Nuclear magnetic resonance probe, nuclear magnetic resonance measuring apparatus, and nuclear magnetic resonance measuring method

Abstract

To provide a nuclear magnetic resonance probe capable of expanding of an adjustable frequency band and enhancing measurement work efficiency in measurement of NMR signals.SOLUTION: A nuclear magnetic resonance probe 2 includes: an NMR signal detection unit 23 that is constituted of a sample coil 230 and a tuning matching circuit 231 and detects an NMR signal from a sample S; and a coaxial resonator 24 having coaxial power lines connected to the NMR signal detection unit 23. The coaxial resonator 24 includes a length adjustment mechanism that causes a short circuit bridge 242 to slide along a coaxial direction of the power lines 241A, 241B to adjust length of the power lines 241A, 241B in the coaxial direction.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a nuclear magnetic resonance probe (hereinafter referred to as an "NMR probe") using the principle of nuclear magnetic resonance (NMR), a nuclear magnetic resonance measurement apparatus (hereinafter referred to as an "NMR apparatus"), and a nuclear magnetic resonance measurement method.

Background Art

[0002] In an NMR apparatus, as a detection circuit for detecting a nuclear magnetic resonance signal (hereinafter referred to as an "NMR signal") from a nuclide to be observed contained in a sample, for example, an LC resonance circuit composed of a coil, a variable capacitor, etc. is provided, and it is necessary to synchronize and match the resonance frequency of the detection circuit with the resonance frequency corresponding to the nuclide to be observed.

[0003] In the measurement of an NMR signal using a high frequency, when the adjustable limit value of the variable capacitor is exceeded, there is a problem that the resonance frequency of the detection circuit cannot be adjusted to a specific frequency. Therefore, in an NMR apparatus, a method of adjusting the resonance frequency of the detection circuit by connecting a λ / 4 resonator using a λ / 4 coaxial line to the detection circuit is adopted (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the NMR apparatus adopting the λ / 4 resonator disclosed in Patent Document 1, for example, when measuring a proton 1 H as a nuclide to be observed, a proton 1Since the change in frequency is small in the measurement under a constant magnetic field, a λ / 4 coaxial line corresponding to a specific frequency λ is used. However, for example, in the measurement of an NMR signal when the sample is a magnetic material or the like, due to the formation of magnetic order, the electron spin generates a strong effective magnetic field on the nucleus. Further, since the magnitude of the effective magnetic field by this electron spin generally changes according to temperature changes and the like, the resonance frequency also changes greatly.

[0006] In such a case, with a conventional λ / 4 coaxial line of a fixed length, it was difficult to adjust the resonance frequency of the detection circuit to the resonance frequency of the nuclide to be observed. Further, even if a plurality of types of λ / 4 coaxial lines having different lengths were prepared, in the measurement of the NMR signal, since the entire sample and the NMR probe are generally cooled to a low temperature, recooling is required every time the λ / 4 coaxial line is exchanged, leading to a decrease in the measurement work efficiency from the viewpoints of time and energy.

[0007] The present invention has been made in view of such circumstances, and an object thereof is to provide a nuclear magnetic resonance probe, a nuclear magnetic resonance measurement apparatus, and a nuclear magnetic resonance measurement method that enable an expansion of an adjustable frequency band and an improvement in measurement work efficiency in the measurement of an NMR signal.

Means for Solving the Problems

[0008] The present invention solves the above problems, and a nuclear magnetic resonance probe according to one embodiment of the present invention is composed of a sample coil and a tuning matching circuit, and an NMR signal detection unit that detects an NMR signal from a sample, and a coaxial resonator having a coaxial power line connected to the NMR signal detection unit. The coaxial resonator includes a length adjustment mechanism for adjusting the length of the coaxial direction of the power line.

[0009] Further, a nuclear magnetic resonance measurement apparatus according to another embodiment of the present invention is the nuclear magnetic resonance probe, A control unit that processes the NMR signal detected by the nuclear magnetic resonance probe is provided.

[0010] Moreover, a nuclear magnetic resonance measurement method according to another aspect of the present invention is a nuclear magnetic resonance measurement method for measuring the sample using the nuclear magnetic resonance probe, comprising: a step of setting the sample in the nuclear magnetic resonance probe; a step of adjusting the length in the coaxial direction by the length adjustment mechanism; a step of detecting the NMR signal by the NMR signal detection unit; and a step of processing the NMR signal detected by the NMR signal detection unit.

