JP2022173651A - electron beam generator - Google Patents

Abstract

To provide a downsized electron beam generator that can get an electron beam of a long-time stable electric current.SOLUTION: An electron beam generator comprises: a negative pole 2 that emits an electronic beam; a tape-like positive pole 3 that is electrically insulated with the negative pole; a high-voltage power source 4 that applies a high-voltage between the negative pole and the tape-like positive pole, and accelerates the electron beam emitted from the negative pole toward the tape-like positive pole; and a vacuum container 5 that holds the negative pole and tape-like positive pole in a vacuum. The tape-like positive pole is fed from a feeding mechanism 7 and wounded by a winding mechanism 8, which in turn the take-like positive pole is conveyed.SELECTED DRAWING: Figure 1

Description

The present application relates to an electron beam generator.

Electron beam generators are provided in X-ray generators, microwave oscillators, and the like. An electron beam generator used in these devices generates an electron beam with a large current of several amperes or more. In an electron beam generator, an electron beam emitted from a cathode collides with an anode partially made of metal. The energy of the electron beam that collides with the anode is converted into heat and absorbed by the surface of the anode. The heat generated on the surface of the anode melts the anode, thus deforming the anode. If the anode deforms, the electron beam current becomes unstable, and if the anode further deforms, the electron beam may not be output. In that case, replacement of the anode is required. The cathode and anode of the electron beam generator are placed in a high vacuum chamber. Therefore, it is necessary to open the vacuum container to the atmosphere when replacing the anode, and to evacuate the inside of the vacuum container to a high vacuum after the replacement of the anode. As described above, since the work of replacing the anode takes a long time, there is a problem that the operation time of the electron beam generator is limited.

As a conventional electron beam generator for coping with such problems, a structure using a disk-shaped anode is disclosed. In this electron beam generator, the disc-shaped anode is rotated to diffuse the heat load caused by the collision of the electron beams, thereby preventing deformation of the anode (see, for example, Patent Document 1).

U.S. Pat. No. 8,121,258

However, in the conventional electron beam generator, when the current of the electron beam increases, even if the anode rotates, thermal deformation of the portion irradiated with the electron beam cannot be avoided. Then, thermal deformation of the anode progresses. Therefore, there is a problem that an electron beam with a stable current for a long time cannot be secured. In order to reduce the number of electron beam irradiations, it is conceivable to increase the diameter of the disk-shaped anode. In other words, in the conventional electron beam generator, it was not possible to ensure an electron beam with a stable current for a long period of time and to suppress an increase in the size of the apparatus.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a compact electron beam generator capable of generating an electron beam with a stable current for a long period of time.

The electron beam generator of the present application comprises a cathode for emitting an electron beam, a tape-shaped anode electrically insulated from the cathode, and electrons emitted from the cathode by applying a high voltage between the cathode and the tape-shaped anode. It has a high voltage power supply that accelerates the beam toward the tape-shaped anode, and a vacuum vessel that holds the cathode and tape-shaped anode in vacuum. Then, the tape-shaped anode is transported by being delivered from the delivery mechanism and wound up by the winding mechanism.

In the electron beam generator of the present application, the tape-shaped anode is delivered from the delivery mechanism, wound up by the winding mechanism, and conveyed, so that a compact electron beam with a stable current for a long time can be obtained.

1 is a schematic cross-sectional view of an electron beam generator according to Embodiment 1; FIG. 1 is a schematic diagram of a tape-shaped anode according to Embodiment 1. FIG. 1 is a schematic cross-sectional view of an electron beam generator according to Embodiment 1; FIG. 1 is a schematic cross-sectional view of an electron beam generator according to Embodiment 1; FIG. FIG. 8 is a schematic cross-sectional view of an electron beam generator applied to the X-ray generator according to Embodiment 2; FIG. 10 is a schematic cross-sectional view of an electron beam generator applied to a klystron microwave oscillator according to a third embodiment; FIG. 12 is a schematic cross-sectional view of an electron beam generator applied to a traveling-wave tube microwave oscillator according to a fourth embodiment; FIG. 11 is a schematic cross-sectional view of an electron beam generator applied to a virtual cathode oscillator type microwave oscillator according to a fifth embodiment;

Hereinafter, electron beam generators according to embodiments for carrying out the present application will be described in detail with reference to the drawings. In each figure, the same reference numerals denote the same or corresponding parts.

