JPS5824896B2 - Continuous wave magnetron for high power - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a continuous wave magnetron, and more particularly to a novel high-power continuous wave magnetron capable of generating an oscillation output exceeding 100 KW.

Continuous wave magnetrons are used for dielectric heating of materials, and are used for various purposes, ranging from ordinary microwave ovens with an oscillation output of several 100 kW to industrial heating with an oscillation output of several tens of kW.

These magnetrons have high oscillation efficiency and can heat materials from within, so their range of use is gradually expanding, and recently they have been used to treat incinerated ash containing radioactive waste generated from nuclear power plants, etc. Research is underway to use microwaves to treat municipal garbage, industrial waste, etc. to burn, melt, and solidify the waste, reducing its volume to a very small size and making it easier to dispose of.

As a result of this, the number of objects to be processed increases, and therefore a high output magnetron is required, and a high output continuous wave magnetron exceeding 1100K is required.

However, there is only one type of high-output continuous wave magnetron that currently exists in the world, which has an output of 100 KW. It is impossible to achieve high output with conventional design due to the problems such as vegetative damage, etc.

That is, for example, even if the cathode is used, the anode DC power (oscillation output/
The factor of 2 (oscillation efficiency) is applied to the cathode as a reverse shock, and if you try to increase the oscillation output, the power applied to the cathode will also increase, and if the cathode is of a normal size, the heat generated at the cathode will not be completely dissipated. It will not be possible to do so and it will melt.

Therefore, the size of the cathode must be increased,
If the length of the cathode is increased, the length of the anode piece must also be increased, and if the anode piece is lengthened, the potentials at both ends will differ, causing problems.

In addition, if the cathode diameter is increased to make the cathode larger, the anode diameter must also be increased, and generally speaking, the anode voltage Va, the anode radius γ8, and the cathode radius γ.

, γC/γ8=σ, the number of divisions 2n, the wavelength λ, and the magnetic field B have the following relationship.

Therefore, if γa is increased while σ, λ, and B are kept constant, the anode voltage Va increases in proportion to the square of the anode radius γa, and in a magnetron with an output of 1100K, Va is 23.5.
Although only KV can be used, if the output exceeds 1001@, it will far exceed the practical limit of 50 KV, which is not preferable.

Therefore, if you try to lower the anode voltage by increasing the number of divisions 2n, the capacitance of the cavity increases and the inductance decreases. For example, if you double the number of divisions 2n, the Q of the unloaded cavity increases.
%, and if we try to maintain the same Q under load, the circuit efficiency will drop by about 10%, which is undesirable.

Furthermore, if a conventional ceramic dome is used to cover the output antenna to form a vacuum envelope, there is a strong possibility that the heat generated by microwave loss will not be sufficiently cooled and the dome will be destroyed. difficult to do.

The object of the present invention is to create a new number 10 that eliminates these drawbacks.
The objective is to provide a zero continuous wave magnetron, specifically by increasing the number of anode divisions to increase the cathode and anode diameters, and electrically coupling a high Q external cavity to a low Q internal cavity. This configuration increases the Q of the entire cavity and improves circuit efficiency by leading out the output antenna from the anode piece and directly coupling it to the coupling waveguide that is part of the vacuum envelope. .

This will be explained in detail below with reference to the drawings.

FIG. 1 is a cross-sectional view of a magnetron that is an embodiment of the present invention, in which 1 is a directly heated cathode made of, for example, pure tungsten, 2 is an internal cavity surrounded by an anode piece, 3 is an anode piece, and 4 is an external A cavity, 5 is an input side magnetic pole piece, 6 is an output side magnetic pole piece, 7 is an output antenna, 8 is an anode tube serving as the outer wall of the inner cavity 2, 9 is a shell that is the outer wall of the outer cavity 4 and is a vacuum wall, 10 is an input section equipped with the cathode 1, 11 and 12 are pipes for liquid cooling of the input section 10, 13 is a choke that prevents microwave leakage from the input section, 14 is an absorber for preventing unnecessary modes, and 15 is an output antenna. A coupling waveguide that combines the outputs from 7 and can be directly connected to the transmission line, 16 a window with a vacuum-tight wall, 1
Reference numeral 7 denotes a spare yoke constituting a magnetic circuit, which can be connected to the input side magnetic pole piece 5 and the output side magnetic pole piece 6 with screws 1B.

19 is a coil for an electromagnet. With this magnetron,
The vacuum wall is formed by the input section 10, the input side magnetic pole piece 5, the shell 9, the output side magnetic pole piece 6, the coupling waveguide 15, and the window 16, and the electromagnetic coil 19 is arranged outside the vacuum wall.

As mentioned above, the characteristics of the magnetron are that the cathode diameter is increased to increase the cathode area to help dissipate heat from the cathode as the input power increases, and the anode diameter is also increased accordingly. The number of divisions is doubled to 24.

As a result, the Q of the cavity is reduced, so the external cavity 4 is provided.

A magnetron with such an external cavity is a pulsed magnetron and is used especially when it is desired to increase the Q to improve resolution in radar, but in this case, the output is extracted from the external cavity. There is no example of providing an auxiliary external cavity for the purpose of obtaining a normal Q as in the present invention.

