Electron gun for terahertz traveling wave tube, using method and traveling wave tube

Abstract

The invention discloses an electron gun for a terahertz traveling wave tube, a using method and a traveling wave tube. The electron gun comprises a cathode, a focusing electrode, a first anode and a second anode which are sequentially and coaxially arranged in the advancing direction of an electron beam. The second anode is positioned on one side of the first anode away from the cathode; the first anode comprises an anode plate and an anode head located in the center of the anode plate, and the anode head is opposite to the emitting surface of the cathode; the first anode is provided with a first anode hole for an electron beam to pass through, the second anode is provided with a second anode hole for the electron beam to pass through, the first anode hole penetrates through the anode plate and the anode head, and the first anode hole, the second anode hole and the cathode hole are coaxially arranged. By adding the second anode and enabling the second anode to be used as a convergent lens through the interaction between the first anode and the second anode, the multi-dimensional control of the electron beam is realized, and the waist radius of the electron beam is reduced, so that the electron flow rate of the electron beam in the traveling wave tube is improved.

Description

Technical Field

[0001] The present invention relates to the field of microwave vacuum electronic technology, and more specifically to an electron gun for a terahertz traveling wave tube, a use method and a traveling wave tube. Background Art

[0002] Terahertz traveling wave tubes are of great significance for high-speed data transmission and are widely used in the field of terahertz communications. As an important component of the traveling wave tube, the electron gun has the important function of emitting electrons. The electron beam flow rate of the electron gun is one of the important factors that determine whether the traveling wave tube can achieve continuous wave operation. Too low an electron beam flow rate will cause excessive heat consumption of the traveling wave tube, which is not conducive to the stable operation of the traveling wave tube. In addition, as the operating frequency of the terahertz traveling wave tube continues to increase, the radius of the electron beam channel will become smaller and smaller, which will cause the electron beam channel filling current density to become higher and higher, making it much more difficult for the traveling wave tube to achieve a high electron flow rate. Therefore, it is very important for the traveling wave tube to improve the level of electron flow rate.

[0003] The injection waist radius and range of the electron beam are two important parameters that affect the electron flow rate. The electron beam waist radius is used to characterize the minimum radius of the electron beam's motion trajectory envelope before entering the magnetic field, and the electron injection range is the distance from the cathode to the injection waist position in the axial direction. The smaller the injection waist radius, the better the focusing performance of the electron beam; the larger the range, the better the stability of the electron beam during transmission. Summary of the invention

[0004] In view of the above problems, an object of the present invention is to provide an electron gun for a terahertz traveling wave tube that can improve the electron flux.

[0005] Another object of the present invention is to provide a method for using an electron gun for a terahertz traveling wave tube.

[0006] Another object of the present invention is to provide a traveling wave tube including an electron gun for a terahertz traveling wave tube.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] According to one aspect of the present invention, there is provided an electron gun for a terahertz traveling wave tube, comprising:

[0009] A cathode, a focusing electrode, a first anode and a second anode are coaxially arranged in sequence along the traveling direction of the electron beam;

[0010] A cathode hole is provided at the center of the cathode;

[0011] The second anode is located on a side of the first anode away from the cathode;

[0012] The first anode comprises an anode plate and an anode head located at the center of the anode plate, wherein the anode head is opposite to the emission surface of the cathode;

[0013] The first anode has a first anode hole for electron injection, the second anode has a second anode hole for electron injection, the first anode hole runs through the anode plate and the anode head, and the first anode hole, the second anode hole and the cathode hole are coaxially arranged. In addition, an optional solution is that the radius of the first anode hole is greater than the radius of the second anode hole.

[0014] In addition, an optional solution is that the hole wall of the second anode hole includes a first transition portion and a second transition portion respectively connected to the two side end surfaces of the second anode, the first transition portion and the second transition portion are both arc surfaces, and the connection between the first transition portion and the second transition portion is a smooth transition connection.

