SNM detection based on X-ray scattering

We present in this paper the study ofspecial nuclear materials(SNM) detection method based on Pair production and Compton scattering Atomic Number Identification (PCANI) technique. PCANI, a technique that uses the information of annihilation and Compton scattered photons from target is applied at first to achieve the atomic number(Z) identification. Because of the Z² and Z¹ relationship of pair production cross section and Compton scattering cross section with Z, the ratio of 511keV γ number versus scattered γ number is proportional to Z, which gives us a chance to know what the atom is. PCANI is sensitive to high Z materials so it is not difficult to separate heavy metal from common goods that are mixed together in cargoes. The results of Monte Carlo calculations show that PCANI method can identify elements effectively, especially for high Z materials such as SNM. An experimental facility based on 7 MeV LINAC has been setup for feasibility study. Annihilation and backscattered photons have been observed with LaBr₃(Ce) detector. Preliminary results show that high Z materials can be discriminated successfully.