Double differential cross sections of neutron production by 135 and 180 MeV protons on A-150 tissue-equivalent plastic

The double differential cross sections (DDXs) of neutron production by 135 and 180 MeV protons were measured to obtain benchmark data for calculating neutron doses in proton therapy. The incident proton energies correspond to those of protons decelerating in a patient. An A-150 tissue-equivalent plastic was used as the target. The measured DDXs were compared with those calculated using PHITS, FLUKA, and Geant4. The calculated DDXs were found to be underestimated compared with the measured ones, especially at forward angles. In proton therapy, exposure evaluations using one of these simulation codes would underestimate the neutron dose.