Measurements of spallation neutrons from a thick lead target bombarded with 0.5 and 1.5 GeV protons

Double differential neutron spectra from a thick lead target bombarded with 0.5 and 1.5 GeV protons have been measured with the time-of-flight technique. In order to obtain the neutron spectra without the effect of the flight time fluctuation by neutron scattering in the target, an unfolding technique has also been employed in the low energy region below 3 MeV. The measured data have been compared with the calculated results of NMTC/JAERI-MCNP-4A code system. It has been found that the code system gives about 50% lower neutron yield than the experimental ones in the energy region between 20 and 80 MeV for both incident energies. The disagreements, however, have been improved well by taking account of the in-medium nucleon-nucleon scattering cross sections in the NMTC/JAERI code. (author) 11 figs., 2 tabs., 27 refs