Measurements of secondary neutrons produced from thick targets bombarded by high-energy helium and carbon ions

The angular and energy distributions of neutrons produced by 100 and 180 Me V/nucleon He and 100 180 and 400 MeV/nucleon C ions stopping in thick C, Al , Cu, and Pb targets were measured wing the Heavy-Ion Medical Accelerator i n Chiba of the National Institute of Radiological Science (NIRS), Japan. Th e neutron spectra in the forward direction have Broad peaks of similar to 6 0 to 70% of the incident particle energy per nucleon due to the break-rep p rocess, and they spread up to almost twice the projectile energy per nucleo n. The neutron spectra are similar for the same incident energy of 100 MeV/ nucleon for both He and C ions. The phenomenological hybrid analysis, based on the moving source model and the Gaussian fitting of the break-lip proce ss, could well represent the measured thick target neutron spectra. The exp erimental results are also compared with the calculations using the heavy-i on code, and the calculated results agree with the measured results within a factor of 2 margin of accuracy. This systematic study on neutron producti on from thick targets by high-energy heavy ions is the first experimental w ork performed by NIRS and will be useful for designing the shielding for th e high-energy heavy-ion accelerator facility.