JP7746928B2 - Electromagnetic wave generator - Google Patents

Description

This disclosure relates to an electromagnetic wave generating device capable of propagating electromagnetic waves.

In recent years, an electron tube called a virtual cathode oscillator (Vircator) has attracted attention as an electromagnetic wave generator capable of generating high-power electromagnetic waves. In a virtual cathode oscillator, an electron beam exceeding the space-charge-limited current is injected into a waveguide maintained in a vacuum. The injected electrons accumulate inside the waveguide to form a virtual cathode. The formed virtual cathode causes electrons to oscillate temporally and spatially within the waveguide. Electromagnetic wave generators using a virtual cathode oscillator generate high-power electromagnetic waves through electron oscillation (see, for example, Patent Document 1).

Another technique for increasing the output of an electromagnetic wave generator is to configure the electromagnetic wave generator with one or more reflectors inside its waveguide (see, for example, Patent Document 2, Non-Patent Document 1, and Non-Patent Document 2). In an electromagnetic wave generator with a reflector inside the waveguide, an electron beam emitted from a virtual cathode and transmitted through the reflector forms a new virtual cathode. By forming multiple virtual cathodes, the electromagnetic wave generator generates electromagnetic waves with even higher output.

When oscillating electromagnetic waves in this way, it is necessary to satisfy certain vacuum and electric field conditions inside the waveguide. Ideally, the vacuum conditions should have a spatially uniform pressure distribution. This is because if there are localized areas with low vacuum, high-frequency discharges will occur there, inhibiting the creation of a plasma state that generates electromagnetic waves. Furthermore, it is desirable for the electric field conditions to have a spatially axially symmetric electric field distribution inside the waveguide, with a local electric field strength of around several MV/m.

Japanese Patent Application Publication No. 5-266810 International Publication No. 2006/037918 Special Publication No. 2005-505112

S. Champeaux et. al, “3-D PIC Numerical Investigation of a Novel Concept of Multistage Axial Vircator for Enhanced Microwave Generation”, IEEE Transactions on Plasma Science 43, 3841 (2015) S. Champeaux et. al, “Improved Design of Multistage Axial Vircator with Reflectors for Enhanced Performances”, IEEE Transactions on Plasma Science 44, 3841 (2016) M. ElfsBerg et al., “Experimental Studies of Anode and Cathode Materials in a Repetitive Driven Axial Vircator”, IEEE Transactions on Plasma Science 36, 688 (2008)

However, with conventional electromagnetic wave generating devices, it was difficult to create uniform electric field and pressure distributions inside the waveguide, which posed a problem of impeding the generation and propagation of electromagnetic waves.

The present disclosure has been made to solve the above-mentioned problems, and aims to provide an electromagnetic wave generator that can uniformly form electric field and pressure distributions inside a waveguide and prevent the generation and propagation of electromagnetic waves from being obstructed.

The electromagnetic wave generating device according to the present disclosure includes a cathode that generates an electron beam, an anode arranged opposite the cathode, a vacuum vessel in which the cathode and anode are provided and the interior of which is evacuated to a vacuum, and a waveguide that is provided inside the vacuum vessel and consists of a cylindrical conductor electrically connected to the anode and the vacuum vessel, and has spatial openings formed symmetrically about the central axis of the cylinder.

The electromagnetic wave generator disclosed herein uses a cylindrical waveguide with a spatial gap symmetrically positioned around its central axis. When the air inside the vacuum container located outside the waveguide is evacuated, the electric field and pressure distributions inside the waveguide are uniformly formed, preventing the generation and propagation of electromagnetic waves from being obstructed.

