Design of a multi-shell portable neutron spectrometry system based on indium foil detectors

A portable neutron spectrometry system was designed based on thermal neutron detectors embedded in concentric polyethylene spherical shells. The system is flexible and can accommodate the use of either active or passive neutron detectors in different configurations. In this work, the response matrix of the system with In-115 foil detectors was calculated with MCNP5 v.1.6. Activation foils were chosen as an ideal detector for the planned use of the system in medical accelerator environments. Calculations were performed using ENDF/B VII.0 and ENDF/B VIII.0 data libraries. The response functions calculated with the two libraries differ by as much as 11.6% in the thermal energy region for the largest moderator. A sensitivity analysis was also performed to evaluate the effect of main design parameters on the response matrix. •A portable neutron spectrometry system (PNSS) that can accommodate neutron detectors in various configurations is designed.•The current work focused on indium activation foils due to its advantages as a passive thermal neutron detector.•Response functions calculated with ENDF/B VIII.0 and ENDF/B VII.0 deviate by as much as 11.6% for the largest moderator.•The effect of relevant design parameters on the PNSS response matrix is negligible within a certain range.•PNSS provides an alternative flexible configuration for Bonner sphere spectrometers.