Advantages of the Invention

[0011] According to the nuclear magnetic resonance probe, the nuclear magnetic resonance measurement apparatus, and the nuclear magnetic resonance measurement method according to the above aspect of the present invention, since the coaxial resonator connected to the NMR signal detection unit includes a length adjustment mechanism for adjusting the length in the coaxial direction of the power line, it is possible to expand the adjustable frequency band in the detection and measurement of the NMR signal by the NMR signal detection unit and improve the measurement work efficiency.

Brief Description of the Drawings

[0012]

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Figure 10

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0014] Fig. 1 is an overall configuration diagram showing an example of the nuclear magnetic resonance measurement apparatus 1. The nuclear magnetic resonance measurement apparatus (NMR apparatus) 1 is an apparatus for observing a nuclear magnetic resonance signal (NMR signal) from a nuclide to be observed contained in the sample S. The sample S may be any substance such as a synthetic compound or a natural compound, and may be a magnetic substance or a non-magnetic substance.

[0015] The NMR apparatus 1 mainly includes a magnetic field generation unit 10, a cooling unit 11, a vacuum generation unit 12, a control unit 13, and a nuclear magnetic resonance probe (NMR probe) 2.

[0016] The magnetic field generation unit 10 is a system for generating a static magnetic field. For example, the NMR probe 2 is disposed in the cavity portion at the center thereof. The cooling unit 11 is a system for cooling the NMR probe 2. For example, a refrigerant (such as helium gas) cooled to a predetermined temperature (2K, 4K, etc.) by a refrigerator is supplied to the NMR probe 2. The vacuum generation unit 12 is a system for controlling the NMR probe 2 to a vacuum state, and is composed of, for example, a vacuum pump or the like.

[0017] The control unit 13 includes a transmission system 130 that transmits a high-frequency signal to the NMR probe 2, a reception system 131 that receives the NMR signal detected by the NMR probe 2, a signal switch (duplexer) 132 provided between the NMR probe 2 and the transmission system 130 and the reception system 131, and a control computer 133 that processes the NMR signal detected by the NMR probe 2.

[0018] The transmission system 130 is composed of, for example, an oscillator that generates a high-frequency signal, an amplifier that amplifies the high-frequency signal, etc. The amplified high-frequency signal is transmitted to the NMR probe 2 via the signal switch 132. The reception system 131 is composed of, for example, an amplifier that amplifies the NMR signal received via the signal switch 132, a demodulation detector that converts the amplified NMR signal to an audio frequency, an A / D converter that converts the converted NMR signal to a digital signal, etc. The converted digital signal is supplied to the control computer 133.

[0019] The control computer 133 is composed of a general-purpose or dedicated computer and includes, for example, an arithmetic unit (processor) such as a CPU, a storage unit, an input unit, a display unit, and a communication unit. The control computer 133 has functions of controlling the transmission system 130 and the reception system 131, performing processing such as Fourier transform on the digital signal based on the NMR signal by the reception system 131 to generate an NMR spectrum, and operating the input unit and the display unit as a user interface. Also, the control computer 133 is connected to an external device (not shown) via a wired or wireless network and is configured to be able to transmit and receive various data.

[0020] The NMR probe 2 is connected to the signal switch 132 via a coaxial cable 20 and a coaxial connector 21. The NMR probe 2 irradiates the sample S placed in the static magnetic field with the high-frequency signal transmitted from the transmission system 130 and detects the NMR signal generated from the sample S by the irradiation of the high-frequency signal.

[0021] (Configuration of the Nuclear Magnetic Resonance Probe 2) FIG. 2 is a front view showing an example of the nuclear magnetic resonance probe 2. FIG. 3 shows an example of the nuclear magnetic resonance probe 2, where (a) is a partially enlarged front view and (b) is a partially enlarged side view. FIG. 4 shows an example of the nuclear magnetic resonance probe 2, where (a) is a perspective view and (b) is a partially enlarged perspective view. FIG. 5 is a schematic diagram showing an example of the coaxial resonator 24. FIG. 6 is a circuit diagram showing an example of the nuclear magnetic resonance probe 2.

