Miniature Ultra-Low-Field Nuclear Magnetic Resonance Spectrometer

Abstract

The present invention discloses a small ultra-low field nuclear magnetic resonance spectrometer, which includes a sample flow module for driving a liquid sample to flow between a polarization region and a detection region; a hyperpolarization module for polarizing the liquid sample; a probe and sample fixation module for fixing a sample tube in the detection region and a nuclear magnetic detection module; a pulse application module for applying a pulse to the liquid sample to rotate the nuclear magnetization vector of the sample to the transverse direction and perform free evolution of the sample spin; a nuclear magnetic detection module for detecting the free evolution spin signal of the liquid sample and converting it into a voltage signal; a magnetic shielding module for shielding the geomagnetic field to ensure an ultra-low field environment; and a timing control module for controlling the operation of each module and collecting the voltage signal. Through the combination of each module, the detection process of the present invention is carried out in a magnetic shielding environment, eliminating the dependence on a strong magnetic field of a traditional nuclear magnetic resonance spectrometer, effectively reducing the system complexity and cost; making the overall structure simple, small in size, easy to move, and adaptable to nuclear magnetic detection in various environments.

Description

Technical Field

[0001] The present invention belongs to the technical field of nuclear magnetic resonance, and particularly relates to a small ultra-low field nuclear magnetic resonance spectrometer for detecting the composition of liquid samples. Background Art

[0002] Nuclear magnetic resonance technology is based on the widespread existence of nuclear spins in matter. Using this technology, information on the composition and structure of matter can be accurately, quickly, and non-destructively obtained, making it one of the most important material exploration technologies in contemporary science. It is also widely applied in many fields such as physics, chemistry, biology, medicine, and engineering.

[0003] Traditional nuclear magnetic resonance spectrometers are mostly high-field spectrometers. High-field spectrometers measure signals through electromagnetic induction. The probe, as a link connecting the sample and the spectrometer, has multiple sets of coils wound around its outer layer, mainly used for applying pulses and receiving signals. The console is mainly implemented by a computer, used to control parameters such as pulse frequency and intensity and the processing of digital signals. The static magnetic field in high-field spectrometers is usually generated by superconducting coils, that is, coils composed of superconducting materials are immersed in liquid helium to make them in a superconducting state, and a static magnetic field is generated by applying current to the coils. Increasing the magnetic field strength is the main method to improve the sensitivity of high-field spectrometers. However, with the increase of the magnetic field, the requirements for the design, processing, and installation of the magnet are higher, and the cryogenic system for generating a strong magnetic field and the shimming system for ensuring magnetic field uniformity are becoming more and more complex, making high-field spectrometers have a complex structure, a large volume, and a high cost.

[0004] Many achievements have also been made in the development of zero-field nuclear magnetic resonance spectrometers. However, zero-field nuclear magnetic resonance spectrometers need to build a complex optical path and have extremely high requirements for the stability of the optical path. Therefore, they can only work in a quiet, stable, constant temperature, constant pressure, and constant humidity environment. And currently, zero-field nuclear magnetic resonance spectrometers are large in size and very bulky, with a size of 1-2 meters, so they are difficult to move and lack flexibility. Summary of the Invention

[0005] The purpose of the present invention is to provide a small ultra-low field nuclear magnetic resonance spectrometer, which adopts a modular structure, has a small volume, high sensitivity, and is convenient to move.

[0006] To achieve the above-mentioned invention purpose, the technical solution adopted by the present invention is: a small ultra-low field nuclear magnetic resonance spectrometer, including a sample flow module, a hyperpolarization module, a probe and sample fixation module, a pulse application module, a nuclear magnetic detection module, a magnetic shielding module, and a timing control module;

[0007] The sample flow module includes a polarization zone sample tube and a detection zone sample tube that are interconnected, and a vacuum pump drives the liquid sample to flow bidirectionally between the polarization zone sample tube and the detection zone sample tube;