Embodiment 1.
FIG. 1 is a schematic cross-sectional view of an electron beam generator according to Embodiment 1. FIG. As shown in FIG. 1, the electron beam generator 1 of this embodiment includes a cathode 2 for emitting an electron beam, a tape-shaped anode 3 electrically insulated from the cathode 2, and a cathode 2 and a tape-shaped anode 3. A high-voltage power supply 4 that applies a high voltage between and accelerates the electron beam emitted from the cathode 2 toward the tape-shaped anode 3, and a vacuum vessel 5 that holds the cathode 2 and the tape-shaped anode 3 in vacuum. and A part of the vacuum container 5 is composed of an insulating member 5a, and the cathode 2 and the tape-shaped anode 3 are electrically insulated by the insulating member 5a. The inside of the vacuum vessel 5 is evacuated by an evacuation device 6 .

As indicated by the white arrow in FIG. 1, the tape-shaped anode 3 is delivered from the delivery mechanism 7, wound up by the winding mechanism 8, and conveyed. A high-voltage power supply 4 applies a voltage of several kV to several MV between the cathode 2 and the tape-shaped anode 3 . Electrons emitted from the cathode 2 are accelerated toward the tape-shaped anode 3 as an electron beam. The electron beam accelerated toward the tape-shaped anode 3 passes through the tape-shaped anode 3 and reaches the target 9 . The potential of the target 9 is set to be the same as the potential of the tape-shaped anode 3 .

A metallic collimator 10 is installed between the cathode 2 and the tape-shaped anode 3 . The collimator 10 is installed to prevent the electron beam emitted from the cathode 2 from irradiating a portion other than the tape-shaped anode 3. As shown in FIG. The collimator 10 has a hole at its center with a width equal to or smaller than the width of the tape-shaped anode 3 . The shape of this hole may be circular or square. The potential of the collimator 10 is set to be the same as the potential of the tape-shaped anode 3 .

Cathode 2 is any of the following four types of cathodes. However, a cathode of a method other than this may be used. The first method is the hot cathode. This hot cathode is a filament-type cathode made of a metallic material such as tungsten, tantalum, or thorium-tungsten. The shape of this filament type cathode is a linear shape, a hairpin shape, a mesh shape, a ribbon shape, or the like. The filament is heated by passing a current through the filament cathode, and thermal electrons emitted from the filament are extracted as an electron beam. The second type is a field emission cathode. This field emission cathode has one or a plurality of needle-like structures with pointed ends made of a metal material with a high melting point such as tungsten. Electron beams are extracted from the tips of the needle-like structures by field emission. A third approach is the plasma cathode. The plasma cathode is a cylindrical cavity electrode with a hole in the beam extracting direction, the inside of which is filled with plasma from which an electron beam is extracted. A fourth scheme is the short pulse plasma cathode. This short-pulse plasma cathode is a cylindrical, prismatic, or Rogowski electrode-shaped cathode of 1 to 10 cm made of a metal material such as aluminum, brass, stainless steel, tungsten, molybdenum, or titanium. is used as As cathodes of other shapes, a metal with a pinhole structure such as stainless steel, a fabric with pile on the metal surface, graphite, an oriented carbon nanotube sheet, and a plate with electromagnetic flocking of carbon fibers on the metal surface are attached. The cathode may also have a structure in which carbon fibers or the like are directly electromagnetically implanted on a metal surface. In this short-pulse plasma cathode, a pulse voltage of several kV to several MV is applied between the cathode and extraction electrode with a pulse width of about 100 nsec to generate plasma on the surface of the cathode, and an electron beam is extracted from this plasma.

For the tape-shaped anode 3, for example, a resin film having a thickness of about 10 μm and a metal film deposited thereon can be used. The thickness of the resin film of the tape-shaped anode 3 is made thinner than the electron beam range calculated using the electron energy calculated from the potential difference between the cathode 2 and the tape-shaped anode 3 . With this setting, some of the energy of the electron beam is attenuated by the tape-shaped anode 3, but most of the electron beam passes through the tape-shaped anode 3 and reaches the target 9. FIG. As the tape-shaped anode 3, a metal sheet having openings can be used instead of using a resin film. As the metal sheet having openings, for example, a metal mesh, a punching metal, a sheet-like metal having fine holes etched, and the like can be used. In the tape-shaped anode 3 using a metal sheet, most of the energy of the electron beam that collides with the metal portion is attenuated there, but the energy of the electron beam that has passed through the opening reaches the target 9 without being attenuated.

