Optimization of the limits of detection & quantitation on pulsed compact neutron systemsthe cases of chlorine & sulfur in cementitious media

The use of pulsed compact neutron systems to implement energy-resolved prompt-gamma activation analysis is herein assessed in detail for the quantitative and non-intrusive detection of chlorine and sulfur in cementitious media, two exogenous contaminants commonly found in buildings, civil infrastructures, or archeological artefacts. To this end, we have examined the current capabilities of the RIKEN RANS-I pulsed source across its neutron-energy spectrum using its room-temperature moderator. We achieve up to a threefold improvement relative to previously reported limits of detection via the selective use of the γ-ray yield in the wavelength interval 2-4 Å. Under these conditions, measurement times 1 of a few minutes are sufficient to attain sensitivities in the sub-millimol%, and this figure can be improved further via the optimization of the existing detection system. Monte Carlo simulations of a validated model of RIKEN RANS-I show that order-of-magnitude gains in sensitivity are also within reach via the use of cold moderators, such as those based on solid methane or mesitylene. Altogether, these developments would enable limits of detection in the µmol% range.