Regular and stochastic variations in different components of secondary cosmic rays

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In the Laboratory of Cosmic Rays continuous monitoring of the different
components of secondary cosmic rays has been carried out for several years. At
the present time, besides the standard neutron monitor (NM), a gamma-ray photon
detector on the scintillation crystal, lead-free section of neutron monitor
(BNM), charged particle detectors (CPD) and a detector for thermal neutrons
(DTN) are in operation. Scintillation detector registers photons with energies
from 20 keV up to 5 MeV, NM is sensitive to neutrons with energies more then 50
MeV, BNM is to neutrons with energies from hundreds keV to a few MeV, DTN is
for thermal neutrons (about 0.03 eV). CPD detects all charged particles (muons,
electrons, positrons) with energies >2 MeV. Data from all the instruments are
gathered to the general registration system. Analysis of the data over the past
few years has shown the presence of seasonal variations in some components of
cosmic rays. The HM has a zero variation, the DTN it is about 10%. The largest
in amplitude and the more clearly defined is the variation observed in the
channel of the scintillation detector, it is more than 20%. Gamma radiation in
the near ground layer of the atmosphere appears as Bremsstrahlung of energetic
electrons generating during muon decay. Moreover during precipitation the
increase of gamma background up to 50% are observed; they last for many hours.
Experiments have shown, that precipitation is free from any radionuclide of
natural or artificial origin, and additional radiation is of Bremsstrahlung
origin. On the basis of epoch superposition method, small variations in other
components, synchronous with gamma background increase, were determined.