JP2008020397A - Nmr probe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an NMR probe equipped with a switching mechanism of a multi-element method for providing elements of kinds sharply exceeding the kinds of installed elements in number. <P>SOLUTION: This NMR probe is equipped with: a disk-shaped disk supported in an NMR probe body and formed by disposing a plurality of tuning elements on a surface of a support body made of a nonmagnetic material; a contact means selectively putting the tuning elements into contact with a sample coil built in the probe body or with a lead wire led out from the sample coil; and a rotative drive means rotating the disk or the contact means. The contact means is capable of simultaneously choosing a single or a plurality of tuning elements from among the plurality of arbitrarily together combined tuning elements. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an NMR probe that can vary a tuning frequency, and more particularly to an NMR probe that incorporates a disk-type tuning element block in which tuning elements such as an inductance and a capacitance constituting a resonance circuit are arranged on both sides.

  FIG. 1 shows a main part of a conventional NMR apparatus. In the measurement by the multiple resonance NMR apparatus 200, the sample tube 1 containing the sample 30 is set in the static magnetic field of the magnet 2 whose magnetic field distortion is corrected by the room temperature shim 3 controlled by the magnetic field correction apparatus 6. 30 is irradiated with an RF pulse having a frequency corresponding to the strength of the static magnetic field to cause an NMR phenomenon.

In that case, as the RF pulse, a pulse signal from the oscillator 14 is selected from a plurality of frequency bands (in the illustrated example, 3 bands; hereinafter, described as 3 bands) according to the nuclide to be observed in the sample 30. The multiple resonance NMR probe 4 is amplified by a power amplifier 13 corresponding to the frequency f ₁ , a power amplifier 15 corresponding to the frequency f ₂ , and a power amplifier 16 corresponding to the frequency f ₃ , and the duplexer 9 for switching input / output. , The sample 30 in the sample tube 1 is irradiated from the multiple resonance NMR probe 4.

  Then, because the sample 30 outputs an NMR signal having a resonance frequency specific to the nuclide due to the NMR phenomenon, the NMR signal is captured by the multiple resonance NMR probe 4.

  At that time, when it is necessary to measure the sample 30 at a predetermined temperature, the temperature around the sample tube 1 in the NMR probe 4 for multiple resonance is variably controlled by the temperature variable device 5 controlled by the computer 7. It has become.

  Then, the NMR signal captured by the multiple resonance NMR probe 4 is sent to the amplifier 10 via the duplexer 9 and amplified, and then converted to an audio frequency by the demodulation detector 11, and further, an A / D converter (ADC). 12 to convert to a digital signal.

  In this way, the digital signal is taken into the computer 7 and the computer 7 analyzes the signal, whereby the sample 30 is analyzed, the analysis result is displayed on the display 8, and the structure of the substance is examined by the multiple resonance NMR apparatus. It is done.

  FIG. 2 shows an RF resonant circuit incorporated in an NMR probe. Conventional example 1 on the left is an example of an unbalanced resonance circuit, where C1 is a tuning capacitive element for tuning, variable capacitor 1 is an auxiliary tuning variable capacitive element for tuning, and variable capacitor 2 is a matching variable capacitive element for matching. It is. In order to avoid interference between the tuning matching section and the sample coil section, the sample coil section is electromagnetically shielded from the tuning matching section by a conductor support having a ground potential. Then, two lead wires are drawn out from the sample coil section through two small holes provided in the support, one of which is connected to the tuning matching circuit, and the other one of the ground potential surrounding the NMR probe. Connected to conductor frame. Since this resonance circuit is an unbalanced circuit, the amplitude of the RF magnetic field becomes maximum at the upper end of the sample coil and becomes zero at the lower end of the sample coil.

  On the other hand, Conventional Example 2 on the right is an example of a balanced resonance circuit, where C1 and C2 are tuning capacitance elements for tuning, variable capacitor 1 is an auxiliary tuning variable capacitance element for tuning, and variable capacitor 2 is for matching for matching. It is a variable capacitance element. In order to avoid interference between the tuning matching section and the sample coil section, the sample coil section is electromagnetically shielded from the tuning matching section by a conductor support having a ground potential. Then, two lead wires are drawn out from the sample coil section through two small holes provided in the support, one of which is connected to the tuning matching circuit and the other through the tuning capacitance element C2. It is connected to a grounded conductor frame surrounding the NMR probe. Since this resonance circuit is a balanced circuit, the amplitude of the RF magnetic field becomes maximum at the upper and lower ends of the sample coil and becomes zero at the center of the sample coil.

