Neutron yield from a 13C thick target irradiated by protons of intermediate energy

Angular and energy distributions of neutrons produced by the interaction of protons of 20, 25 and 40 MeV in 13C targets, in which they are stopped, have been measured by time-of-flight and activation methods. Neutron yields are compared with a Monte-Carlo based model prediction and with the experimental neutron yields of proton and deuteron beams impinging on natural carbon thick targets. The gain with respect to p+p+12C is only sizeable at the lowest proton energies. The neutron yield curve of p+p+13C versus proton energy is definitely lower than the one of d+d+12C, in contrast to the suggestion by an earlier published measurement at 30 MeV.