Attenuation curves in concrete of neutrons from 100-400 MeV per nucleon HE, C and NE ions (original) (raw)

Data on transmission of neutrons in concrete generated by heavy ions of intermediate energies (of typically up to 1 GeV per nucleon) are of interest for shielding design of accelerators for use in both the research and in the medical field. The energy distributions of neutrons produced by ions of different species (from He to Xe) striking various targets at energies from 100 to 800 MeV per nucleon were recently measured by Kurosawa et al. in the angular range 0º -90º. These spectra were used as input data for Monte Carlo simulations performed with the FLUKA code to determine source terms and attenuation lengths in ordinary concrete. Here calculations are presented for 100 MeV/u helium ions on a Cu target, 100 MeV/u carbon ions on C and Cu, 100 MeV/u neon ions on Cu and Pb, 400 MeV/u carbon ions on C, Al, Cu and Pb. The results include the contributions of all secondaries. Some of the resulting attenuation curves are best fitted by a double exponential function rather than the usual single one. The effect of various approximations introduced in the simulations is discussed.