[0008] The hyperpolarization module is arranged on the outer periphery of the sample tube in the polarization region to polarize the liquid sample in the sample tube in the polarization region;

[0009] The probe and sample fixing module is arranged on the outer periphery of the sample tube in the detection region and is used to fix the sample tube in the detection region and the nuclear magnetic detection module;

[0010] The pulse application module is arranged on the outer periphery of the probe and sample fixing module and applies a pulse to the liquid sample in the sample tube in the detection region to turn the nuclear magnetization vector of the liquid sample to the transverse direction for free evolution of the sample spin;

[0011] The nuclear magnetic detection module is arranged in the probe and sample fixing module and is in close contact with the sample tube in the detection region, and is used to detect the free evolution spin signal of the liquid sample in the sample tube in the detection region and convert it into a voltage signal for output;

[0012] The magnetic shielding module is used to shield the geomagnetic field to ensure the ultra-low field environment in the detection region;

[0013] The timing control module is connected to each module and is used to control the operation of each module and collect the voltage signal.

[0014] Further, the sample tube in the polarization region and the sample tube in the detection region are connected through a plexiglass tube, and a guiding coil is wound around the plexiglass tube.

[0015] Further, a first conical flask and a first solenoid valve are arranged between the sample tube in the polarization region and the vacuum pump, a second conical flask and a second solenoid valve are arranged between the sample tube in the detection region and the vacuum pump, and a speed limiting valve is also arranged between the vacuum pump and the first solenoid valve and the second solenoid valve.

[0016] Further, the hyperpolarization module includes a Halbach magnet, the Halbach magnet is circular tubular, and the sample tube in the polarization region is placed in the hollow tube cavity of the Halbach magnet.

[0017] Further, the probe and sample fixing module includes a wire winding tube with both ends closed. A round hole is opened at one end of the wire winding tube, and a square hole is opened at the other end. The sample tube in the detection region is placed into the wire winding tube from the round hole, and the nuclear magnetic detection module is placed into the wire winding tube from the square hole. The nuclear magnetic detection module and the sample tube in the detection region are in contact in the tube cavity of the wire winding tube; a plurality of transverse grooves and a plurality of vertical grooves are also opened on the outer tube wall of the wire winding tube.

[0018] Further, the pulse application module includes a plurality of groups of magnetic coils arranged on the outer wall of the wire winding tube, and the plurality of groups of magnetic coils form a three-dimensional pulse magnetic field for the wire winding tube.

[0019] Further, the nuclear magnetic detection module includes an atomic magnetometer, the atomic magnetometer is placed into the wire winding tube from the square hole at the end of the wire winding tube, and the probe end of the atomic magnetometer is in contact with the sample tube in the detection region.

[0020] Further, the magnetic shielding module is a magnetic shielding barrel composed of 5 layers of permalloy, and demagnetizing coils are arranged on the innermost and outermost layers of the magnetic shielding barrel.

[0021] Further, the timing control module includes a voltage output module, a voltage input module, and a logic level module. The voltage output module outputs a voltage of 0 - 10V at a given time; the voltage input module collects the voltage data output by the nuclear magnetic detection module; the logic level module is used to control the operation of each module.

[0022] The beneficial effects of adopting the above technical solutions are as follows:

[0023] 1. Through the combination of each module, the entire detection process of the present invention is carried out in a magnetic shielding environment, eliminating the dependence on strong magnetic fields of traditional nuclear magnetic resonance spectrometers, effectively reducing the system complexity; making the entire nuclear magnetic resonance spectrometer structure simpler, smaller in volume, easier to move, and capable of adapting to nuclear magnetic detection in various environments.

[0024] 2. In the present invention, the nuclear magnetic detection module adopts a high-sensitivity nuclear magnetic probe, which is closely attached to the sample tube, effectively improving the sensitivity of nuclear magnetic detection of the sample, and can also achieve nuclear magnetic detection of samples with natural abundance, with low detection cost. Description of the Drawings

[0025] Figure 1 is a schematic structural diagram of the nuclear magnetic resonance spectrometer of the present invention;

[0026] Figure 2 is a schematic structural diagram of the sample flow module of the present invention;

[0027] Figure 3 、 4 is a schematic structural diagram of the probe and sample fixing module of the present invention;

[0028] Figure 5 is a top view of the probe and sample fixing module of the present invention.

