RU2602425C1 - Method and device for excitation and detection of nuclear magnetic and quadrupole resonance - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention can be used for excitation and detection of nuclear magnetic and quadrupole resonance. Essence of invention is that an object, placed in a coil of an oscillating circuit, is exposed to modulated shortwave radiation of a generator. Shortwave radiation is modulated with radio-frequency (RF) pulses formed in transmitting channel, filling frequency of which is determined by NMR or NQR frequency. Disclosed solution does not use pulses of exciting electromagnetic field directly at nuclear resonance frequency. Nuclear resonance signals induced in oscillatory circuit are transmitted to input of receiving channel. After amplification and conversion in receiving channel signals are transmitted to input of microprocessor controller, processed therein and displayed on an indicator (display).

EFFECT: enabling reduction of transient processes in oscillatory circuit and therefore increase in sensitivity of device.

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Description

The invention relates to the field of nuclear magnetic spectroscopy (NMR) and nuclear quadrupole (NQR) resonances. A system for the excitation and detection of NMR and NQR is proposed. Excitation is performed by exposing the object to a beam of short-wave radiation (for example, millimeter-wave microwave), modulated by radio-frequency (RF) pulses with a filling that matches the frequencies of NMR or NQR. A receiving inductor can be wound around the object or located near the object. The device of the NMR spectrometer differs from the NQR spectrometer only in the presence of a system for creating a uniform constant magnetic field in the area of the object [1], which is not considered in the claimed technical solution.

There is a source of information [2], according to which the use of double electron-nuclear resonance (DECR) is known (p. 12) and the use of an electron-paramagnetic resonance (EPR) spectrometer (p. 25). Moreover, the use of microwave radiation of the millimeter range, which is modulated by a transmitting channel with a NQR frequency, which is a type of NMR, is inherent in DEYAR. In DEYAR they act resonantly on both electronic and nuclear systems. In this analogue, the effect of a nuclear system on the electronic and, conversely, electronic on the nuclear, is studied only in the presence of paramagnetism.

The disadvantage of the described device is that the effect is performed only at resonant frequencies (DYaER, EPR) and only in the presence of paramagnetism.

A close technical solution (prototype) is “System and method for contraband detection using nuclear quadrupole resonance including a sheet coil and RF shielding via waveguide below cutoff” US Pat. 5592083 [3]. The device contains an RF pulse shaper loaded on an oscillatory circuit, which includes a transceiver inductance coil, where the object under study is placed; a receiving channel, an indicator (display), and a microprocessor system controlling an RF pulse shaper, a receiving channel, and an indicator. In the device, powerful radio frequency pulses have a huge negative effect on the receiving channel, causing transients that greatly reduce the sensitivity of the method.

The disadvantage of the prototype is that in it powerful radio-frequency pulses have a negative effect on the receiving coil and the receiving channel, causing transients that greatly reduce the sensitivity of the method, and also that the effect is performed only at the resonant frequency of the NQR, which coincides with the resonant frequency of the receiving circuit ( antennas).

The objective of the invention is to eliminate the influence of powerful radio frequency pulses on the receiving coil and the receiving channel due to exposure to the object under study with microwave pulses with a repetition frequency equal to the frequency of nuclear resonance, and the pulse filling frequency is outside nuclear resonance.

The problem is solved in that in the method of excitation and detection of nuclear magnetic and quadrupole resonances, which consists in using methods of nuclear magnetic and quadrupole resonances, according to the invention, the object is irradiated with short-wave radiation (for example, millimeter-wave microwave), the microwave oscillations of which do not coincide with which either by resonance, they are modulated by radio-frequency pulses formed by the transmitting channel, with a filling frequency coinciding with the frequency of nuclear resonance, i.e. The object being irradiated is irradiated with portions of microwave oscillations with a repetition frequency coinciding with the nuclear resonance frequency, and the signals emitted by the object and induced in the oscillatory circuit are converted by the receiving channel, processed in the microprocessor controller, and displayed on the display.

