Abstract: A method for exciting an NQR signal in a substance within a material that may include the substance and detecting the NQR signal in the presence of coherent noise. The method comprises irradiating the material with multiple RF pulses in the form of a complex pulse sequence containing a plurality of blocks. The basis of each block comprises a composite pulse formed by phase cycling a plurality of pulse elements. The method includes receiving a response signal after each composite pulse and processing the response signals to progressively mitigate the effect of coherent noise and to distinguish the existence of an NQR signal if present. The phase cycling comprises generating at least three pulse elements of equal duration but of differing phase to form the composite pulse. In this manner, successive blocks progressively mitigate the effect of coherent noise, and ameliorate the NQR signal if present. An apparatus for performing the method is also described.

Abstract: A probe (80) for irradiating a sample with RF energy during transmitting periods and detecting an NQR or NMR signal from a substance contained within the sample during receiving periods. The probe (80) comprises a variable impedance unit (20) for changing the Q-factor of the probe and a probe coil. The probe (80) is responsive to powerful RF pulses applied thereto to excite an RF magnetic field in the probe coil during the transmitting periods. The variable impedance unit (20) is controllable to provide a Q-factor for the probe (80) at: (i) an optimal level during a prescribed transmitting period of an RF pulse for irradiating the sample with said RF energy; (ii) a minimal level during a prescribed recovery period immediately following said transmitting period to rapidly dampen transient signals from the probe; and (iii) a maximal level during a prescribed receiving period for detecting an NQR or NMR signal from the target substance if present, immediately following the recovery period.

Abstract: A method for analysing signals received from an object. The method initially comprises deriving the parameters of frequency and phase of said signals in either the time domain or frequency domain. It then comprises identifying whether the signals conform to a linear relationship between the two parameters to ascertain whether a true signal representative of a character of the object is present. The character may be a nuclear or electronic resonance, such as NQR, NMR or ESR, which is indicative of a particular substance. Signal processing methods involving HTLS, HSVD, MPM, MMPM, FFT, STFT and STMPM are also described.

Abstract: A coil assembly (11) comprising two coil sections (13a and 13b). Each of the sections (13) consists of a combination of a spiral coil (15) having a variable coil pitch arranged in a saddle shape configuration. The saddle shape has a central portion (17) and a pair of outer coextending portions (19). The coil sections (13) are located opposite each other with the central portions (17) of the respective sections disposed in parallel spaced apart relationship and the corresponding coextending portions (19) of the respective sections disposed in coplanar alignment with each other so that the sections combine to circumscribe a scanned volume within which the target substance is to be disposed.

Abstract: An apparatus and a method for producing a multi-pulse sequence for irradiating a substance provided with quadrupole nuclei with either integer or half-integer spins to detect an NQR signal emitted therefrom. The apparatus has pulse sequence generating means adapted to produce a combination of two or more pulse sequences, arranged so that a definite regularity of the phase alteration of pulses in each of the pulse sequences occurs that is equivalent to a shift of spectral components of the pulse sequences in relation to each other. Furthermore, in at least one of the pulse sequences, there are not less than two phases alternating. A preparatory pulse may be included in one of the pulse sequences to reduce the effect of temperature, increase the intensity of the NQR signal and simultaneously eliminate intensity anomalies. Alternatively, the combination of pulse sequences may be different from a combination of PAPS and NPAPS, and none of the pulse sequences contain a preparatory pulse.

Abstract: An apparatus for exciting and detecting NQR in a substance containing quadrupole nuclei responsive to the NQR phenomenon. The apparatus includes a coil 15 for irradiating an item that may contain a substance with RF waves to excite NQR in quadrupole nuclei within the substance and for receiving an NQR signal emitted in response thereto. The apparatus also includes a transmitter unit 10, a receiver unit 11, a sensing means and a computer 12 for processing the treated received signal to identify a said NQR signal therein.

Abstract: An NQR scanner for detecting the presence of a substance containing quadrupole nuclei within an object. A pulse generating means (1) generates pulse sequences that are used to irradiate the object in a pulsed magnetic field at a requisite NQR frequency for the substance to be detected. A high power RF transmit amplifier (2) amplifies the signal to produce sufficient magnetic field strength to irradiate a scan volume within which the object is disposed for detection purposes and cause an NQR transition to a detectable level within the substance if present within the object.

Abstract: An apparatus and method for producing a multi-pulse sequence for irradiating a substance provided with quadrupole nuclei with either integer or half-integer spins to detect an NQR signal emitted therefrom. The apparatus has pulse sequence generating means adapted to produce multi-pulse sequences with pulse intervals exceeding T2* and containing a preparatory pulse or group of pulses for creating echo signals between the pulses. The pulse sequence is organised so that the resulting signal contains a prevailing echo component produced by the preparatory pulse or group of pulses.

Abstract: An antenna and shield apparatus for detecting phenomenal signals using nuclear and electronic resonance detection technology, comprising: a transmit and receive antenna, an electric field shield 60 and an outer shield 52. The antenna is a multiple parallel loop transmit-receive antenna forming a main coil assembly 11 having a plurality of loop segments 20 optionally interconnected by connectors in the form of conducting bars 10, relays 16, or nothing. The electric field shield 60 comprises an inner sleeve of conducting material 60, 68 disposed on the inside of the coil assembly 11 for shielding the electric field emanating from the coil assembly 11 from the target volume circumscribed by the assembly. The outer shield 52 comprises a central screen portion 55, waveguides 57 at either end thereof and a sloping channel portion for interconnecting the two. The coil assembly 11 and the electric field shield 60 are housed within the outer shield 52.

Abstract: A probe (80) for irradiating a sample with RF energy during transmitting periods and detecting an NQR or NMR signal from a substance contained within the sample during receiving periods. The probe (80) comprises a variable impedance unit (20) for changing the Q-factor of the probe and a probe coil. The probe (80) is responsive to powerful RF pulses applied thereto to excite an RF magnetic field in the probe coil during the transmitting periods. The variable impedance unit (20) is controllable to provide a Q-factor for the probe (80) at: (i) an optimal level during a prescribed transmitting period of an RF pulse for irradiating the sample with said RF energy; (ii) a minimal level during a prescribed recovery period immediately following said transmitting period to rapidly dampen transient signals from the probe; and (iii) a maximal level during a prescribed receiving period for detecting an NQR or NMR signal from the target substance if present, immediately following the recovery period.