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WO2004068159A1 - Appareil et procede de detection de signaux de resonance nucleaire quadripolaire en presence de bruit incoherent - Google Patents

Appareil et procede de detection de signaux de resonance nucleaire quadripolaire en presence de bruit incoherent Download PDF

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Publication number
WO2004068159A1
WO2004068159A1 PCT/AU2004/000108 AU2004000108W WO2004068159A1 WO 2004068159 A1 WO2004068159 A1 WO 2004068159A1 AU 2004000108 W AU2004000108 W AU 2004000108W WO 2004068159 A1 WO2004068159 A1 WO 2004068159A1
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WO
WIPO (PCT)
Prior art keywords
signals
nqr
detecting
signal
incoherent noise
Prior art date
Application number
PCT/AU2004/000108
Other languages
English (en)
Inventor
Taras Nikolaevitch Rudakov
Paul Warrick Chisholm
Vassili Timofeevitch Mikhaltsevitch
John Harold Flexman
Peter Alaric Hayes
Original Assignee
Qr Sciences Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Qr Sciences Limited filed Critical Qr Sciences Limited
Publication of WO2004068159A1 publication Critical patent/WO2004068159A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/441—Nuclear Quadrupole Resonance [NQR] Spectroscopy and Imaging
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N24/00—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects
    • G01N24/08—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects by using nuclear magnetic resonance
    • G01N24/084—Detection of potentially hazardous samples, e.g. toxic samples, explosives, drugs, firearms, weapons