[0029] Reference numerals in the figures: 10 sample flow module, 20 hyperpolarization module, 30 probe and sample fixing module, 40 pulse application module, 50 nuclear magnetic detection module, 60 magnetic shielding module, 70 timing control module, 11 sample tube in the polarization area, 12 sample tube in the detection area, 13 vacuum pump, 14 organic glass tube, 15 first conical flask, 16 first solenoid valve, 17 second conical flask, 18 second solenoid valve, 19 speed limiting valve, 31 wire winding tube, 32 round hole, 33 square hole, 34 horizontal groove, 35 vertical groove, 71 voltage output module, 72 voltage input module, 73 logic level module. Detailed Embodiments

[0030] In combination with the attached drawings, a small ultra-low field nuclear magnetic resonance spectrometer includes a sample flow module 10, a hyperpolarization module 20, a probe and sample fixing module 30, a pulse application module 40, a nuclear magnetic detection module 50, a magnetic shielding module 60, and a timing control module 70;

[0031] The sample flow module 10 includes a polarization region sample tube 11 and a detection region sample tube 12. As Figure 2 shown, the polarization region sample tube 11 and the detection region sample tube 12 are connected through an acrylic tube 14. The polarization region sample tube 11 and the detection region sample tube 12 are respectively connected to a vacuum pump 13. The liquid sample is pumped by the vacuum pump 13 to flow from the polarization region sample tube 11 to the detection region sample tube 12 or from the detection region sample tube 12 to the polarization region sample tube 11. A conical flask one 15 and a solenoid valve one 16 are arranged between the polarization region sample tube 11 and the vacuum pump 13, and a conical flask two 17 and a solenoid valve two 18 are arranged between the detection region sample tube 12 and the vacuum pump 13. The conical flask one 15 and the conical flask two 17 are mainly provided to prevent the liquid sample from flowing into the vacuum pump 13 under the action of the vacuum pump 13 and causing damage to the vacuum pump 13. The solenoid valve one 16 and the solenoid valve two 18 are not opened simultaneously and are used to control the flow direction of the liquid sample. A speed limiting valve 19 is also arranged between the vacuum pump 13 and the solenoid valve one 16 and the solenoid valve two 18. The speed limiting valve 19 is used to adjust the pumping speed of the vacuum pump 13 to adapt to different types of liquid samples. A guiding coil is wound around the acrylic tube 14, and the acrylic tube 14 is used to generate a guiding magnetic field of 1 G to make the polarization direction of the liquid sample always along the acrylic tube 14.

[0032] The hyperpolarization module 20 includes a Halbach magnet. The Halbach magnet is circular tubular, and the polarization region sample tube 11 is placed in the hollow tube cavity of the Halbach magnet. The magnetic field of the Halbach magnet is selected as 2 T and is used to polarize the liquid sample in the polarization region sample tube 11.

[0033] The probe and sample fixing module 30 is a solenoid 31 with closed ends at both ends. As Figure 3 、 4 shown, a round hole 32 is opened at one end of the solenoid 31, and a square hole 33 is opened at the other end. The detection region sample tube 12 is placed into the solenoid 31 from the round hole 32, and the atomic magnetometer of the nuclear magnetic detection module 50 is placed into the solenoid 31 from the square hole 33. The atomic magnetometer probe of the nuclear magnetic detection module 50 is closely attached to the detection region sample tube 12 in the tube cavity of the solenoid 31.

