JP4403274B2 - Electromagnetic wave output measuring device - Google Patents

Description

  The present invention relates to an electromagnetic wave output measuring apparatus that measures high-power microwaves such as a gyrotron.

When high-frequency heating is performed using a microwave output device such as a gyrotron, it is necessary to grasp how much microwave is being output, and an output measuring device for that purpose has been proposed. For example, in Patent Document 1, it is formed of a mirror that focuses a beam-shaped microwave in a direction different from its propagation direction, and a metal or dielectric that introduces and heats the microwave focused by the mirror through a small hole. A tank, a cooling medium passage through which a cooling medium for cooling the tank passes, and means for measuring a microwave output from a temperature difference between an inlet and an outlet of the cooling medium passage are provided. A microwave power measuring device is described. In Patent Document 2, a mirror that focuses a beam-like microwave in a direction different from the propagation direction thereof, a slide plate having a plurality of small holes having different diameters through which the focused microwave is passed, and other than the selected small hole A frame that covers the small holes of the metal plate, a tank formed of a metal or dielectric that heats the microwave introduced through the small holes of the slide plate, an outer cylinder that houses the tank via a vacuum heat insulating layer, and a tank The cooling medium passage through which the cooling medium for cooling the liquid passes, the means for measuring the microwave output from the temperature difference and flow rate between the inlet and outlet of the cooling medium passage, and the distance between the mirror and the slide plate can be adjusted A microwave output measuring device having a focal length adjusting mechanism is described. Patent Document 3 describes a microwave calorimeter that mixes a liquid that absorbs microwaves with a compound having a weaker microwave absorption than water and measures the amount of heat generated by microwave irradiation.
JP-A-1-162164 Japanese Patent No. 2670351 JP-A-62-250370

  In the above-described prior art, a measuring device is provided attached to a waveguide through which microwaves propagate, and measurement is performed by introducing a main beam of microwaves into the measuring device using a mirror. Therefore, measurement is performed at the time of test output for measurement, and output measurement is not performed in real time at the time of microwave output in actual operation, so that the microwave output during actual operation cannot be measured. If the output measurement is performed during actual operation, the influence on the main beam is unavoidable and the operation must be interrupted.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an electromagnetic wave output measuring apparatus capable of measuring an electromagnetic wave output in real time during actual operation without affecting the main beam of the electromagnetic wave propagating in the waveguide. is there.

The electromagnetic wave output measuring apparatus according to the present invention has a groove formed in the circumferential direction on the entire inner peripheral surface, and proceeds by a predetermined wavelength from a plurality of holes formed corresponding to the groove along the tube axis direction. Based on the propagation direction angle of the plane wave with respect to the tube axis direction of the corrugated waveguide, the corrugated waveguide from which the electromagnetic wave having a shifted distance leaks and the plane wave formed by interference of the electromagnetic wave leaking outside from each hole Measuring means for measuring in the set measuring direction, and calculating means for calculating an output value of the electromagnetic wave based on measurement data from the measuring means.

  A high-power microwave heating device according to the present invention includes the above-described electromagnetic wave output measuring device.

  Since the present invention has the above-described configuration, the output of the electromagnetic wave is measured using the electromagnetic wave leaked to the outside from a plurality of holes formed in the waveguide. Measurement can be performed without affecting the main beam. Also, by shifting the electromagnetic wave leaking from each hole by a predetermined wavelength, a plane wave is formed by interference of the leaked electromagnetic wave, and the output of the leaked electromagnetic wave is accurately measured by measuring the formed plane wave It becomes possible to do. Then, the correlation between the output of the plane wave to be measured and the output of the electromagnetic wave is obtained in advance by experiments or the like, and if a calculation formula or a correspondence table is created based on the correlation, the measurement is performed by the measuring means during operation. Based on the result, the output value of the electromagnetic wave can be calculated in real time.

  And when using as a waveguide the corrugated waveguide in which the several groove part was formed in the inner peripheral surface along the circumferential direction, if a hole part is drilled corresponding to a groove part, each from each hole part, An electromagnetic wave shifted by a predetermined wavelength is leaked, and a plane wave with less noise can be easily formed by the leaked electromagnetic wave.