Definitions

  • This invention relates to an apparatus and method for detecting nuclear quadrupole resonance (NQR) signals from a substance responding to the NQR phenomenon in a sample material irradiated with radio frequency (RF) energy in the presence of incoherent noise.
  • NQR nuclear quadrupole resonance
  • Nuclear quadrupole resonance is a phenomenon widely used for detection and investigation of various chemical compounds. These methods are also successfully used for detecting the presence of specific substances, such as explosives and narcotics.
  • the probe of a pulsed NQR detection system is a device providing interaction between the radio frequency (RF) field of the resonant RF transmitter of the NQR detection system with the target substance, as well as the RF field response from the target substance with the receiving part of the NQR detection system. Strong RF pulses, typically with power of hundreds of watts are used. In practical NQR devices, when detecting specific substances (for example explosives and narcotics), the power of the RF pulses can reach several kW.
  • RF radio frequency
  • FIG. 1 illustrates a conventional system for detecting NQR signals.
  • Transmitter unit 60' and receiver unit 50' are connected to probe 30' through a duplexer and matching circuit 40' which switches probe 30' between the transmit and the receive mode.
  • Transmitter unit 60' generates RF pulses and applies the pulses to probe 30' to excite the response from the substance.
  • the pulses have a frequency corresponding to the resonance frequency of the nuclei of the substance.
  • probe 30' can detect the NQR signal. This signal is received by the receiver unit 50' and processed by control and signal processing unit 70', which also generates all control and RF signals.
  • the detected NQR signals have low intensity, therefore the presence of noise sources can present a serious problem, particularly for the detection of specific substances.
  • the investigated volume can contain objects which when irradiated with strong radio frequency (RF) pulses can become sources of coherent or incoherent noise (or spurious signals).
  • the objects in which strong magneto-acoustic or piezo-electric signals are generated can be sources of coherent noise.
  • these signals are coherent with RF pulses, they are reduced considerably by using a special multi-pulse technique. This technique is extensively developed and described in literature. Unfortunately this technique does not achieve similar good results in cancelling any incoherent noise, sources of which can also be located in the investigated volume.
  • incoherent noise created by external sources is to a great extent diminished by screening the examined volume.
  • Electronic devices such as calculators, cameras, laptop computers or mobile telephones located in the investigated volume can generate incoherent noise.
  • the signals they. generate can have high intensity and are not averaged by the normally used multi-pulsed technique.
  • the NQR signal from a substance is hidden behind the incoherent noise.
  • the incoherent noise can be perceived by the detection system as the NQR signal, which leads to false alarms.
  • RF pulses applied to a probe for NQR signal detection within a volume targeted for NQR signals generate an electro-magnetic field in the volume, which at a certain level induces signals in the circuits of electronic devices. These signals can lead to the re-activation of the circuit even if the electronic device itself is deactivated and the resulting generation of incoherent noise. This does not cause any harm to the devices (if the level of the RF field does not exceed the permissible value). It should be noted that in some cases the RF pulses that cause the re-activation need not be very powerful.
  • the purpose of this invention is to provide for the high probability of NQR signal detection in the presence of incoherent noise.
  • a method for detecting an NQR signal from a volume that may also generate incoherent noise comprising:
  • an apparatus for detecting NQR signals from a substance comprising:
  • a probe comprising a tank circuit including a coil
  • a transmitter for providing and applying powerful RF pulses at the output thereof to the tank circuit
  • a receiving means comprising two channels, one channel for detecting and amplifying signals received in the coil and the other channel for detecting and amplifying signals received in the antenna;
  • processing means for processing the signals amplified by said receiving means to distinguish the presence of any NQR signals from incoherent noise by comparing the amplified signals from both channels.
  • RF pulses from the output of the transmitter may be applied to the tank circuit, where an RF magnetic field is excited in the coil with a sample placed in it. This magnetic field can act on the sample and lead to the excitation of a resonance signal in it. If there is a source of incoherent noise in the coil, then after the RF pulse stops, a resonance signal may appear in the probe and exist there together with incoherent noise. Only incoherent noise is induced in the antenna, as it is positioned orthogonally to the coil. Signals from the output of the tank circuit and antenna may then be simultaneously amplified and detected by the separate receiving channels, after which the signal processing takes place.
  • FIG. 1 (prior art) is a block diagram of a conventional apparatus for detecting a resonance signal in a specimen.
  • FIG. 2 is a block diagram illustrating an NQR apparatus for detecting a resonance signal in the specimen, according to an embodiment of the present invention.
  • FIG. 3 is a flow chart illustrating a method for detecting a resonance signal in the specimen, according to an embodiment of the present invention.
  • FIG. 4 shows the probe, according to an embodiment of the present invention.
  • FIG. 5 shows the probe comprising a solenoid coil and a loop antenna, according to an embodiment of the present invention.
  • FIG. 6 shows the probe comprising a solenoid coil and a saddle shaped antenna, according to an embodiment of the present invention.
  • FIG. 7 shows the probe comprising a saddle shaped coil and a saddle shaped antenna, according to an embodiment of the present invention.
  • FIG. 8 shows the probe comprising a spiral coil system and a loop antenna, according to an embodiment of the present invention.
  • the embodiments of the present invention are directed towards an apparatus and method using NQR for detecting the presence of target substances.
  • FIG. 2 is a block diagram illustrating an NQR apparatus for detecting a resonance signal in the specimen, according to the best mode for carrying out the present invention.
  • probe 30 is connected to channel-1 80 of receiver unit 50 and conventional transmitter unit 60 via duplexer and matching circuit 40.
  • Probe 30 includes tank circuit 10 and antenna unit 20.
  • Tank circuit 10 is tuned to a frequency of interest.
  • Duplexer and matching circuit 40 switch tank circuit 10 between the transmit and receive mode as well as match receiver unit 50 and transmitter unit 60 to tank circuit 10.
  • Antenna unit 20 is connected to channel-2 90 of receiver unit 50.
  • Transmitter unit 60 generates RF pulses and transfers the pulses to tank circuit 10. These RF pulses can excite NQR signals in the specimen under investigation, which is located in probe 30. This signal is amplified and detected by channel-1 80 of receiver unit 50 and is then delivered for further mathematical processing into control and signal processing unit 70, the first input of which is connected with the output of channel-l 80 of receiver unit 50.
  • the signal that appears in antenna unit 20 is amplified and detected by channel-2 90 of receiver unit 50 and is then delivered for further mathematical processing into control and signal processing unit 70, the second input of which is connected with the output of channel-2 90 of receiver unit 50.