[0034] A plurality of transverse grooves 34 and a plurality of vertical grooves 35 are also opened on the outer tube wall of the solenoid 31. The transverse grooves 34 and the vertical grooves 35 are used to wind pulse coils. Specifically, the depth of the transverse grooves 34 is 5 mm, and the depth of the vertical grooves 35 is 7 mm. The transverse grooves 34 are arranged at equal intervals, and a total of 31 are provided; a total of 9 vertical grooves 35 are provided. As Figure 5As shown, they are distributed according to the 12 scale positions of the clock and are respectively set at the positions of 1, 2, 4, 5, 7, 8, 10, 11, and 12 o'clock.

[0035] Furthermore, the bobbin 31 is made of polytetrafluoroethylene material, which is a non-magnetic material and can avoid generating magnetic field noise.

[0036] The pulse application module 40 includes several groups of magnetic coils arranged on the outer wall of the bobbin 31. The several groups of magnetic coils form a three-dimensional pulsed magnetic field for the bobbin 31, apply a pulse to the liquid sample in the sample tube 12 in the detection area, rotate the nuclear magnetization vector of the liquid sample to the transverse direction, and perform the free evolution of the sample spin. Specifically, the pulse application module 40 altogether includes nine groups of magnetic coils, with three groups wound around in each of the x, y, and z three-dimensional directions. Each group has a different number of turns. The magnetic coils to be used can be selected according to the size and direction of the pulse to be applied, and complex pulse combinations with arbitrary directions and a large adjustable range of pulse intensities can be achieved. The nine groups of magnetic coils are all wound in the wire grooves on the outer wall of the bobbin 31. Among them, the z-direction coil is a spiral coil, and the x- and y-direction coils are saddle-shaped coils. When specifically set, the z-direction coil groove is composed of 29 horizontal grooves 34 and one vertical groove 35. The z-direction coil winds n turns (n is the planned number of turns to be wound, the same below) in the horizontal groove 34, then enters the next horizontal groove 34 from the vertical groove 35 until all 29 horizontal grooves 34 in the middle are wound with coils, and then the end of the coil returns to the starting point of the coil through the vertical groove 35 and is welded and closed with the starting point of the coil to form a spiral coil.

[0037] The y-direction coil passes through the vertical groove 35 at the 1 o'clock position, the bottom horizontal groove 34, the vertical groove 35 at the 11 o'clock position, and the top horizontal groove 34 as one turn, winds n turns, and then winds from the top horizontal 34 to the vertical groove 35 at the 5 o'clock position. It passes through the vertical groove 35 at the 5 o'clock position, the bottom horizontal groove 34, the vertical groove 35 at the 7 o'clock position, and the top horizontal groove 34 as one turn, and winds n turns. Then the end of the coil returns to the starting point of the coil through the top horizontal groove 34 and is closed, thus forming a pair of saddle-shaped coils wound on the side of the bobbin 31. The winding method of the x-direction coil is the same as that of the y-direction coil, and the vertical grooves 35 at the 1, 11, 5, and 7 o'clock positions of the y-direction coil are replaced with the vertical grooves 35 at the 2, 4, 8, and 10 o'clock positions. Such a design can ensure the magnetic field in the center of the bobbin 31, that is, in the detection area, to be uniform and accurate to the greatest extent. When passing current, first, the electromagnetic relay accepts the control signal and closes, the pulse voltage is input to the power amplifier, and a 20-fold power enhancement is obtained and output to the coil. After the pulse ends, the electromagnetic relay accepts the signal and disconnects to ensure that the coil does not generate a noise magnetic field.

[0038] The nuclear magnetic detection module 50 includes an atomic magnetometer. The atomic magnetometer is placed into the solenoid 31 through the square hole 33 at the end of the solenoid 31, and the probe end of the atomic magnetometer is closely attached to the sample tube 12 in the detection area, so as to improve the sensitivity of nuclear magnetic detection, detect the free evolution spin signal of the liquid sample in the sample tube 12 in the detection area, and convert it into a voltage signal for output. In this embodiment, a miniaturized atomic magnetometer is selected for the atomic magnetometer. It has a small volume and high sensitivity, can effectively reduce the volume of the entire nuclear magnetic resonance spectrometer, and make it convenient to move.