[0022] In addition to the coaxial cable 20 and the coaxial connector 21 described above, the NMR probe 2 mainly includes a container 22, an NMR signal detection unit 23, a coaxial resonator 24, an operation mechanism unit 25, and an equipment connector 26.

[0023] The container 22 is made of a vacuum-insulating member. For example, it has a cylindrical outer shape and a hollow portion inside which can accommodate the NMR signal detection unit 23 and the coaxial resonator 24. The container 22 includes a container body 220, a circular accommodation port 221 provided on one axial side of the container body 220, a flange-shaped lid 222 for sealing the accommodation port 221, radiation shield plates 223A and 223B for preventing radiant heat from the outside, and a refrigerant inlet pipe 224A and a refrigerant outlet pipe 224B for the refrigerant to flow in and out by the cooling unit 11.

[0024] The lid 222 is integrally attached with the coaxial cable 20, the NMR signal detection unit 23, the coaxial resonator 24, the operation mechanism unit 25, and the equipment connector 26. When setting the sample S, it is removed from the container body 220, and when measuring the sample S, it is attached to the container body 220. As shown in FIG. 2 (omitted in FIGS. 3 and 4), the radiation shield plate 223A is arranged inside the container 22 and is formed in a cylindrical shape so as to surround the NMR signal detection unit 23 and the coaxial resonator 24. The radiation shield plate 223B is arranged at a predetermined interval with respect to the axial direction of the container 22 and is formed in a disc shape.

[0025] The NMR signal detection unit 23 is composed of a sample coil 230 and a tuning and matching circuit 231, irradiates the sample S with a high-frequency signal, and detects the NMR signal from the sample S.

[0026] The sample coil 230 is disposed at the innermost part of the container 22, and the sample S is disposed at the center thereof.

[0027] As shown in FIG. 6, the tuning and matching circuit 231 includes a variable capacitor 232 for tuning connected between the sample coil 230 and the coaxial cable 20, and a variable capacitor 233 for matching connected in parallel with the sample coil 230. The electrostatic capacitance of the variable capacitor 232 for tuning and the variable capacitor 233 for matching is variable according to the operation amount with respect to the operation mechanism unit 25. Note that the connection relationship of the tuning and matching circuit 231 is not limited to the example of FIG. 6. For example, the variable capacitor 233 for matching may be connected in series with the sample coil 230. Further, the tuning and matching circuit 231 is not limited to the example of FIG. 6, and may further include other circuit elements (capacitors, coils, resistors, etc.).

[0028] The coaxial resonator 24 has coaxial power lines 241A and 241B connected to the NMR signal detection unit 23 (between the sample coil 230 and the variable capacitor 232 for tuning in the example of FIG. 6). The coaxial resonator 24 includes a length adjustment mechanism for adjusting the coaxial direction length of the power lines 241A and 241B. The coaxial direction of the power lines 241A and 241B is the same as the axial direction of the container 22. Note that the connection relationship of the coaxial resonator 24 to the NMR signal detection unit 23 is not limited to the example of FIG. 6 and may be appropriately changed.

[0029] The coaxial resonator 24 includes an insulating substrate 240 having a shape elongated in the coaxial direction, a first power line 241A and a second power line 241B that extend in the coaxial direction with respect to the substrate 240 and one of which is connected to the NMR signal detection unit 23, and a short-circuit bridge 242 that short-circuits the first power line 241A and the second power line 241B at a short-circuit end 243B on the opposite side of the connection end 243A connected to the NMR signal detection unit 23 and is provided on the substrate 240 so that the position of the short-circuit end 243B can be adjusted in the coaxial direction. In the present embodiment, the first power line 241A is connected to the NMR signal detection unit 23, and the second power line 241B is grounded.

[0030] The substrate 240 is formed of a columnar or cylindrical insulating member. In the present embodiment, the substrate 240 is formed in a cylindrical shape as shown in FIG. 5.

[0031] The first power line 241A and the second power line 241B are respectively arranged at a predetermined interval so as to cover the outer peripheral surface of the substrate 240 in a spiral shape. The first power line 241A and the second power line 241B are formed of a conductive member.

