ESTIMATION OF NEUTRON YIELDS FROM THICK TARGETS BY HIGH-ENERGY HE-4 IONS FOR THE DESIGN OF SHIELDING FOR A HEAVY-ION MEDICAL ACCELERATOR

For the design of shielding for a high energy heavy ion medical accelerator, neutron yields differential in energy and angle for thick copper and beryllium targets under He-4 ion bombardment were estimated with the intranuclear-cascade evaporation Monte Carlo code HETC/KFA. The calculations were made for He-4 ion energies from 100 to 800 MeV/nucleon, where only one earlier report on experimental data exists for 710 MeV (177.5 MeV/nucleon) He-4 ions. The neutron spectra and the angular distributions could be fitted well to simple exponential-type formulas. The total neutron yield per one He-4 particle is about 5 times larger than the yield per one proton for projectile energies of 225 and 500 MeV/nucleon.