Measurement of secondary neutron spectra induced by 480 MeV proton and 430 MeV/u 4He beams with a thick aluminum target

Knowledge of the characteristics of secondary neutrons produced by the interaction ofGalactic Cosmic Radiation with spacecraft shielding materials is becoming increasingly importantfor predicting and mitigating biological risks of space explorers during deep-space travel. Hadronaccelerators for medical applications are well suited to reproduce part of the conditions found indeep-space in terms of ion species and energies. The objectives of this work are to measure thesecondary neutron spectra produced by proton and helium ion beams hitting an aluminum target withenergies that correspond to the Galactic Cosmic Radiation peak during solar minimal activity andto validate and compare physical models of Monte Carlo simulations. Neutron spectra were measuredwith the extended-range Bonner sphere system NEMUS at two positions, 0° and 90° relative to thedirection of the primary ion beam. The experimental setup consisted of 480 MeV proton and 430 MeV/u 4He beams colliding with a 30×30×63.5 cm3 aluminumtarget. The experimental neutron spectra were analyzed using the MAXED unfolding code and comparedto several Monte Carlo simulation codes. The results show deviations in terms of the shape of theneutron energy distributions ranging between 1% and 14% and of the integral quantities offluence and ambient dose equivalent ranging between 1% and 5.2%.