JPH0572551B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a probe used in a nuclear magnetic resonance apparatus, and particularly to a variable frequency probe suitable for use in solid-state double resonance measurements.

[Prior Art] Conventionally, a configuration shown in FIG. 5, for example, is known as a variable frequency probe used for solid-state double alliance measurement. In the figure, reference numeral 1 denotes a sample coil disposed close to the sample, to which a high frequency fd for decoupling is supplied from one end A via an input terminal 2 and a capacitor 3 for matching, and a high frequency fd for observation is supplied to the coil 1 through an input terminal 2 and a matching capacitor 3. is supplied from the other end B via the input/output terminal 4 and the matching capacitor 5.
6 and 7 are 1/4 wavelength cables having a length of 1/4 of the wavelength of the high frequency wave for decoupling, and are connected to the A end and B end of the sample coil, respectively.
has a terminated tip, and the cable 7 has an open tip. Tuning capacitors 8 and 9 are inserted between the A and B ends and the ground.

By adjusting the tuning capacitor 8, it is tuned to the decoupling high frequency, and by adjusting the tuning capacitor 9, it is tuned to the observation high frequency.

[Problems to be Solved by the Invention] This conventional example has the advantage that even if the tuning state on the observation side changes, the tuning state on the high frequency side for decoupling does not change.
A wavelength cable 7 is connected, and due to the stray capacitance of this cable, the tuning frequency is lowered, and there is a problem that tuning cannot be achieved when the observation frequency is high.

Therefore, as shown in FIG. 6, instead of the 1/4 wavelength cable 7, the present inventor combined in series a trap coil 10 and a cable 11 having a length shorter than 1/4 wavelength of the decoupling high frequency. In addition to using a trap coil and cable 11
The combined electrical length is 1/1 of the high frequency for large springs.
A patent application was filed in 1982 for a double resonance frequency variable probe that solved the above problems by setting four wavelengths.
It is proposed as No. 103380.

According to this proposed device, the observation frequency can be increased, but this time a new problem arises in that it becomes difficult to tune on the side where the observation frequency is low.Furthermore, this proposal There are limits to the equipment.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a double-resonant variable frequency probe that can further increase the observation frequency and also be able to tune even on the lower frequency side. .

[Means for Solving the Problems] In order to achieve this object, the double resonance variable frequency probe according to the present invention includes a sample coil and a terminated decoupling high frequency probe connected to one end A of the sample coil. a 1/4 wavelength cable, a trap coil connected to the other end of the sample coil,
One end is connected to the trap coil, the other end is open, and the length is 1/4 of the high frequency for decoupling.
a second cable shorter than the wavelength, and the combined electrical length of the trap coil and the second cable is set to 1/4 wavelength of the decoupling high frequency;
A variable frequency probe for double resonance is configured to supply a high frequency for decoupling from the A end and a high frequency for observation from the connecting end B between the sample coil and the trap coil, wherein The first is to insert a capacitor in series between
The present invention is characterized in that a switching means is provided for switching between this state and a second state in which the B terminal is grounded via a capacitor.

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

FIG. 1 shows the configuration of an embodiment of the present invention, in which the same components as in FIGS. 5 and 6 are designated by the same numbers. What is different in FIG. 1 from the proposed device in FIG. 6 is that a capacitor 12 is inserted in series with the sample coil 1, and electrodes 13, 14 and a ground electrode 18 are used to short-circuit the capacitor 12. The point is that this is provided.

In the state shown in FIG. 1, since the electrodes 13 and 14 are open, the trap coil 10 and the cable 11
The stray capacitance of is canceled and reduced by the capacitor 12, and the tuning frequency can be increased compared to the proposed device of FIG. 6, moving the tuning range into a higher region.

FIG. 2a shows a state in which the measurement is switched to a region where the observation frequency is low. 1 in Figure 2a
5 is a stake used for switching, which has a conical electrode 16 at its tip;
A capacitor 17 having one end connected to 6 is housed inside. Capacitor 17 is grounded by ground electrode 18 .

