JPS6411897B2 - - 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, the configuration shown in FIG. 1, for example, is known as a variable frequency probe used for solid-state double resonance measurement. In the figure, reference numeral 1 denotes a sample coil disposed close to the sample, to which a decoupling high frequency f1 is supplied from one end A via an input terminal 2 and a matching capacitor 3, and an observation high frequency f0 is supplied to the coil 1. is supplied from the other end B via the input/output terminal 4 and the matching capacitor 5. 6 and 7 are 1/1 of the wavelength of the high frequency for decoupling.
The cables are 1/4 wavelength cables having a length of 4 and are connected to the A end and the B end of the sample coil, respectively, with the cable 6 having a terminated tip and the cable 7 having an open tip. Tuning capacitors 8 and 9 are inserted between the A and B ends and 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 Present Invention] This conventional example has the advantage that the tuning state on the high frequency side for decoupling does not change even if the tuning state on the observation side changes.
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 observed frequency is high.

[Structure of the invention] The present invention has been made in view of this point,
Double resonance solves the above problem by using a series combination of a trapping coil and a cable with a length shorter than 1/4 wavelength of the high frequency for decoupling, instead of the 1/4 wavelength cable 7. Provides variable frequency probes for Hereinafter, the present invention will be explained in detail using the drawings.

[Embodiment] FIG. 2 shows the configuration of an embodiment of the present invention, in which the same components as in FIG. 1 are given the same numbers. In Fig. 2, the difference from the conventional example is that instead of the 1/4 wavelength cable 7, a trap coil 10 and a cable 11 shorter than 1/4 wavelength of the decoupling high frequency are connected in series. be.

The trap coil 10 and cable 11 described above
The length L1 of the cable 11 is selected to be shorter than 1/4 of the wavelength λ of the high frequency wave for decoupling, and the electrical length L2 of the trap coil 10 is selected to be λ/4-L1. Therefore, when both are combined in series, the electrical length is λ/4, and the cable 11
Since the tip of the trap coil 10 and the cable 11 are open, the combination of the trap coil 10 and the cable 11 functions exactly the same as the cable 7 as a trap for the high frequency wave f1 for decoupling.

Figure 3 shows an equivalent circuit for the observation high frequency f0, where the 1/4 wavelength cable 6 becomes a stray inductance L' that is added to that of the sample coil 1, and the connection body connecting the trap coil 10 and cable 11 has a stray inductance L'. becomes C′. Since the length of the cable 11 is shorter than that of the 1/4 wavelength cable, this stray capacitance C' has a much smaller value than in the conventional case where the 1/4 wavelength cable 7 is used. Therefore, the tuning frequency related to the observation high frequency can be increased accordingly, and it becomes possible to perform tuning even when the frequency of the observation high frequency is high.

The arrangement of the tuning capacitor and the matching capacitor need not be limited to the embodiment shown in FIG. 2; for example, the arrangement shown in FIG. 4 may also be considered. In FIG. 4, 12 is a coupling capacitor with sufficient capacity.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration used in a conventional variable frequency probe, Fig. 2 is a diagram showing the configuration of an embodiment of the present invention, Fig. 3 is an equivalent circuit regarding observation high frequency f0, and Fig. 4 is a diagram of the present invention. FIG. 7 is a diagram showing the configuration of another embodiment of the invention. 1: Sample coil, 2, 4: Terminal, 3, 5: Matching capacitor, 6: 1/4 wavelength cable, 8,
9: Tuning capacitor, 10: Trap coil, 1
1: Cable.

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 B, 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 decoupling high frequency,
The combined electrical length of the trap coil and the second cable is set to 1/4 wavelength of the decoupling high frequency, and the decoupling high frequency is transmitted from the A end.
A variable frequency probe for double resonance, in which high frequency waves for observation are supplied from the B end.