Electromagnetic wave generation device

Abstract

Provided is an electromagnetic wave generation device capable of determining the cause of an abnormality that has occurred internally.　The present invention includes: a negative electrode (1); a first positive electrode (2) that is disposed facing the negative electrode and through which electrons can pass; a cylindrical waveguide (3) that guides electromagnetic waves and is disposed on the opposite side of the first positive electrode from the negative electrode; an output window (30) that outputs electromagnetic waves and is disposed at the opposite end of the waveguide to the first positive electrode; a first current sensor (41) that detects current data of electron beams emitted from the negative electrode; a second current sensor (42) that detects current data of electron beams traveling in the waveguide; and an abnormality determination device (60) that determines an internal abnormality on the basis of the current data detected by the first current sensor and the current data detected by the second current sensor.

Description

Electromagnetic wave generator

[0001] The present disclosure relates to an electromagnetic wave generating device.

[0002] An electron tube called a virtual cathode oscillator (Vircator) is known as an electromagnetic wave generator that generates 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 are densely packed inside the waveguide to form a virtual cathode. The formed virtual cathode causes the electrons to oscillate temporally and spatially within the waveguide. The virtual cathode oscillator generates high-power pulsed electromagnetic waves (electromagnetic pulses) by oscillating these electrons (see, for example, Patent Document 1).

[0003] A conventional electromagnetic wave radiation system using such a virtual cathode oscillator as an electromagnetic wave generator has been disclosed, which has a pulse generator, an electromagnetic wave generator, and a radiation antenna connected in series. In this conventional electromagnetic wave radiation system, a discharge detector for detecting discharge due to insulation failure and an output detector for detecting output current, etc. are provided for each device, and a determination is made as to which device is experiencing an abnormality based on signals detected by these detectors (see, for example, Patent Document 2).

[0004] Japanese Patent Application Laid-Open No. 5-266810 Japanese Patent Application Laid-Open No. 2022-10583

[0005] However, in conventional electromagnetic wave radiation systems, it is only possible to determine which device has an abnormality based on signals detectable outside the pulse generator, the electromagnetic wave generating device, and the radiation antenna, so there is a problem in that even if an abnormality occurs in the electromagnetic wave generating device, it is not possible to determine the cause of the abnormality that has occurred inside it.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an electromagnetic wave generating device that can determine the cause of an abnormality that occurs inside.

[0007] The electromagnetic wave generating device of the present disclosure includes a cathode, a first anode arranged opposite the cathode and allowing electrons to pass through, a cylindrical waveguide that guides electromagnetic waves and is arranged on the opposite side of the first anode from the cathode, an output window that outputs electromagnetic waves and is arranged on the end of the waveguide opposite the first anode, a first current sensor that detects current data of the electron beam emitted from the cathode, a second current sensor that detects current data of the electron beam traveling within the waveguide, and an abnormality determination device that determines internal abnormalities based on the current data detected by the first current sensor and the current data detected by the second current sensor.

[0008] The electromagnetic wave generating device disclosed herein is equipped with a first current sensor that detects current data of the electron beam emitted from the cathode, a second current sensor that detects current data of the electron beam traveling within the waveguide, and an abnormality determination device that determines internal abnormalities based on the current data detected by the first current sensor and the current data detected by the second current sensor, so that the cause of an internal abnormality can be determined.

[0009] Fig. 1 is a schematic cross-sectional view of an electromagnetic wave generator according to embodiment 1. Fig. 2 is a schematic cross-sectional view of an electromagnetic wave generator according to embodiment 2. Fig. 3 is a schematic cross-sectional view of an electromagnetic wave generator according to embodiment 3. Fig. 4 is a diagram showing an example of the hardware configuration of an abnormality determination device for an electromagnetic wave generator according to embodiments 1 to 3.

[0010] Hereinafter, electromagnetic wave generating devices according to embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the same reference numerals in the various drawings indicate the same or corresponding parts.

