Remote Detection of Ammonium Nitrate by Nuclear Quadrupole Resonance using a Portable System

This paper shows the advances in the development of a portable system for remote detection of ammonium nitrate by nuclear quadrupole resonance. Three different probe coils were constructed and compared in terms of the signal intensity and the noise rejection under different environments, using the developed system. For the gradiometer probe coil, which showed the best performance in terms of noise rejection, the ‘90°’ equivalent pulse was determined for different distances between the sample and the probe, and the remote detection of ammonium nitrate was achieved not only in a shielded room inside the laboratory, but also in the outdoors. The system was capable of detecting 200 g ammonium nitrate at 3 cm apart from the probe within 12 s with a steady-state free precession pulse sequence. The comparable results were obtained with a free induction decay sequence in 25 min for the total acquisition time. The compact size of the system will allow the applications for the substance detection in the outdoors especially for landmines made from ammonium nitrate and fuel oil mixtures instead of military explosives.