Neutron ambient dose equivalent from 5 MeV/u 10,11B, 12,13C and 16,18O projectiles incident on a thick Al target

The neutron ambient dose equivalent has been measured from 10B, 11B, 12C, 13C, 16O and 18O projectiles of energy 5 MeV/amu incident on a thick Al target at 0°, 30°, 60° and 90° with respect to the beam direction using a conventional dose equivalent meter. The calculated results obtained using previously reported empirical relations do not reproduce the experimental data. The results obtained from the PACE nuclear reaction code are closer to the experimental data as compared to the various empirical expressions. The ratio of the increase in the dose rates when the projectile is changed from the lighter to the heavier isotopes is fairly reproduced by most of the empirical formulations and the PACE code. A previously reported relation for the slope parameter is used to predict the directional distribution of the neutron dose for the projectiles used in this study. The calculated doses are lower than the experimental results in the forward directions but agree within the uncertainties at the backward directions. A new set of projectile-based parameters have been derived from the present experimental data which can be used in an empirical formulation.

► Neutron H*(10) from 5 MeV/amu ions depend on neutron to proton (n/p) ratio. ► Higher n/p leads to larger neutron H*(10). ► Existing empirical relations are unable to predict the measured H*(10). ► PACE code reproduces the H*(10) at the 90° but not at 0°. ► New parameters are given to calculate the neutron H*(10).