In this state as shown in FIG. . In this state, the capacitance of the capacitor 17 is added to the stray capacitance of the trap coil 10 and the cable 11, so the tuning frequency becomes low and the tuning range shifts to a reduction.

Figure 2b shows the tuning range between the high range of Figure 1 and Figure 2a.
This shows the state where the setting is switched to the middle range of the low range. In FIG. 2b, the stake 19 has only a conical electrode 16 at its tip. In this state, electrodes 13 and 14 are short-circuited by electrode 16, and capacitor 12 is disabled, resulting in the same configuration as the proposed device shown in FIG.

In the above embodiment, the capacitor 12 is connected to the sample coil 1.
This capacitor was connected in series with the coil 1 and shorted using electrodes 13 and 14 to disable this capacitor in the low and mid ranges, but only in the high range, the capacitor 12 was inserted with a stake and connected in series with the sample coil 1. You may also connect it.

FIG. 3 shows an embodiment based on this idea, and has a configuration in which the capacitor 12 is removed from the embodiment of FIG. FIG. 4a shows a stake used for high-frequency measurements, and this stake is equipped with a tip electrode 16 in contact with the electrode 13 and an electrode 19 in contact with the electrode 14, and the electrodes 16 and 19 are connected by a capacitor 12. ing. Therefore, this stake is connected to the electrode 1 as shown by the broken line in FIG.
If installed at positions 3 and 14, the circuit becomes exactly the same as that shown in FIG. 1, and high-frequency measurements are possible.

FIG. 4b shows the stake used for mid-range measurements, with electrodes 16 and 19 short-circuited. Therefore, if this stake is attached to the positions of the electrodes 13 and 14, the circuit becomes the same as the proposed device shown in FIG. 6, and mid-range measurement is possible.

FIG. 4c shows a stake used for low frequency measurements, in which electrodes 16 and 19 are short-circuited and a capacitor 17 is connected to electrode 19. This stake is attached to electrodes 13 and 14.
If the capacitor 17 is installed in the position shown in FIG. 2, the capacitor 17 is grounded by the ground electrode 18, so the circuit becomes the same as that shown in FIG. 2a, and low frequency measurement becomes possible.

In the above embodiment, the mid-range measurement mode was also explained, but this mode is equivalent to setting the capacitance of the capacitor 17 to infinitely small (setting the impedance to infinite) in the low-range measurement mode. If it is unnecessary, it can be removed.

[Effects of the Invention] As described in detail above, according to the present invention, a double resonant variable frequency probe is realized in which the observation frequency can be increased and the probe can be tuned even in a low frequency region.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of one embodiment of the present invention, FIG. 2 is a diagram showing a state switched to low-frequency measurement and mid-range measurement, and FIG. 3 is a diagram showing the configuration of another embodiment of the present invention. Figure 4 is a diagram showing the stakes used to switch between high, middle and low frequencies; Figure 5 is a diagram showing the configuration used in a conventional variable frequency probe;
FIG. 6 is a diagram showing the configuration of the device previously proposed by the present inventor. 1: Sample coil, 2, 4: Input terminal, 3, 5:
Matching capacitor, 6:1/4 wavelength cable,
8, 9: Tuning capacitor, 10: Trap coil, 11: Cable, 12, 17: Capacitor,
13, 14, 16, 19: electrode, 15: stake, 18: ground electrode.

Claims (1)

[Claims] 1 Sample coil and 1/4 of the terminated decoupling high frequency connected to one end A of the sample coil.
a wavelength cable, a trap coil connected to the other end of the sample coil, and a second cable having one end connected to the trap coil and the other end open and having a length shorter than 1/4 wavelength of the high frequency for decoupling. , the combined electrical length of the trap coil and the second cable is set to 1/4 wavelength of the high frequency for decoupling, and the high frequency for decoupling is transmitted from the end A, and the high frequency for observation is transmitted from the connection end B between the sample coil and the trap coil. A double resonance variable frequency probe configured to supply high frequencies respectively, wherein a first state in which a capacitor is inserted in series between the sample coil and the B end, and a first state in which the B end is connected through the capacitor. A variable frequency probe for double resonance, characterized in that it is provided with a switching means for switching to a second state of being grounded.