FIG. 2 is a schematic diagram of a tape-shaped anode according to this embodiment. As shown in FIG. 2 , the tape-shaped anode 3 is delivered from the delivery mechanism 7 and wound up by the winding mechanism 8 . A plurality of guide rollers 11 are provided between the delivery mechanism 7 and the winding mechanism 8 . A tension adjusting mechanism 12 is provided between the delivery mechanism 7 and the winding mechanism 8 to adjust the tension of the tape-shaped anode 3 at the position where the electron beam is incident. When the winding mechanism 8 winds the tape-shaped anode 3, tension is applied to the tape-shaped anode 3, and the arm 12a in the tension adjustment mechanism 12 is displaced. The tension adjusting mechanism 12 detects the amount of displacement of the arm 12a and sends the information to the sending mechanism 7. As shown in FIG. The delivery mechanism 7 receives the information and delivers the tape-shaped anode 3 . As the tape-shaped anode 3 is replenished from the feeding mechanism 7, the tension is released and the arm 12a in the tension adjusting mechanism 12 returns to its original position. By performing such an operation, the tape-shaped anode 3 can be transported without causing slack in the tape-shaped anode 3 . The arrangement and number of the delivery mechanism 7, the winding mechanism 8, the guide roller 11, the tension adjustment mechanism 12, etc. in the tape-shaped anode 3 shown in FIG.

The operation of the electron beam generator 1 of this embodiment will be described. It is assumed that the delivery mechanism 7 and the winding mechanism 8 for the tape-shaped anode 3 are stopped. In this state, the high voltage power supply 4 applies a high voltage between the cathode 2 and the tape-like anode 3 to start generating electron beams. When the electron beam is generated for a certain period of time, the surface of the tape-shaped anode 3 irradiated with the electron beam is damaged. Therefore, it is necessary to transport the tape-shaped anode 3 at the position to be irradiated with the electron beam so that the surface to be irradiated with the electron beam is a new surface that is not damaged. At this time, the winding mechanism 8 winds up the tape-shaped anode 3 to convey the tape-shaped anode 3 at the position irradiated with the electron beam, and replace the surface irradiated with the electron beam with a new surface that is not damaged. can do. The timing of transporting the tape-shaped anode 3 at the position irradiated with the electron beam can be determined based on the accumulated time during which the electron beam is irradiated.

FIG. 3 is a schematic cross-sectional view of another electron beam generator according to this embodiment. As shown in FIG. 3, this electron beam generator 1 has a surface measuring device 20 inside a vacuum container 5 . This surface measuring instrument 20 can observe the surface state of the tape-shaped anode 3 at the position irradiated with the electron beam. In this electron beam generator 1, the tape-shaped anode 3 at the position irradiated with the electron beam is transported based on the surface state of the tape-shaped anode 3 at the position irradiated with the electron beam observed by the surface measuring instrument 20. You can decide when to let The surface measuring instrument 20 may, for example, irradiate the surface of the tape-shaped anode 3 with light and observe the surface state based on the characteristics of the reflected light or transmitted light. Another surface measuring device 20 may take an image of the surface of the tape-shaped anode 3 using a camera and observe the surface state based on the image. Another surface measuring device 20 may measure the temperature of the surface of the tape-shaped anode 3 and observe the surface state based on the temperature. Furthermore, another surface measuring device 20 measures X-rays emitted from the surface of the tape-shaped anode 3 by being irradiated with an electron beam, and measures the surface based on the dose of the X-rays or the energy spectrum of the X-rays. You can observe the state.

FIG. 4 is a schematic cross-sectional view of another electron beam generator according to this embodiment. This electron beam generator 1 is provided with a current detector for detecting the current of the electron beam emitted from the cathode inside the vacuum vessel 5 . This electron beam generator 1 includes a current detector 21 arranged between the cathode 2 and the collimator 10, a current detector 22 arranged between the collimator 10 and the tape-shaped anode 3, and a tape-shaped anode 3 and a target. 9 and any one of the current detectors 23 arranged between the current detectors. The accumulated current amount of the electron beam irradiated to the tape-shaped anode 3 can be measured by this current detection section. In this electron beam generator 1, the timing for transporting the tape-shaped anode 3 at the position irradiated with the electron beam can be determined based on the accumulated current amount of the electron beam measured by the current detector.

