Abstract:

Detection of explosives is a challenge topic. A number of detection techniques have been developed for it. Among them the nitrogen-14 nuclear quadrupole resonance (¹⁴N-NQR) technique gives the best detection of explosives, which is able to chemically fingerprint specific explosives.

The principle of NQR is the same as that of the well known nuclear magnetic resonance (NMR). The NQR has the advantage of making use of the electric field internally produced in solids, rather then the strong magnetic field externally applied in NMR. Almost all explosives contain ¹⁴N, which is non-spherically symmetric and has a quadrupole moment of ~0.015 b. The interaction of the quadrupole moment with the electric field causes energy level splitting. The ¹⁴N-NQR technology exploits the transitions between these energy states to detect the presence of explosives. Each transition occurs at a very specific resonant frequency giving quadrupole resonance. Since the electric field depends strongly on the unique chemical signature of solids, each explosive is characterized by its own NQR frequency. Therefore, the ¹⁴N-NQR provides a way of the so called DNA detection and identification of explosives with low false alarm rate, high sensitivity, fast speed and easy operation. The ¹⁴N-NQR screening systems of explosives have been developed and used at airports for aviation security purpose.

This presentation describes the principle and applications of ¹⁴N-NQR to detections of explosives, landmines, etc and the research activities at China Institute of Atomic Energy (CIAE). Several ¹⁴N-NQR screening systems have been manufactured for the detection of explosives RDX, PETN and HMX in luggage and parcels, and the detection of explosive TNT and the detection of landmines have been investigating at CIAE. An overview of the present status of researches on the detections of explosives and landmines at CIAE will be given.