  In such an RF resonance circuit, when expanding the tuning range, C1 and C2 are removed and replaced with another element (for example, a capacitive element having a different capacity or an inductive element such as a coil). This exchange is not performed by soldering, but is performed by inserting and removing a shaft called an “stick” on which the element is fixed (Patent Documents 1 and 2).

  3 to 4 are multi-elements so that they can be automated. Among these, the type of device shown in FIG. 3 is applied to an unbalanced resonance circuit such as Conventional Example 1 on the left side of FIG. 2, and is used to replace the tuning capacitor C1 with another element. A replacement element is disposed on a disk-shaped disk provided on the rotating shaft. As the disk rotates, the element is replaced from C1 to another element. As a result, the resonance frequency of the unbalanced resonance circuit as in Conventional Example 1 is shifted and the tuning range is expanded (Patent Document 3).

  On the other hand, the apparatus of the type shown in FIG. 4 is applied to a balanced resonance circuit as in Conventional Example 2 on the right side of FIG. 2, and the tuning capacitors C1 and C2 are replaced with other elements in pairs. Used for. Replacement elements are arranged in pairs in a rectangular slider provided on the rail. As the slider slides, the element is replaced from a pair of C1 and C2 to another pair of elements. This shifts the resonance frequency of the balanced resonance circuit as in Conventional Example 2 and widens the tuning range.

  These elements are arranged at a sufficient interval so that no discharge or the like occurs between the elements.

Japanese Utility Model Publication 2-45477 Japanese Utility Model Publication No. 3-10282 JP-A-3-223686

  The problem with such a multi-element switching type NMR probe is that only one reactance element could be connected to each hot terminal (terminal floating from the ground) of the sample coil. Therefore, if there are three elements of 10 pF, 20 pF, and 30 pF, the conventional multi-element switching device can only select three types of 10 pF, 20 pF, and 30 pF.

  However, if there are three types of elements of 10 pF, 20 pF, and 30 pF, it should be theoretically possible to create a synthetic capacity of 40 pF, 50 pF, and 60 pF from them and select them. If the selection is realized, the frequency band of the sample coil can be lowered to a frequency that is 1 / √2 times the lower frequency limit so far.

  An object of the present invention is to provide an NMR probe provided with a multi-element switching mechanism capable of providing a type of element that greatly exceeds the type of installed element.

In order to achieve this object, the NMR probe according to the present invention comprises:
A disk-shaped disk that is supported in the NMR probe body and is configured by arranging a plurality of tuning elements on the surface of the support made of a non-magnetic material,
Contact means for selectively bringing the tuning element into contact with a sample coil incorporated in the NMR probe body or a lead wire drawn from the sample coil;
Rotation drive means for rotating the disk-like disk or contact means,
The contact means is characterized in that one or a plurality of tuning elements can be simultaneously selected in any combination from a plurality of tuning elements.

  Further, the present invention is characterized in that the reproducibility of the contact position is obtained by connecting a rotary encoder to the disk drive disk or the rotation drive means for rotating the contact means.

  The disk-shaped disc is housed in a shielded conductor case.

  In addition, the shielded conductor case is maintained at a ground potential.

  The disk-shaped disk or the contact means is made of a nonmagnetic metal such as gold-plated phosphor bronze or nonmagnetic brass.

  Further, it is characterized in that magnetic metal plating such as nickel plating is not applied to the base of the plate-shaped disk or the gold plating of the contact means.

According to the NMR probe of the present invention,
A disk-shaped disk that is supported in the NMR probe body and is configured by arranging a plurality of tuning elements on the surface of the support made of a non-magnetic material,
Contact means for selectively bringing the tuning element into contact with a sample coil incorporated in the NMR probe body or a lead wire drawn from the sample coil;
Rotation drive means for rotating the disk-like disk or contact means,
Since the contact means can simultaneously select one or a plurality of tuning elements in any combination from a plurality of tuning elements,
It has become possible to provide an NMR probe equipped with a multi-element switching mechanism that can provide a type of element that greatly exceeds the type of installed element.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 5 is a diagram illustrating an NMR probe according to the present invention.