[0011] Embodiment 1. FIG. 1 is a cross-sectional schematic diagram of an electromagnetic wave generator according to embodiment 1. FIG. 1 is a cross-sectional view taken along a direction parallel to the central axis of a cylindrical waveguide (described later). The electromagnetic wave generator 100 includes a cathode 1 and a first anode 2 disposed opposite the cathode 1. A cylindrical waveguide 3 is provided on the side of the first anode 2 opposite the cathode 1. Here, the side closer to the cathode 1 is referred to as the upstream side, and the side farther from the cathode 1 is referred to as the downstream side. An insulator 15 is provided between the cathode 1 and the first anode 2 to electrically insulate the cathode 1 from the first anode 2. An output window 30 is provided at the end of the waveguide 3 opposite the end where the first anode 2 is provided, allowing electromagnetic waves to pass through and be output. To maintain a vacuum in the space between the cathode 1 and the first anode 2 and the inside of the waveguide 3, the cathode 1 and the first anode 2 are disposed within a vacuum vessel 4, and the inside of the waveguide 3 is in communication with the vacuum vessel 4. An output window 30 provided at the end of the waveguide 3 is fixed airtight to the waveguide 3 .

[0012] The waveguide 3 is a cylindrical conductive waveguide, and its central axis intersects with the output window 30. The vacuum vessel 4 is also a cylindrical conductive part. The cathode 1 is located on an extension of the central axis of the waveguide 3. The first anode 2, the vacuum vessel 4, and the waveguide 3 are electrically connected and maintained at the same potential. Since the vacuum vessel 4 is normally set to ground potential, the potential of the first anode 2 is also ground potential. A pulse generator 10 is connected to the cathode 1 via a conductor 11, and an electron beam 20 is generated by applying a high-voltage pulse from the pulse generator 10 to the cathode 1. The first anode 2 is made of a metal mesh or a thin metal film with a thickness of about 10 μm, through which electrons can pass.

[0013] Next, the operation of the electromagnetic wave generator 100 of this embodiment will be described. When a high-voltage pulse is applied to the cathode 1 from the pulse generator 10, electrons are emitted from the cathode 1 toward the first anode 2 by field emission, generating an electron beam 20. Under a strong electric field, the electrons move toward the first anode 2. After passing through the first anode 2, which allows electrons to pass through, they are injected into the downstream waveguide 3 by inertial force. There is a potential difference between the cathode 1 and the first anode 2, and the electrons, which are charged particles, are accelerated by the energy of this potential difference. As the number of electrons injected into the waveguide 3 increases, a potential group called a virtual cathode 5, where electrons are densely packed, is formed inside the waveguide 3. The condition for the virtual cathode 5 to be formed is when the current of the electron beam traveling through the waveguide 3 exceeds the spatially limited current of the waveguide 3.

[0014] When a virtual cathode 5 is formed inside the waveguide 3, electrons with energy lower than the potential of the virtual cathode 5 are repelled by the virtual cathode 5. This reduces the amount of electrons supplied to the virtual cathode 5, causing the potential of the virtual cathode 5 to drop. Then, electrons flow into the virtual cathode 5 again, causing the potential of the virtual cathode 5 to rise, and the virtual cathode 5 begins to repel the electrons. This process is repeated, i.e., the virtual cathode 5 fluctuates temporally and spatially, causing electromagnetic waves, i.e., microwaves 6, to be generated from the virtual cathode 5. The microwaves 6 generated inside the waveguide 3 are emitted to the outside through the output window 30.

[0015] Next, a mechanism for generating electromagnetic waves in the electromagnetic wave generator 100 of this embodiment will be described. When a high-voltage pulse is applied to the cathode 1 from the pulse generator 10, electrons are emitted from the cathode 1 toward the first anode 2 by field emission, generating an electron beam 20. The current I of the electron beam 20 at this time is ＣＬ is expressed by the following equation (1).

