JPH0460556B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a coil device used in a probe of a nuclear magnetic resonance apparatus (NMR apparatus), and particularly to a coil structure that can increase the tuning frequency.

[Prior art] In an NMR device, a probe containing a sample is placed in a uniform static magnetic field, and a high-frequency magnetic field for excitation is irradiated from a coil placed close to the sample in the probe, and resonance from the sample is emitted. A signal is received by this coil, sent to a computer via a receiving circuit, and an NMR spectrum is obtained by Fourier transform processing. At this time, great attention is paid to the shape and structure of the coil, since the quality of the coupling between the coil and the resonator of the sample greatly affects the sensitivity of the NMR device. In the case of NMR devices using superconducting magnets, for example, a cylindrical saddle-shaped coil as shown in FIG. 4 has been commonly used. In the saddle-shaped coil shown in Fig. 4, two spirally wound coil parts 1 and 2 are arranged symmetrically around the cylindrical axis Z around a cylindrical region of radius R in which a sample tube containing a sample is arranged. has been done. This spirally wound coil portion consists of straight portions 1A, 2A parallel to the cylindrical axis Z, and arcuate portions 1B, 2B lying in a plane perpendicular to the cylindrical axis Z. FIG. 5 shows a cross-sectional view of the linear portion A taken along a plane perpendicular to the cylindrical axis Z. The linear portions 1A and 2A are arranged symmetrically on the circumference of the radius R with the Y plane in between. A high frequency magnetic field is generated in the X direction by the coil.

The idea common to conventional coils as mentioned above is
Two spiral-wound coil parts 1 and 2 with the same shape are arranged facing each other from both sides with a cylindrical area in between, and therefore the number of turns of the coil is an even number such as 2, 4, 6, 8, etc. It will be a turn.

By the way, in recent years it has become possible to obtain strong static magnetic fields using superconducting magnets, and along with this, the observation frequency has also been increased from about 400MHz to 500MHz and 600MHz. In order to increase the observation frequency in this way, the sample coil is required to have low inductance, increase the tuning frequency, and have a high Q value to increase the SN ratio and sensitivity.

Conventionally, the two-turn coil shown in FIG. 4, which has the smallest number of turns and can minimize the induction, has been used in such cases. However, even if such a coil is used, the inductance cannot be made sufficiently small, and in the past, this coil has had to be used even though it is undesirable.

Therefore, the present inventor proposed a novel one-turn coil as shown in FIG. 6, in which the winding is arranged on the Y axis in FIG. Proposed as No. 60-18444.
FIG. 6a shows the shape when punched out from the conductor plate, and FIG. 6b shows the state when it is formed into a cylindrical shape. In Figures 6a and 6b, the coil consists of linear conductors L1, L2 parallel to the cylindrical axis Z, and arc-shaped conductors L3, L4 connected in series to form a coil. , second arc-shaped conductors L5 to L8, and leads L9 and L10 for connecting the coil to an external circuit.
As can be seen from the fact that they are not connected to each other, the second arc-shaped conductors L5 to L8 do not have a role as a coil, and are located at the center point O of the cylindrical area where the sample is placed. This is provided for the purpose of compensating for disturbances in the uniformity of the static magnetic field by arranging a conductor having substantially the same shape at a position symmetrical to the first arc-shaped conductor.

According to such a proposed coil, a one-turn coil having a smaller inductance than a conventional two-turn coil can be realized. Moreover, in this proposed coil, the linear conductor L that plays the role of the coil
1. YZ where L2 is perpendicular to the axis of the high frequency magnetic field (X axis)
Although the straight conductor is placed on a plane, the high-frequency magnetic field strength generated in the X-axis direction at the center origin O of the cylindrical area where the sample is placed by the straight conductor placed at this position is different from that of the straight conductor at any other position. Since it is stronger than when it is placed, it has a high Q as a coil.

The present invention aims to further improve this proposed coil and provide a coil that can further increase the tuning frequency.