[0032] The short-circuit bridge 242 is formed of a cylindrical conductive member that is fitted on the outer periphery of the first power line 241A and the second power line 241B and is slidable in the coaxial direction with respect to the first power line 241A and the second power line 241B. In the present embodiment, the short-circuit bridge 242 is formed of a cylindrical member as shown in FIG. 5. Note that the shape of the short-circuit bridge 242 is not limited to the example of FIG. 5, and may be, for example, a U-shaped cross section.

[0033] When the short - circuit bridge 242 moves in the coaxial direction while in contact with the first power line 241A and the second power line 241B according to the amount of operation on the operation mechanism part 25, the position where the short - circuit bridge 242 contacts the first power line 241A and the second power line 241B (the position of the short - circuit end 243B) is displaced, so that the coaxial length of the power lines 241A and 241B is adjusted. Therefore, when the short - circuit bridge 242 moves in the coaxial direction while in contact with the first power line 241A and the second power line 241B, it functions as a length adjustment mechanism for the coaxial resonator 24.

[0034] The operation mechanism part 25 includes a tuning capacitor operation part 250 for operating the tuning variable capacitor 232, a matching capacitor operation part 251 for operating the matching variable capacitor 233, and a resonator operation part 252 for operating the short - circuit bridge 242 of the coaxial resonator 24.

[0035] The resonator operation part 252 includes a rotary knob 253 provided on the lid 222 of the container 22, a nut 254 provided at the end of the rotary knob 253, and a shaft 255 having a bolt - shaped end screwed into the nut 254 and with the opposite end attached to the short - circuit bridge 242. The rotary knob 253 of the operation mechanism part 25 may be manually operated by the measurer, or may be connected to a drive mechanism such as a motor and a gear and automatically operated by the control computer 133. Since the tuning capacitor operation part 250 and the matching capacitor operation part 251 are configured in the same way as the resonator operation part 252, the description thereof is omitted.

[0036] The device connector 26 is attached to communication lines and power lines connected to devices (not shown) such as a temperature sensor and a heater provided in the container 22, and is connected to the control part 13 and the power supply.

[0037] FIG. 7 shows modified examples of the coaxial resonators 24a to 24c, and (a) is a schematic view showing a first modified example, (b) is a schematic view showing a second modified example, and (c) is a schematic view showing a third modified example.

[0038] In the coaxial resonator 24a according to the first modification example (Fig. 7(a)), the base body 240 is formed in a quadrangular prism shape, and the first power line 241A and the second power line 241B are arranged on the same outer surface of the base body 240. The first power line 241A is formed as one power line extending in the coaxial direction, and the second power line 241B is arranged on both sides of the first power line 241A and is formed as two power lines respectively extending in the coaxial direction. The short - circuit bridge 242 is formed of a flat - plate - shaped member slidable with respect to the first power line 241A and the second power line 241B.

[0039] In the coaxial resonator 24b according to the second modification example (Fig. 7(b)), the base body 240 is formed in a quadrangular prism shape, and the first power line 241A and the second power line 241B are respectively arranged on the opposing outer surfaces of the base body 240. The first power line 241A is formed as a power line extending in the coaxial direction and having a narrow width, and the second power line 241B is formed as a power line extending in the coaxial direction and having a wide width. The short - circuit bridge 242 is formed of a member slidable on the outer surfaces of the first power line 241A and the second power line 241B.

[0040] In the coaxial resonator 24c according to the third modification example (Fig. 7(c)), the base body 240 is formed in a cylindrical shape, and the first power line 241A and the second power line 241B are arranged on the outer peripheral surface of the base body 240. The first power line 241A is formed as a power line extending in the coaxial direction and having a narrow width, and the second power line 241B is formed as a power line extending in the coaxial direction and having a wide width. The short - circuit bridge 242 is formed of a cylindrical member slidable on the outer surfaces of the first power line 241A and the second power line 241B.

[0041] (Nuclear magnetic resonance measurement method) Fig. 8 is a flowchart showing an example of a nuclear magnetic resonance measurement method using the nuclear magnetic resonance measurement apparatus 1 and the nuclear magnetic resonance probe 2.