Since the electron beam generator having such a structure has a tape-shaped anode, even if the surface of the tape-shaped anode is damaged by irradiation with the electron beam, the tape-shaped anode is conveyed and the electron beam is irradiated. The surface can be a new undamaged surface. Therefore, in this electron beam generator, an electron beam with a stable current can be obtained for a long time. Moreover, since the tape-shaped anode is delivered from the delivery mechanism and wound up by the take-up mechanism, it is not necessary to increase the size of the electron beam generator even if the length of the tape-shaped anode is lengthened. Therefore, the electron beam generator of the present embodiment is small and can obtain an electron beam with a stable current for a long period of time.

In the electron beam generator of this embodiment, the collimator 10 is made of metal. The potential of this metal is set to be the same as the potential of the tape-shaped anode 3 . The surface of the collimator 10 facing the cathode 2 may be coated with an insulating film containing a hydrogen element, such as polyethylene resin or polyethylene terephthalate resin. When the insulating film is irradiated with an electron beam, negative charges are accumulated on the surface of the insulating film. As a result, the potential difference between the metal portion of the collimator 10 and the surface of the insulating film increases, and dielectric breakdown occurs in the insulating film. An insulating film in which dielectric breakdown has occurred releases a gas containing hydrogen. Plasma is generated in the vicinity of the collimator 10 when the emitted gas is irradiated with the electron beam. From this plasma, mainly positive ions such as hydrogen ions are accelerated toward the cathode 2 .

In general, a large-current electron beam is influenced in the direction in which the beam size diverges due to the effect of the space charge generated by the electron beam itself between the cathode and the anode. Especially when the cathode is a plasma cathode or a short-pulse plasma cathode, the amount of electron beam current that can be extracted is affected by this space charge. That is, the current of the high-current electron beam becomes a current called space charge limited current. The value of the space charge limited current calculated from the one-dimensional electromagnetic field only in the electron traveling direction is represented by the following equation (1). where _ISC is the space charge limited current value, V is the voltage between the cathode and the anode, and d is the distance between the cathode and the anode.

The positive ions emitted from the plasma generated in the vicinity of the collimator 10 have the effect of neutralizing the space charge produced by the negatively charged electron beam. This cation thus makes it possible to draw a current beyond the space-charge-limited current effected by a plasma cathode or a short-pulse plasma cathode, together with a suppressive effect on beam divergence. This current is generally called a bipolar current, and if this current value is I _BSC , I _BSC is considered to be expressed by the following equation (2).

Thus, by forming an insulating film of a resin containing a hydrogen element in its composition on the cathode-side surface of the collimator 10, it is possible to draw out a current exceeding the space-charge limited current shown in formula (1). . If the collimator 10 is not coated with an insulating film, plasma is generated in the vicinity of the anode, which has the effect of neutralizing the space charge generated by the electron beam. Plasma generated near the anode can damage the anode. By forming an insulating film of a resin containing a hydrogen element in its composition on the cathode side surface of the collimator 10 as in the present embodiment, damage to the anode due to plasma can also be suppressed.

This electron beam generator is used for the purpose of obtaining information desired by the user from the target 9 by irradiating the electron beam. For example, this electron beam generator is used for the purpose of investigating the structure of the target 9, changing the structure of the target 9, processing the target 9, and the like. Therefore, in order to control the beam diameter of the electron beam at the position of the target 9, an electric field lens such as a single hole or an Einzeln lens, a solenoid type magnetic field lens, or the like is arranged between the tape-shaped anode 3 and the target 9. may be In some cases, an electric-field deflection electrode, a two-pole coil for generating a deflection magnetic field, or the like is arranged between the tape-shaped anode 3 and the target 9 in order to control the position where the electron beam is irradiated.

In the electron beam generator of the present embodiment, the description has been given of the operation in which the tape-shaped anode is not conveyed while the electron beam is being irradiated. can be transported by By operating in this manner, the stability of the electron beam current with respect to time is improved.