That is, in the present invention, since the electromagnetic coil is arranged around the cavity (an electromagnet is easier to obtain a stable magnetic field, and when the oscillation output is made variable, it is possible to adjust the oscillation output by adjusting the anode voltage. It is necessary to control the dog's power,
If the oscillation output is adjusted by controlling the current of the electromagnet, the power required will be about 1/1000 of the former, which is practical. Despite this, the structure is such that the output is extracted from the output antenna from the anode piece.

Another feature of the present invention is that the output dome is destroyed due to temperature rise (in output domes with complex shapes, the dome (ceramic) is abnormally heated and cooled due to the generation of higher-order modes near the dome). In order to prevent the risk of cracking due to insufficient cooling, the vacuum-walled metallic coupling waveguide 15
is fixed directly to the output part, and the output antenna 7 and the coupling waveguide 1 are connected directly to the output part.
5 are combined in a vacuum region.

An enlarged view of the structure of the coupling portion between the output antenna 7 and the coupling waveguide 15 is shown in FIG.

In Figure 2, the output antenna 7 has two anode pieces 3 with different potentials.
The high-frequency current flows along with the oscillation.

(Ordinary magnetrons, including the magnetron according to the present invention, are configured to oscillate in the π mode, and the even number of anode pieces has a phase difference of π radians. Therefore, if the anode pieces with different phases are connected, the maximum Current can be obtained.

) When a current flows through this output antenna 7, a magnetic field is generated around the antenna wire 7.

This generated magnetic field is coupled (so-called magnetic field coupling) to the circular waveguide formed by the cylindrical part (the part indicated by 20 in Fig. 2) surrounded by the output side magnetic pole piece 6, and the microwave power is transferred to the cylindrical part. 20, and this cylindrical portion 20 (circular waveguide) is coupled to the coupling waveguide 15 by a normal waveguide coupling method.

This coupling waveguide 15 may be a circular waveguide or a rectangular waveguide, and an example is shown in which a cylindrical portion 20 (circular waveguide) is formed in a portion surrounded by the output side magnetic pole piece 6. It does not necessarily have to be composed of the output side magnetic pole piece 6, and may be composed of the anode tube 8.

FIG. 3 is an enlarged sectional view of an output coupling section showing another embodiment of a coupling method between the output antenna 7 and the coupling waveguide 15.

In this embodiment, a plurality of output antennas 7 derived from anode pieces 3 having the same potential are coupled in the middle or at the tips, and are coupled to a direct coupling waveguide 15.

In this embodiment, since the output antenna 7 is derived from the anode piece 3 which has the same potential as the π mode, no circulating current flows through the output antenna 7, and there is no problem with the position of the joint, and the length up to the tip is for coupling. Since the adjustment may be made so that the highest coupling efficiency with the waveguide 15 can be obtained, the light may not be led out from a plurality of anode pieces 3 but may be led out from only one anode piece.

However, higher-order modes other than the π mode do not have the same potential, and considering suppression of these higher-order modes, multiple output antenna wires 7 are derived from multiple anode pieces 3 to reduce the load for the higher-order modes. It is effective to suppress higher-order modes if they are joined with the same dimensions.

As mentioned above, the magnetron according to the present invention can obtain high output power with high efficiency compared to conventional continuous wave magnetrons, has high reliability because there is no fear of vacuum wall destruction due to temperature rise, and is also compact and compact. It has the advantage of being able to generate high-output microwave power with a simple device, and as a result, it can be effectively used for processing municipal garbage, industrial waste, etc., and has a great effect on environmental conservation.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a magnetron that is an embodiment of the present invention, FIG. 2 is an enlarged sectional view of the output coupling section of FIG. 1, and FIG. 3 is an enlarged sectional view of the output coupling section that is another embodiment of the present invention. It is an enlarged sectional view. 1... Cathode, 2... Internal cavity, 3... Anode piece, 4
... External cavity, 5... Input side magnetic pole piece, 6... Output side magnetic pole piece, 7... Output antenna, 8... Anode tube, 9
...Shell, 10...Input section, 15...Coupling waveguide, 16...Window.

Claims (1)

[Scope of Claims] 1. A cathode, an anode tube concentric with the cathode, a plurality of anode pieces disposed on the inner surface of the anode tube, and an internal space formed by the anode pieces and the anode tube. an external cavity electrically coupled to the body, an output antenna derived from at least two of the anode pieces, and an opening to which the output antenna is coupled, one end of which is sealed and the other end of which is a dielectric window. 1. A continuous wave magnetron for high output, characterized in that the magnetron has a waveguide which forms a vacuum space together with at least the internal cavity. 2. The output antenna is formed in a loop shape by being derived from two anode pieces having different potentials, and is magnetically coupled to a circular waveguide configured in a space surrounded by an inner cylinder of the outer cavity, 2. The high-output continuous wave magnetron according to claim 1, wherein the high-output continuous wave magnetron is coupled to the coupling waveguide through the circular waveguide. 3. The antenna according to claim 1, characterized in that the output antenna is derived from a plurality of anode pieces having the same potential, joined at least at their tips, and electrically coupled to the coupling waveguide. Continuous wave magnetron for output.