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At least 1,009 records · Page 56

Energy Spectrum of Ultrahigh-Energy Cosmic Rays according to Data from the Ground-Based Scintillation Detectors of the Yakutsk EAS Array

The energy spectrum of cosmic rays with energies E{sub 0} ≥ 10{sup 17} eV over the period of continuous observations in 1974–2017 is analyzed. A refined formula for estimating the primary particle energy is used for individual events. It is derived from our calculations of the responses of the ground-based and underground scintillation detectors of the Yakutsk extensive air shower array within the QGSjet-01-d, QGSjet-II-04, SIBYLL-2.1, and EPOS-LHC models by applying the CORSIKA package. The new estimate of E{sub 0} is appreciably lower than its previously used value.

79 ASTRONOMY AND ASTROPHYSICS↗

Possible application of scintillation detectors with semiconductor PMT for cosmic-neutron and gamma-ray detection

Solar system planets exploration and cosmic neutrons and gamma-ray flux research have been dynamically evolving for several decades. Different scintillation crystals are used for this purpose along with photo signal receivers, such as vacuum photomultiplier tubes (PMT). Many studies are being performed in order to provide alternative devices for photon signal capture: PIN-diodes,avalanche photodiodes, semiconductor silicon photomultipliers. We study the applicability of a silicon PMT in employing highresolution crystals in space applications.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Forty Years to the Artemovsk Scintillation Detector for Neutrinos

The current status of the ASD (Artemovsk scintillation detector) experiment aimed at search for a neutrino flux from gravitational collapses of stellar cores is presented. Experimental data obtained for 40 years of operation of the detector situated in a salt mine at a depth of 570 mwe are processed. The results obtained by calculating the expected signal in the detector on the basis of two models of supernova explosion are described. No candidates for neutrino bursts from gravitational star collapses have been revealed: the limit on the frequency of gravitational collapses was found to be less than one event per 17.15 yr at a 90% confidence level (f{sub col} < 0.058 yr{sup −1}).

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Energy Spectrum of Ultrahigh-Energy Cosmic Rays according to Data from Ground-Based Scintillation Detectors of the Yakutsk EAS Array

Results obtained from an analysis of the energy spectrum of cosmic rays with energies in the region of E{sub 0} ≥ 10{sup 17} eV over the period of continuous observations from 1974 to 2017 are presented. A refined expression for estimating the primary-particle energy is used for individual events. This expression is derived from calculations aimed at determining the responses of the ground-based and underground scintillation detectors of the Yakutsk array for studying extensive air showers (EAS) and performed within theQGSJET-01-d, QGSJET-II-04, SIBYLL-2.1, and EPOS-LHCmodels by employing the CORSIKA code package. The new estimate of E{sub 0} is substantially lower than its counterpart used earlier.

79 ASTRONOMY AND ASTROPHYSICS↗

Efficiency Of Charged-Particle Detection with Scintillation-Detector Prototype for the Anticoincidence System of the Signal Experiment

The results obtained by measuring the efficiency of detection of charged particles (atmospheric muons) for a prototype of a polyvinyltoluene-based scintillation detector being created for the anticoincidence system of the Signal experiment on board the Interhelioprobe spacecraft are presented. These measurements rely on determining the ratio of the numbers of triple and double coincidences of pulses that arise as atmospheric muons traverse the detector system.

43 PARTICLE ACCELERATORS↗

Search for low-energy neutrinos from gamma-ray bursts at the Baksan Underground Scintillation Telescope

The origin of gamma-ray bursts is still one of the unresolved problems in physics. They are short, intense, and non-repeating flashes of MeV gamma-rays with a wide range of spectral and temporal properties. Also these bursts are perhaps sources of neutrino emission. Unlike the photons, which may scatter or be absorbed, the neutrinos, due to their small interaction cross section, arrive at the Earth unaffected. This paper describes experimental methods for detection of low energy neutrinos in the range from 20 MeV to 100MeV at the Baksan Underground Scintillation Telescope. In the analysis we search neutrinos in time coincidence with a gamma-ray burst. We use filtered data collected at the Telescope during 2012. We also use the catalogue of gamma-ray bursts of the SWIFT satellite experiment.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Search for Local Neutrino Sources with the Baksan Underground Scintillation Telescope