To implement the proposed method, a device is proposed (Fig. 1), which contains a transmitting channel 1 that generates RF pulses, a resonant oscillating circuit 3, which includes an inductor, where the object under investigation is connected to the input of the receiving channel 4, a microprocessor system (controller ) 5 and indicator (display) 6, which additionally introduces a microwave radiation generator 2, the oscillations of which are modulated by radio-frequency pulses generated by the transmitting channel 1. The signal induced in the inductor coil ivnosti oscillation circuit 3, is amplified and detected by the receiving channel 4, is converted into a microprocessor controller 5 and displayed on the display (display) 6.

In the claimed invention, the nuclear system is affected by portions of microwave energy, the oscillation frequency of which does not coincide with any resonance, and the repetition frequency of the portions coincides with the frequency of nuclear resonance. In other words, microwave oscillations are modulated by radio frequency pulses, the filling frequency of which coincides with the frequency of nuclear resonance. In this case, the reaction of the nuclear system (nuclear magnetic and quadrupole resonances) is directly studied when it interacts with a pulsed electromagnetic field whose microwave frequency is far from the resonance (magnetic or quadrupole), that is, the transmitting system does not excite transient processes in the receiving channel on nuclear resonance frequency. In other words, the claimed solution does not use pulses of the exciting electromagnetic field directly at the nuclear resonance frequency.

Thus, the claimed invention eliminates the influence of powerful radio frequency pulses on the receiving coil and the receiving channel, to reduce transients in the oscillatory circuit, which, in turn, leads to an increase in the sensitivity of the device. The transceiver matching system of coils is simplified, where the studied object is placed, especially in multi-frequency experiments [4, 5].

In a device that provides the implementation of the proposed method, the RF pulses formed in the transmission channel 1, the filling frequency of which is determined by the frequency of NMR or NQR, modulate the generator 2 of short-wave (microwave) radiation. An object placed in the coil of the oscillating circuit 3 is affected by this modulated short-wave radiation. The nuclear resonance signals induced in the oscillatory circuit 3 are fed to the input of the receiving channel 4. After amplification and conversion in the receiving channel 4, the signals are fed to the input of the microprocessor controller 5, which controls, in turn, the transmit and receive channels, are converted into it and displayed on the indicator (display) 6.

Using the claimed invention allows to increase the sensitivity of systems using NMR and NQR methods, for example magnetic resonance imaging.

Information sources

1. T. Farrar, E. Becker. High resolution NMR spectroscopy. Per. from English., t. 1-2, M., 1968-69.

2. V.N. Sedalischev. The physical basis for obtaining information. Part 3. Modern fundamental and applied research in instrument making. Tutorial. Publishing house Alt. GTU, 2012, p. 1-30.

3. "System and method for contraband detection using nuclear quadrupole resonance including a sheet coil and RF shielding via waveguide below cutoff" Erik E. Magnuson et al., US Pat. 5592083 Jan. 7, 1997, Quantum Magnetics, Inc., San Diego, Calif.

4. Fedotov V.V., Grechishkin V.S. A technique for studying weak signals of a two-frequency echo in nuclear quadrupole resonance / Journal of Physical Chemistry of the Academy of Sciences of the USSR, 1979, v. 43, No. 1, p. 60-62.

5. Patent No. 2289124 of the Russian Federation, MKI G01 22/04, G01 33/46. The method of detection and identification of chemical compounds / Mozhuhin GV, Bodnya A.V., Fedotov V.V., decl. 06/27/2005, publ. 12/10/2006.

Claims (1)

A method of excitation and detection of nuclear magnetic and quadrupole resonances, which consists in using nuclear magnetic and quadrupole resonance methods, characterized in that the object is affected by the microwave electromagnetic field with a microwave electromagnetic field frequency that is not resonant, but a portion of microwave energy are supplied with a nuclear resonance frequency, the signals emitted by the object, induced in the oscillatory circuit, are fed to the input of the receiving channel, from the output of which th input to the microprocessor, converted therein and displayed on the display.

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