  • Control and signal processing unit 70 generates an RF signal, which from its first output is transmitted to one of the inputs of transmitter unit 60 for further formation of the RF carrier of RF pulses and to one of the inputs of channel-1 80 and channel-2 90 of receiver unit 50 as the reference frequency. Control and signal processing unit 70 generates control signals, which are transferred to the inputs of channel-1 80 and channel-2 90 of receiver unit 50 for tuning their parameters. Control and signal processing unit 70 also generates control signals, which are transferred to another input of transmitter unit 60 and prescribe parameters for RF
  • Control and signal processing unit 70 usually consists of a computer, an RF signal source and electronic circuits (for producing control signals), which are not specific for the present invention and are not described here in any detail.
  • FIG. 3 is a flow chart illustrating a method for detecting the resonance signal in the specimen, according to the best mode of the present invention.
  • the process starts in step S100 by determining the presence of incoherent noise in the probe without exciting the NQR signal in the sample.
  • the RF excitation either is not transferred to the coil of the tank circuit at all, or is transferred at a frequency different from the NQR frequency of the target substance. It is desirable that this frequency is close to the NQR frequency of the target substance, but not too close so as not to excite a resonance signal in the nuclei. This excitation can activate electronic appliances that could be located together with the sample.
  • step S110 envisages the adjustment of parameters of the receive system.
  • the two channels of the receive system with one of the channels containing a coil with a sample, and the other one containing an antenna, cannot be made absolutely identical for the purpose of detecting incoherent noise. Therefore the two signals of incoherent noise detected in those two channels usually have parameters that differ a little from each other, and this complicates their further use for diminishing the value of incoherent noise in the resulting output signal.
  • the location and orientation of the possible source of incoherent noise are also significant.
  • step S110 the process moves to step S120, where the RF excitation at the NQR frequency is applied to the tank circuit, which has a sample in its coil.
  • step S130 when the first signal, containing the NQR signal with incoherent noise, and the second signal, consisting of only the incoherent noise, are detected simultaneously.
  • step S110 the process moves to step S120, where the detected first and second signals are used to receive a resulting signal with a lower level of incoherent noise.
  • Transmitter unit 60 generates one or several RF pulses at a frequency different from the NQR frequency and provides the pulses to tank circuit 10 of probe 80.
  • Transmitter unit 60 generates RF pulses on the frequency corresponding to the NQR frequency and provides the pulses to tank circuit 10 of probe 80.
  • Signal processing unit 70 distinguishes the NQR signal from the incoherent noise.
  • the best mode of the present invention two signals are used, one of them containing the NQR signal and incoherent noise, and the other one containing only incoherent noise.
  • the first signal appears in the direction of the exciting magnetic field ie. in tank circuit 10, with the sample placed in its coil.
  • a special antenna also located close to the sample, is used.
  • NMR nuclear magnetic resonance
  • NQR nuclear magnetic resonance
  • FIG. 4 is a diagram illustrating a probe, according to the best mode of the present invention.
  • Probe 30 includes tank circuit 10 and antenna unit 20.
  • Tank circuit 10 includes coil 11 , where the examined specimen is placed, and variable capacitance 12 for tuning to the resonance frequency.
  • Antenna unit 20 contains antenna 21 and matching circuit 22, connected to antenna 21. NQR signal is excited in coil 11 in the direction of axis Y 24.
  • Antenna 21 is aligned in the direction of axis X 23, orthogonal to axis Y 24.
  • FIG. 5 illustrates a first specific embodiment of probe 30, including tank circuit 10 and antenna unit 20.
  • tank circuit 10 includes solenoid coil 11 , where the investigated specimen is placed. Coil 11 contains n turns where n >1.
  • Tank circuit 10 also includes variable capacitance 12 for tuning to the resonance frequency.
  • Antenna unit 20 contains antenna 21 which is a loop type antenna, and matching circuit 22, which serves for tuning the antenna and matching it to the input of the receiver.
  • Antenna 21 consists of two loops 25 and 26, each of them can contain k turns (where k >1). Loops 25 and 26 are placed strictly opposite each other in the internal area of coil 11 close to its sides as shown in FIG. 4. Loops 25 and 26 are aligned to receive signal in the direction of axis X 23, while the NQR signal is detected in coil 11 in the direction of axis Y 24, orthogonal to axis X 23.
  • FIG. 6 illustrates a second embodiment of the probe 30, including a tank circuit 10 and antenna unit 20.
  • antenna 21, which is a saddle shaped coil, also located inside coil 11 close to its sides as shown in FIG. 5.
  • Antenna 21 can contain k turns (where k >1) and is aligned to receive signal in the direction of axis X 23, while the NQR signal is detected in coil 11 in the direction of axis Y 24, orthogonal to axis X 23.
  • FIG. 7 illustrates a third embodiment of probe 30, including tank circuit 10 and antenna unit 20.
  • tank circuit 10 includes saddle shaped coil 11 , where the investigated specimen is placed. Coil 11 contains n turns, where n >1.
  • Tank circuit 10 also includes variable capacitance 12 for tuning to the resonance frequency.
  • Antenna unit 20 contains antenna 21 , which is also a saddle shaped coil. Antenna 21 can contain k turns (where k >1) and is aligned to receive signal in the direction of axis X 23, while the NQR signal is detected in coil 11 in the direction of axis Y 24, orthogonal to axis X 23.
  • FIG. 8 illustrates a forth embodiment of probe 30, including tank circuit 10 and antenna unit 20.
  • the tank circuit 10 includes coil 11 , which is a system of two spiral coils 27 and 28, between which the investigated specimen is placed.
  • Tank circuit 10 also includes variable capacitance 12 for tuning to the resonance frequency.
  • Antenna 21 consists of two loops 25 and 26, and each of them can contain k turns (where k >1 ). Loops 25 and 26 are placed strictly opposite each other orthogonally to the surfaces of spiral coils 27 and 28 as shown in FIG. 6. Loops 25 and 26 are aligned to receive signal in the direction of axis X 23, while the NQR signal is detected in coil 11 in the direction of axis Y 24, orthogonal to axis X 23.
  • an additional receiving channel with an antenna aligned orthogonally to the direction in which the NQR signal is excited, permits to distinguish signal containing incoherent noise and not containing the NQR signal. Simultaneous detection of this signal and the signal containing the NQR signal with the subsequent signal processing permits to decrease considerably the value of the incoherent noise in the resulting signal and thus to increase the efficiency of detecting target substances.
  • Tests have been carried out on a probe containing a tank circuit with a 6 L solenoidal type coil and a loop antenna system, consisting of two loops, positioned inside the coil opposite each other.
  • a source of incoherent noise was placed in the middle of the coil.
  • Signals from the outputs of the tank circuit and the loop antenna were amplified by two independent receivers with regulated parameters. Using weighted amplification of these two signals with subsequent mutual extraction permitted to decrease the value of incoherent noise by 18 dB.