1 is a configuration diagram of an electromagnetic wave generating system including an electromagnetic wave generating device according to a first embodiment of the present disclosure. 1 is a cross-sectional view showing the internal configuration of an electromagnetic wave generating device according to a first embodiment of the present disclosure. FIG. 1 is a schematic configuration diagram of a waveguide according to a first embodiment of the present disclosure. FIG. 2 is a plan view illustrating a configuration of an anode of the electromagnetic wave generating device according to the first embodiment of the present disclosure. 1 is a cross-sectional view illustrating the operating principle of an electromagnetic wave generating device according to a first embodiment of the present disclosure. FIG. 10 is a cross-sectional view showing the internal configuration of an electromagnetic wave generating device according to a second embodiment of the present disclosure. FIG. 10 is a cross-sectional view illustrating a configuration of a waveguide according to a second embodiment of the present disclosure. FIG. 11 is a cross-sectional view showing the internal configuration of an electromagnetic wave generating device according to a third embodiment of the present disclosure. FIG. 10 is a cross-sectional view illustrating a configuration of a waveguide according to a third embodiment of the present disclosure. FIG. 10 is a cross-sectional view showing the internal configuration of an electromagnetic wave generating device according to a fourth embodiment of the present disclosure. FIG. 10 is a cross-sectional view illustrating a configuration of a waveguide according to a fourth embodiment of the present disclosure. FIG. 10 is a cross-sectional view showing the internal configuration of an electromagnetic wave generating device according to a fifth embodiment of the present disclosure. FIG. 11 is a plan view showing the configuration of a reflector holder and a reflector of an electromagnetic wave generating device according to a fifth embodiment of the present disclosure. FIG. 11 is a plan view illustrating the configuration of a reflector of an electromagnetic wave generating device according to a fifth embodiment of the present disclosure.

Embodiment 1.
FIG. 1 is a configuration diagram of an electromagnetic wave generating system including an electromagnetic wave generator according to a first embodiment of the present disclosure. As shown in FIG. 1 , the electromagnetic wave generating system 100 is connected to a high-voltage pulse generator 200 and a vacuum pump 300. When generating electromagnetic waves using this electromagnetic wave generating system, the inside of the electromagnetic wave generating system 100 is first evacuated using the vacuum pump 300 to a predetermined vacuum level. When a high-voltage pulse is input from the high-voltage pulse generator 200 while the internal vacuum level is maintained, electrons are accelerated inside the electromagnetic wave generating system 100, and a virtual cathode formed by the electrons clustering in the waveguide is generated, thereby generating electromagnetic waves 400. Note that while FIG. 1 illustrates an example in which the system is configured only with the electromagnetic wave generating system 100 and the high-voltage pulse generator 200, it is also possible to use only the electromagnetic wave generating system 100 and the high-voltage pulse generator 200 without using the vacuum pump 300. In such a case, the inside of the electromagnetic wave generator 100 is evacuated to a predetermined vacuum level during manufacturing, and then the electromagnetic wave generator 100 is sealed to maintain the internal vacuum level.

2 is a cross-sectional view showing the internal configuration of the electromagnetic wave generating device according to embodiment 1 of the present disclosure. As shown in FIG. 2, the electromagnetic wave generating device 100 includes a first vacuum vessel 110, which maintains a predetermined vacuum level inside, and a second vacuum vessel 110A, which are arranged side by side. A cathode 150 that generates an electron beam is provided inside the second vacuum vessel 110A. An anode 130 is provided between the first vacuum vessel 110 and the second vacuum vessel 110A, facing the cathode 150. While FIG. 2 shows an example in which the electromagnetic wave generating device 100 is separated into the first vacuum vessel 110 and the second vacuum vessel 110A, the first vacuum vessel 110 and the second vacuum vessel 110A may be integrated into a single vacuum vessel containing the anode 130 and the cathode 150. The current amount of the generated electron beam and the frequency of the electromagnetic waves are determined by adjusting the distance d [mm] between the anode 130 and the cathode 150.

The first vacuum vessel 110 is, for example, a hollow cylinder with both ends open. Hereinafter, the central axis of the first vacuum vessel 110 is referred to as the Z-z axis. A transmission window 111 that transmits electromagnetic waves is provided at the end of the first vacuum vessel 110 in the z-axis direction, intersecting the Z-z axis. Furthermore, an anode 130 is provided at the end of the first vacuum vessel 110 opposite the transmission window 111, intersecting the Z-z axis. A cylindrical waveguide 120 is provided inside the first vacuum vessel 110. The waveguide 120 is open at both ends and extends from the position where the anode 130 is provided toward the position where the transmission window 111 is provided. Hereinafter, the end of the waveguide 120 facing the anode 130 will be referred to as one end, and the end facing the transmission window 111 will be referred to as the other end. The vacuum pump 300 evacuates the interior of the first vacuum vessel 110 and the interior of the second vacuum vessel 110A.

