Neutron Energy Spectra and Dose Equivalent Rates from Heavy-ion Reactions below 20 Mev/u Using the Phits Code *

Neutron energy spectra from 6.25 MeV/u C ions incident on a copper target, 10 MeV/u C ions incident carbon, copper, and lead targets, and O ions incident on a copper target have been calculated using the Quantum Molecular Dynamics model (QMD) [1] coupled to the Generalized Evaporation Model (GEM) [2] in the Particle and Heavy Ion Transport Code (PHITS) [3]. In particular, the influence of the “switching time”, defined as the time when the QMD calculation stops and the GEM calculation begins, was studied. The calculated neutron energy spectra obtained using a value of 100 fm/c agree well with the experimental data from reactions on Cu and Pb targets, but not so for the 10 MeV/u C+C reaction. We have also used PHITS to simulate an experimental study by Ohnesorge et al. [4], by calculating neutron dose equivalent rates from 3-16 MeV/u C, O and Ne beams incident on Fe, Ni and Cu targets. The calculated neutron dose equivalent rates agree very well with the data.