Modelling of the neutron and light-ion components of the field inside the International Space Station: Support for PADC neutron dose measurements within the HAMLET project

ABSTRACT Monte Carlo simulations have been performed to provide estimates of the secondary light-ion and neutron fluence-energy distributions inside the International Space Station (ISS) that result from cosmic rays impinging on its hull. A greatly simplified model of the ISS was employed, with the work performed to supply approximate results in support of measurements made using PADC neutron dosemeters, which were located on the anthropomorphic MATROSHKA phantom and undertaken as part of the HAMLET project (Reitz et al , 2009). The components of the secondary particle field depend on the exposure and orbit parameters of the ISS and are associated with large uncertainties, but in terms of fluence are shown to be dominated by neutrons; data for the 2007-2009 MTR-2B mission are presented explicitly, for which the phantoms were located inside the ISS close to solar minimum. The secondary particle field resulting from exposure to cosmic photons was also evaluated, but shown to be negligible for the purposes of PADC neutron dosimetry.