Figure 3 is a schematic diagram of the waveguide of the electromagnetic wave generating device according to embodiment 1 of the present disclosure. The waveguide 120 is composed of a cylindrical conductor and has a spatial gap symmetrical about the central axis. The cylindrical shape is not limited to a shape with side surfaces formed along the circumferential direction, but also includes a shape with multiple conductors arranged along the circumferential direction. The waveguide 120 is electrically connected from one end to the other by conductors, and the first vacuum container 110, the second vacuum container 110A, and the anode 130 are maintained at the same potential.

The waveguide 120 is positioned, for example, so that its central axis coincides with the central axis (Z-z axis) of the first vacuum vessel 110. The cathode 150 is positioned, for example, on an extension of the Z-z axis. Inside the waveguide 120, an electron beam is incident from one end, and an electromagnetic wave 400 is output from the other end.

As shown in Figure 3, the waveguide 120 in this embodiment is formed as a hollow cylinder with a side surface along the circumferential direction, and multiple through-holes 140 are formed in the side surface as spatial gaps. Here, Figure 3 shows an example in which the through-holes 140 are round holes, but they may be formed symmetrically with respect to the central axis of the cylindrical shape, and may be, for example, slit-shaped.

In order for the electromagnetic wave generator 100 to generate electromagnetic waves, the inside of the waveguide 120 must be evacuated to a predetermined vacuum condition. Because the waveguide 120 has a cylindrical shape with a spatial gap symmetrical about the central axis, when the first vacuum container 110 and the second vacuum container 110A are evacuated by the vacuum pump 300, a uniform degree of vacuum can be maintained inside the waveguide 120.

Figure 4 is a plan view showing the configuration of the anode of the electromagnetic wave generating device according to embodiment 1 of the present disclosure. As shown in Figure 4, the anode 130 has an anode body 131 made of a metal mesh or a metal thin film with a thickness of about μm, through which electrons can easily pass, and an anode frame 132 that holds the anode body 131.

FIG. 5 is a cross-sectional view illustrating the operating principle of the electromagnetic wave generator according to the first embodiment of the present disclosure. The following describes the operation of the electromagnetic wave generator 100, which generates an electron beam from the cathode 150 and generates electromagnetic waves. Here, the insides of the first vacuum vessel 110 and the second vacuum vessel 110A are assumed to be maintained at a vacuum of, for example, approximately 0.1 mPa. In this state, when a high voltage (several hundred kV or more) in a pulsed form (with a pulse width of approximately 10 ns to 100 ns) is applied between the anode 130 and the cathode 150 by the high-voltage pulse generator 200, an electron beam is generated from the cathode 150 toward the anode 130. The electron beam passes through the anode 130 and enters the waveguide 120. When the current of the electron beam exceeds the space-charge-limited current _Ic expressed by the following equation (1), a virtual cathode 420 is formed inside the waveguide 120.

In equation (1), γ, r [mm], and b [mm] are the electron Lorentz factor, the waveguide radius, and the electron beam radius, respectively. The electron Lorentz factor γ is expressed by the following equation (2).

In equation (2), the applied voltage V [V], the elementary charge e [C], the electron mass me [kg], and the speed of light c [m/s].

The virtual cathode 420 is a spatial region where electrons are concentrated. Therefore, electrons passing through the anode 130 and heading toward the virtual cathode 420 are decelerated and reflected by the potential of the virtual cathode 420, as shown in electron beam 410. This phenomenon causes the electrons to vibrate between the cathode 150 and the virtual cathode 420, generating electromagnetic waves 400.

The relationship between the distance d [mm] between the anode 130 and the cathode 150 and the frequency f [Hz] of the electromagnetic wave 400 is expressed by equation (3).

