USA As Represented by Secretary of the Navy

Allen M Garroway

Joel B Miller

Michael L Buess

James P Yesinowski

Roy P Lindquist

A method and apparatus for screening samples to determine which samples include a target material. Generally, the samples are pre-screened to determine which of the samples have a piezoelectric resonance when irradiated with an electric field, to thereby indicate the presence of the target material. The samples that have the piezoelectric resonance are then further screened by a different process to confirm the presence of the target material. For example, samples that have the piezoelectric resonance are further screened for a specific nuclear quadrupole resonance (NQR), a specific nuclear magnetic resonance (NMR) or a specific visual characteristic, to confirm the presence of the target material in the sample. The apparatus and method can be used, for example, to search luggage at ports of entry for the presence of cocaine hydrochloride or heroin hydrochloride.

Method and apparatus for detecting a target material in a sample by pre-screening the sample for piezoelectric resonance

An NQR apparatus for irradiating a sample with an RF magnetic field and for determining the presence of a target material by detecting an NQR signal includes a transmitter for generating an output signal at a selected frequency, a receiver for detecting the NQR signal, a probe, and a switch coupling the receiver and the transmitter with the probe for alternately connecting and disconnecting the receiver and the transmitter to the probe, thereby switching the NQR apparatus between a transmitting mode and a receiving mode. The probe consists of a resonant circuit that includes a coil array. The coil array includes a first figure-8 coil and a partially overlapping, second figure-8 coil for generating an RF magnetic field in a detecting region outside the probe. The first and second coils together alternate between a transmitting mode for irradiating a sample in the detecting region with an RF magnetic field, and a receiving mode for detecting an NQR signal indicative of the presence of a target material in the sample. The coil array produces a highly uniform rotating RF magnetic field, increasing its detection sensitivity and enhancing its ability to separate magnetic resonance signals from piezoelectric and acoustic ringing.

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Fort Washington, MD, United States of America

Allen M Garroway