Production of helium in iron by proton irradiation

The d-t fusion reactions produce neutron with energies up to 14.1MeV. These neutrons, in addition to producing atomic displacement damage, will induce nuclear transmutation reactions. In particular, helium will be generated at high rate in materials. Since helium is a potent agent in nucleating cavities, the mechanical properties of materials may be affected significantly. It is important, therefore, to determine experimentally the helium accumulation effect on radiation damage of materials under conditions similar to those in a fusion reactor. We indicated that proton beam experiments are a useful tool to study radiation damage by fast neutron in fusion reactor. Productions of both atomic displacement damage and helium in materials have been simulated by computer code. Energy deposition in target materials is also estimated to consider the heating problem. The transmutation calculations indicated that the proton beam experiments imitate satisfactorily the ratios of transmutation rates to displacement rates calculated for the first wall of fusion reactor. Constant concentration of accumulated helium can be achieved across the target thickness. Cooling of target of 1mm thickness could be handled without experimental difficulty in samples in the case of irradiation of 0.1mA/cm² proton beam.