[0016]

[0017] Here, V is the potential difference between the cathode 1 and the first anode 2, d is the distance between the cathode 1 and the first anode 2, S is the electrode area of ​​the cathode 1, and a is a constant. Under a strong electric field, electrons move toward the first anode 2, and after passing through the first anode 2 through which the electrons can pass, they are incident on the downstream waveguide 3 due to inertial force. The condition for forming a virtual cathode 5 inside the waveguide 3 is that the current I of the electron beam 20 is at least ＣＬ is the spatially limited current I of the waveguide 3. Ｃ The spatial limiting current I Ｃ is expressed by the following equation (2).

[0018]

[0019] where γ is the Lorentz factor of the electron, r ０ is the radius of the internal space of the waveguide 3, r ｂ is the radius of the electron beam. The Lorentz factor γ of the electron is expressed by the following equation (3):

[0020]

[0021] Here, m is the electron mass, e is the elementary electron quantity, and c is the velocity. The frequency f of the microwave 6 emitted from the virtual cathode 5 is expressed by the following equation (4).

[0022]

[0023] In order for the virtual cathode 5 to be generated, it is necessary for electrons emitted from the cathode 1 to pass through the first anode 2 and for a certain amount of electrons to be incident on the waveguide 3. If the amount of electrons incident on the waveguide 3 is small, the virtual cathode 5 will not be generated, or even if it is generated, the amount generated will be less than expected. As a result, if the amount of electrons incident on the waveguide 3 is small, microwaves will not be generated, or even if they are generated, the microwave output will be smaller than expected. At least the current I of the electron beam 20 ＣＬ is the spatial limiting current I Ｃ If the current does not exceed this value, microwaves will not be generated. If microwaves suddenly stop being output while the electromagnetic wave generator 100 is in operation, it is quite possible that the virtual cathode 5 is the cause. Therefore, measuring the amount of electrons in the virtual cathode 5, i.e., the current, is necessary to determine whether or not there is an abnormality in the electromagnetic wave generator 100.

[0024] In the electromagnetic wave generator 100 of this embodiment, as shown in FIG. 1 , a first current sensor 41 is provided near the cathode 1, and a second current sensor 42 is provided downstream of the first anode 2. The first current sensor 41 detects current data of the electron beam 20 emitted from the cathode 1. The second current sensor 42 detects current data of the electron beam traveling through the waveguide. In this embodiment, the first current sensor 41 and the second current sensor 42 are configured with Rogowski coils. The current data detected by the first current sensor 41 and the second current sensor 42 are sent to the abnormality determination device 60 via detectors 51 and 52, respectively. The detectors 51 and 52 convert the current data sent from the first current sensor 41 and the second current sensor 42, respectively, from analog to digital and amplify them as needed.

[0025] The abnormality determination device 60 determines an abnormality in the electromagnetic wave generator 100 based on the current data of the electron beam emitted from the cathode 1 sent from the first current sensor 41 and the current data of the electron beam traveling in the waveguide sent from the second current sensor 42. For example, if the current value of the electron beam 20 sent from the first current sensor 41 is smaller than the spatial limiting current I of the waveguide 3, Ｃ However, the current value of the electron beam traveling in the waveguide sent from the second current sensor 42 is greater than the spatial limiting current I Ｃ If the difference is less than , a virtual cathode is not generated. In this case, the abnormality determination device 60 determines that some abnormality has occurred in the first anode 2. In this case, the abnormality in the first anode 2 may be caused by, for example, a break in the metal mesh if the first anode 2 is made of a metal mesh. Another possible cause of the abnormality may be an unstable electrical connection of the first anode 2.

