SYSTEM AND METHOD FOR CONTRABAND DETECTION USING NUCLEAR QUADRUPOLE RESONANCE

A system for detecting a target substance within a class of explosives and narcotics containing quadrupolar nuclei through the use of nuclear quadrupol e resonance (NQR). The system applies an RF signal to a coil (34) to excite the substanc e under test. If the target material is present, an NQR signal will be picked up by the same coil. That signal is compared with known NQR signals in frequency and amplitude. A signal is displayed in an appropriate way if a threshold value of the NQR signal is equalled or exceeded. The empty coil is statically tuned by means of adjusting the location or capacitance values, or both, of static tuning capacitors (102) in the coil. The coil is tuned after the specimen is inserted into the coil by means of an auto-tune feature (36). Effective RFI shielding (37) is provided to prevent external contaminating signals from being detected by the coil and to prevent RF signals from escaping from the scanner. The invention also includes the method for performing tests with the system.