[0042] First, in step S1, the sample S is set in the NMR probe 2. Specifically, the lid 222 of the NMR probe 2 is removed from the container body 220, and the sample S is placed inside or near the sample coil 230. Then, the sample S in this state, the NMR signal detector 23 and the coaxial resonator 24 integrally attached to the lid 222 are inserted into the container body 220, and the lid 222 is sealed.

[0043] Next, in step S2, the magnetic field generation unit 10, the cooling unit 11, and the vacuum generation unit 12 operate, and the NMR probe 2 is controlled to a state where it can measure the sample S. Specifically, the NMR probe 2 is arranged in the static magnetic field generated by the magnetic field generation unit 10, and the inside of the container 22 is controlled to be cooled and in a vacuum state by the cooling unit 11 and the vacuum generation unit 12.

[0044] Next, in step S3, as the operation mechanism unit 25, the tuning capacitor operation unit 250, the matching capacitor operation unit 251, and the resonator operation unit 252 are respectively operated, and the tuning (adjustment) of the tuning and matching circuit 231 and the coaxial resonator 24 when measuring the NMR signal is performed. Specifically, the capacitance of the tuning variable capacitor 232 and the matching variable capacitor 233 and the length of the coaxial resonator 24 in the coaxial direction are adjusted. As the tuning method, for example, there are a manual method in which the operator manually operates the operation mechanism unit 25 while checking the return loss level of the NMR probe 2 displayed on the display unit of the control computer 133, and an auto method in which the control computer 133 automatically operates the operation mechanism unit 25 according to the return loss level of the NMR probe 2.

[0045] Next, in step S4, the sample S is measured by detecting the NMR signal. Specifically, a high-frequency signal is supplied from the transmission system 130 of the control unit 13 to the NMR probe 2, and the NMR signal from the sample S is detected by the NMR probe 2 and further received by the reception system 131.

[0046] Then, in step S5, the control computer 133 performs processing such as Fourier transform on the digital signal based on the NMR signal, thereby generating an NMR spectrum, which is displayed, for example, on the display unit of the control computer 133 as the measurement result of the sample S. Further, the measurement result of the sample S may be stored in the storage unit of the control computer 133.

[0047] FIG. 9 is a graph showing the measurement result of the return loss in the nuclear magnetic resonance probe 2. In FIG. 9, when the impedance of the NMR apparatus 1 is 50 [Ω], the return loss S 11 of the NMR probe 2 is shown with respect to the frequency dependence.

[0048] In the NMR probe 2, by adjusting the length of the coaxial resonator 24, for example, the detection characteristics of the NMR probe 2 can be adjusted so that the absorption of the high-frequency signal (return loss S 11 ) peaks at an arbitrary frequency in the range of 60 MHz to 1075 GHz.

[0049] FIG. 10 is a graph showing the measurement result of the Mn nucleus of MnCO3 by the nuclear magnetic resonance probe 2. 55 As the measurement conditions of the NMR apparatus 1, the Hahn echo method was adopted, and the 1st pulse was 0.5 [μs] and the 2nd pulse was 1 [μs]. In FIG. 10, the NMR probe 2 shows the measurement result of the NMR signal when measuring the Mn nucleus of manganese carbonate MnCO3 at a temperature of 3 [K], a magnetic field of 2 [kOe], and the magnetic field in the [11-20] direction of the crystal. 55

[0050] As described above, according to the nuclear magnetic resonance probe 2, the nuclear magnetic resonance measuring apparatus 1, and the nuclear magnetic resonance measuring method according to the present embodiment, since the coaxial resonator 24 connected to the NMR signal detection unit 23 includes a length adjustment mechanism for adjusting the coaxial direction lengths of the power lines 241A and 241B, it is possible to expand the adjustable frequency band in the detection and measurement of the NMR signal by the NMR signal detection unit 23 and improve the measurement work efficiency. Therefore, for example, even when the sample S is a substance with a large resonance frequency change width such as a magnetic material, by adjusting the coaxial direction lengths of the power lines 241A and 241B by the length adjustment mechanism of the coaxial resonator 24, the NMR signal can be detected with high sensitivity.

[0051] Further, since the short - circuit bridge 242 of the coaxial resonator 24 is provided on the base body 240 such that the position of the short - circuit end 243B that short - circuits the first power line 241A and the second power line 241B can be adjusted in the coaxial direction, the coaxial resonator 24 can realize a length adjustment mechanism with a simple structure.

