JPS61200450A - Nuclear magnetic resonance probe - Google Patents

Abstract

PURPOSE:To make the inductance of a coil variable without disturbing the uniformity of a static magnetic field, by providing a pair of conductive members close to a coil and arranged almost symmetrically so as to hold the coil therebetween and a moving mechanism for moving a pair of the conductive members to mutually opposite directions while holding the symmetric relation interposing the coil. CONSTITUTION:Conductor rings 3, 4 are symmetrically arranged so as to hold transmitting and receiving coils 1 and, because the nuts 7, 8 supporting said rings 3, 4 take the relation of mutually reverse screws, the conductor rings 3, 4 are moved by the same distance to opposite directions by rotating a screw rod 10 while hold the center surfaces of the transmitting and receiving coils 1. By this method, the inductances shown by the transmitting and receiving coils 1 can be regulated and the variable range of tuning frequency can be drastically enlarged. Further, by taking the capacity of a condenser in a high range (relatively small capacity) of Q and reducing the inductances of the transmitting and receiving coils, the capacity Q of a tuning circuit can be enhanced even in a high frequency region.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a nuclear magnetic resonance probe (NMR probe) used in a nuclear magnetic resonance bag M (NMR apparatus).

[Prior art] In an NMR apparatus, a sample placed in a static VNS is irradiated with a high-frequency pulsed magnetic field, a resonance signal generated from the sample due to resonance is detected, and a Fourier transform process is performed to obtain an NMR signal.
Obtaining a spectrum. In this case, the NMR probe plays extremely important roles, such as holding and rotating the sample, irradiating high-frequency pulses using the built-in transmitter/receiver coil and transmitter/receiver circuit, and receiving resonance signals.

Conventionally, this NMR probe was prepared specifically for each type of observation nucleus, and the probe had to be replaced each time the observation nucleus changed, but recently, one probe can be used for multiple observation nuclei. Variable tuning probes that can perform measurements are becoming popular.

FIG. 3 shows an example of a transmitter/receiver circuit used in such a variable tuning probe. In Fig. 3, there are transmitting and receiving coils,
CV is a variable capacitor for tuning variation, and CI is a variable capacitor for matching adjustment. By adjusting CV from outside the probe, the tuning frequency can be changed. Instead of adjusting the variable capacitor, a changeover switch SW is provided as shown in Figure 4, and the capacitor C1 and capacitor C are connected to the transmitting and receiving coil.
2 and an external coil LO are selectively connected to change the tuning frequency.

[Problem to be solved by the invention 1 However, in the circuit shown in Fig. 3, the variable capacitance of the variable capacitor cannot be varied widely, so there is a limit to the variable range of the tuning frequency, and the Q of the tuning circuit is influenced by the Q of the variable capacitor. In order to be
In particular, it was not possible to achieve a high Q in a high frequency region.

Furthermore, the circuit shown in FIG. 4 has a problem in that the external coil LO greatly reduces the Q of the tuned circuit.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide an NMR probe that solves the above-mentioned problems by making it possible to adjust the inductance of the transmitter/receiver coil itself.

[Means for Solving the Problem 1] In order to achieve this object, the NMR probe according to the present invention includes a coil wound around a region where a sample is placed, and a coil located close to and sandwiching the coil. a pair of conductive members disposed approximately symmetrically, and a moving mechanism for moving the pair of conductive members in opposite directions while maintaining a symmetrical relationship with the coil sandwiched therebetween. This is marked as a ¥# sign.

[Example] Hereinafter, one embodiment of the present invention will be explained in detail based on the drawings.

FIG. 1 shows the main parts of an NMR probe embodying the present invention, and FIG. 2 is a cross-sectional view of the probe taken along the X-Y plane. In FIGS. 1 and 2, 1 is a saddle-shaped transmitting/receiving coil, 2 is a coil bobbin, and a sample tube containing a sample is inserted into this bobbin along the Z axis to which a static magnetic field is applied. 3.4
is a conductor ring made of copper, for example, which has a slightly larger diameter than the bobbin, and is attached to the nut 7.8 via the stator 5.6. The nuts 7 and 8 have opposite threads to each other, half of the total length is a right-hand thread, half is a left-hand thread, and the nuts 7 and 8 are fully threaded, and are screwed into a threaded rod 10 rotatably held on the probe base 9. ing. Reference numeral 11 denotes a guide rod that passes through the stator 5.6 to prevent rotation of the ring, and the base 9.
installed on. 12 is a knob for rotating the threaded rod 10 from outside the probe.