The impedance of the virtual cathode oscillator 100 is expressed as in equation (4) using the distance d [mm] between the anode 130 and the cathode 150 and the surface area A [mm ² ] of the cathode 150 .

The distance d and the area A are adjusted in accordance with the frequency of the electromagnetic wave 400 to be generated by the electromagnetic wave generator 100 and the impedance of the high-voltage pulse generator 200 .

The frequency of the electromagnetic wave 400 generated by the electromagnetic wave generator 100 is expressed by Equation (3). Therefore, to change the frequency of the electromagnetic wave 400, it is necessary to adjust the distance d between the anode 130 and the cathode 150 or the voltage V of the electrons passing through the waveguide 120. For example, when the distance d is fixed at 10 mm, if an electromagnetic wave with a frequency of 3 GHz is to be generated, the voltage V must be adjusted to 80 kV, and if an electromagnetic wave with a frequency of 4 GHz is to be generated, the voltage V must be adjusted to 200 kV. Furthermore, when the voltage V is fixed at 200 kV, if an electromagnetic wave with a frequency of 3 GHz is to be generated, the distance d must be adjusted to 13 mm, and if an electromagnetic wave with a frequency of 4 GHz is to be generated, the distance d must be adjusted to 10 mm. In order for the electromagnetic wave 400 to pass through the waveguide 120, it is necessary to satisfy the cutoff frequency of the waveguide 120. One example of the electromagnetic wave assumed in this disclosure is the TM mode. In order to oscillate electromagnetic waves in a single mode inside the waveguide 120, the fundamental mode TM ₀₁ is oscillated by utilizing the cutoff phenomenon. For this reason, the frequency f of the oscillating electromagnetic waves needs to be selected in accordance with the condition of equation (5).

where f ₀₁ and f ₀₂ are the cutoff frequencies of the TM ₀₁ mode and the TM ₀₂ mode, respectively. The cutoff frequencies are generally given as roots of a Bessel function and are expressed as in equations (6) and (7).

In the electromagnetic wave generating device 100, electromagnetic waves other than those in the _TM01 mode are attenuated by adjusting the length L of the waveguide 120. To ensure sufficient attenuation, a length of about 10 times the wavelength is required. Since the relationship between wavelength λ and frequency f is c = fλ, as described above, for an electromagnetic wave of 2 GHz, the wavelength λ is 15 cm. In this case, the length L of the waveguide 120 needs to be about 1.5 m.

As described above, the electromagnetic wave generating device 100 according to embodiment 1 comprises a cathode 150 that generates an electron beam, an anode 130 that is arranged opposite the cathode 150, vacuum vessels 110, 110A that have the cathode 150 and anode 130 disposed therein and that are evacuated to a vacuum, and a waveguide 120 that is disposed inside the vacuum vessel 110 and is made of a cylindrical conductor electrically connected to the anode 130 and the vacuum vessel 110, with a spatial gap formed symmetrically about the central axis of the cylinder.

In this way, a waveguide 120 is provided in which a spatial gap is formed symmetrically about the central axis of the cylindrical shape. An axially symmetric electric field is formed inside the waveguide 120 under the condition that the degree of vacuum around the virtual cathode 420 is uniform. This prevents the generation and propagation of electromagnetic waves from being obstructed.

Embodiment 2.
6 is a cross-sectional view showing the configuration of an electromagnetic wave generator according to a second embodiment of the present disclosure. In the first embodiment, the waveguide 120 of the electromagnetic wave generator 100 is formed as a hollow cylinder having a side surface along the circumferential direction, and a plurality of through holes 140 are formed in the side surface symmetrically with respect to the axis as spatial gaps. In contrast, the waveguide 120A of the electromagnetic wave generator 100A according to the second embodiment is formed by a plurality of metal rods 121 arranged in a ring shape at equal intervals. The following description will focus on the differences from the first embodiment, and similarities will be omitted as appropriate.

