CN-122016906-A - Polynuclear nuclear magnetic resonance instrument

CN122016906ACN 122016906 ACN122016906 ACN 122016906ACN-122016906-A

Abstract

The embodiment of the application provides a polynuclein nuclear magnetic resonance instrument. The polynuclear nuclear magnetic resonance instrument comprises a radio frequency receiving and transmitting module, a switch control module, a duplexer module, an impedance matching network and a sample feeding tube. The radio frequency transceiver module is connected with the switch control module, a first output end of the switch control module is connected with the duplexer module, and a second output end of the switch control module is connected with the impedance matching network. The impedance matching network comprises a resistance-capacitance circuit and a radio frequency coil, and the radio frequency coil is arranged on the outer side of the sample feeding tube. The switch control module switches the circuit structure of the impedance matching network based on the radio frequency pulse transmitted by the radio frequency transceiver module, so that the radio frequency coil outputs radio frequency waves with target frequency to excite nuclides of samples in the sample feeding tube. The multi-nuclide nuclear magnetic resonance instrument enables the radio frequency coil to stably resonate under different frequencies by switching the circuit structure of the impedance matching network, realizes stable resonance and impedance matching under a larger frequency span, and improves the signal acquisition efficiency and the signal-to-noise ratio.

Inventors

LIAO GUANGZHI
CHE CHENG
LIN TINGTING
LIU HUABING
XIAO LIZHI

Assignees

中国石油大学(北京)

Dates

Publication Date: 20260512
Application Date: 20260227

Claims (10)

1. The multi-nuclear magnetic resonance instrument is characterized by comprising a radio frequency transceiver module, a switch control module, a duplexer module, an impedance matching network and a sample feeding tube; the radio frequency transceiver module is connected with the switch control module, a first output end of the switch control module is connected with the duplexer module, and a second output end of the switch control module is connected with the impedance matching network; The impedance matching network comprises a resistance-capacitance circuit and a radio frequency coil, and the radio frequency coil is arranged on the outer side of the sample feeding tube and is used for emitting radio frequency waves when the impedance matching network resonates so as to excite nuclides of samples in the sample feeding tube; The switch control module is used for switching the circuit structure of the impedance matching network based on the radio frequency pulse transmitted by the radio frequency transceiver module so that the radio frequency coil outputs radio frequency waves with target frequency, and the target frequency is used for exciting nuclides of samples in the sample feeding tube.
2. The nuclear magnetic resonance apparatus according to claim 1, wherein the resistance-capacitance circuit comprises a series resistance, a series capacitance branch, and a parallel capacitance branch; The series resistor, the radio frequency coil and the series capacitor branch are connected in series to obtain a series main circuit; The first end of the parallel capacitor branch is connected with the first end of the serial main circuit, and the second end of the parallel capacitor branch is connected with the second end of the serial main circuit.
3. The apparatus of claim 2, wherein the series capacitance branch comprises a plurality of series capacitances and at least one first switch; The plurality of series capacitors comprise a first series capacitor and at least one second series capacitor, and the second series capacitor is connected with the branch after the first switch is connected in series and is connected with the first series capacitor in parallel.
4. A polynuclear nuclear magnetic resonance apparatus as claimed in claim 3, wherein the shunt capacitance branch comprises a plurality of shunt capacitances and at least one second switch; the plurality of parallel capacitors comprise a first parallel capacitor and at least one second parallel capacitor, and the second parallel capacitor is connected with the branch after the second switch is connected in series and connected to two sides of the first parallel capacitor in parallel; The first switches and the second switches are arranged in pairs, and when one pair of the first switches and the second switches are simultaneously closed, the other pairs of the first switches and the second switches are disconnected.
5. The apparatus of claim 4, wherein the switch control module is configured to control the first switch and the second switch arranged in pairs to be opened or closed simultaneously; When the at least one first switch and the at least one second switch are both opened, the impedance matching network is in a first working circuit, and when the first working circuit resonates, the radio frequency coil emits radio frequency waves with a first frequency; When the first pair of first switches and the second switch are simultaneously closed, the impedance matching network is positioned in a second working circuit, and when the second working circuit resonates, the radio frequency coil emits radio frequency waves with a second frequency; The radio frequency wave with the first frequency is used for exciting a first nuclide in the sample, and the radio frequency wave with the second frequency is used for exciting a second nuclide in the sample.
6. The nuclear magnetic resonance apparatus according to any one of claims 1 to 5, wherein the diplexer module includes a high frequency diplexer and a low frequency diplexer, each of the high frequency diplexer and the low frequency diplexer being connected to the switch control module, The radio frequency transceiver module comprises a radio frequency transmitting end and a radio frequency receiving end; Wherein the switch control module is used for controlling the high-frequency duplexer to be connected with the radio-frequency transmitting end or the radio-frequency receiving end and The switch control module is used for controlling the low-frequency duplexer to be connected with the radio frequency transmitting end or the radio frequency receiving end.
7. The apparatus of claim 6, wherein the switch control module comprises a pulsed voltage source and a controller; the controller is connected with the pulse voltage source and used for controlling the pulse voltage source to generate and output a switch control signal; The positive pole of the pulse voltage source is connected with the first end of the switch, the negative pole of the pulse voltage source is grounded, the second end of the switch is grounded, and the switch comprises a first switch and a second switch.
8. The apparatus of claim 1, wherein a cavity is present between the delivery tube and the radio frequency coil, and a faraday cage is disposed in the cavity; the outside of the radio frequency coil is provided with a constant temperature permanent magnet, and a cavity is arranged between the radio frequency coil and the constant temperature permanent magnet.
9. The apparatus of claim 8, wherein the faraday cage is an axially slotted, cylindrical or polygonal surrounding conductive foil for suppressing electromagnetic field drift caused by high dielectric constant samples.
10. The nuclear magnetic resonance apparatus according to claim 7, wherein the switch comprises at least one of a P-intrinsic-N PIN diode switch, a gallium nitride GaN radio frequency switch, and a complementary metal oxide semiconductor CMOS radio frequency switch.

