Measurement of a 9 kg C4 simulant target dissimulated at 26 cm in depth in an iron-filled container. Panel (b) displays the gamma spectrum for materials located at a distance between 220 and 230 cm from the neutron generator, which is the position of the C4 target (the peak at 200 cm corresponds to the container wall)selected in red dashed lines on panel (a). The “Elemental count fractions” displayed in panel (c) are coming from the unfolding procedure, which leads to the fit curve in red in panel (b).