Embodiment 2.
FIG. 5 is a schematic cross-sectional view of an electron beam generator applied to the X-ray generator according to the second embodiment. As shown in FIG. 5, in the electron beam generator 1 of the present embodiment, a cathode 2, a tape-shaped anode 3, a high-voltage power source 4, an evacuation device 6, a delivery mechanism 7, a winding mechanism 8, and a collimator 10 are provided. The configuration is similar to that of the electron beam generator of the first embodiment. In the electron beam generator 1 of this embodiment, the target 9 is composed of an X-ray generator. Heavy metals such as tungsten, molybdenum, and copper are used as X-ray generators. The vacuum vessel 5 is provided with a vacuum window 24 . When the target 9, which is an X-ray generator, is irradiated with the electron beam, the target 9 generates continuous energy X-rays that maximize the voltage applied between the cathode 2 and the tape-shaped anode 3. FIG. The X-rays are extracted outside the electron beam generator 1 through the vacuum window 24 . As the material of the vacuum window 24, glass, resin, ceramic, beryllium, or the like having a high X-ray transmittance is used.

When the electron beam generator 1 is used as an X-ray generator, X-rays near the maximum energy are mainly extracted and used. Low-energy X-rays lose all their energy on the surface of an object to be irradiated, such as a material or a human body, and can adversely affect the object to be irradiated. Therefore, a filtering plate 25 for absorbing low-energy X-rays is provided between the target 9 and the vacuum window 24 in order to prevent unnecessary X-rays having low energy from being emitted outside the electron beam generator 1 . Aluminum, molybdenum, lead, or the like is used as the material of the filter plate 25 .

An electron beam generator applied to the X-ray generator constructed in this way is small and can obtain X-rays stably for a long period of time.

Embodiment 3.
FIG. 6 is a schematic cross-sectional view of an electron beam generator applied to a klystron microwave oscillator according to a third embodiment. As shown in FIG. 6, in the electron beam generator 1 of the present embodiment, a cathode 2, a tape-shaped anode 3, a high-voltage power source 4, an evacuation device 6, a delivery mechanism 7, a winding mechanism 8, and a collimator 10 are provided. The configuration is the same as that of the electron beam generator of the first embodiment. In the electron beam generator 1 of this embodiment, a velocity modulation tube 30 integrated with the vacuum vessel 5 is provided in the traveling direction of the electron beam that has passed through the tape-shaped anode 3 . The velocity modulation tube 30 has a cylindrical shape, and a solenoid coil 31 is arranged on its outer periphery. Further, the velocity modulation tube 30 is connected to an input-side resonant cavity 32 on the upstream side and an output-side resonant cavity 33 on the downstream side in the direction in which the electron beam travels. Further, the input-side resonance cavity 32 is provided with an input circuit 34, and the output-side resonance cavity 33 is provided with an output circuit 35, respectively. A collector 36 is arranged at the most downstream position in the electron beam traveling direction.

A solenoid coil 31 generates a converging magnetic field for the electron beam inside the velocity modulation tube 30 . The input circuit 34 inputs a low-power high-frequency signal for velocity modulation to the input-side resonant cavity 32 . The input-side resonant cavity 32 has a high Q value and generates a high electric field with a high-frequency signal input from the input circuit 34 . The electron beam velocity-modulated by the high-frequency electric field generated in the input circuit 34 and the input-side resonance cavity 32 has a drift space, which is an electric field-free space. In the field-free space, a fast electron beam advances relatively forward, and a slow electron beam retreats relatively. As a result, electron beams have different densities in the traveling direction. The density-modulated electron beam is amplified by the output-side resonance cavity 33 and generated as a microwave by generating a large induced current in the output circuit 35 . The density-modulated electron beam collides with the collector 36 arranged at the most downstream position in the traveling direction, and its energy is converted into heat and lost.

The electron beam generator applied to the klystron type microwave oscillator configured in this way is small and can obtain stable microwaves for a long period of time. In particular, when applied to a microwave oscillator intended to output a large current, it is necessary to increase the current of the electron beam. As a result, the damage to the anode becomes large in a short time, but the electron beam generator of the present embodiment uses a tape-shaped anode, so that a stable microwave generation time can be ensured.