As shown in FIG. 6, the electromagnetic wave generating device 100A has a first vacuum vessel 110 and a second vacuum vessel 110A arranged side by side. An anode 130 is provided between the first vacuum vessel 110 and the second vacuum vessel 110A, facing the cathode 150. A cathode 150 that generates an electron beam is also provided inside the second vacuum vessel 110A. A transmission window 111 that transmits electromagnetic waves is provided at one end of the first vacuum vessel 110, intersecting the central axis Z-z axis of the first vacuum vessel 110. An anode 130 is provided at the end of the first vacuum vessel 110 opposite the transmission window 111, intersecting the Z-z axis. The waveguide 120A is provided inside the first vacuum vessel 110, and the multiple metal rods 121 that form the waveguide 120A each extend from one end on the anode 130 side to the other end on the transmission window 111 side inside the first vacuum vessel 110. The waveguide 120A is electrically connected by a conductor from one end on the anode 130 side to the other end on the transmission window 111 side, and the first vacuum vessel 110, second vacuum vessel 110A, and anode 130 are maintained at the same potential.

Figure 7 is a cross-sectional view showing the configuration of a waveguide according to embodiment 2 of the present disclosure. As shown in Figure 7, multiple metal rods 121 are arranged at equal intervals circumferentially about the central axis Z-z direction of the first vacuum vessel 110. When the inside of the first vacuum vessel 110 is evacuated using a vacuum pump 300, an axially symmetric electric field is formed inside the waveguide 120A formed by the metal rods 121 under conditions of a uniform degree of vacuum. Here, Figure 7 shows an example in which 16 metal rods 121 are provided, but the number does not have to be 16 as long as the structure is spatially symmetric.

As described above, the waveguide 120A of the electromagnetic wave generating device 100A according to this embodiment is formed by a plurality of metal rods 121 arranged in a ring shape at equal intervals. In this embodiment, as in embodiment 1, the electric field distribution and pressure distribution inside the waveguide 120A can be made uniform, preventing the generation and propagation of electromagnetic waves from being obstructed.

Embodiment 3.
FIG. 8 is a cross-sectional view showing the configuration of an electromagnetic wave generator according to a third embodiment of the present disclosure. FIG. 9 is a cross-sectional view showing the configuration of a waveguide according to the third embodiment of the present disclosure. Waveguide 120B of electromagnetic wave generator 100B of this embodiment is a wire mesh 122 rolled into a cylindrical shape. Wire mesh 122 is, for example, woven from metal wires to have a mesh size of 10 mm or less. The following description will focus on differences from the first embodiment, and similarities will be omitted as appropriate.

As shown in FIG. 8, the electromagnetic wave generating device 100B has a first vacuum vessel 110 and a second vacuum vessel 110A arranged side by side. An anode 130 is provided between the first vacuum vessel 110 and the second vacuum vessel 110A, facing the cathode 150. A cathode 150 that generates an electron beam is also provided inside the second vacuum vessel 110A. A transmission window 111 that transmits electromagnetic waves is provided at one end of the first vacuum vessel 110, intersecting the central axis Z-z axis of the first vacuum vessel 110. An anode 130 is provided at the end of the first vacuum vessel 110 opposite the transmission window 111, intersecting the Z-z axis. The waveguide 120B is provided inside the first vacuum vessel 110, extending from one end on the anode 130 side to the other end on the transmission window 111 side. The waveguide 120B is electrically connected by a conductor from one end on the anode 130 side to the other end on the transmission window 111 side, and the first vacuum container 110, the second vacuum container 110A, and the anode 130 are maintained at the same potential.

Waveguide 120B is positioned, for example, so that its central axis coincides with the central axis Z-z axis of first vacuum vessel 110. Cathode 150 is positioned, for example, on an extension of the Z-z axis. Inside waveguide 120B, an electron beam is incident from one end, and electromagnetic wave 400 is output from the other end.

As described above, the waveguide 120B of the electromagnetic wave generator 100B according to this embodiment is formed by rolling the wire mesh 122 into a cylindrical shape. As with embodiment 1, this embodiment also makes it possible to make the electric field distribution and pressure distribution in the waveguide 120B uniform, thereby preventing the generation and propagation of electromagnetic waves from being obstructed.

