Characterization of a Gold-and-Indium Dual-Activation-Foil-Based Bonner Sphere System

A gold-and-indium dual-activation-foil-based Bonner sphere system (BSS) for neutron spectral measurements was investigated. A customized polyethylene holder was designed to simultaneously accommodate one indium foil and one gold foil placed orthogonally to each other. The holder, which fits into the center of a Bonner sphere, resembles a standard ⁶LiI(Eu) detector. The response of the dual-activation-foil-based system was calculated using the MCNPX code with different activation cross-section libraries (ACTL and ENDF/VI for gold foils and ACTL and 532DOS2 for indium foils). To verify and correct the calculated response functions, measurements were performed using ²⁵²Cf and AmBe neutron sources of known strengths. Working response functions were determined for neutrons with energies ranging from thermal to 20 MeV by applying correction factors from measurements in well-characterized beams to the Monte Carlo-calculated response functions. Measured data were successfully unfolded with the corrected response functions and found to be in good agreement with the known spectra.