In the above configuration, the conductor ring 3.4 is connected to the transmitter/receiver coil 1.
The conductor rings 3 and 4 are arranged symmetrically across the transmitter/receiver coil 1, and since the nuts 7 and 8 supporting each are in a reverse threaded relationship with each other, when the threaded rod 10 is rotated, the conductor rings 3 and 4
move the same distance in opposite directions across the center plane (X-Y plane). That is, by rotating the threaded rod 10, the two rings can be rotated while maintaining the symmetry of the two rings with respect to the X-Y plane.
The distance or the degree of overlap between the two rings and the transmitting/receiving coil 1 can be set appropriately.

By the way, when a conductive member is placed close to a coil, an eddy current flows inside or on the surface of the conductive member due to the alternating magnetic field generated by the coil, and the magnetic flux generated by the eddy current changes the distribution of magnetic flux inside the coil. Therefore, the inductance of the coil has a value different from that without the conductive member.

By changing the relative positional relationship between the conductive member and the coil, it is possible to arbitrarily change the inductance of the coil.

Therefore, by appropriately adjusting the distance or degree of overlap between the ring and the transmitting/receiving coil 1 as described above, the inductance exhibited by the transmitting/receiving coil 1 can be adjusted.
If such a transmitting/receiving coil is used in the circuit shown in FIG. 3, for example, the range of tuning frequency can be dramatically expanded compared to the conventional method in which the tuning frequency is adjusted by varying only the capacitance using a variable capacitor.

In addition, the capacitance of the capacitor should be set in a high Q range (relatively small
f1), and it is possible to increase the rt451 frequency by reducing the inductance of the transmitting and receiving coils,
It becomes possible to increase the Q of the tuned circuit even in a high frequency region.

Furthermore, if the transmitter/receiver coil shown in FIG. 1 is used in the circuit shown in FIG. 4, it is possible to omit the external coil LO, and the problem of Q reduction due to the coil LO can be solved.

As described above, according to the present invention, a great effect can be obtained in terms of tuning frequency variation, but if the uniformity of the static magnetic field is disturbed by the movement of the ring, a large price must be paid in terms of a decrease in resolution. In this regard, in the present invention, the two rings are arranged symmetrically across the transmitter/receiver coil (strictly speaking, across the X-Y plane) and move symmetrically, so that the disturbance imparted to the static magnetic field is reduced to 2. The two rings cancel each other out, and the reduction in uniformity can be minimized.

In the above embodiments, the present invention is applied to the transmitter/receiver coil of the observation system, but it goes without saying that it can also be applied to the decoupling coil of the irradiation system.

Providing a scale or a meter to indicate the amount of rotation of the threaded rod will make operations easier and more practical when reading the tuned frequency and setting the observation nucleus.

[Effect of the invention J As described above, according to the present invention, the inductance of the coil can be varied without disturbing the uniformity of the static magnetic field.
An R probe is implemented.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the main parts of an NMR probe embodying the present invention, Fig. 2 is a cross-sectional view taken along the X-Y plane, and Figs. 3 and 4 are for explaining the conventional transmitting/receiving circuit. This is a diagram. 1: Transmitting/receiving coil 2: Coil bobbin 3.4: Conductor ring 5.6: Stator 7.8: Nut 9 Nibro One base 10: Threaded rod
11 Guide rod 12: Knob

Claims (1)

[Claims] a coil wound around an area where a sample is placed; a pair of conductive members disposed close to the coil and approximately symmetrically across the coil; A nuclear magnetic resonance probe characterized in that it is equipped with a movement mechanism for moving in opposite directions while maintaining a symmetrical relationship with a coil in between.