Introduction
In July 1999, during the TUNGUSKA99 expedition in the Vanavara region (Siberia), one detector for the monitoring of the Environmental Radiation (ER) [1] {cosmic radiation plus radioactivity with E > 50 keV} was operated on board of the aeroplane that took the expedition from Forli (Italy) to Krasnoyarsk (Siberia) and back, and while at the base camp of the expedition close to Cheko Lake [2]. The main purpose was to measure the cut-off and altitude variations of the secondary cosmic radiation with energies in the range 3-10 MeV and to monitor the presence of radionuclides either of local or airborne origin.
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