[0039] The magnetic shielding module 60 is used to shield the geomagnetic field to ensure an ultra-low magnetic field environment in the detection area; it is a magnetic shielding barrel composed of 5 layers of permalloy. Demagnetizing coils are arranged on the innermost layer and the outermost layer of the magnetic shielding barrel. Using the characteristics of the magnetic hysteresis loop, the residual magnetic field in the magnetic shielding barrel is eliminated. A round hole is opened at the center of the top surface of the magnetic shielding barrel for placing the sample tube 12 in the detection area; there is a small hole at the bottom of the side for the probe wire of the miniaturized atomic magnetometer to pass through; there is a small hole at the edge of the top surface for the magnetic coil wire of the pulse application module 40 to pass through. Placing the entire detection area in a magnetic shielding environment for nuclear magnetic detection can eliminate the dependence on the magnetic field of traditional nuclear magnetic resonance spectrometers, effectively reduce the system complexity, make the structure of the entire nuclear magnetic resonance spectrometer simpler, and also facilitate moving the spectrometer out of the laboratory to facilitate nuclear magnetic detection in different external magnetic field environments.

[0040] The timing control module 70 includes a voltage output module 71, a voltage input module 72, and a logic level module 73. The voltage output module 71 outputs a voltage of 0 - 10V for a given time; the voltage input module 72 collects the voltage data output by the nuclear magnetic detection module 50; the logic level module 73 is used to control the operation of each module.

[0041] The specific experimental principle of the nuclear magnetic resonance spectrometer of the present invention is as follows:

[0042] (1) In the initial state, the liquid sample is placed in the sample tube 11 in the polarization area. The voltage outputs of each channel of the voltage output module 71 and the logic level module 73 are 0, the relay is in the off state, the solenoid valve 16 and the solenoid valve 18 are in the closed state, and the vacuum pump 13 is turned on;

[0043] (2) After three times the longitudinal relaxation time of the sample, the voltage output module 71 outputs a voltage to the guiding coil to generate a guiding magnetic field. The logic level module 73 sends a signal to open the solenoid valve 18, transfers the liquid sample from the sample tube 11 in the polarization area to the sample tube 12 in the detection area, and then sends a signal to close the solenoid valve 18;

[0044] (3) The voltage output module 71 stops outputting voltage to the guiding coil, and the logic level module 73 sends a signal to open the relay of the pulse coil;

[0045] (4) The voltage output module 71 outputs a pulsed voltage, which is amplified by a pulsed power amplifier and applied to the pulsed coil through a relay to generate a pulsed magnetic field;

[0046] (5) After the pulsed voltage is applied, the logic level module 73 sends a signal to turn off all relays and activates the voltage input module 72 to start recording the voltage signal generated by the atomic magnetometer probe;

[0047] (6) The acquisition process of the voltage input module 72 lasts for five times the longitudinal relaxation time of the sample, completes the acquisition of a time-domain nuclear magnetic signal once, and outputs the voltage signal data;

[0048] (7) The logic level module 73 sends a signal to open the first solenoid valve 16, transfer the liquid sample back to the sample tube 11 in the polarization region, then close the first solenoid valve 16, and the experiment ends. If multiple experiments are needed to detect more data, return to step (2) and repeat the steps.