Embodiment 4.
FIG. 7 is a schematic cross-sectional view of an electron beam generator applied to the traveling wave tube according to the fourth embodiment. As shown in FIG. 7, in the electron beam generator 1 of the present embodiment, a cathode 2, a tape-shaped anode 3, a high-voltage power source 4, an evacuation device 6, a delivery mechanism 7, a winding mechanism 8 and a collimator 10 are provided. The configuration is the same as that of the electron beam generator of the first embodiment. In the electron beam generator 1 of this embodiment, a cylindrical cavity 40 integrated with the vacuum vessel 5 is provided in the traveling direction of the electron beam that has passed through the tape-shaped anode 3 . The cylindrical cavity 40 has a cylindrical shape, and a solenoid coil 41 is arranged on its outer periphery. A spiral conductor 42 is installed inside the cylindrical cavity 40 . The cylindrical cavity 40 is connected to an input section 43 on the upstream side and an output section 44 on the downstream side in the direction in which the electron beam travels. Furthermore, a collector 45 is arranged at the most downstream position in the electron beam traveling direction.

A solenoid coil 41 generates a converging magnetic field for the electron beam inside the cylindrical cavity 40 . The input unit 43 inputs low-power microwaves to the spiral conductor 42 . By making the traveling speed of the electron beam equal to the phase speed of the microwave traveling through the spiral conductor 42, the electron beam undergoes density modulation in the traveling direction. The electron beam subjected to density modulation is amplified at the output section 44 and taken out as microwaves. The density-modulated electron beam collides with the collector 45 arranged at the most downstream position in the traveling direction, and its energy is converted into heat and lost.

The electron beam generator applied to the traveling wave tube configured as described above is compact and can generate stable microwaves for a long period of time. In particular, when applied to a traveling wave tube intended to output a large current, it is necessary to increase the current of the electron beam. As a result, the damage to the anode becomes large in a short time, but the electron beam generator of the present embodiment uses a tape-shaped anode, so that a stable microwave generation time can be ensured.

In addition, in this embodiment, instead of the spiral conductor 42, a configuration in which a large number of permanent magnets are arranged in the traveling direction of the electron beam can also be used. Further, when the electron beam generator of this embodiment is applied to a backward traveling wave tube, the output section 44 is set to the ground potential, and the traveling direction of the microwave propagating through the spiral conductor 42 is reversed to the traveling direction of the electron beam. By doing so, microwaves can be extracted from the input unit 43 .

Embodiment 5.
FIG. 8 is a schematic cross-sectional view of an electron beam generator applied to the virtual cathode oscillator according to the fifth embodiment. As shown in FIG. 8, in the electron beam generator 1 of the present embodiment, a cathode 2, a tape-shaped anode 3, a high-voltage power source 4, an evacuation device 6, a sending mechanism 7, a winding mechanism 8, and a collimator 10 are provided. The configuration is the same as that of the electron beam generator of the first embodiment. In the electron beam generator 1 of this embodiment, a cylindrical cavity 50 integrated with the vacuum vessel 5 is provided in the traveling direction of the electron beam that has passed through the tape-shaped anode 3 . This cylindrical cavity 50 has a cylindrical shape, and has a vacuum window 51 at the end in the direction in which the electron beam travels. The vacuum window 51 is made of ceramic, glass, or the like. Further, in the electron beam generator 1 of this embodiment, the tip of the cathode 2, the tape-shaped anode 3 and the collimator 10 are arranged in the vicinity of the cylindrical cavity 50. As shown in FIG.

In the electron beam generator constructed in this way, when the current amount of the electron beam is greatly increased, the electron beam passing through the tape-like anode 3 is decelerated in the traveling direction due to its own space charge. The electron group stopped inside the cylindrical cavity 50 begins to behave as if it were a metal with the same potential as the cathode. This group of electrons is therefore called the virtual cathode. When a virtual cathode is generated inside the cylindrical cavity 50, electrons start appearing to reciprocate between this virtual cathode and the cathode 2 facing each other with the tape-shaped anode 3 interposed therebetween. Also, this virtual cathode itself is plasma and starts plasma oscillation. Microwaves are generated from the reciprocating motion of such electrons and the plasma oscillation of the virtual cathode itself. The frequency f (unit: GHz) of the generated microwave is considered to be expressed by the following equation (3).

