Accession Number : ADD015708

Title :   Background of the Invention.

Descriptive Note : Patent Application, Filed 30 Nov 92,

Corporate Author : DEPARTMENT OF THE NAVY WASHINGTON DC

Personal Author(s) : Buess, M L ; Garroway, A N ; Yesinowski, J P

Report Date : 30 Nov 1992

Pagination or Media Count : 33

Abstract : Acoustic ringing and adverse effects from variations in the NQR detection of explosives and narcotics are minimized or eliminated. A specimen is irradiated with a modified steady state steady state free precession (SSFP) pulse sequence which combines a phase-alternated pulse sequence (PAPS) with a non-phase-alternated pulse sequence (NPAPS). The resulting signals from the PAS and NPAS may then be coadded to cancel out the FID contributions to the signals. By canceling out the FID contributions to the signals, the effects of probe ringing and other extraneous responses, as well as the effect of temperature variation, are minimized or removed. The present method is especially effective in the detection of explosives and narcotics having 14N or 35,37Cl nuclei. A steady state free precession pulse which is especially useful with the method of the present invention is the strong off-resonance comb (SORC). In another embodiment of the invention, the effects of probe ringing can also be minimized or removed by repeating the detection procedure at a frequency which is sufficiently off-resonance so that only frequently independent effects, such as probe-ringing, can be observed

Descriptors :   *PATENT APPLICATIONS, *ACOUSTIC DETECTION, RINGS, EXPLOSIVES, NARCOTICS, STEADY STATE, PROBES

Subject Categories : Acoustic Detection and Detectors

Distribution Statement : APPROVED FOR PUBLIC RELEASE