[0052] Also, since the first power line 241A and the second power line 241B of the coaxial resonator 24 are arranged at a predetermined interval so as to cover the outer peripheral surface of the base body 240 in a spiral shape, the distance between the first power line 241A and the second power line 241B can be made longer with respect to the unit length in the coaxial direction. Therefore, when constructing the coaxial resonator 24, the frequency band of the NMR signal detection unit 23 can be further expanded with respect to the unit length in the coaxial direction.

[0053] (Other embodiments) Although the embodiments of the present invention have been described above, the present invention is not limited to the above - described embodiments and can be appropriately changed without departing from the technical idea of the present invention.

[0054] In the above - described embodiment, the coaxial resonators 24, 24a to 24c have been described as including a length adjustment mechanism as shown in FIGS. 5 and 7. However, the length adjustment mechanism is not limited to the above example as long as it is a mechanism capable of adjusting the coaxial direction lengths of the power lines 241A and 241B, and can be appropriately changed.

Explanation of Symbols

[0055] 1…Nuclear Magnetic Resonance Measuring Apparatus (NMR Apparatus), 2…Nuclear Magnetic Resonance Probe (NMR Probe), 10…Magnetic Field Generation Unit, 11…Cooling Unit, 12…Vacuum Generation Unit, 13…Control Unit, 20…Coaxial Cable, 21…Coaxial Connector, 22…Container, 23…NMR Signal Detection Unit, 24, 24a~24c…Coaxial Resonators, 25…Operation Mechanism Unit, 26…Equipment Connector, 130…Transmission System, 131…Receiving System, 132…Signal Switcher, 133…Control Computer, 220…Container Body, 221…Containment Opening, 222…Cover, 223A, 223B…Radiation Shield Plates, 224A…Refrigerant Inflow Pipe, 224B…Refrigerant Outflow Pipe, 230…Sample Coil, 231…Tuning and Matching Circuit, 232…Variable Capacitor for Tuning, 233…Variable Capacitor for Matching, 240…Substrate, 241A…First Power Line, 241B…Second Power Line, 242…Short - Circuit Bridge, 243A…Connection End, 243B…Short - Circuit End, 250…Operation Unit for Tuning Capacitor, 251…Operation Unit for Matching Capacitor, 252…Operation Unit for Resonator, 254…Nut, 255…Shaft, S…Sample

Claims

1. An NMR signal detection unit configured by a sample coil and a tuning matching circuit, for detecting an NMR signal from a sample, and a coaxial resonator having a coaxial power line connected to the NMR signal detection unit. The coaxial resonator has an insulating substrate having a shape elongated in the coaxial direction of the power line, a first power line and a second power line that extend in the coaxial direction with respect to the substrate and one of which is connected to the NMR signal detection unit, and a short-circuit bridge that short-circuits the first power line and the second power line at a short-circuit end opposite to the connection end connected to the NMR signal detection unit, and is provided on the substrate so that the position of the short-circuit end can be adjusted in the coaxial direction. The short-circuit bridge functions as a length adjustment mechanism for adjusting the length of the power line in the coaxial direction by moving in the coaxial direction while being in contact with the first power line and the second power line. An NMR probe characterized by the above.

2. The substrate is formed of a columnar or cylindrical member, The first power line and the second power line are respectively arranged at a predetermined interval so as to spirally cover the outer peripheral surface of the substrate. The short-circuit bridge is fitted on the outer periphery of the first power line and the second power line and is formed of a member slidable in the coaxial direction with respect to the first power line and the second power line. The NMR probe according to claim 1, characterized by the above.

3. An NMR probe according to claim 1 or claim 2, and a control unit that processes the NMR signal detected by the NMR probe. An NMR measuring apparatus characterized by the above.

4. An NMR measurement method for measuring the sample using the NMR probe according to claim 1 or claim 2, comprising the steps of setting the sample in the NMR probe, adjusting the length in the coaxial direction by the length adjustment mechanism, detecting the NMR signal by the NMR signal detection unit, and processing the NMR signal detected by the NMR signal detection unit. An NMR measurement method characterized by the above.

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