JP2006278285A - Gyrotron - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gyrotron which saves on power and is designed compact. <P>SOLUTION: In this gyrotron, the inside 2 of an oscillation tube is constituted of three areas comprising: an electron gun part 21 provided with an electron gun 3; a cavity part 22 corresponding to a position where a magnet 5 is provided; and a collector part 23 located in donwstream of the cavity part, in the electron gun part, an electron beam outputted from the electron gun reaches the cavity through a tube line 211 whose diameter gradually decreases, the electron beam outputted from the electron gun is converted into electromagnetic waves in the cavity, the collector part is provided with a taper tube line part 231 whose diameter continuously increases from the cavity part, electromagnetic waves are oscillated from an output window through the collector part and a collector part wall surface catches the electrons of the electron beam passing the cavity. An outer diameter of the middle part of the oscillation tube is smaller than maximum diameters of the electron gun part and the taper shape part in the collector part, and a ring magnet externally fitted with the middle part has a sprit structure. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a gyrotron that generates millimeter waves, and more particularly to a power-saving and compactly designed gyrotron.

  With recent developments in communication technology, the opportunities for industrial use of electromagnetic waves have increased significantly. The history of electromagnetic technology development began with Franklin's experiment in 1752, Maxwell's electromagnetic field theory (1864), Hertz's demonstration of electromagnetic field (1888), and Marconi's transatlantic communication (1901). It is well known that

Looking at the history of the use of electromagnetic waves in the communications field, it started with radio broadcasting (medium wave) and developed into international communications using short waves. After that, ultra-short waves and ultra-high frequencies were used in television broadcasting. Microwaves are used for satellite broadcasting.
In this way, the use of electromagnetic waves is indispensable in modern life, and the range of use continues to increase, but such technological development has one problem.

Consider an example of the use of electromagnetic waves in the above communication field.
There is a problem that interference occurs when multiple radio waves exist at the same frequency. In general, since one radio wave has a spread in frequency, for example, when one radio wave has a spread of 1 MHz, ten or more radio waves cannot be arranged between 100 MHz and 110 MHz. From this point of view, radio waves can be said to be a finite resource, and the above technical development leads to the depletion of available frequency bands, that is, the depletion of resources.

  The use of millimeter waves (electromagnetic waves with a wavelength of 1 mm or more and 1 cm or less and a frequency of about 30 GHz or more and about 300 GHz or less) has been mostly developed so far due to the lack of a high-power, stable light source and a highly sensitive receiver. This is the only electromagnetic field that did not exist, and is considered to be an “electromagnetic valley”. The use of millimeter waves has so far been used only for special purposes such as military radar.

  As a characteristic of the millimeter wave, it is mentioned that the straightness is strong and the property of going around behind the object is low. It also has the property of being shielded by objects other than metal. Further, it is easily affected by molecular vibrations, and for example, has the property that millimeter waves are absorbed when water or oxygen is present. Due to the characteristics of the millimeter wave, the millimeter wave has a property that it cannot fly far away. This characteristic means that it is not suitable for far-distance communication but is difficult to receive interference from a long distance, and can be said to be an electromagnetic wave that is very suitable for short-distance communication. Due to such characteristics of millimeter waves, millimeter waves are expected to be applied to fields such as automobile collision prevention radars and high-speed wireless LANs.

  Furthermore, heating using millimeter waves can provide a heat generation effect with higher efficiency than self-heating efficiency using microwaves used in conventional microwave ovens and the like. This is because the amount of heat generated by the heated object irradiated with the electromagnetic wave is proportional to the frequency of the irradiated electromagnetic wave, and the millimeter wave has a higher frequency than the microwave. Further, the millimeter wave can heat a metal, and can uniformly heat a metal body without generating an arc.

  For this reason, millimeter waves are being applied to technical fields that require high temperatures, such as plasma heating in fusion experiments. Furthermore, in recent years, it has been used in the field of material research, for example, sintering experiments of ceramics and development of metal nitrides.

