Implementation of a low energy neutron transport module into a Monte Carlo hadronic shower code and its applications for accelerator shielding problems

Abstract

The high energy particle cascade code FLUKA (version 1990 of CERN) was extended down below the usual 50 MeV cutoff to account for emission and transport of the lower energy neutrons. This was accomplished by adopting the evaporation module extracted from the HETC code and the multigroup neutron collision subroutine extracted from the MORSE code to FLUKA program environment, and by slightly modifying sampling of the excitation energy and of the intranuclear cascade energy in the EVENTQ inelastic interaction generator, following the experimental data and phenomenological suggestions published elsewhere. The resulting FLUNEV code is briefly described; common and distinct features of the CALOR and HERMES systems which can be used alternatively for simulation of the neutrons originated from hadronic cascades are also mentioned. Recent applications of our program to shielding problems at high energy proton accelerators are reviewed and new comparisons are presented with measurements of low energy neutron spectra in collider tunnels.