  The two lead wires 41 from the sample coil 40 pass through a support 43 made of a conductor that electromagnetically shields between the sample coil 40 and the tuning matching portion 42, and from the sample coil 20 side to the tuning matching portion 42 side. Pulled out. The lead wire 41 is insulated by a bush (not shown) made of glass so as not to short-circuit the support 43.

  The two lead wires 41 are drawn into an element switching box 44, which is the core of the present invention, and are configured so that elements corresponding to the tuning frequency of the NMR probe can be selected and connected. Further, a shield container made of a non-magnetic conductor is employed for the case of the element switching box 44. This case is connected to a ground potential frame (not shown) of the NMR probe and always maintains the ground potential.

  One of the lead wires 41 is also connected to a variable capacitor 1 as an auxiliary tuning variable capacitance element and a variable capacitor 2 as a matching variable capacitance element to adjust the tuning matching between an external transmission path (not shown) and the sample coil 40. The variable capacitor 1 has one end of an electrode grounded. In contrast, the variable capacitor 2 maintains a hot state in which the electrode floats from the ground potential.

  FIG. 6 shows the contents of the elements stored in the element switching box 44. A plurality of capacitive elements are housed in the element switching box 44, and these elements are switched by a rotating mechanism. In switching, not only can each element be selected, but a plurality of elements can be selected in any combination from a plurality of elements.

  A contact for selecting an element is composed of a fan-shaped metal piece as shown in FIG. 7, and there are four types of central angles of 0 °, 90 °, 180 °, and 270 °. A piece of metal with a central angle of 0 ° contacts only one element. A piece of metal with a central angle of 90 ° contacts the two elements. A metal piece with a central angle of 180 ° contacts three elements. A piece of metal with a central angle of 270 ° contacts all four elements. These contacts correspond to the parallel connection of the elements.

  The contact is preferably made of phosphor bronze or non-magnetic brass. Although gold plating is applied to the surface, magnetic metal plating such as nickel plating is not applied to the base of the gold plating in order to avoid the influence on the static magnetic field.

  By selecting an element as shown in FIG. 8 while such a contactor is rotated, the four elements A, B, C, D, A, B, C, D, A + B, A + D, B + C are selected. , C + D, A + B + C, A + B + D, A + C + D, B + C + D, and A + B + C + D can be selected.

  The example of FIG. 8 is a case where four different elements are arranged on a disk-shaped disc, but the present invention is not limited to this. For example, as shown in FIG. 9, when there are two elements (when the arrangement angle is 180 °), there are three ways, when there are three elements (when the arrangement angle is 120 °), seven ways and when there are five (placement angle). In the case of 72 °, it is possible to select 21 ways, and in the case of 6 pieces (when the arrangement angle is 60 °), 31 ways can be selected.

  A contact (rotor) 45 for selecting an element is stored in a plastic holder 46 as shown in FIG. Then, the contactor 45 is automatically selected and taken out from the stored holder 46, and is attached to a rotating shaft of a rotating mechanism having a position reproducibility provided with a rotary encoder (not shown) by a ratchet mechanism. . The parts including the ratchet mechanism are grounded, and the operation as a high frequency circuit is guaranteed.

  As shown in FIG. 11, there are two attached contacts, section i (four ways of 1, 2, 3, 4) and angle φ (four ways of 0 °, 90 °, 180 °, 270 °). It is driven by the rotation of a rotary mechanism having a position repeatability with a rotary encoder so that a desired element can be selected, controlled by parameters. Each time the NMR measurement conditions change, the contact is exchanged by an automatic exchange device (not shown), and is replaced with another contact on the rotating shaft of the rotating mechanism as necessary.

  In this way, N elements are allocated on a disk-like disk at equal intervals (360 ° / N) so that a plurality of elements can be selected, so that it is possible to set a wider range of frequencies than ever before.