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)

Abstract

L'invention concerne un appareil de détection de signaux de résonance nucléaire quadripolaire (NQR) provenant d'une substance en présence de bruit incohérent. Ledit appareil comporte une sonde (30) comprenant un circuit résonnant (10), lequel comprend une bobine (11). Une antenne (20) est orientée de manière orthogonale par rapport à la bobine du circuit résonnant (10). Ledit appareil comporte également un émetteur (60) qui fournit et applique des impulsions RF puissantes à sa sortie en direction du circuit résonnant et un récepteur (50) comprenant deux canaux. Un canal (80) détecte et amplifie des signaux reçus dans la bobine (11) et l'autre canal (90) des signaux reçus à l'antenne (20). Des moyens de traitement (70) permettent de traiter les signaux amplifiés par le récepteur (50) afin de distinguer la présence de tous signaux NQR du bruit incohérent par comparaison des signaux amplifiés des deux canaux. L'invention concerne également des procédés de détection de signaux NQR dans le bruit incohérent.
PCT/AU2004/000108 2003-01-30 2004-01-30 Appareil et procede de detection de signaux de resonance nucleaire quadripolaire en presence de bruit incoherent WO2004068159A1 (fr)

Applications Claiming Priority (2)

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AU2003900419A AU2003900419A0 (en) 2003-01-30 2003-01-30 Apparatus and method for detecting nuclear quadrupole resonance signals in the presence of incoherent noise
AU2003900419 2003-01-30

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102624411A (zh) * 2012-02-28 2012-08-01 西安电子科技大学 一种适用于爆炸物探测的低频调谐天线
GB2506753A (en) * 2012-09-07 2014-04-09 Morpho Detection Inc A nuclear quadrupole resonance (NQR) sensor assembly with interference removal
US9575147B2 (en) 2012-09-07 2017-02-21 Morpho Detection, Llc Nuclear quadrupole resonance system and method of using the same to remove interference components from sensor signals

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999045409A1 (fr) * 1998-03-06 1999-09-10 Btg International Ltd. Procede et dispositif de test par resonance quadripolaire nucleaire
US6486838B1 (en) * 1998-03-06 2002-11-26 Btg International Limited Apparatus for and method of Nuclear Quadrupole Resonance testing a sample

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999045409A1 (fr) * 1998-03-06 1999-09-10 Btg International Ltd. Procede et dispositif de test par resonance quadripolaire nucleaire
US6486838B1 (en) * 1998-03-06 2002-11-26 Btg International Limited Apparatus for and method of Nuclear Quadrupole Resonance testing a sample

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102624411A (zh) * 2012-02-28 2012-08-01 西安电子科技大学 一种适用于爆炸物探测的低频调谐天线
GB2506753A (en) * 2012-09-07 2014-04-09 Morpho Detection Inc A nuclear quadrupole resonance (NQR) sensor assembly with interference removal
US9575147B2 (en) 2012-09-07 2017-02-21 Morpho Detection, Llc Nuclear quadrupole resonance system and method of using the same to remove interference components from sensor signals

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