  In addition, if the measurement direction of the measurement means is set based on the propagation direction angle of the plane wave with respect to the tube axis direction of the waveguide, it becomes possible to accurately measure the plane wave and easily set the measurement means. Can do.

  The depth of the hole is set to be equal to or less than the wavelength of the electromagnetic wave propagating in the waveguide, and the length of the waveguide in the tube axis direction is set to be equal to or less than the wavelength of the electromagnetic wave in the opening shape of the hole. Thus, the influence on the main beam propagating in the waveguide can be surely prevented.

  Hereinafter, embodiments according to the present invention will be described in detail. The embodiments described below are preferable specific examples for carrying out the present invention, and thus various technical limitations are made. However, the present invention is particularly limited in the following description. Unless otherwise specified, the present invention is not limited to these forms.

  FIG. 1 is a front view relating to a high-power microwave heating apparatus including an embodiment according to the present invention. The high-power microwave heating device includes a gyrotron 1 as a high-frequency microwave output device, a corrugated waveguide 2 that propagates the output microwave in a desired direction, and an applicator 3 in which an object to be heated is installed. I have. An electromagnetic wave output measuring device 4 is disposed adjacent to the corrugated waveguide 2.

  The gyrotron 1 can generate a high-power electromagnetic wave at a high frequency by emitting an electron beam upward from an electron gun 10 disposed below and driving the electron beam into an electromagnetic wave oscillation unit including a superconducting magnet 11. The generated electromagnetic wave is guided to enter the corrugated waveguide 2 by the direction changing unit 12 including a mirror that reflects the electromagnetic wave.

  The corrugated waveguide 2 is a cylindrical straight tube, and a groove is formed in the circumferential direction on the inner peripheral surface. The groove is formed in a rectangular cross section with a depth of about 1/4 of the wavelength of the incident electromagnetic wave, and the interval between adjacent grooves is also set to about 1/4 of the wavelength of the incident electromagnetic wave. Yes. The groove portion may be formed in a spiral shape, or a plurality of groove portions may be formed in parallel along the circumferential direction. By using the corrugated waveguide 2 in which such a groove is formed, the incident electromagnetic wave can be propagated by being excited in a low-loss linear polarization mode. The corrugated waveguide 2 may be configured by combining waveguides having a predetermined unit length.

  In a part of the corrugated waveguide 2, a plurality of holes are formed in the lower part, and electromagnetic waves leak out toward the electromagnetic wave output measuring device 4. FIG. 2 is an enlarged cross-sectional view when cut along the tube axis direction CC with respect to a portion where electromagnetic waves leak. A plurality of grooves 20 are formed at equal intervals on the inner peripheral surface of the corrugated waveguide 2, and holes 21 through which electromagnetic waves leak are respectively formed in some of the grooves 20. Are arranged along the tube axis direction CC. FIG. 3 shows a cross-sectional view taken along the line AA in FIG. As shown in FIG. 3, the region in which the hole 21 is provided is cut into a flat shape so as to have a small thickness, and the depth T of the hole 21 has an electromagnetic wave propagating through the corrugated waveguide 2. It is set to be less than the wavelength. Moreover, as shown in FIG. 4, the opening shape of the hole part 21 can be made into a circular shape (FIG. 4A) or a rectangular shape (FIG. 4B), for example. However, the length in the tube axis direction C-C is set to be equal to or less than the wavelength of the electromagnetic wave propagating in the corrugated waveguide 2. In the case of a circle, the diameter r shown in FIG. 4 (a) may be set to be equal to or smaller than the wavelength. In the case of a rectangle, the length L shown in FIG. 4 (b) is equal to or smaller than the wavelength. Should be set. In this way, by setting the depth and the opening shape of the hole portion 21, it is possible to leak electromagnetic waves to the outside without affecting the main beam propagating through the corrugated waveguide 2.

  Although it is possible to increase the output of electromagnetic waves leaking by increasing the area of the opening shape of the hole 21 or increasing the number of the holes 21, the main beam of the electromagnetic wave propagating in the waveguide It is necessary to adjust so as not to affect For example, although there is no effect when the output of the main beam of electromagnetic waves propagating in the waveguide is large, the effect is likely to occur when the output is small, so it is desirable to adjust according to the output of the main beam.