Description

Polynuclear nuclear magnetic resonance instrument Technical Field The application relates to the technical field of nuclear magnetic resonance, in particular to a polynuclear nuclear magnetic resonance instrument. Background Low field nuclear magnetic resonance (nuclear magnetic resonance, NMR) instruments enable multicomponent analysis and structural characterization of samples by detecting the resonance signals of different nuclear species. For example, in the field of oil exploration, the pore structure of a core and the composition of fluids in the core are determined by measuring hydrogen nuclei (1 H) and sodium nuclei (23 Na) in a sample core. In the prior art, a probe for multi-nuclear magnetic resonance measurement mainly comprises a multi-coil independent measurement scheme and a double-resonance notch structure scheme. The multi-coil independent measurement scheme is characterized in that independent radio frequency coils are configured for different nuclear species, and measurement of multi-core elements is realized in a mechanical switching mode. However, there is cross-coupling interference between the multiple coils, resulting in increased signal crosstalk and noise, and the process of mechanically switching the coils is time consuming and prone to introducing errors, affecting measurement continuity. The dual resonance notch structure scheme implements multi-frequency resonance on a single coil using a notch or band reject filter. However, the matching bandwidth of the notch structure is limited, so that stable resonance and impedance matching are difficult to realize under a large frequency span, and the signal acquisition efficiency is low and the signal to noise ratio is reduced. Disclosure of Invention The embodiment of the application provides a polynuclear nuclear magnetic resonance instrument, which is difficult to realize stable resonance and impedance matching under a large frequency span, so that the technical problems of low signal acquisition efficiency and reduced signal-to-noise ratio are solved. In a first aspect, an embodiment of the present application provides a polynuclein nuclear magnetic resonance apparatus, including: the device comprises a radio frequency transceiver module, a switch control module, a duplexer module, an impedance matching network and a sample feeding tube; the radio frequency transceiver module is connected with the switch control module, a first output end of the switch control module is connected with the duplexer module, and a second output end of the switch control module is connected with the impedance matching network; The impedance matching network comprises a resistance-capacitance circuit and a radio frequency coil, and the radio frequency coil is arranged on the outer side of the sample feeding tube and is used for emitting radio frequency waves when the impedance matching network resonates so as to excite nuclides of samples in the sample feeding tube; The switch control module is used for switching the circuit structure of the impedance matching network based on the radio frequency pulse transmitted by the radio frequency transceiver module so that the radio frequency coil outputs radio frequency waves with target frequency, and the target frequency is used for exciting nuclides of samples in the sample feeding tube. In one possible implementation, the resistance capacitance circuit comprises a series resistance, a series capacitance branch and a parallel capacitance branch; The series resistor, the radio frequency coil and the series capacitor branch are connected in series to obtain a series main circuit; The first end of the parallel capacitor branch is connected with the first end of the serial main circuit, and the second end of the parallel capacitor branch is connected with the second end of the serial main circuit. In one possible embodiment, the series capacitance branch comprises a plurality of series capacitances and at least one first switch; The plurality of series capacitors comprise a first series capacitor and at least one second series capacitor, and the second series capacitor is connected with the branch after the first switch is connected in series and is connected with the first series capacitor in parallel. In one possible embodiment, the parallel capacitance branch comprises a plurality of parallel capacitances and at least one second switch; the plurality of parallel capacitors comprise a first parallel capacitor and at least one second parallel capacitor, and the second parallel capacitor is connected with the branch after the second switch is connected in series and connected to two sides of the first parallel capacitor in parallel; The first switches and the second switches are arranged in pairs, and when one pair of the first switches and the second switches are simultaneously closed, the other pairs of the first switches and the second switches are disconnected. In a possible embodiment, the switch control modul