Electricity: measuring and testing – Particle precession resonance – Using a magnetometer
Patent
1993-09-30
1995-10-10
Arana, Louis
Electricity: measuring and testing
Particle precession resonance
Using a magnetometer
324300, G01V 300
Patent
active
054573858
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to methods and apparatus for detecting the presence of specific substances containing quadrupolar atomic nuclei, in larger articles, by direct observation of nuclear quadrupole resonance (NQR) effects.
BACKGROUND OF THE INVENTION
Quadrupolar nuclei have nuclear spin quantum numbers greater than one half. Common nuclei of this Kind include .sup.7 Li, .sup.9 Be, .sup.11 B, .sup.14 N, .sup.23 Na, .sup.27 Al, .sup.35 Cl, .sup.39 K, .sup.55 Mn, .sup.59 Co, .sup.75 As, .sup.79 Br, .sup.81 Br, .sup.127 I, .sup.197 Au, .sup.209 Bi and many others--this list should not be interpreted in any limiting way, it is given simply to note the potential range of substances which might be detectable by this technique.
In the sub-molecular environment of compounds or crystals, the nature and disposition of the adjacent electrons and atomic nuclei produce electric field gradients which modify the energy levels of any quadrupolar nuclei, and hence give rise to transition frequencies, to such an extent that measurements of these transition frequencies and/or relaxation time constants can indicate not merely the nuclei which are present but also their chemical environment.
NQR measurements have the great advantage that they do not require the sample to be placed in a strong magnetic field, and therefore do not require the large, expensive and sample-size limiting magnet structures which are needed for nuclear magnetic resonance (NMR) measurements. It should be noted that the rules governing NQR effects are so significantly different from the rules controlling NMR effects that practices and principles established in NMR studies do not necessarily apply in NQR work.
United Kingdom Patent Application No. GB-A-2159626 discloses a nuclear magnetic resonance spectrometer comprising: a means for producing a static magnetic field; a plurality of transmitter/receiver coils placed in the magnetic field; a means for repeatedly producing an RF pulse containing the resonance of a nuclide to be observed; a switching means for allowing the RF pulses to be successively supplied to the coils and applied to a sample under examination; a receiver circuit for picking up the resonance signals detected by the coils after the application of the RF pulses; and means for separately storing the data about the picked up resonance signals for the different coils. Means is also provided for moving the sample relative to the coils, or vice versa.
U.S. Pat. No. 4,887,034 describes methods by which the presence of various drugs or explosives may be detected indirectly through the interaction of NQR and NMR effects, but these methods require a strong magnetic field and the presence of NMR nuclei as well as quadrupolar nuclei in the substances to be detected. The strong magnetic field would require relatively large magnets with the added complication that the magnetic field has to be varied between strong and weaker values.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a method of detecting the presence of selected nuclei in an article, including providing an array of excitation devices (preferably coils), causing relative motion between the article and the array in a given direction, and applying excitation pulses to the article via the array to excite the selected nuclei to resonance and detecting via the array the resonance responses thus excited, the excitation devices in the array being disposed such that if viewed in the given direction they would appear to overlap one another.
Hence, if the article is moved in he given direction past the array of excitation devices, a part of the article which passes adjacent the side of one excitation device can be arranged to pass adjacent the center of another excitation device.
The present invention also provides a method for detecting the presence within a larger article of a specific substance containing quadrupolar atomic nuclei wherein tests of parts of the article are performed by placing the article adjacent to an array of coils
REFERENCES:
patent: 4166972 (1979-09-01), King et al.
patent: 4514619 (1985-04-01), Kugelman
patent: 4514691 (1985-04-01), De Los Santos et al.
patent: 4825162 (1989-04-01), Roemer et al.
patent: 4887034 (1989-12-01), Smith
patent: 4908578 (1990-03-01), Van Liere
patent: 5233300 (1993-08-01), Bvess et al.
WO,A,84/04173 (Southwest Research Institute) 25 Oct. 1984 see p. 4, line 34-p. 6, line 28; see page 19, line 12-line 31.
Journal of Magnetic Resonance, vol. 92, No. 2, 1 Apr. 1991, Orlando, Minn. US pp. 348-362; M. L. Buess et al "NOR Detection Using a Meanderline Surface Coil" see p. 2, line 1-line 33.
Electro Conference Record, vol. 4,24 Apr. 1979, Los Angeles, Calif. US, pp. 1841-1845 J. R. Gonano, "Nuclear Magnetic Resonance . . . " see the whole document.
Shaw Julian D.
Sydney John A.
Arana Louis
British Technology Group Limited
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