A gyrotron is known as a device that generates millimeter waves, and various gyrotrons have been proposed (for example, Patent Documents 1 and 2).
FIG. 4 shows an outline of a basic configuration of a conventional gyrotron.
The gyrotron (J) includes an oscillation tube (T). Inside the oscillation tube (T), an electron gun (G) is disposed at one end of the oscillation tube (T), and the electron gun (G) outputs an electron beam in the axial direction of the oscillation tube (T). Then, the electron beam travels toward the other end of the oscillation tube (T). An output window (W) is disposed at the other end of the oscillation tube (T).

The inside of the oscillation tube (T) is divided into three regions, which are an electron gun part (T1), a cavity part (T2) and a collector part (T3) from the left in FIG.
As described above, the electron gun (G) is arranged in the electron gun section (T1). The tube of the electron gun portion (T1) extending from the electron gun (G) first has a tapered shape that continuously narrows toward the cavity portion (T2).
The cavity part (T2) is a narrowly formed pipe having a constant cross section that communicates with the pipe of the electron gun part (T1) as described above.
The collector part (T3) is arranged after the cavity part (T2). The pipe line of the collector part (T3) includes a part formed in a tapered shape gradually increasing in diameter from the cavity part (T2), and a part thereafter having a constant cross section.
An annular magnet (M) is disposed at a position corresponding to the cavity portion (T2). The magnet (M) is formed longer than the length of the cavity portion (T2), and both end portions thereof reach the positions of the middle portions of the tapered pipe line portions formed on the inlet side and the outlet side of the cavity portion (T2). .

The electron beam output from the electron gun (G) is drawn out to the magnet (M), and is guided to the tapered pipe line of the electron gun section (T1) to form a tornado-like electron vortex with large rotational energy. The number of rotations per second (relativistic electron cyclotron frequency) of the electrons constituting the electron vortex is determined by the electrons emitted from the electron gun (G) and the magnetic field of the magnet (M). This electron vortex is introduced into the cavity portion (T2).
When the resonance frequency matches the number of rotations of the electrons, the kinetic energy of the electrons is converted into an electromagnetic wave (millimeter wave). This conversion is based on the maser principle.
The electromagnetic wave converted from the electron kinetic energy in the cavity part (T2) travels straight along the axis of the oscillation tube (T), passes through the pipe line of the collector part (T3), and passes through the output window (W). Are output to the outside of the oscillation tube (T). On the other hand, the electrons passing through the cavity (T2) collide with the wall surface of the collector (T3) and are absorbed by the collector (T3).
The electromagnetic wave output from the output window (W) is guided further by the electromagnetic wave guide tube (F) attached to the downstream side of the output window (W) and further advances straight.

Japanese Patent Laid-Open No. 6-196099 JP 7-94106 A

As described above, the gyrotron that generates millimeter waves expected to be used in various fields has the following problems.
When trying to produce a higher output millimeter wave, it is necessary to strengthen the magnetic field for rotating the electrons. For this reason, when a permanent magnet is used for the magnet (M), the annular magnet (M) that fits the middle part of the oscillation tube (T) becomes large, and this is a device incorporating a gyrotron and a gyrotron. Was supposed to lead to an increase in size. When the magnet (M) is an electromagnet, it is necessary to supply a high current to the magnet (M).
Alternatively, the use of an electron gun (G) that generates electrons at a high speed is one of the means for generating a high-power millimeter wave. However, such an electron gun (G) is expensive and has a high speed. There are also technical limitations.
Therefore, conventionally, only high-power millimeter-wave gyrotrons that require high power or large-sized gyrotrons are available, and low-power or small-sized gyrotrons that can generate high-power millimeter waves have emerged. It was desired.

  According to a first aspect of the present invention, there is provided a cylindrical oscillating tube whose inside is evacuated, an electron gun disposed at one end of the oscillating tube and outputting an electron beam in the axial direction of the oscillating tube, and the electron An output window disposed at an end opposite to the end where the gun is disposed, and an annular magnet that externally fits the middle portion of the oscillation tube, and the inside of the oscillation tube includes an electron gun portion where an electron gun is disposed And an electron beam is output from the electron gun in the electron gun portion, and a cavity portion corresponding to a position where the magnet is disposed and a collector portion located downstream of the cavity portion. The output electron beam reaches the inside of the cavity through a pipe having a gradually decreasing diameter, and the electron beam output from the electron gun in the cavity is converted into an electromagnetic wave. Continuous from the cavity A tapered pipe portion having a large diameter, the electromagnetic wave is oscillated from the output window through the collector portion, and the collector wall surface is a gyrotron that captures electrons of the electron beam that has passed through the cavity, The outer diameter of the middle part of the oscillation tube is smaller than the maximum diameter of the tapered portion in the electron gun part and the collector part, and the annular magnet that fits the middle part has a divided structure. It is a gyrotron.

