Study of the Radiation Environment Caused by Galactic Cosmic Rays at Flight Altitudes, at the Summit of the Zugspitze and at PTB Braunschweig

The high energy Monte Carlo codes MARS and FLUKA are compared as applied to calculations of neutron spectra in the atmosphere resulting from interactions of primary galactic cosmic rays (GCR) with the nuclei in the atmosphere. The calculational strategies of either code are discussed. The primary galactic spectrum at the top of the atmosphere and the model used for the atmosphere are presented in detail. MARS is used to calculate neutron energy spectra which before had been calculated with FLUKA and measured with Bonner spheres. The comparison shows acceptable agreement. Therefore, MARS is used to provide new data for the analysis of dosimetric measurements at flight altitudes. The new data encompass calculated angular distributions and energy spectra of neutrons, protons, photons and pions for the geographical position of Braunschweig and the Zugspitze. In addition, the influence of aluminium layers on these spectra is studied. These new data are expected to provide valuable support in the analysis of dosimetric measurements at flight altitudes. Throughout the paper, emphasis is placed on the discussion of the main sources of variance for these calculations.