NRL developed an explosive and contraband detector that uses nuclear quadrupole resonance (NQR) to detect nitrogenous explosives or narcotics carried in luggage, mail, small cargo, or on a person.

NQR detector coil

The NQR detector coil is loaded with a large suitcase. The metal cabinet with door provides shielding from electromagnetic interference.

Advantages of the NQR system include:

  • sensitivity "threat" quantities of RDX-based explosives can be detected in suitcases;
  • specificity because the NQR resonance frequencies are highly specific to chemical structure, signals from other nitrogenous materials do not interfere;
  • throughput inspection time is approximately 6 seconds for suitcases;
  • no magnets are required, therefore, magnetic media are not damaged;
  • radio frequency (RF) field strengths are low, minimizing RF exposure to operators and allowing the possibility of examining people;
  • minimal operator intervention and interpretation -- an alarm is triggered when the NQR signal from an explosive within the interrogated volume exceeds a preset threshold; and
  • inherently simple and low cost; unit comprises RF electronics and a PC system.

This NQR approach has been demonstrated for RDX-based explosives in a laboratory setting. The technology can be extended to detect other nitrogenous explosives as well as certain drugs of abuse. As envisioned, such an NQR explosives detector could be useful in airports and other fixed site installations.