Improvements of FLUKA calculation of the neutron albedo

This paper presents Monte-Carlo simulations based on the Fluka code aiming to calculate the contribution of the neutron albedo at a given date and altitude above the Earth chosen by the user. Results consist of a two-parameter distribution, the neutron energy and the angle to the tangent plane of the sphere containing the orbit of interest, and are provided by geographical position above the Earth at the chosen altitude. In this paper, a major improvement was introduced with respect to the previous model concerning the filtering of incoming cosmic rays hitting the upper atmosphere. This more accurate estimation of neutron albedo is of prime importance for the radiation belts modelers because it constitutes the main source of protons >40 MeV of the inner radiation belt.