  FIG. 5 is a diagram for explaining that a plane wave is formed by interference of electromagnetic waves leaking from the hole 21 formed in the corrugated waveguide 2.

  When the wavelength of the electromagnetic wave propagating in a predetermined direction is λ, the time advances by a distance λ corresponding to one wavelength when one period elapses. Therefore, at a certain time, the phase is shifted by 2π at a position separated by a distance of one wavelength in the traveling direction of the electromagnetic wave. This also holds for electromagnetic waves propagating in free space and in the corrugated waveguide 2.

At a position advanced by a distance d from a certain position in the traveling direction of the electromagnetic wave, the phase φ is φ = 2πd / λ.
It is only shifted. Where the wavenumber κ is κ = 2π / λ
Then, the phase φ is given by the product of the wave number κ and the distance d.

In the corrugated waveguide 2, it can be considered that the electromagnetic wave is propagating in an oblique direction with respect to the tube axis direction C-C. Therefore, the wave vector 向 き having the magnitude of the wave number κ is set in the traveling direction of the electromagnetic wave. When considered, the wave vector Κ can be expressed as the sum of a wave vector Κ _H parallel to the tube axis direction and a vector Κ _V perpendicular to the tube axis direction.
Κ = Κ _H + Κ _V
The size of the wave vector kappa kappa, when the magnitude of the wave vector kappa _H and kappa _V and kappa _H and kappa _V,
κ = (κ _H ² + κ _V ² ) ^1/2
It becomes.
Here, the magnitude κ of the wave vector Κ is κ = 2π / λ = 2πf / c where f is the frequency and c is the speed of light.
It becomes. The size kappa _V wave vectors kappa _V is a distance from the bottom surface of the groove of the corrugated waveguide 2 to the tube axis when the a (see FIG. 2),
κ _V = ρ / a
It becomes. Here, ρ is a constant (value is 2.405).

として導かれる。ここで、ω＝２πｆである。 In FIG. 5, it is assumed that the electromagnetic wave radiated from the hole 21 on the most upstream side in the traveling direction of the electromagnetic wave propagates in the tube axis direction by the distance d _w while propagating through the free space by the distance d _s . In that case, at the position indicated by the dotted line, the phases are equal and a plane wave is formed. The phase delay when propagating by the distance d _s is κ d _s , and the phase delay when propagating by the distance d _w in the tube axis direction is κ _H d _w , so the condition for forming the plane wave is
κd _s = κ _H d _w
It becomes. Therefore, the radiation angle θ of the plane wave radiated from the hole 21 with respect to the tube axis direction CC is

As led. Here, ω = 2πf.

  FIG. 6 is a graph showing the relationship between the radiation angle θ and the frequency f of the electromagnetic wave propagating in the corrugated waveguide 2. In this example, a = 31.75 mm. Therefore, since the radiation angle of the plane wave due to the electromagnetic wave leaking from the hole 21 is obtained based on this graph, accurate output measurement can be performed by measuring according to the radiation angle.

  The applicator 3 places an object to be heated in a vacuum chamber coupled to the corrugated waveguide 2, introduces electromagnetic waves propagated in the corrugated waveguide 2 into the vacuum chamber, absorbs the object to be heated, and heats it. It is supposed to be. FIG. 7 is a schematic cross-sectional view regarding a specific configuration example. The vacuum chamber 30 is provided with an exhaust port portion 31 connected to a vacuum pump (not shown) and a coupling portion 32 connected to the corrugated waveguide 2 in a cylindrical body portion, and at one opening end portion of the body portion. A chamber lid 32 is attached. The chamber lid 32 is provided with a viewing window 33 for confirming the heating state of the article to be heated T installed in the vacuum chamber 30. In the vacuum chamber 30, a reflection plate 35 for irregularly reflecting electromagnetic waves introduced from the corrugated waveguide 2 is disposed, and a diffusion blade 36 is disposed at the other end of the body portion. The diffusion blade 36 is rotationally driven by a motor 37 attached to the outer surface of the vacuum chamber 30.