Claims

1. A small ultra-low field nuclear magnetic resonance spectrometer, characterized in that: it includes a sample flow module (10), a hyperpolarization module (20), a probe and sample fixation module (30), a pulse application module (40), a nuclear magnetic detection module (50), a magnetic shielding module (60) and a timing control module (70); the sample flow module (10) includes a polarization region sample tube (11) and a detection region sample tube (12) that are interconnected, and a vacuum pump (13) drives a liquid sample to flow bidirectionally between the polarization region sample tube (11) and the detection region sample tube (12); the hyperpolarization module (20) is arranged on the outer periphery of the polarization region sample tube (11) to polarize the liquid sample in the polarization region sample tube (11); the probe and sample fixation module (30) is arranged on the outer periphery of the detection region sample tube (12) and is used to fix the detection region sample tube (12) and the nuclear magnetic detection module (50); the pulse application module (40) is arranged on the outer periphery of the probe and sample fixation module (30) to apply a pulse to the liquid sample in the detection region sample tube (12), transfer the nuclear magnetization vector of the liquid sample to the transverse direction, and perform free evolution of the sample spin; the nuclear magnetic detection module (50) is arranged in the probe and sample fixation module (30) and is in close contact with the detection region sample tube (12), and is used to detect the free evolution spin signal of the liquid sample in the detection region sample tube (12) and convert it into a voltage signal for output; the magnetic shielding module (60) is used to shield the geomagnetic field to ensure an ultra-low field environment in the detection region; the timing control module (70) is connected to each module and is used to control the operation of each module and collect voltage signals.

2. The small ultra-low field nuclear magnetic resonance spectrometer according to claim 1, characterized in that: the polarization region sample tube (11) and the detection region sample tube (12) are connected through a plexiglass tube (14), and a guiding coil is wound around the plexiglass tube (14).

3. The small ultra-low field nuclear magnetic resonance spectrometer according to claim 2, characterized in that: a first conical flask (15) and a first solenoid valve (16) are arranged between the polarization region sample tube (11) and the vacuum pump (13), a second conical flask (17) and a second solenoid valve (18) are arranged between the detection region sample tube (12) and the vacuum pump (13), and a speed limiting valve (19) is also arranged between the vacuum pump (13) and the first solenoid valve (16) and the second solenoid valve (18).

4. The small ultra-low field nuclear magnetic resonance spectrometer according to claim 2, characterized in that: the hyperpolarization module (20) includes a Halbach magnet, the Halbach magnet is circular tubular, and the polarization region sample tube (11) is placed in the hollow tube cavity of the Halbach magnet.

5. The small ultra-low field nuclear magnetic resonance spectrometer according to claim 1, characterized in that: The probe and sample fixing module (30) includes a solenoid tube (31) with closed ends. A round hole (32) is provided at one end of the solenoid tube (31), and a square hole (33) is provided at the other end. The sample tube (12) in the detection area is placed into the solenoid tube (31) through the round hole (32), and the nuclear magnetic detection module (50) is placed into the solenoid tube (31) through the square hole (33). The nuclear magnetic detection module (50) is in contact with the sample tube (12) in the detection area within the lumen of the solenoid tube (31). A plurality of transverse grooves (34) and a plurality of longitudinal grooves (35) are also provided on the outer wall of the solenoid tube (31).

6. The small ultra-low field nuclear magnetic resonance spectrometer according to claim 5, characterized in that: The pulse application module (40) includes a plurality of groups of magnetic coils arranged on the outer wall of the solenoid tube (31), and the plurality of groups of magnetic coils form a three-dimensional pulsed magnetic field for the solenoid tube (31).

7. The small ultra-low field nuclear magnetic resonance spectrometer according to claim 5, characterized in that: The nuclear magnetic detection module (50) includes an atomic magnetometer. The atomic magnetometer is placed into the solenoid tube (31) through the square hole (33) at the end of the solenoid tube (31), and the probe end of the atomic magnetometer is in contact with the sample tube (12) in the detection area.

8. The small ultra-low field nuclear magnetic resonance spectrometer according to claim 1, characterized in that: The magnetic shielding module (60) is a magnetic shielding barrel composed of 5 layers of permalloy, and demagnetizing coils are provided on the innermost layer and the outermost layer of the magnetic shielding barrel.

9. The small ultra-low field nuclear magnetic resonance spectrometer according to claim 1, characterized in that: The timing control module (70) includes a voltage output module (71), a voltage input module (72), and a logic level module (73). The voltage output module (71) outputs a voltage of 0 to 10V for a given time; the voltage input module (72) collects the voltage data output by the nuclear magnetic detection module (50); the logic level module (73) is used to control the operation of each module.

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