A second aspect of the present invention is the gyrotron according to the first aspect, wherein the magnet is a permanent magnet.
A third aspect of the present invention is the gyrotron according to the first aspect, wherein the magnet is an electromagnet.

According to the first aspect of the present invention, the distance from the magnet to the cavity portion is shortened, and even if less power is supplied to a smaller magnet or electromagnet, the millimeter wave has the same output as the conventional gyrotron. Can be generated.
In addition, if a magnet having a high magnetic force is used, it is possible to generate a millimeter wave having a higher output than a conventional gyrotron.
According to the second aspect of the present invention, it is possible to construct a gyrotron that is smaller than the conventional gyrotron.
According to the third aspect of the present invention, it is possible to construct a gyrotron having a required power lower than that of the conventional gyrotron.

Hereinafter, embodiments of the gyrotron according to the present invention will be described with reference to the drawings. FIG. 1 is a sectional view taken along the axial direction of a gyrotron according to the present invention.
The gyrotron (1) includes a cylindrical oscillating tube (2). The inside of the oscillation tube (2) is in a vacuum state. The inside of the oscillation tube (2) is divided into three regions. A space formed on the left side in FIG. 1 is an electron gun part (21) in which an electron gun (3) is arranged, and a space communicating with the electron gun part (21) is a cavity part (22). A space that is arranged to the right of the part (22) and communicates with the cavity part is a collector part (23).

An electron gun (3) is disposed in the electron gun section (21). The electron gun (3) includes a rod-like cathode (31) and an anode (32) formed so as to surround the cathode (31) at a predetermined distance from the outer periphery of the cathode (31). The electron gun (3) is fixed to the left end of the electron gun section (21). The electron gun (3) is supplied with power from a power cord (311) extending from the left end of the cathode (31), and emits an electron beam from the tip of the cathode (31) toward the right.
The right end of the anode (32) is positioned to the right of the tip of the cathode (31), and guides the electron beam irradiated from the tip of the cathode (31) to travel along the oscillation tube (1).

The electron gun section (21) further includes a tapered pipe section (211). The tapered pipe line (211) is formed on the right side of the tip of the cathode (31), and is a tapered pipe line that continuously decreases in diameter as the distance from the tip of the cathode (31) increases.
The electron beam irradiated from the cathode (31) reaches the cavity part (22) through the tapered pipe line (211) having a gradually decreasing diameter.

  The cavity part (22) is a thin pipe line having a constant cross section. The rotational kinetic energy of the electron beam from the tapered pipe (211) to the cavity (22) is converted into electromagnetic waves (millimeter waves) by the cavity (22).

The electron beam that has passed through the cavity portion (22) reaches the collector portion (23).
The collector part (23) communicates with the cavity part (22), and with the tapered pipe line (231) and the tapered pipe line (231) that continuously increase in diameter as the distance from the cavity part (22) increases. It consists of a constant pipe line (232) having a constant cross section and extending in the downstream direction.

The electrons constituting the electron beam passing through the cavity portion (22) are making a swivel motion. When the electrons reach the taper pipe (231), the electrons are caused to oscillate in the oscillation tube (2) by the centrifugal force caused by the swivel motion. Move away from the axis. That is, the radius of the turning motion increases. Then, the electrons collide with the wall surface of the collector part (23) and are captured by the wall surface of the collector part (23). On the other hand, since the electromagnetic wave produced in the cavity part (22) has straightness, it goes straight along the axis of the oscillation tube (2) and goes to the output window (4) fixed to the right end of the collector part (23).
The output window (4) is preferably formed from diamond. By using the output window (4) made of diamond, thermal damage can be minimized.

