DETECTING HAZARDOUS MATERIALS IN CONTAINERS UTILIZING NUCLEAR MAGNETIC RESONANCE BASED MEASUREMENTS

摘要

A method of detecting hazardous materials in containers utilizing nuclear magnetic resonance (NMR) technology. The presence of precursors (e.g., H202) and/or nitrogen in the liquid in the container is determined by placing the container in a static magnetic field, exciting the container with electromagnetic pulses having a frequency corresponding to proton NMR and 14N NMR, and receiving radio frequency (RF) signals through a probe. The excitation pulses are configured to enable detection of the presence of precursors and nitrogen in the container, and may comprise a sequence of short RF pulses. The presence of nitrogen and/or explosive precursors is determined by detecting and evaluating NMR measurement signal amplitudes and relaxation times from the received RF signals. An apparatus comprising a magnet that generates a magnetic field and a probe that generates RF pulses and receives NMR measurement signals from the sampled container in accordance with the aforementioned method.

主权项

1. A method for detecting hazardous materials, the method comprising:
positioning a non-metallic container holding a liquid sample in a static magnetic field; applying a first nuclear magnetic resonance (NMR) pulse sequence to the liquid sample having a frequency corresponding to a proton NMR frequency in the static magnetic field; receiving a first plurality of NMR measurement signals from the liquid sample responsive to the proton NMR frequency; measuring relaxation times of the plurality of NMR measurement signals received, wherein said measuring comprises measuring spin-lattice relaxation times (T1 and effective multi-pulse sequence signal decay time T2eff and measuring T2eff times having different echo times (TE); applying a second NMR pulse sequence to the liquid sample having a frequency corresponding to a 14N NMR frequency in the static magnetic field; receiving a second plurality of NMR measurement signals from the liquid sample responsive to the 14N or the proton NMR frequency; measuring signal amplitudes of the second plurality of NMR measurement signals; calculation ratios of the T1 times and the T2eff times; comparing each of the ratios determined from the first plurality of NMR measurement signals received to corresponding predetermined thresholds; generating an alarm indication if any of the ratios exceeds the corresponding predetermined threshold that indicates the presence of explosive precursors in the liquid sample; after generating the alarm indication, applying a third NMR pulse sequence having a frequency corresponding to a proton NMR frequency to the liquid sample providing a higher sensitivity scan; receiving a third plurality of NMR measurement signals; and measuring additional relaxation times and signal amplitudes of the third plurality of NMR measurement signals received.