Fast Neutron Dose Equivalent Rates in Heavy Ion Target Areas

At heavy ion accelerators, personnel access to areas near the target is sometimes important for successful performance of experiments. Radiation levels determine the amount of time that can be spent in these areas without exceeding maximum permissible exposures. Inasmuch as the fast neutrons contribute the major part of the Rem dose rates in these areas, knowledge of the fast neutron levels is important for planning permissive entry to target areas. We have measured fast neutron dose rates near thick medium mass targets bombarded with beams of C, N, O, and Ne ions. Beam energies ranged from 3 to 16 MeV/ amu. Dose rates (mrem/h) 1 meter from the target 90 degrees from the beam direction range from ~ 0.05 at 3 MeV/amu to ~ 50 at 16 MeV/amu. These data should be helpful in planning permissive entry to heavy ion target areas.