Benchmark Experiments for Bulk and Maze Shielding Using Activation Detectors with 24-GeV/c Protons at CERN/CHARM

Measurements of high-energy neutrons through shield penetration and maze streaming were performed at the Conseil Européen pour la Recherche Nucléaire (CERN) High-energy Accelerator Mixed-Field (CHARM) facility. The protons of 24 GeV/c were injected onto a 50-cm-thick copper target and the released neutrons were transmitted through shields and a maze in the facility. The transmitted neutrons in the shield and maze were measured using activation detectors placed behind various materials and thicknesses of the shields and at several locations in the maze. From the radionuclide production rates in the activation detectors, the attenuation profiles though the shield thickness and along the maze were obtained for the reactions of ²⁰⁹Bi(n,xn)^210-xBi(x = 4–9), ²⁷Al(n,α)²⁴Na, ¹¹⁵In(n,n’)^115mIn, and ¹²C(n,2n)¹¹C. Monte Carlo simulations were performed with three codes, PHITS, FLUKA, and GEANT, which had good agreement with the measurements within a factor of 2 for the production rates.