[0015] In addition, an optional solution is that the end face of the anode head close to the cathode and the outer circle of the anode head are connected through a first transition surface, and the end face of the anode head close to the cathode and the inner circle of the anode head are connected through a second transition surface, the first transition surface and the second transition surface are both arc-shaped structures, and the connection between the first transition surface and the second transition surface is a smooth transition connection.

[0016] In addition, an optional solution is that the distance between the anode plate and the cathode is inversely proportional to the current required by the electron gun to emit the electron beam. The greater the current required by the electron gun to emit the electron beam, the smaller the distance between the anode plate and the cathode.

[0017] In addition, an optional solution is that the focusing electrode is arranged around the outer peripheral surface of the cathode and extends to the anode head.

[0018] In addition, an optional solution is that the thickness of the anode head along the axial direction is equal to the thickness of the anode plate.

[0019] According to another aspect of the present invention, there is provided a method for using an electron gun for a terahertz traveling wave tube, the method comprising: applying a positive voltage to a first anode, the voltage value being U1, applying a positive voltage to a second anode, the voltage value being U2, and applying a negative voltage to a cathode, the voltage value being U3;

[0020] Among them, U1>U2.

[0021] In addition, an optional solution is that the voltage value U2 of the second anode is ≠0.

[0022] According to another aspect of the present invention, there is provided a traveling wave tube, comprising a tube housing and an electron gun for a terahertz traveling wave tube.

[0023] The beneficial effects of the present invention are as follows:

[0024] In view of the technical problems existing in the prior art, the present invention provides an electron gun for a terahertz traveling wave tube, a method of use and a traveling wave tube, and by adding a second anode, the second anode can be used as a converging lens through the interaction between the first anode and the second anode, thereby realizing multi-dimensional control of the electron beam, reducing the injection waist radius of the electron beam, thereby improving the electron flow rate of the electron beam in the traveling wave tube, reducing the influence of the thermal initial velocity effect on the electron beam, and enhancing the focusing ability of the electron beam. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The specific implementation modes of the present invention will be further described in detail below in conjunction with the accompanying drawings.

[0026] Figure 1 The figure shows a schematic diagram of the structure of an electron gun in the prior art.

[0027] Figure 2 A schematic structural diagram of an electron gun provided by an embodiment of the present invention is shown.

[0028] Figure 3 Graph showing the electron injection waist radius of a prior art electron gun.

[0029] Figure 4 A graph showing the electron injection waist radius of the electron gun provided by an embodiment of the present invention.

[0030] Figure 5 Graph showing the electron beam lateral velocity of a prior art electron gun.

[0031] Figure 6 A graph showing the electron beam lateral velocity of the electron gun provided by the embodiment of the present invention.

[0032] Figure 7 A graph showing the electron injection waist radius of an electron gun in a specific example. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0034] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] In the present invention, unless otherwise clearly stipulated and limited, a first feature being “on” or “under” a second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through another feature between them.

[0036] In the description of this embodiment, the terms "upper", "lower", "left", "right" and other directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0037] Figure 1 The electrode structure of an existing electron gun is shown. The electron gun has a simple structure and is composed of a filament, a cathode 10, a focusing electrode 20, an anode 30, and a ceramic component supporting each electrode. The electron beam is controlled by the regulating function of the focusing electrode 20. In the electron gun, only the focusing electrode 20 can regulate the motion trajectory of the electron beam, and the control ability of the electron beam is limited. It is impossible to further reduce the beam waist radius of the electron beam on the basis of maintaining the original range; in addition, in the terahertz frequency band, the influence of the thermal initial velocity effect on the electron beam cannot be ignored. The thermal initial velocity effect will cause the lateral velocity of the electron beam to increase, which is not conducive to the bunching of the electron beam. The existing electron gun structure cannot reduce the influence of the thermal initial velocity effect on the electron beam.