Embodiment 4.
10 is a cross-sectional view showing the configuration of an electromagnetic wave generator according to embodiment 4 of the present disclosure. A waveguide 120C of an electromagnetic wave generator 100C of this embodiment is formed using a metal wire 123. The following description will focus on differences from embodiment 1, and similarities will be omitted as appropriate.

Figure 11 is a cross-sectional view showing the configuration of a waveguide according to embodiment 4 of the present disclosure. As shown in Figure 11, an electromagnetic wave generating device 100C includes a first vacuum vessel 110 and a second vacuum vessel 110A arranged side by side. An anode 130 is provided between the first vacuum vessel 110 and the second vacuum vessel 110A, facing the cathode 150. A cathode 150 that generates an electron beam is also provided inside the second vacuum vessel 110A. A transmission window 111 that transmits electromagnetic waves is provided at one end of the first vacuum vessel 110, intersecting the central axis (Z-z axis) of the first vacuum vessel 110. An anode 130 is provided at the end of the first vacuum vessel 110 opposite the transmission window 111, intersecting the Z-z axis.

The waveguide 120C is located inside the first vacuum vessel 110. The waveguide 120C is formed into a cylindrical shape by extending a metal wire 123 from the position where the anode 130 is located to the position where the transmission window 111 is located, and moving the metal wires 123 back and forth multiple times while shifting them circumferentially so that they do not overlap. The waveguide 120C is electrically connected by a conductor from one end on the anode 130 side to the other end on the transmission window 111 side, and the first vacuum vessel 110, the second vacuum vessel 110A, and the anode 130 are maintained at the same potential.

The waveguide 120C is positioned, for example, so that its central axis coincides with the central Z-z axis of the first vacuum vessel 110. The cathode 150 is positioned, for example, on an extension of the Z-z axis. Inside the waveguide 120C, an electron beam is incident from one end, and electromagnetic waves 400 are output from the other end.

As described above, the waveguide 120C of the electromagnetic wave generator 100C according to this embodiment is formed by running the metal wire 123 back and forth between the anode 130 and the transmission window 111. In this embodiment, as in embodiment 1, the electric field distribution and pressure distribution inside the waveguide 120C can be made uniform, preventing the generation and propagation of electromagnetic waves from being impeded.

Embodiment 5.
FIG. 12 is a cross-sectional view showing the configuration of a reflector of an electromagnetic wave generator according to a fifth embodiment of the present disclosure. Electromagnetic wave generator 100D includes first reflector 180 and second reflector 180A for reflecting electromagnetic waves inside first vacuum vessel 110. First reflector 180 and second reflector 180A are made of a metal mesh or a metal thin film with a thickness of about μm, which allows electrons to easily pass through. Hereinafter, as an example, electromagnetic wave generator 100D will be described as including waveguide 120A in which multiple metal rods 121 are arranged in a ring shape at equal intervals. The following description will focus on differences from the first embodiment, and similarities will be omitted as appropriate.

As shown in FIG. 12, a first reflector 180 and a second reflector 180A are provided inside the first vacuum vessel 110, spaced apart, so as to face the anode 130. The first reflector 180 is supported by a first reflector holder 181, and the second reflector 180A is supported by a second reflector holder 181A. The first reflector holder 181 and the second reflector holder 181A are each provided so that a plurality of metal rods 121 pass through them. The first reflector holder 181 and the second reflector holder 181A are arranged so as to be spatially symmetrical inside the first vacuum vessel 110.

13 is a plan view showing the configuration of a reflector holder and a reflector of an electromagnetic wave generating device according to embodiment 5 of the present disclosure. FIG. 14 is a plan view showing the configuration of a reflector holder and a reflector of an electromagnetic wave generating device according to embodiment 5 of the present disclosure. As shown in FIGS. 13 and 14, the first reflector holder 181 and the second reflector holder 181A each have an annular surface, and a first metal connection portion 182 and a second metal connection portion 182A extend from the inner periphery of the annular surface toward the center, respectively. The first reflector 180 and the second reflector 180A are fixed to the center of the first reflector holder 181 and the second reflector holder 181A by the first metal connection portion 182 and the second metal connection portion 182A. Here, the first metal connection portion 182 and the second metal connection portion 182A are made thick enough to form a virtual cathode 420 without hindering the transmission of electrons.

