A. P. Chubenko

Effect of solar eclipses on neutron flux variations at the Earth’s surface

The results of the investigation of the neutron flux variations at the Tien Shan high-altitude scientific station during solar eclipses on September 23, 1987; August 11, 1999; and March 29, 2006 are reported. It is established that, during these periods, the dynamics of neutron intensity variations in the frequency range 10−5–10−3 Hz is due to geophysical sources of disturbances. An increase in the thermal neutron flux from the Earth’s Crust is observed.

New complex EAS installation of the Tien Shan mountain cosmic ray station

In this paper we present a description of the new complex installation for the study of extensive air showers which was created at the Tien Shan mountain cosmic ray station, as well as the results of the test measurements made there in 2014-2016. At present, the system for registration of electromagnetic shower component consists of ∼100 detector points built on the basis of plastic scintillator plates with the sensitive area of 0.25m2 and 1m2, spread equidistantly over ∼104 m2 space. The dynamic range of scintillation amplitude measurements is currently about (3 − 7) · 104, and there is a prospect of it being extended up to ∼106. The direction of shower arrival is defined by signal delays from a number of the scintillators placed cross-wise at the periphery of the detector system. For the investigation of nuclear active shower components there was created a multi-tier 55m2 ionization-neutron calorimeter with a sum absorber thickness of ∼1000g/cm2, typical spatial resolution of the order of 10cm, and dynamic range of ionization measurement channel about ∼105. Also, the use of saturation-free neutron detectors is anticipated for registration of the highand lowenergy hadron components in the region of shower core. A complex of underground detectors is designed for the study of muonic and penetrative nuclear-active components of the shower. The full stack of data acquisition, detector calibration, and shower parameters restoration procedures are now completed, and the newly obtained shower size spectrum and lateral distribution of shower particles occur in agreement with conventional data. Future studies in the field of 1014 − 1017eV cosmic ray physics to be held at the new shower installation are discussed.

Characterization and simulation of fast neutron detectors based on surface-barrier VPE GaAs structures with polyethylene converter

Fast neutron detectors with an active area of 80 mm2 based on surface-barrier VPE GaAs structures were fabricated and tested. Polyethylene with density of 0.90 g/cm3 was used as a converter layer. The recoil-proton surface-barrier sensor was fabricated on high purity VPE GaAs epilayers with a thickness of 50 μm. The neutron detection efficiency measured with a 241Am-Be source was 1.30 10−3 puls./neutr. for the PE converter thickness of 670 μm. The signal-to-gamma-background ratio was at the level of 50. Simulation of the detector characteristics with Geant4 toolkit has showed good correlation with the experimental data and allowed to estimate the maximal theoretical detection efficiency of the detector which is determined by the PE converter and equals to 1.37 10−3 puls./neutr. The difference between the measured and simulated values of the detection efficiency is due to the fact that the events with energies below 0.5 MeV were not taken into account during the measurements.

Interactions between hadrons and nuclei of air atoms at PCR energies of 0.3–3 PeV

The Tien Shan experimental data on hadrons with energies 1–50 TeV in extensive air showers from (0.3–3)-PeV primary cosmic rays are compared with the results of different model calculations, including the CORSIKA + QGSJET1 program. On the basis of the comparison of the energy spectra of hadrons, conclusions are drawn about the increase in the interaction cross section between protons and nuclei of air atoms with an increase in energy from 0.1 TeV (accelerators with a fixed target) to 3 PeV (extensive air showers) and the behavior of other main interaction parameters.

Effect of variations in the Earth’s electrical field caused by weather conditions on neutron monitoring

Variations in cosmic rays are investigated on the basis of the Tien Shan neutron monitor data. The Earth’s electrical field during snowfall, rain, and thunderstorm activity is considered as a modulating factor. It is established that the effect of the electrical field on the monitor data becomes apparent at values exceeding 15–20 kV m−1 in the atmosphere of a thunderstorm. The response is as high as 1.5% for recorded particles with energies lower than 10 GeV.

The effect of the thunderstorm activity on the tien shan neutron monitor data

Variations in the neutron monitor counting rate at the at the mountain level (3340 m above sea level) during the passage of electrically charged clouds above the installation have been investigated. It is established that the decrease in the counting rate with respect to fair-weather level is due to positive values of the atmospheric electric field (∼40–50 kV m−1). This effect is observed in the low-energy part of the neutron component intensity and is absent in the high-energy part (neutron emission multiplicity exceeds 6).

On EAS spectrum with extremely low content of hadrons in the primary-energy range ∼1014−1015 eV

The distribution of energy fluxes of the hadron component of extensive air showers through an ion-ization calorimeter in the primary-energy range ∼3 × 1013−1016 eV is considered. Extensive air showers with zero and minimum energy fluxes of the hadron component are selected. It is concluded that the primary-energy range E0 ≈ 1 × 1014−2 × 1015 eV contains isotropic γ radiation with a spectrum close to bell-shaped, having a maximum near E0 ≈ 2.2 × 1014 eV and an additional peak near E0 ≈ 1.6 × 1015 eV.

Possibility of increasing proton rejection by detecting primary cosmic radiation electrons using an ionization-neutron calorimeter

Measurements were made of the neutron yields from a lead absorber 60 cm thick in electromagnetic cascades initiated by 200–600 MeV electrons. A comparison between the neutron yields obtained for electrons and the results of similar measurements for protons and pions suggests that the rejection factor of the proton background is increased ∼102 times when an ionization-neutron calorimeter is used to measure primary cosmic radiation electrons at energies above 100 GeV.

Investigation of the characteristics of an ionization-neutron calorimeter in 4–70 GeV hadron beams at the IHEP accelerator

As a step in the development of an ionization-neutron calorimeter, a device which combines the properties of ionization and neutron calorimeters, measurements are made of the mean values and fluctuations of the neutron yield from a lead target 60 cm thick and 20×20 cm in area. The measurements were made at the U-70 accelerator in pion and proton beams with energies of 4 and 70 GeV, respectively. The mean values of the neutron yield are in good agreement with the data calculated using the SHIELD code.