In the external structure of the oscillating tube (2), a portion corresponding to the axial position of the cavity portion (22) is an intermediate portion (220).
In the middle part (220), the outer diameter of the oscillation pipe (2) is formed smaller than the diameter of the maximum diameter part of the tapered pipe lines (211 and 231) formed on the left and right sides of the cavity part (22).
The outer diameter of the oscillation pipe (2) in the middle part (220) is preferably 10% or more and 80% or less with respect to the maximum diameter of the tapered pipe lines (211 and 231). If the diameter is less than 10%, it is difficult to produce electromagnetic waves, and if it is 80% or more, the effect of power saving or design compactness cannot be obtained so much. In addition, the range of the outer diameter dimension of the most preferable middle part (220) is 30% or more and 60% or less with respect to the maximum diameter of the taper pipes (211 and 231).

FIG. 2 shows a magnet. 2A, 2B, and 2C show different magnet division structures.
An annular magnet (5) is fitted on the middle part (220). As shown in FIG. 2, the magnet (5) has a divided structure. The form of the divided structure is not particularly limited as long as the middle part (220) can be fitted, and for example, it may be divided into two equal parts as shown in FIG. Further, the division does not necessarily have to be performed equally. For example, as shown in FIG. 2B, the divided magnet (5) may be a small piece portion and a large piece portion.
In addition, as shown in FIG.2 (c), it is preferable to divide | segment a magnet (5) into a large piece and a small piece so that a parallel tangent line may be drawn from the internal diameter part of an annular magnet (5). If it does in this way, since the part which consists of large pieces will cover most outer periphery of a middle part (220), it will become easy to obtain a uniform magnetic field in a cavity part (22). Further, since the intermediate part (220) and the inner wall of the magnet (5) are in close contact, a stronger magnetic field can be provided to the cavity part (22).

  In this way, by using the magnet (5) having the divided structure, the inner wall surface of the magnet (5) can be brought into close contact with the intermediate portion (220) formed to be constricted. Since the strength of the magnetic field is inversely proportional to the square of the distance, the inner wall of the magnet (5) is brought into close contact with the intermediate portion (220) of the constricted oscillating tube (1), so that the inside of the cavity (22) It is possible to create a stronger magnetic field.

  The middle part (220) is formed longer than the cavity part (22), the right and left ends of the middle part (220) are located in the middle part of the taper pipes (211 and 231), and the left and right end surfaces of the magnet (5) are also Similarly, it is located in the middle part of a taper pipe line (211, 231).

  As shown in FIG. 1, a cylindrical output guide tube (6) is attached to the right side of the output window (4). The output guide tube (6) adjusts the direction of the electromagnetic wave immediately after coming out of the output window (4). Thereby, the electromagnetic wave after coming out from the output window (4) also goes straight in the axial direction of the oscillation tube (2).

FIG. 3 is a diagram showing the operating principle of the gyrotron (1).
The electrons emitted from the electron gun (3) move so as to wrap around the magnetic lines of force from the magnet (5) due to the discharge pressure of the magnet (5) and the electron gun (3), and while rotating, the electron gun part ( 21) to the tapered pipe line (211). In the taper pipe (211), the turning radius of electrons gradually decreases, while the rotation speed increases. In this way, the electron beam from the electron gun (3) forms a tornado-like electron vortex. Then, the electron beam reaches the cavity portion (22).
Since the inner wall surface of the magnet (5) is disposed at a position close to the cavity part (22), a higher magnetic field is formed in the cavity part (22). Thereby, the frequency of the electromagnetic wave generated by the conversion of the kinetic energy of the electron into the electromagnetic wave by tuning the rotation speed of the electron and the resonance frequency can be made higher.
The electrons (e) that have passed through the cavity portion (22) are caused by the centrifugal force of the rotational movement and the shape of the tapered pipe line (231) that continuously increases in diameter from the connection portion with the cavity portion (22). It moves away from the axis of (2), collides with the wall surface of the collector part (23), and is captured by the collector part (23).
On the other hand, the electromagnetic wave (w) travels straight along the axis of the oscillation tube (2) and is emitted out of the oscillation tube (2) through the output window (4).

