JPH07109961B2 - Loop gap resonator - Google Patents

Description

The present invention relates to a loop gap resonance used for measurement of microwave spectrum using continuous microwave and pulsed microwave, and particularly for measurement of electron spin resonance (ESR) spectrum. It is related to vessels.

[Prior Art] A microwave spectrum measuring device, especially an ESR spectrum measuring device has been widely used as a device for measuring a small amount of atoms and molecules. This ESR spectrum measuring device inserts a sample containing paramagnetic species into a microwave resonator placed in a static magnetic field, and applies a microwave magnetic field to the sample to measure the Q value and resonance frequency of the resonator. Changes are measured through microwaves.

Recently, a loop gap resonator has been proposed as a microwave resonator suitable for measuring the ESR spectrum of a sample with a large dielectric loss and the pulse ESR spectrum (W. Fronci
sz and JSHyde, Journal of Magnetic Resonance, 7,51
5,1982).

As shown in FIG. 5, this resonator has a structure in which a cylindrical electrode 3 having one or several slits 2 vertically arranged in a cylindrical electrode 1 for electromagnetic shielding is provided. Is a cylindrical electrode 3
Inserted inside. It is coupled to an external microwave circuit via a coaxial line 5 having a loop-shaped antenna 4 at the tip of a core wire, and the degree of coupling is adjusted by changing the distance between the antenna loop 4 and the cylindrical electrode 3.

[Problems to be Solved by the Invention] Although several examples of using this loop gap resonator for ESR measurement have been reported, it has not necessarily been successful in a practical sense. This is due to the structure of the coupling portion between the external microwave circuit and the loop gap resonator. That is, the microwave transfer from the external microwave circuit to the loop gap resonator should be done by the magnetic field coupling between the antenna loop and the resonator in principle, but in reality, the contribution of the electric field coupling is large. is there. Since the electric field is concentrated in a narrow space, for example, when using X-band microwave, the degree of coupling is large even if the position of the antenna loop, which has low mechanical stability, slightly changes due to contact with the inserted sample. It changed, and it was difficult to adjust the bond, and it took time to obtain an appropriate bond.

In addition, even if proper connection is obtained once, the degree of connection is likely to change due to slight vibrations, and adjustments must be made frequently.

Further, there is a problem that the antenna loop becomes an obstacle and it is difficult to insert the sample into the resonator.

The present invention has been made in view of the above-mentioned points, and it is possible to easily perform coupling adjustment in a short time, maintain a stable coupling state for a long time, and easily insert a sample in a loop gap resonance. The purpose is to provide a vessel.

[Means for Solving the Problem] In order to achieve this object, a loop gap resonator of the present invention has a tubular electrode having one or a plurality of slits in the length direction, and surrounds the tubular electrode. In the loop gap resonator having the shield electrodes arranged concentrically as described above, a coupling hole is provided on the side surface of the shield electrode, and a wedge-shaped dielectric plate can be moved inside the waveguide at the portion of the coupling hole. A coupler having the inserted structure is attached, and the microwave from the external microwave circuit is supplied to the inside of the cylindrical electrode through the coupler and the coupling hole.

[Operation] In the loop gap resonator of the present invention, the waveguide is attached to the coupling hole portion opened on the side surface of the shield electrode, and the microwave is supplied from the waveguide to the inside through the coupling hole. .

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Embodiment] FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a plan view thereof. In both figures, the shielding tubular electrode 11 has a square cross section, and a quartz glass tube 12 is inserted therein. A cylindrical electrode 13 is attached to the inner peripheral surface of the central portion of the glass tube 12, and a rectangular coupling hole 14 is formed in the shielding cylindrical electrode 11 so as to face the cylindrical electrode 13.
Reference numeral 15 is a coupler having one end attached to the coupling hole portion of the shielding tubular electrode 11, and the other end is connected to a waveguide 16 from an external microwave circuit.