[0026] Furthermore, the abnormality determination device 60 determines an abnormality in the electromagnetic wave generator 100 based on the current waveform of the electron beam emitted from the cathode 1, which is transmitted from the first current sensor 41, and the current waveform of the electron beam traveling through the waveguide, which is transmitted from the second current sensor 42. For example, consider a case where a virtual cathode 5 is generated. In this case, the current waveform of the electron beam 20 transmitted from the first current sensor 41 follows the pulse waveform of the high voltage applied from the pulse generator 10. On the other hand, if the current waveform of the electron beam traveling through the waveguide, which is transmitted from the second current sensor 42, does not follow the current waveform of the electron beam 20 transmitted from the first current sensor 41, the abnormality determination device 60 determines that some abnormality has occurred in the first anode 2. In this case, the abnormality in the first anode 2 is likely due to discharge occurring in the first anode 2. The abnormality determination device 60 transmits the determination result to the display device 70. The display device 70 displays the determination result transmitted from the abnormality determination device 60.

[0027] As described above, the electromagnetic wave generating device 100 of this embodiment is equipped with a first current sensor 41 that detects current data of the electron beam 20 emitted from the cathode 1, a second current sensor 42 that detects current data of the electron beam traveling within the waveguide, and an abnormality determination device 60 that determines an internal abnormality based on the current data detected by the first current sensor 41 and the current data detected by the second current sensor 42, and therefore it is possible to determine the cause of an internal abnormality.

[0028] 1, a driving device 55 may be provided that enables the second current sensor 42 to move in a direction parallel to the central axis of the waveguide 3. By moving the position of the second current sensor 42 in the axial direction of the waveguide 3, the location of an abnormality can be identified in detail when an abnormality occurs.

[0029] Second Embodiment Fig. 2 is a cross-sectional schematic diagram of an electromagnetic wave generator according to a second embodiment. As shown in Fig. 2, the electromagnetic wave generator 100 of this embodiment is the same as the electromagnetic wave generator described in the first embodiment, except that a third current sensor 43 is added. The third current sensor 43 is disposed downstream of the region where the virtual cathode 5 is generated. In the electromagnetic wave generator 100 of this embodiment, the second current sensor 42 detects the current of the electron beam upstream of the virtual cathode 5, and the third current sensor 43 detects the current of the electron beam downstream of the virtual cathode 5. Current data detected by the third current sensor 43 is sent to the abnormality determination device 60 via the detector 53.

[0030] In the electromagnetic wave generator 100 configured as described above, it is possible to determine whether the virtual cathode 5 is being generated normally while the virtual cathode 5 is being generated. For example, when the difference between the current value of the electron beam upstream of the virtual cathode 5 detected by the second current sensor 42 and the current value of the electron beam downstream of the virtual cathode 5 detected by the third current sensor 43 is small, the abnormality determination device 60 determines that the virtual cathode 5 is being generated normally. When the difference is large, the abnormality determination device 60 determines that an abnormality has occurred in the virtual cathode 5. Possible causes of the abnormality in the virtual cathode 5 include, for example, abnormal discharge in the waveguide 3.

[0031] 2, a driving device 55 may be provided that enables the second current sensor 42 and the third current sensor 43 to move in a direction parallel to the central axis of the waveguide 3. By moving the positions of the second current sensor 42 and the third current sensor 43 in the axial direction of the waveguide 3, the location of an abnormality when it occurs can be identified in detail.

[0032] Embodiment 3. Fig. 3 is a cross-sectional schematic diagram of an electromagnetic wave generator according to embodiment 3. As shown in Fig. 3, the electromagnetic wave generator 100 of this embodiment is the electromagnetic wave generator described in embodiment 1, except that a plurality of second anodes 21, 22 are provided downstream of the first anode 2. A third current sensor 43 is provided downstream of the second anode 21, and a fourth current sensor 44 is provided downstream of the second anode 22. Current data detected by the third current sensor 43 and the fourth current sensor 44 is sent to the abnormality determination device 60 via detectors 53 and 54, respectively.

[0033] In the electromagnetic wave generator configured in this manner, virtual cathodes 5 are generated between the first anode 2 and the second anode 21, between the second anode 21 and the second anode 22, and downstream of the second anode 22. In this electromagnetic wave generator, the generation of multiple virtual cathodes 5 enables the output of microwaves 6 to be improved.

