Projectile dependence of radioactive spallation products induced in copper by high-energy heavy ions

Abstract

Irradiation experiments were performed at the HIMAC (heavy-ion medical accelerator in Chiba) facility, National Institute of Radiological Sciences. The radioactive spallation products in a thick Cu target were obtained for 230 and 100 MeV/nucleon Ne, C, He, and p ions. The gamma-ray spectra from irradiated Cu pieces inserted into the composite Cu target were measured with a high-purity Ge detector. From the gamma-ray spectra, we obtained the variation of radioactive yields with depth in the Cu target and the mass-yield distribution of nuclides produced on the surface. The results show that the cross sections strongly depend on the projectile mass and, consequently, on the mass number difference between Cu and the produced nuclides. The most important feature of the present data is the extraction of the energy dependence of the cross sections. The measured cross sections were fitted to a modified form of Rudstam's semiempirical formula in order to evaluate the cross sections of unmeasured nuclides. These estimated cross sections were added to the experimental yields for each mass number and the total mass yield and isobaric charge distributions, and the slope of the mass-yield distribution were obtained.