[Means for achieving the objective] In order to achieve this objective, the present invention
A coil device for an NMR probe is a coil device that is wound around a cylindrical sample area and generates or detects a high-frequency magnetic field in a direction perpendicular to the axis of the cylinder, and in a direction parallel to the axis of the cylinder. a pair of straight conductive parts extending and arranged approximately symmetrically across the cylindrical axis and connected to an external circuit through respective end parts; a first arc-shaped conductive piece for connecting the tips to each other to form a one-turn coil; and a first arc-shaped conductive piece that is symmetrical to the first arc-shaped conductive piece across the center origin of the cylindrical sample area. a second arc-shaped conductive piece disposed at a position, a capacitor is inserted in the middle of the first arc-shaped conductive piece, and the second arc-shaped conductive piece It is characterized in that it is electrically connected only to the end of one linear conductive piece.

[Example] Hereinafter, an example of the present invention will be described in detail using the drawings.

FIG. 1 is a perspective view showing an example of a coil device for an NMR probe embodying the present invention. The coil device shown in Fig. 1 differs from the proposed coil shown in Fig. 6b as follows.
The point is that a capacitor is inserted between each of the arcuate conductors L3 and L4. In this embodiment, as can be seen from FIG. 2, which is a cross-sectional view of the coil taken along a plane perpendicular to the cylindrical axis Z at the positions of the first arc-shaped conductors L3 and L4, the arc-shaped conductors L3 and L4 are By dividing it into two parts, providing an overlapping part, and insulating the part by sandwiching a dielectric film F, the overlapping part has a capacitance, thereby forming a capacitor.

Therefore, if the coil in Fig. 1 is represented as an equivalent circuit, it will be as shown in Fig. 3, and the inductance mainly contributed by the linear conductors L1 and L2 will be
is substantially reduced in a way that is canceled by the composite capacitance of , so that it is possible to raise the resonant frequency (tuning frequency) more than the proposed coil of FIG. 6b.

It goes without saying that the capacitor constructed by sandwiching a dielectric film between arcuate conductors in the above embodiment may be replaced with a small chip capacitor.

In addition to being punched out from a conductor plate as described above, the coil of the present invention can also be formed by attaching a conductor wire to a bobbin, by vapor deposition technology on the surface of a bobbin, or by forming a printed circuit on a substrate with or without flexibility. It can be manufactured by forming it as.

Further, in the above embodiment, the linear conductors are arranged exactly symmetrically with respect to the Z axis, but the linear conductors only need to be arranged substantially symmetrically, and a slight deviation is allowed.

[Effects of the Invention] As detailed above, according to the present invention, an NMR device with small inductance and usable up to high frequencies can be obtained.
A probe coil device is realized.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of a coil device for an NMR probe embodying the present invention, and FIG. 2 is a cross section of the coil taken along a plane perpendicular to the cylindrical axis Z at the positions of the second arcuate conductors L3 and L4. Figures 3 and 3 are diagrams showing the equivalent circuit of the coil in Figure 1, Figures 4 and 5 are diagrams for explaining conventional saddle-shaped coils, and Figures 6a and b are proposed by the inventor. FIG. 2 is a diagram for explaining a new coil. L1, L2: linear conductor, L3 to L8: arcuate conductor, F: dielectric film, C1 to C6: capacitor.

Claims (1)

[Scope of Claims] 1. A coil device that is wound around a cylindrical sample area and generates or detects a high-frequency magnetic field in a direction perpendicular to the axis of the cylinder, the coil device being wound in a direction parallel to the axis of the cylinder. a pair of linear conductive pieces extending and arranged substantially symmetrically across the cylindrical axis and connected to an external circuit via respective end portions; a first arc-shaped conductive piece for connecting the tips to each other to form a one-turn coil; and a first arc-shaped conductive piece that is symmetrical to the first arc-shaped conductive piece across the center origin of the cylindrical sample area. a second arc-shaped conductive piece disposed at a position, a capacitor is inserted in the middle of the first arc-shaped conductive piece, and the second arc-shaped conductive piece A coil device for an NMR probe, characterized in that it is electrically connected only to the end of one linear conductive piece. 2. The coil according to claim 1, wherein the conductive piece is formed of a plate-shaped conductor. 3. The first arcuate conductive pieces are provided in pairs symmetrically across the sample area, and a capacitor is inserted into each of the pair of first arcuate conductive pieces. The coil device for an NMR probe according to any one of items 1 and 2.