Measurement of Neutron Yields from 500 MeV/u Helium Ions Bombarding a Thick Lead Target

The secondary neutron yields induced by 500 MeV/u ⁴He ions bombarding a thick lead target at the 0-, 12-, 30-, 45-, and 60-deg directions have been measured at the Heavy Ion Research Facility in Lanzhou using the time-of-flight method. The measurement was compared with GEANT4, FLUKA, and PHITS simulations. The result shows that the three Monte Carlo codes exhibit distinct capabilities and limitations in predicting thick target neutron yields in specific energy and spatial ranges. This study provides fundamental data support for cosmic ray shielding, design of accelerator-driven subcritical systems, and other related fields.