FIG. 3 shows the electromagnetic field distribution in the shielding tubular electrode 11 in the resonance state, the electric field (solid line) becomes stronger in the slit of the cylindrical electrode 13, and the magnetic field (dashed line) is in the cylindrical electrode 13 and the shielding cylinder. It becomes stronger near the inner wall surface of the electrode 11. Therefore, if an electromagnetic field is injected from the external microwave circuit 16 into the cylindrical electrode 13 through the coupling hole 14 and the coupler 15 on the side surface of the shielding cylindrical electrode 11, the resonance state can be maintained.

The coupler 15 has a structure in which a wedge-shaped dielectric plate (for example, Teflon (registered trademark)) 15b is movably inserted inside a waveguide 15a having a cutoff frequency higher than the microwave frequency used, Dielectric pair plate 15b for resonator
It is possible to change the degree of coupling between the external microwave circuit and the resonator by changing the position of, and to change the strength of the electromagnetic field supplied to the inside of the resonator through the coupling hole 14. The alternate long and short dash line in FIG. 1 shows the distribution of the microwave magnetic field from the waveguide 16 to the resonator in the optimal coupling state.

Since the degree of coupling changes slightly depending on the positional relationship between the coupling hole 14 and the slit of the cylindrical electrode 13, for example, if the glass tube 12 holding the cylindrical electrode is rotatably provided, the degree of coupling can be finely adjusted. is there.

FIGS. 4 (a) and 4 (b) show the case where the resonator of FIG. 1 is used as a resonator for measuring the pulsed ESR signal of the coloring center in the silica glass, and the ordinary cavity resonator is used. The respective signal strengths are shown. However, FIG. 4 (b)
The result of measurement by the cavity resonator of Fig. 4 is obtained by using the microwave whose intensity is 25 times as high as that of the measurement by the resonator of the present invention shown in Fig. 4 (a). Therefore, it can be seen that the sensitivity in FIG. 4 (a) is five times higher.

Using a conventional loop-gap resonator that uses an antenna loop makes it possible to perform measurements with the same high sensitivity, but it takes a long time to adjust the coupling degree, and the coupling degree fluctuates immediately, so it frequently occurs. In the resonator of the present invention, the degree of coupling can be adjusted in a short time, and the optimum state can be maintained for a long time.
No need to readjust.

[Effects of the Invention] As described in detail above, in the present invention, a coupling hole is formed in the side surface of the shielding cylindrical electrode, and the microwave is supplied from the external microwave circuit to the loop gap resonator through the coupling hole. With this configuration, the degree of coupling between the resonator and the external microwave circuit can be easily adjusted outside the shielding cylindrical electrode. Further, as the coupler for coupling, a coupler having much higher mechanical strength and stability than that of the antenna loop can be used, so that the optimum state once adjusted can be maintained for a long time.

Further, since the coupling portion between the resonator and the external microwave circuit is located outside the shielding cylindrical electrode, the sample can be easily inserted, and the device for controlling the temperature of the sample for measurement and the static magnetic field are modulated. It is also possible to arrange the modulation coil or the like inside the shielding cylindrical electrode.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a view showing an electromagnetic field distribution in the shielding cylindrical electrode 11 in a resonance state, and FIG. ) And (b) show the signal intensity when the resonator shown in FIG. 1 is used as a resonator for measuring the pulsed ESR signal of the colored center in the silica glass and when a normal cavity resonator is used. Figures shown respectively, No. 5
The figure shows a conventional example of a loop gap resonator. 11: Shielding cylindrical electrode 12: Quartz glass tube 13: Cylindrical electrode 14: Coupling hole 15: Coupler 15a, 16: Waveguide 15b: Wedge-shaped dielectric plate

Claims (1)

[Claims] 1. A loop gap resonator comprising: a tubular electrode having one or a plurality of slits in the lengthwise direction; and a shield electrode concentrically arranged so as to surround the periphery of the tubular electrode, A coupling hole is provided on the side surface of the shield electrode, and a coupler having a structure in which a wedge-shaped dielectric plate is movably inserted inside the waveguide is attached to the coupling hole portion, and an external microwave is provided through the coupler and the coupling hole. A loop gap resonator, wherein microwaves from a circuit are supplied to the inside of the cylindrical electrode.