[0034] Furthermore, in the electromagnetic wave generating device of this embodiment, current sensors are provided downstream of the first anode and each of the second anodes, so that when the output of the microwaves 6 attenuates or becomes unstable, it is possible to determine at which of the multiple virtual cathodes an abnormality has occurred.

[0035] 3, a driving device 56 may be provided that can move the positions of the plurality of second anodes 21, 22 in the axial direction of the waveguide 3. By moving the positions of the plurality of second anodes 21, 22 in the axial direction of the waveguide 3, an optimal arrangement can be found and the output of the microwaves 6 can be improved.

[0036] An abnormality determination device 60 for an electromagnetic wave generator according to any one of the first to third embodiments includes a processor 61 and a storage device 62, as shown in FIG. 4 , which is an example of hardware. The storage device 62 includes a volatile storage device such as a random access memory and a non-volatile auxiliary storage device such as a flash memory, although these are not shown. Alternatively, a hard disk auxiliary storage device may be used instead of the flash memory. The processor 61 executes a program used for abnormality determination input from the storage device 62. In this case, the program is input from the auxiliary storage device to the processor 61 via the volatile storage device. The processor 61 may output data such as calculation results to the volatile storage device of the storage device 62, or may store the data in the auxiliary storage device via the volatile storage device.

[0037] Although various exemplary embodiments are described in this disclosure, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are contemplated within the scope of the technology disclosed in this specification. For example, this includes cases where at least one component is modified, added, or omitted, or where at least one component is extracted and combined with components of another embodiment.

[0038] 1 Cathode, 2 First anode, 3 Waveguide, 4 Vacuum vessel, 5 Virtual cathode, 6 Microwave, 10 Pulse generator, 11 Conductor, 15 Insulator, 20 Electron beam, 21, 22 Second anode, 30 Output window, 41 First current sensor, 42 Second current sensor, 43 Third current sensor, 44 Fourth current sensor, 51, 52, 53, 54 Detector, 55, 56 Drive device, 60 Abnormality determination device, 61 Processor, 62 Storage device, 70 Display device.

Claims

1. An electromagnetic wave generator comprising: a cathode; a first anode disposed opposite the cathode and allowing electrons to pass therethrough; a cylindrical waveguide for guiding electromagnetic waves and disposed on the opposite side of the first anode from the cathode; an output window for outputting the electromagnetic waves and disposed on the end of the waveguide opposite the first anode; a first current sensor for detecting current data of an electron beam emitted from the cathode; a second current sensor for detecting current data of the electron beam traveling within the waveguide; and an abnormality determination device for determining internal abnormalities based on the current data detected by the first current sensor and the current data detected by the second current sensor.

2. The electromagnetic wave generating device described in claim 1, characterized in that the abnormality determination device determines an abnormality in the first anode based on the current value detected by the first current sensor and the current value detected by the second current sensor.

3. The electromagnetic wave generating device described in claim 1, characterized in that the abnormality determination device determines an abnormality in the first anode based on the current waveform detected by the first current sensor and the current waveform detected by the second current sensor.

4. An electromagnetic wave generating device as described in any one of claims 1 to 3, further comprising at least one third current sensor located closer to the output window than the second current sensor to detect current data of the electron beam traveling within the waveguide, and the abnormality determination device determines internal abnormalities based on the current data detected by the first current sensor, the current data detected by the second current sensor, and the current data detected by the third current sensor.

5. The electromagnetic wave generating device according to claim 4, wherein the first current sensor, the second current sensor and the third current sensor are movable in a direction parallel to the axial direction of the waveguide.

6. An electromagnetic wave generating device according to claim 4 or 5, further comprising at least one second anode inside said waveguide between said first anode and said output window.

7. The electromagnetic wave generating device according to claim 6, wherein the second anode is movable in a direction parallel to the axial direction of the waveguide.

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