When using a waveguide 120A formed from multiple metal rods 121, multiple through-holes are formed in the annular surfaces of the first reflector holder 181 and the second reflector holder 181A to allow the multiple metal rods 121 to pass through. This allows the waveguide 120A formed from multiple metal rods 121 to be positioned without interfering with its function. In this case, the first reflector 180 and the first reflector holder 181, and the second reflector 180A and the second reflector holder 181A, are at the same potential.

Electrons generated from the cathode 150 are accelerated or transmitted between the anode 130 and the first and second reflectors 180 and 180A, which are spaced apart from the anode, to form multiple virtual cathodes that generate electromagnetic waves.

As described above, in the electromagnetic wave generator 100D according to this embodiment, the first reflector 180 and the second reflector 180A are provided at a distance from each other so as to face the anode 130 inside the waveguide 120A. As in embodiment 1, this embodiment also makes it possible to uniformize the electric field distribution and pressure distribution inside the waveguide 120A and prevent the generation and propagation of electromagnetic waves from being impeded. Furthermore, in this embodiment, by providing the first reflector 180 and the second reflector 180A, electrons can be effectively utilized to increase the output efficiency of the electromagnetic waves.

In this embodiment, as an example, the electromagnetic wave generator 100D is shown to include a first reflector 180 and a second reflector 180A, but the number of reflectors is not limited to this, and the device may include a single reflector, or multiple reflectors. However, there are optimal values for the number and diameter of the reflectors installed inside the waveguide 120 that maximize the output for each electromagnetic wave generation condition. Therefore, it is preferable to determine the number and diameter of the reflectors taking into consideration the output value and manufacturability required for the electromagnetic wave generator 100D.

In addition, in this embodiment, an example is shown in which 16 metal rods 121 are provided, but the number does not have to be 16 as long as the structure is spatially symmetrical.

Furthermore, while an example is shown in which four first metal connection portions 182 and four second metal connection portions 182A are provided, this is not limitative and any number of connection portions may be provided as long as the first reflector holder 181 and the second reflector holder 181A can support the first reflector 180 and the second reflector 180A, respectively.

In addition, in this embodiment, as an example, the electromagnetic wave generating device 100D is shown to include a waveguide 120A in which multiple metal rods 121 are arranged in a ring shape at equal intervals, but the waveguides 120, 120B, and 120C may also be configured to include multiple reflectors.

In this embodiment, as an example, the electromagnetic wave generator 100E is shown to include a first reflector 180 and a second reflector 180A, but the number of reflectors is not limited to this, and the device may include a single reflector, or multiple reflectors. However, there are optimal values for the number and diameter of the reflectors installed inside the waveguide 120 that maximize the output for each electromagnetic wave generation condition. Therefore, it is preferable to determine the number and diameter of the reflectors taking into consideration the output value and manufacturability required for the electromagnetic wave generator 100E.

Note that the configurations shown in the above embodiments are merely examples of the content of this disclosure, and may be combined with other known technologies. Furthermore, parts of the configuration may be omitted or modified without departing from the spirit of this disclosure.

The various aspects of this disclosure are summarized below as appendices.