Here, d is the distance (unit: cm) between the cathode ₂ and the tape-shaped anode 3, and γ0 is the Lorentz factor of the electron beam calculated from the voltage applied between the cathode 2 and the tape-shaped anode 3. . The inner diameter of the cylindrical cavity 50 is set larger than the inner diameter of the cylinder whose cutoff frequency is the frequency of the generated microwave. The electron group that has become a virtual cathode inside the cylindrical cavity 50 loses momentum only in the direction of travel, and does not lose momentum in the direction perpendicular to the direction of travel. Therefore, the electron group that has become the virtual cathode diverges and collides with the inner wall of the cylindrical cavity 50 and is lost. Microwaves generated from the virtual cathode are propagated in the direction in which the electron beam travels and are taken out from the vacuum window 51 provided at the end of the cylindrical cavity 50 .

The electron beam generator applied to the virtual cathode oscillator configured as described above is compact and can obtain stable microwaves for a long period of time. In particular, when applied to a virtual cathode oscillator intended to output a large current, it is necessary to increase the current of the electron beam. As a result, the damage to the anode becomes large in a short time, but the electron beam generator of the present embodiment uses a tape-shaped anode, so that a stable microwave generation time can be ensured.

Although this application describes various exemplary embodiments, the various features, aspects, and functions described in one or more embodiments are limited to the application of particular embodiments. can be applied to the embodiments alone or in various combinations.
Therefore, countless modifications not illustrated are envisioned within the scope of the technology disclosed in the present application. For example, modification, addition or omission of at least one component, extraction of at least one component, and combination with components of other embodiments shall be included.

REFERENCE SIGNS LIST 1 electron beam generator 2 cathode 3 tape anode 4 high voltage power supply 5 vacuum container 5a insulating member 6 evacuation device 7 delivery mechanism 8 winding mechanism 9 target 10 collimator 11 guide roller , 12 tension adjustment mechanism, 12a arm, 20 surface measuring instrument, 21, 22, 23 current detector, 24, 51 vacuum window, 25 filter plate, 30 velocity modulation tube, 31, 41 solenoid coil, 32 input side resonant cavity, 33 output side resonance cavity, 34 input circuit, 35 output circuit, 36, 45 collector, 40, 50 cylindrical cavity, 42 spiral conductor, 43 input part, 44 output part.

Claims (9)

a cathode that emits an electron beam;
a tape-shaped anode electrically insulated from the cathode;
a high voltage power source that applies a high voltage between the cathode and the tape-shaped anode to accelerate the electron beam emitted from the cathode toward the tape-shaped anode;
An electron beam generator comprising a vacuum container for holding the cathode and the tape-shaped anode in vacuum,
The electron beam generator, wherein the tape-shaped anode is transported by being delivered from a delivery mechanism and wound up by a winding mechanism. 2. An electron beam generator according to claim 1, wherein said tape-shaped anode is composed of a resin film having a metal film or a metal sheet having a plurality of openings. 3. The electron beam generator according to claim 1, further comprising a collimator between said cathode and said tape-shaped anode, wherein a surface of said collimator facing said cathode is made of resin. A current detection unit for detecting a current of the electron beam emitted from the cathode is further provided, and the tape-shaped anode is transported based on an accumulated current amount of the current of the electron beam detected by the current detection unit. 4. An electron beam generator according to any one of claims 1 to 3. The tape-shaped anode is further provided with a surface measuring device for observing the surface state of the tape-shaped anode at the position where the electron beam is incident, and the tape-shaped anode is transported based on the surface state observed by the surface measuring device. 4. The electron beam generator according to any one of claims 1 to 3. 3. The surface measuring instrument irradiates light onto the surface of the tape-shaped anode at a position where the electron beam is incident, and observes the surface state based on transmitted light or reflected light of the light. 6. The electron beam generator according to 5. 6. The surface measuring device according to claim 5, wherein said surface measuring device captures an image of the surface of said tape-shaped anode at a position where said electron beam is incident, and observes said surface condition based on said captured image. electron beam generator. 6. The surface measuring device according to claim 5, wherein said surface measuring instrument measures the surface temperature of said tape-shaped anode at a position where said electron beam is incident, and observes said surface condition based on said measured temperature. electron beam generator. The surface measuring device observes the surface state based on the dose of X-rays emitted from the surface of the tape-shaped anode at the position where the electron beam is incident or the energy spectrum of the X-rays. Item 6. An electron beam generator according to item 5.

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