The on-line prompt gamma neutron activation analysis (PGNAA) system is used to measure a series of prepared experimental samples to obtain the prompt characteristic γ -rays of the elements Ca, Fe, Si, Al, Mg and S in the examples of SiO 2 , Al 2 O 3 , MgO, CaO (powder), CaO (block), CaCO 3 , Fe 2 O 3 , Fe 3 O 4 and S. The γ -ray energies are: