Novel approaches in nuclear magnetic/quadrupole resonance techniques for explosives detection

Abstract

Nuclear Quadrupole Resonance (NQR) and Nuclear Magnetic Resonance (NMR) are very prospective methods of the bulk detection of explosives and illicit substances. Both methods are based on use of apparatus, which are very similar technically and in some cases could be applied simultaneously. We report our experimental works on NQR/NMR techniques for explosives detection. In addition of classical single-frequency NMR/NQR we also explored a potential of double resonance (NMR/NQR) and multifrequency NQR approaches as well as magnetic resonance imaging (MRI) techniques. Multifrequency (two/three) NQR technique involves various (two or three) transitions in the three energy level system of N-14 nuclei. It is shown that this kind of NQR technique allows filtering spurious signal after radiofrequency pulses and increases the sensitivity of NQR detection. On the other hand, various liquids can be detected using NMR. We shown that reliable discrimination among extended set of liquids reveal a need in use of additional NMR parameters or complimentary techniques. It is demonstrated that MRI is also feasible method for detection of explosive/illicit liquids.