ИСТИНА

In the Polar Geophysical Institute a complex installation created for secondary cosmic rays monitoring integrates detectors of neutron, charged (electron-muon) and electromagnetic components of secondary cosmic rays. The fluxes of these components are recorded continuously with the resolution of 1 minute. An integral spectrum is recorded by the scintillation detector on a Ø60×20 mm NaI(Tl) crystal within the range of 20-400 keV with two output channels: >20 and >100 keV. The neutron component is measured by two instruments: a conventional neutron monitor 18-NM-64 (NM) and a leadless section (bare NM, bNM). The conventional NM is sensitive to neutrons with energy exceeding ~50 MeV, while bNM is sensitive to neutrons with energy up to 100 keV only. The detector of a charged component consists of two layers of the Geiger-Muller counters. The output of the upper layer and the coincidence of the two layers are used. The upper layer records both the charged particles and gamma-quanta, the scheme of coincidence between the upper and lower layers selects the signal corresponding to a charged particle. The energy threshold for charged particles is estimated ~7 MeV. The installations operate some years and a great database has been accumulated and analyzed. Every year 50-70 increase events of 5 to 65 % in amplitude were registered in the gamma-ray background. The increase events are connected with precipitation. Simultaneously a small effects are in other components are present. An annual variation of the gamma-ray background with amplitude ~30 % were found too. The same installation is set in Barentsburg station (Spitsbergen). The same increase events and annual variation are present.