Experimental gamma coincidence spectra recorded in prompt gamma neutron activation analysis

A feasibility study of gamma-gamma coincidence measurements in prompt gamma neutron activation analysis is carried out experimentally with a pulsed DT neutron generator, a polyethylene graphite cell and eight large NaI(Tl) scintillators. Detection limits are measured with multidimensional energy spectra created in gamma-gamma coincidence and compared to HPGe detector spectra. With a neutron emisison of 2.5 × 10⁸ n.s⁻¹, the detection limit for sulfur is about 15 g in 20 min, while the detection limit is larger than 200 g when using the HPGe detector spectra. Processing the summ of up to three coincident gamma-ray energies highlights useful signal for a dysprosium sample, and allows for detecting permanent magnets containing 4% mass dysprosium within a rotor mock-up composed of stainless steel.