  In the above-described embodiment, the elements are arranged on the disk-shaped disk with the angle equally divided, but this need not necessarily be equally divided.

  Moreover, the shape of a contact does not necessarily need to be a fan shape. For example, as shown in FIG. 12A, a combination of rectangular plates is used, as shown in FIG. 12A, a combination of elements at opposite positions that are not adjacent to each other can be selected, As shown in (c), it is possible to modify the structure by dividing the element into six so that a combination of elements at positions not adjacent to each other can be selected.

  Alternatively, the contact side may be fixed and the disk-shaped disk side may be rotated. In that case, it is desirable that the rotation axis direction of the disk-shaped disk is substantially orthogonal to the static magnetic field axis applied to the NMR probe in order to avoid disturbance of the static magnetic field due to generation of eddy current during rotation. If the rotational axis direction has a direction component in the direction of the static magnetic field axis applied to the NMR probe, a groove portion that intersects the circumferential direction is provided on the disk-shaped disk surface to block eddy currents. It is necessary to devise it. In that case, the NMR lock may be held at the time of rotation of the disk-shaped disk, the shim operation may be interrupted only during that time period, and the old shim information may be held.

  By doing so, the conventional magnetic field fluctuation and lock fluctuation at the time of driving are reduced, the measurement stability is increased, and this fluctuation time can be ignored, so there is no waiting time and the throughput is improved. .

  In the above-described embodiment, only the capacitive element is taken as an example as an element. However, inductive elements (coils) other than the capacitive element are also targeted.

  In the above embodiment, the disk-shaped disk is the hot side (the side floating from the ground) and the contact is the ground side, but this may be reversed.

  Can be widely used for NMR probes.

It is a figure which shows the conventional multiple resonance NMR apparatus. It is a figure which shows the conventional resonant circuit. It is a figure which shows the conventional element unit. It is a figure which shows the conventional element unit. It is a figure which shows one Example of the multiple resonance NMR apparatus concerning this invention. It is a figure which shows one Example of the element switching box concerning this invention. It is a figure which shows one Example of the contactor of the element switching box concerning this invention. It is a figure which shows one Example of how to switch the element switching box concerning this invention. It is a figure which shows another Example of the element switching box concerning this invention. It is a figure which shows the accommodation method of the contact of the element switching box concerning this invention. It is a figure which shows the control method of the contact of the element switching box concerning this invention. It is a figure which shows another control method of the contact of the element switching box concerning this invention.

Explanation of symbols

1: Sample tube, 2: Magnet, 3: Room temperature shim, 4: NMR probe, 5: Temperature variable device, 6: Magnetic field correction device, 7: Computer, 8: Display, 9: Duplexer, 10: Amplifier, 11: Demodulator, 12: ADC, 13: Power amplifier, 14: Oscillator, 15: Power amplifier, 16: Power amplifier, 30: Sample, 40: Sample coil, 41: Lead wire, 42: Tuning and matching unit, 43: Support 44: Element switching box, 45: Contact, 46: Holder, 200: Multiple resonance NMR apparatus

Claims (6)

A disk-shaped disk that is supported in the NMR probe body and is configured by arranging a plurality of tuning elements on the surface of the support made of a non-magnetic material,
Contact means for selectively bringing the tuning element into contact with a sample coil incorporated in the NMR probe body or a lead wire drawn from the sample coil;
Rotation drive means for rotating the disk-like disk or contact means,
An NMR probe characterized in that the contact means can simultaneously select one or a plurality of tuning elements in any combination from a plurality of tuning elements. 2. The NMR probe according to claim 1, wherein a reproducibility of the contact position is obtained by connecting a rotary encoder to the disk-like disk or a rotation drive means for rotating the contact means. 3. The NMR probe according to claim 1, wherein the disk-shaped disk is housed in a shielded conductor case. The NMR probe according to claim 3, wherein the shielded conductor case is maintained at a ground potential. 11. The NMR probe according to claim 9, wherein the disk-like disk or the contact means is made of a nonmagnetic metal such as phosphor bronze or nonmagnetic brass plated with gold. 6. The NMR probe according to claim 5, wherein a magnetic metal plating such as nickel plating is not applied to the base of the plate-like disk or the gold plating of the contact means.

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