The properties of gamma-radiation and high-energy neutron fluxes in "MIR" station orbit

The study of radiation background components in the near-Earth space is very important for different branches of space research, in particular for space dosimetry and for the planning of gamma-astronomy experiments. Detailed information-on the neutral components (gamma-quanta, neutrons) of background radiation was obtained during the Grif-1 experiment onboard Mir orbital station (OS). The measurements of fluxes of 0.05-50 MeV gamma-quanta and > 30 MeV neutrons with a large area instrument (similar to250 cm(2) for gamma-quanta, similar to30cm(2) for neutrons) as well as corresponding charged particle measurements (0.04-1.5 MeV electrons, 1-200 MeV protons) were made during this experiment. The background components induced by the station's own radiation as well as the albedo gamma-rays from the Earth's atmosphere were revealed as the result of data analysis for about 600 h of observation. A mathematical model describing the latitude and energy dependences of atmospheric albedo gamma-rays as well as of those of gamma-quanta produced in the material of the station due to cosmic ray interactions was developed. An analytical approximation of the spectrum of induced gamma-rays from radioactive isotopes stored in the station and instrument's materials is presented. The dynamics of gamma-quantum background fluxes during the geomagnetic disturbances of January 10-11, 1997 are discussed. An analytical representation of the latitude dependence of the integral flux of neutrons with > 30 MeV is given. (C) 2002 Elsevier Science Ltd. All rights reserved.