  The electromagnetic wave introduced into the vacuum chamber 30 is irregularly reflected by the reflector 35 as shown by a dotted line in FIG. 7, propagates in the vacuum chamber 30 in a random direction, and is further scattered by the rotating diffusion blades 36 to be chambered. It will be distributed uniformly in the inner space. Therefore, electromagnetic waves are uniformly absorbed by the entire object to be heated and a uniform heating state can be obtained.

  The electromagnetic wave output measuring device 4 detects an electromagnetic wave leaking outside from the corrugated waveguide 2 and converts it into an output signal, and the corrugated waveguide 2 based on the output signal transmitted from the antenna part 40 The calculating part 41 which calculates the output value of the electromagnetic wave which propagates is provided.

  The antenna unit 40 includes a pyramid-shaped horn antenna, and an opening surface thereof is set to coincide with a wave surface of a plane wave formed by interference of electromagnetic waves leaking from the corrugated waveguide 2 to the outside. . When setting the measurement direction of the antenna unit, the measurement direction may be adjusted based on the radiation angle of the plane wave as described above. By setting the horn antenna in this way, the direction of the incident electromagnetic wave can be limited to the direction of the plane wave, and the output of the plane wave can be accurately measured.

  When performing measurement, first, an electromagnetic wave is output from the gyrotron 1 with a small output as a test, and the electromagnetic wave output measuring device 4 performs the measurement. Then, the ratio between the measured output value and the output value of the gyrotron 1 is calculated. In this case, if the ratio exceeds 1%, electromagnetic waves leaking from the corrugated waveguide 2 may affect the main beam. Therefore, the number of holes 21 or It is desirable to adjust the opening shape.

  The ratio calculated by the test output is stored in the calculation unit 41, and the output of the electromagnetic wave propagating in the corrugated waveguide 2 is obtained by the output signal and the ratio measured by the antenna unit 40 during the actual operation of the gyrotron 1. . The obtained output value is fed back to the gyrotron 1 and the output of the electron gun 10 is controlled as necessary, so that more stable output control can be performed. Since the gyrotron 1 can be accurately measured in real time without affecting the main beam during the actual operation of the gyrotron 1, stable heat treatment can be continuously performed in the applicator.

  The electromagnetic wave output measuring apparatus according to the present invention can be used for a fusion plasma heating apparatus, a plasma measuring apparatus, and the like in addition to the above-described high-power microwave heating apparatus.

It is a front view regarding the high output microwave heating device provided with the embodiment concerning the present invention. It is an expanded sectional view at the time of cut | disconnecting along the tube-axis direction regarding the part which the electromagnetic wave of a corrugated waveguide leaks. It is AA sectional drawing in FIG. It is a schematic diagram which shows the opening shape of the hole drilled in the corrugated waveguide. It is a figure explaining that the electromagnetic wave leaking out from the hole part 21 drilled in the corrugated waveguide 2 interferes, and a plane wave is formed. It is a graph which shows the relationship between radiation angle (theta) and the frequency f of the electromagnetic wave which propagates the inside of a corrugated waveguide. It is a schematic sectional drawing regarding an applicator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gyrotron 2 Corrugated waveguide 3 Applicator 4 Electromagnetic wave output measuring device
20 Groove
21 hole
40 Antenna section
41 Calculation unit

Claims (2)

A corrugated waveguide in which a groove is formed in the circumferential direction on the entire inner peripheral surface , and electromagnetic waves whose traveling distances are shifted from each other by a predetermined wavelength from a plurality of holes drilled corresponding to the groove along the tube axis direction. Measurement to measure a plane wave formed by interference between a wave tube and an electromagnetic wave leaking outside from each hole in a measurement direction set based on the propagation direction angle of the plane wave with respect to the tube axis direction of the corrugated waveguide An electromagnetic wave output measuring apparatus comprising: a means; and a calculating means for calculating an output value of the electromagnetic wave based on measurement data from the measuring means. A high-power microwave heating device comprising the electromagnetic wave output measuring device according to claim 1.

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