Physical characterization of neutron beams produced by protons and deuterons of various energies bombarding beryllium and lithium targets of several thicknesses

Protons of 35 and 65 MeV and deuterons of 35 MeV were used to bombard beryllium and lithium targets of various thicknesses. Four types of experiments were conducted in order to characterize the neutron fields. They were (1) central axis depth dose measurements in a water phantom, (2) dose buildup at small depths in tissue equivalent plastic, (3) microdosimetric measurements and LET distributions, and (4) neutron yields and energy spectra at an angle of 0 deg. The results generally show that (a) the central axis depth doses for the 35 and 65 MeV particles roughly approximate those of ⁶⁰Co and 4 MeV bremsstrahlung photons, respectively, (b) the neutron dose buildups are more rapid than those of the above mentioned photon sources, (c) the microdosimetric spectra show differences which are consistent with the measured neutron energy spectra, and (d) p–Li compared to p–Be neutron spectra have larger high energy particle flux for similar target and beam configurations.