(Appendix 1)
a cathode for generating an electron beam;
an anode disposed opposite the cathode;
a vacuum vessel in which the cathode and the anode are provided and the inside of which is evacuated to a vacuum;
a waveguide provided inside the vacuum vessel, the waveguide comprising a cylindrical conductor electrically connected to the anode and the vacuum vessel, the waveguide having a spatial gap formed symmetrically with respect to a central axis of the cylindrical shape;
An electromagnetic wave generating device comprising:
(Appendix 2)
2. The electromagnetic wave generating device according to claim 1, wherein a transmission window that transmits electromagnetic waves is provided at one end of the vacuum vessel, and the waveguide extends from a position where the anode is provided toward a position where the transmission window is provided.
(Appendix 3)
The electromagnetic wave generating device according to claim 1 or 2, wherein the waveguide is a hollow cylinder having a side surface along a circumferential direction, and a plurality of through holes are formed in the side surface as the spatial gap.
(Appendix 4)
3. The electromagnetic wave generating device according to claim 1, wherein the waveguide is a plurality of metal rods arranged in a ring shape at intervals.
(Appendix 5)
3. The electromagnetic wave generating device according to claim 1, wherein the waveguide is a wire mesh rolled into the cylindrical shape.
(Appendix 6)
6. The electromagnetic wave generating device according to claim 5, wherein the wire mesh has a mesh size of 10 mm or less.
(Appendix 7)
3. The electromagnetic wave generating device according to claim 1, wherein the waveguide is a metal wire that travels back and forth multiple times from a position where the anode is provided to a position where the transmission window is provided.
(Appendix 8)
8. The electromagnetic wave generating device according to claim 1, wherein a reflector is provided inside the waveguide so as to face the anode.

100 Electromagnetic wave generator, 110 First vacuum vessel, 110A Second vacuum vessel, 111 Transmission window, 120 Waveguide, 121 Metal rod, 122 Wire mesh, 123 Metal wire, 130 Anode, 131 Anode body, 132 Anode frame, 140 Through hole, 150 Cathode, 180 First reflector, 180A Second reflector, 181 First reflector holder, 181A Second reflector holder, 182 First metal connection, 182A Second metal connection, 200 High-voltage pulse generator, 300 Vacuum pump, 400 Electromagnetic wave, 410 Electron beam, 420 Virtual cathode

Claims (8)

a cathode for generating an electron beam;
an anode disposed opposite the cathode;
a vacuum vessel in which the cathode and the anode are provided and the inside of which is evacuated to a vacuum;
a waveguide provided inside the vacuum vessel, the waveguide being made of a cylindrical conductor electrically connected to the anode and the vacuum vessel, the waveguide having spatial openings formed symmetrically with respect to a central axis of the cylindrical shape;
An electromagnetic wave generating device comprising: 2. The electromagnetic wave generating device according to claim 1, wherein a transmission window that transmits electromagnetic waves is provided at one end of the vacuum vessel, and the waveguide extends from a position where the anode is provided toward a position where the transmission window is provided. 3. The electromagnetic wave generating device according to claim 1 , wherein the waveguide is a hollow cylinder having a side surface along a circumferential direction, and a plurality of through holes are formed in the side surface as the spatial opening . a cathode for generating an electron beam;
an anode disposed opposite the cathode;
a vacuum vessel in which the cathode and the anode are provided and the inside of which is evacuated to a vacuum;
a waveguide provided inside the vacuum vessel and consisting of a cylindrical conductor electrically connected to the anode and the vacuum vessel, in which a plurality of metal rods are arranged in an annular shape symmetrically with respect to a central axis of the cylindrical shape at intervals , and gaps are formed between the plurality of metal rods;
An electromagnetic wave generating device comprising : 3. The electromagnetic wave generating device according to claim 1 , wherein the waveguide is a wire mesh rolled into the cylindrical shape , and the opening is a mesh of the wire mesh . 6. The electromagnetic wave generator according to claim 5 , wherein the wire mesh has a mesh size of 10 mm or less. a cathode for generating an electron beam;
an anode disposed opposite the cathode;
a vacuum vessel in which the cathode and the anode are provided and the inside of which is evacuated to a vacuum;
a waveguide made of a cylindrical conductor provided inside the vacuum vessel and electrically connected to the anode and the vacuum vessel;
a transmission window that transmits electromagnetic waves is provided at one end of the vacuum vessel;
The waveguide is an electromagnetic wave generating device in which a metal wire travels back and forth multiple times symmetrically about the central axis of the cylindrical shape from the position where the anode is provided to the position where the transmission window is provided , and gaps are formed between the metal wires . 3. The electromagnetic wave generating device according to claim 1 , wherein a reflector is provided inside the waveguide so as to face the anode.