similar relationship for protons built on the basis of the published data on EJ-299-33, is also applicable to EJ-276 which confirms the information about the equivalence of these scintillators. The experimental response of the EJ-276 to 14 MeV neutrons is compared with Geant4 simulation data. The experimental and simulated data were also presented as the function of light output in electronic equivalent (MeVee) obtained by both exponential and Birks’ laws.
An experimental setup was constructed with Ø51 × 51 mm EJ-276 scintillator. The CAEN DT5730B digitizer was used for PSD signal discrimination. Based on the current experiments and the earlier published data a calibration relation between the setup channels and the light output was obtained in electronic equivalent (MeVee).
The purpose of this work is to analyze the use of detecting materials in radiation monitors as well as the replacement of widely used
3
H-based neutron counters by neutron-detection scintillation ...technology. The replacement of helium counters is a consequence of two factors: the lack of
3
He and widespread use of
3
He-based counters in safety equipment, such as volumetric neutron detectors. Selection criteria for evaluating promising technologies are used in this work, specifically, high absolute neutron detection efficiency – efficiency at least 1.5 counts in 1 sec in detecting 1 ng
252
Cf at distance of 2 m in a 20 mm thick moderator and low sensitivity to γ-ray detection – γ-ray detection efficiency not exceeding 10
–6
with irradiation by a 0.1 μSv/h γ-ray source. Since they can have a large sensitive area and high resolution, scintillation detectors are now being proposed as alternatives to helium counters. But it is necessary to find an optimal scintillator possessing simultaneously low sensitivity to γ-radiation and to choose an optimal method of measuring information. Promising neutron detection technologies based on the glasses Li
2
OSiO
2
:Ce
3+
, LiF/ZnS(Ag
+
), Li
6
Gd(BO
3
)
3
:Ce, Cs
2
LiYCl
6
(Ce) (CLYC) as well as EJ-254 boron-doped plastic are examined from the standpoint of the posed problems.
Fermi-LAT has made a significant contribution to the study of high-energy gamma-ray diffuse emission and the observation of ∼3000 discrete sources. However, one third of all gamma-ray sources (both ...galactic and extragalactic) are unidentified, the data on the diffuse gamma-ray emission should be clarified, and signatures of dark matter particles in the high-energy gamma-ray range are not observed up to now. GAMMA-400, currently developing gamma-ray telescope, will have the angular (∼0.01° at 100 GeV) and energy (∼1% at 100 GeV) resolutions in the energy range of 10-1000 GeV better than the Fermi-LAT (as well as ground gamma-ray telescopes) by a factor of 5-10 and observe some regions of the Universe (such as Galactic Center, Fermi Bubbles, Crab, Cygnus, etc.) in the highly elliptic orbit (without shading the telescope by the Earth) continuously for a long time. It will permit to identify many discrete sources, to clarify the structure of extended sources, to specify the data on the diffuse emission, and to resolve gamma rays from dark matter particles.
The GAMMA-400 γ-ray telescope installed at the Russian space observatory is intended for precision measurements in the energy range of 20 MeV–1000 GeV of γ-ray emission (with the angular and energy ...resolutions several times better than that of current γ-ray telescopes) from discrete sources; measurement of the energy spectra of Galactic and extragalactic diffuse γ-ray emission; studies of γ-ray emission from the active Sun; and measurements of fluxes of γ-ray emission and electron–positron cosmicray component, which are probably associated with the annihilation or decay of dark-matter particles.
There is description of the development of detectors for neutrons, based on polystyrene and cadmium layers. Cadmium is used as neutron's converters via reaction (n,γ) and polystyrene is used as ...scintillation material to register the originated gamma quanta. The simulation and experimental investigations of proposed detectors design are presented. The main advantages of proposed detection are short measurement time - approximately 5 µsec. It is shown that the principle, suggested in the models, can be applied to the detection of neutrons from a pulsed neutron source, for example, secondary neutrons, generated by hadron showers in the space environment or by high-intensity pulsed sources based on accelerators. Detection efficiency for the 24*20 cm2 size detector model, measured during the experiment and simulated by the Monte Carlo technique is about 1% with the measurement time being approximately 5 µsec
A non-destructive method of monitoring the presence and location of metallic components in a fuel element is proposed. It is shown that a nickel plug can be identified by modernizing the measurement ...procedure. A method of performing measurements is described and the results of experimental studies are presented.
The GAMMA-400 gamma-ray telescope is designed to measure the gamma-ray fluxes in the energy range from ∼20 MeV to ∼1 TeV, performing a sensitive search for high-energy gamma-ray emission when ...annihilating or decaying dark matter particles. Such measurements will be also associated with the following scientific goals: searching for new and studying known Galactic and extragalactic discrete high-energy gamma-ray sources (supernova remnants, pulsars, accreting objects, microquasars, active galactic nuclei, blazars, quasars). It will be possible to study their structure with high angular resolution and measuring their energy spectra and luminosity with high-energy resolution; identify discrete gamma-ray sources with known sources in other energy ranges. The major advantage of the GAMMA-400 instrument is excellent angular and energy resolutions for gamma rays above 10 GeV. The gamma-ray telescope angular and energy resolutions for the main aperture at 100-GeV gamma rays are ∼0.01% and ∼1%, respectively. The motivation of presented results is to improve physical characteristics of the GAMMA-400 gamma-ray telescope in the energy range of ∼20-100 MeV, most unexplored range today. Such observations are crucial today for a number of high-priority problems faced by modern astrophysics and fundamental physics, including the origin of chemical elements and cosmic rays, the nature of dark matter, and the applicability range of the fundamental laws of physics. To improve the reconstruction accuracy of incident angle for low-energy gamma rays the special analysis of topology of pair-conversion events in thin layers of converter performed. Choosing the pair-conversion events with more precise vertical localization allows us to obtain significantly better angular resolution in comparison with previous and current space and ground-based experiments. For 50-MeV gamma rays the GAMMA-400 gamma-ray telescope angular resolution is better than 50.
A neutron detector, providing charged particle detection capability, has been designed. The main purpose of the detector is to measure pulsed fluxes of both charged particles and neutrons during ...scientific experiments. The detector consists of commonly used neutron-sensitive ZnS(Ag) / 6LiF scintillator screens wrapping a layer of polystyrene based scintillator (BC-454, EJ-254 or equivalent boron loaded plastic). This type of detector design is able to log a spatial distribution of events and may be scaled to any size. Different variations of the design were considered and modelled in specialized toolkits. The article presents a review of the detector design features as well as simulation results.
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