Local sources of muon neutrinos are searched for with the Baksan underground scintillation telescope. In the period from December 1978 through May 2017 (live-time 31.05 yr), 1635 neutrino events with zenith angles between 95° and 180° have been detected. No local sources of muon neutrinos with energies over 1 GeV have been found. Upper limits on the fluxes of muon neutrinos emitted by known astrophysical objects are established.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Prototype Scintillation Detector with Photosensors Based on Silicon Photomultiplier Arrays

A prototype scintillation detector with photosensors based on silicon photomultiplier (SiPM) arrays is described. Such a method of data-taking will make it possible to obtain an image (snapshot) of the event and, thereby, to separate different types of events (particle interactions) in the detector. For this purpose, the characteristics of SiPMs have been studied and a calibration measurement technique developed.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Search for Neutrino Bursts at the Baksan Underground Scintillation Telescope

The Baksan Underground Scintillation Telescope has been operating under the program of searching for neutrino bursts since the middle of 1980. The target is two parts of the facility with the total mass of 240 t. The actual observation time over the period from June 30, 1980, to December 31, 2016, is 31.27 years. No candidate for the stellar core collapse has been detected during the observation period. The upper bound for the mean rate of the supernova core collapse in our Galaxy is 0.074 y {sup −1} (90% CL).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Growing of Alkaline Earth Halide Scintillation Crystals and Their Optical Properties

The features of using the Bridgman method for growing alkaline earth halides crystals BaBrI, BaClI, and SrBrI are discussed. The results of the study of scintillation characteristics of grown crystals activated by europium ions are presented. The actual content of europium in crystals is determined and the values of the luminescence yield and decay time are estimated. X-ray luminescence and absorption spectra of the obtained crystals are given.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Tests of Scintillator+WLS Strips for Muon System at Future Colliders

Prototype scintilator+WLS strips with SiPM readout for muon system at future colliders were tested for light yield, time resolution and position resolution. Depending on the configuration, light yield of up to 36 photoelectrons per muon per SiPM has been achieved, as well as time resolution of 0.5 ns and position resolution of ~ 7 cm.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Complex Electronic Structure of Rare Earth Activators in Scintillators

To aid and further the understanding of the microscopic mechanisms behind the scintillator nonproportionality that leads to degradation of the attainable energy resolution, we have developed theoretical and experimental algorithms and procedures to determine the position of the 4f energy levels of rare earth dopants relative to the host band edge states.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Summary of Summer Project: Evaluating New Double Perovskite Halide Scintillators for Radiation Detection Applications

Project Outline: • Experimental validation of machine learning based prediction models; • Evaluating double perovskite halides (chlorides, some bromides) – A 2 bb'X 6 :Ce; A = Br + , Cs + ; B = Na + , K + ; B' = RE 3+ ; X = Cl - , Br - ; • Performing single crystal growth and characterization (physical, optical, scintillation properties).

61 RADIATION PROTECTION AND DOSIMETRY↗

Design and Performance of an InAs Quantum Dot Scintillator with Integrated Photodetector

A new scintillation material composed of InAs quantum dots (QDs) hosted within a GaAs matrix was developed, and its performance with different types of radiation is evaluated. A methodology for designing an integrated photodetector (PD) with a low defect density and that is optically matched to the QD’s emission spectrum is introduced, utilizing an engineered epitaxial InAlGaAs metamorphic buffer layer. The photoluminescence (PL) collection efficiency of the integrated PD is examined using two-dimensional scanning laser excitation. The detector response to 5.5 MeV α-particles and 122 keV photons is presented. Yields of 13 electrons/keV for α-particles and 30–60 electrons/keV for photons were observed. The energy resolution of 12% observed with α-particles was mainly limited by noise- and geometry-related optical losses. The radiation hardness of an InAs QDs hosted within GaAs and a wider band gap AlGaAs ternary alloy was studied under a 1 MeV proton implantation up to a 10 14 cm –2 dose. The integrated PL responses were compared to evaluate PL quenching due to non-radiative defects. The QDs embedded in the AlGaAs demonstrated improved radiation hardness compared to QDs in the GaAs matrix and in the InGaAs quantum wells.

36 MATERIALS SCIENCE↗