Neutron activation and prompt gamma intensity in Ar/CO₂-filled neutron detectors at the European Spallation Source

Monte Carlo simulations using MCNP6.1 were performed to study the effect of neutron activation in Ar/CO₂ neutron detector counting gas. A general MCNP model was built and validated with simple analytical calculations. Simulations and calculations agree that only the ⁴⁰Ar activation can have a considerable effect. It was shown that neither the prompt gamma intensity from the ⁴⁰Ar neutron capture nor the produced ⁴¹Ar activity have an impact in terms of gamma dose rate around the detector and background level. - Highlights: • Effect of neutron activation on argon based detector counting gas studied. • Dataset collected for neutron activation and prompt gamma production MCNP simulation. • Generally applicable activity and prompt photon emission data is given. • The activity emission from the studied continuous flow detectors is negligible. • The increase of background from neutron induced gamma radiation is negligible.