Development of a compensation system for thermal neutron measurements based on Cd(Cu)-covered NaI(Tl) detectors

A compensation system based on NaI (Tl) detectors and cadmium sheet was proposed for thermal neutron detection in the neutron/gamma field. The system consisted of two identical NaI (Tl) detectors covered with copper and cadmium sheets, respectively. The Cd-covered NaI (Tl) recorded the prompt gamma rays produced by the ¹¹³Cd (n, γ)¹¹⁴Cd reaction, while the Cu-covered structure "rejected" the background gamma rays. The moderated thermal neutron fluxes at different distances from an Am-Be neutron source, calibrated by the activation foil method, were investigated using the compensation system. The thermal neutron detection efficiency of this compensation system was compared to those obtained by the CdZnTe detector and He-3 proportional counter. The feasibility of the compensation system used as a thermal neutron counter was demonstrated by the obtained results.