Investigation of Wavelet-Based Enhancements to Nuclear Quadrupole Resonance Explosives Detectors
Nuclear Quadrupole Resonance (NQR) is effective for the detection and identification of certain types of explosives such as RDX, PETN and TNT. In explosive detection, the NQR response of certain 14N nuclei present in the crystalline material is probed. The 14N nuclei possess a nuclear quadrupole moment which in the presence of an electric field gradient produces an energy level splitting which may be excited by radio-frequency magnetic fields. Pulsing on the sample with a radio signal of the appropriate frequency produces a transient NQR response which may then be detected. Since the resonant frequency is dependent upon both the quadrupole moment of the 14N nucleus and the nature of the local electric field gradients, it is very compound specific. Under DARPA sponsorship, the authors are using multiresolution methods to investigate the enhancement of operation of NQR explosives detectors used for land mine detection. For this application, NQR processing time must be reduced to less than one second. False alarm responses due to acoustic and piezoelectric ringing must be suppressed. Also, as TNT is the most prevalent explosive found in land mines, NQR detection of TNT must be made practical despite unfavorable relaxation tunes. All three issues require improvement in signal-to-noise ratio, and all would benefit from improved feature extraction. This paper reports some of the insights provided by multiresolution methods that can be used to obtain these improvements. It includes results of multiresolution analysis of experimentally observed NQR signatures for RDX responses and various false alarm signatures in the absence of explosive compounds.
- Research Organization:
- Oak Ridge National Lab., TN (United States)
- Sponsoring Organization:
- Defense Advanced Research Projects Agency, Arlington, VA (United States)
- DOE Contract Number:
- AC05-96OR22464
- OSTI ID:
- 624024
- Report Number(s):
- ORNL/CP--96389; CONF-980412--; ON: DE98004124; CNN: N00164-97-C-004
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
INCLUDING NUCLEAR AND PARTICLE DETECTORS
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE
CHEMICAL EXPLOSIVES
DETECTION
DIGITAL FILTERS
FREQUENCY ANALYSIS
MILITARY EQUIPMENT
NUCLEAR QUADRUPOLE RESONANCE
PETN
QUADRUPOLE MOMENTS
SIGNAL-TO-NOISE RATIO
SIGNALS
TIME DEPENDENCE
TNT
WAVELET TRANSFORMS