Calculation and Validation of the Response Matrix for a Neutron Multisphere Spectrometer with an Indium Central Detector.

Expansion of accelerator technologies into different application areas brings the need for neutron-field measurements in their vicinity. The measurements of neutron energy spectra and neutron dose rates can be done with the aid of neutron multisphere spectrometers with passive neutron detectors. In addition to the usually used thermoluminescent detectors and gold activation foils, another activation material-indium-can be considered. This paper presents a design of such an indium-based neutron multisphere spectrometer. Its response matrix was calculated with Monte Carlo code MCNP5 in the energy interval from 0.001 eV to about 20 MeV. The response matrix was validated with an Am-Be standard neutron source. MAXED code was used for neutron energy spectra unfolding. The values of the neutron fluence rate and neutron ambient dose equivalent rate in a reference point were calculated. The properties and advantages of indium for use in neutron multisphere spectrometry are discussed.