Neutron spectrometry at high mountain observatories

The evaluation of neutron spectra due to primary cosmic ray interactions with the atmosphere requires dedicated detectors: in principle, they should be able to distinguish neutrons from other radiation components, and to be sensitive in a wide energy range. This paper describes the results of experimental measurements of neutron spectra at two High Mountain Observatories (HMOs) in the Northern and Southern Hemisphere, obtained by unfolding the responses of different passive detectors (superheated drop detectors, polycarbonate foils and bottles, bismuth fission detector). Based on the results obtained at the HMOs, the same experimental technique has been applied for the evaluation of neutron spectra at aircraft altitudes and on board stratospheric balloons. A comparison among the results achieved at the two HMOs, on Alitalia intercontinental flights and on ASI (Italian Space Agency) stratospheric balloons has been performed. This experiment highlights the potential of a European HMO Network for the long-term contemporary collection of secondary cosmic ray flux data and atmospheric parameters.