A comparison between the gyrotron of the present invention and the conventional gyrotron without the constriction formed by the middle part (220) is performed using specific numerical values.
Consider a case where a gyrotron with an output of 15 kW, a frequency of 30 GHz, and an oscillation mode TE ₀₁ is designed. In order to obtain an oscillation frequency of 30 GHz with a fundamental wave, a magnetic field of 1.0 Tesla is required at the cavity. When the second harmonic is used, the required magnetic field is 0.5 Tesla, but the oscillation efficiency is lower than that of the fundamental wave.
If a gyrotron having such output characteristics is designed using a conventional mechanism, the outer diameter required for the collector part and the electron gun part will be about φ100 mm, and a constriction structure is not conventionally adopted. The outer diameter of the middle position of the gyrotron, that is, the middle part is about φ100 mm. The outer diameter dimension of the oscillation tube (2) in the middle part (220) of the gyrotron (1) using the constricted and divided structure magnet (5) formed by the middle part (220) of the present invention is Even considering the provision of a water cooling structure, about φ25 mm is sufficient.
The weight of the permanent magnet applied to the gyrotron of the above dimensions is that, in the case of the conventional structure, in order to obtain a magnetic field of 0.5 Tesla, a 500 kg Nd-Fe-B permanent magnet is required. In the present invention, 80 kg of Nd—Fe—B permanent magnet is required. That is, the weight can be reduced to about 1/6. In proportion to this, the manufacturing cost can be similarly reduced.
In addition, when the structure of the gyrotron of the present invention is optimally designed, the dimension of the cavity is about φ9 mm, and the outer diameter of the constricted portion of the gyrotron at this time is about φ20 mm in consideration of the water cooling function and the like. Become.
At this time, in the case of the conventional structure, the power consumption of the electromagnet is 36 kW, whereas in the case of the present invention, only 1.8 kW is required to obtain an equivalent output. Therefore, it is excellent in power saving. In the case of using a permanent magnet, it is possible to use a 50 kg permanent magnet having a weight of about one-tenth of the weight of the permanent magnet required in the conventional structure. The structure of TRON can be constructed.

  The present invention relates to a gyrotron capable of outputting millimeter waves with power saving or a compact design.

It is sectional drawing of the gyrotron which concerns on this invention. It is a figure which shows the magnet used for the gyrotron which concerns on this invention. It is a figure which shows the principle of operation of the gyrotron which concerns on this invention. It is a figure which shows the structure of the conventional gyrotron.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Gyrotron 2 ... Oscillation tube 21 ... Electron gun part 211 ... Tapered pipe line 22 ... Cavity part 23 ... Collector part 231 ... Taper Pipe 3 ... Electron gun 4 ... Output window 5 ... Magnet

Claims (3)

A cylindrical oscillator tube whose inside is evacuated,
An electron gun disposed at one end of the oscillation tube and outputting an electron beam in the axial direction of the oscillation tube;
An output window disposed at an end facing the end where the electron gun is disposed;
It consists of an annular magnet that fits the middle part of the oscillation tube,
The inside of the oscillation tube is composed of three regions: an electron gun portion where an electron gun is disposed, a cavity portion corresponding to a position where the magnet is disposed, and a collector portion located downstream of the cavity portion,
In the electron gun portion, an electron beam is output from the electron gun, and the output electron beam reaches the inside of the cavity through a conduit having a gradually decreasing diameter,
The electron beam output from the electron gun in the cavity is converted into electromagnetic waves,
The collector portion includes a tapered pipe line portion that continuously increases in diameter from the cavity portion, and the electromagnetic wave is oscillated from the output window through the collector portion, and the collector wall surface is an electron beam that has passed through the cavity. A gyrotron that captures the electrons of
The outer diameter of the middle part of the oscillation tube is smaller than the maximum diameter of the tapered part in the electron gun part and the collector part,
A gyrotron characterized in that an annular magnet that externally fits the middle part has a divided structure.   The gyrotron according to claim 1, wherein the magnet is a permanent magnet.   2. The gyrotron according to claim 1, wherein the magnet is an electromagnet.

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