Improvement of the calibration database of the EURITRACK tagged neutron inspection system

The EURopean Illicit TRAfficking Countermeasures Kit (EURITRACK) inspection system uses 14 MeV neutrons produced by the D(T,nα) reaction to detect explosives in cargo containers. Reactions induced by fast neutrons inside the container produce gamma rays, which are detected in coincidence with the associated alpha particle, the detection of which allows to determine the neutron direction. The neutron path length is obtained from a neutron time-of-flight measurement, thus allowing to determine the origin of the gamma rays inside the container, while the chemical composition of the target material is correlated with their energy spectrum. Gamma-ray spectra have been collected with the inspection portal equipped with large volume NaI (Tl) detectors, in order to build a database of signatures for various elements (C, O, N, Fe, Pb, Al, Na, Si, Cl, Cu, Zn) with a low energy threshold of 0.6 MeV. The spectra are compared with previous ones, which were acquired with a 1.35 MeV threshold. The new library is currently being tested to unfold the energy spectra of transported goods into elementary contributions. Results are compared with data processed with the old 1.35 MeV threshold database, thus illustrating the improvement for material identification.