[0038] After analyzing the electron gun, the electron gun can be regarded as an immersion lens. The immersion lens is generally a converging lens. Specifically, the focusing electrode 20 and the anode 30 can be regarded as two single-film hole lenses, where the focal length of the focusing electrode lens is (E1 is the electric field strength between the cathode 10 and the focusing electrode 20, E2 is the electric field strength between the focusing electrode 20 and the anode 30, f M is the center potential of the focusing electrode, V zM is the central potential of the focusing pole film hole), which is always greater than 0, so the focusing pole film hole 200 is a converging lens; similarly, the focal length of the anode lens E2<0 (E2 is the electric field strength between the focusing electrode 20 and the anode 30, f A is the central potential of the anode, V zA is the central potential of the anode film hole), then the anode film hole 300 is a divergent lens. zA Much larger than the center potential of the focusing pole membrane hole 200 V zMTherefore, the converging effect of the electron gun is always greater than the diverging effect. Therefore, by adding a converging lens, it is possible to achieve the purpose of increasing the converging effect of the electron gun and further reduce the injection waist radius of the electron beam.

[0039] In view of the defects of the prior art, the present invention provides an electron gun for a terahertz traveling wave tube, Figure 2-7 As shown, the electron gun includes a cathode 1, a focusing electrode 2 and a cathode 3 which are coaxially arranged in sequence along the traveling direction of the electron beam, and a filament (not shown).

[0040] The filament is usually a tungsten filament, which is used to heat the cathode 1 so that the metal active material on its surface can emit electrons outward after being heated. There are two heating methods: direct heating and indirect heating. Direct heating means that the filament heats the cathode 1 so that the cathode 1 reaches the temperature required for emitting electrons. Indirect heating means that an intermediate medium (such as a nickel tube or a molybdenum tube) is heated to indirectly heat the cathode so that the cathode 1 reaches the temperature required for emitting electrons.

[0041] A cathode hole 11 is formed at the center of the cathode 1 .

[0042] The anode 3 includes a first anode 31 and a second anode 32 which are sequentially arranged along the electron propagation direction. The second anode 32 is located on a side of the first anode 31 away from the cathode 1 .

[0043] The first anode 31 includes an anode plate 311 and an anode head 312 located at the center of the anode plate 311 . The anode head 312 is opposite to the emission surface of the cathode 1 .

[0044] The first anode 31 has a first anode hole 313 for electron injection to pass through, and the second anode 32 has a second anode hole 321 for electron injection to pass through. The first anode hole 313 is located at the center of the anode plate 311 and is coaxially arranged with the anode head 312, passing through the anode plate 311 and the anode head 312. The first anode hole 313, the second anode hole 321 and the cathode hole 11 are coaxially arranged.

[0045] In a specific embodiment, the radius of the first anode hole 313 is greater than the radius of the second anode hole 321. After the electron beam passes through the first anode hole 313, the electron beam will be again affected by the second anode electric field and compressed again because the radius of the second anode hole 321 is smaller than the radius of the first anode hole 313. Specifically, in this embodiment, the voltage applied to the first anode 31 is positive, the voltage applied to the second anode 32 is also positive, and the voltage of the first anode 31 is greater than the voltage of the second anode 32. The voltage relationship between the first anode 31 and the second anode 32 makes the second anode 32 a converging lens, which is equivalent to adding a converging lens after the anode on the basis of the existing electron gun to enhance the converging effect of the electron gun and further reduce the injection waist radius of the electron beam.

[0046] In a specific embodiment, the hole wall of the second anode hole 321 includes a first transition portion 3211 and a second transition portion 3212 respectively connected to the two side end surfaces of the second anode 32, and the first transition portion 3211 and the second transition portion 3212 are both arc-shaped surfaces. The connection between the first transition portion 3211 and the second transition portion 3212 is a smooth transition connection, so that the hole wall of the second anode hole 321 is a smooth hole wall convex inwardly toward the axial direction, and there are no edges and corners in the second anode hole 321 or at the connection between the second anode hole 321 and the two side end surfaces of the second anode hole 322, which can make the distribution of the magnetic field more uniform, so that the electron beam is subjected to uniform force, which is more conducive to the focusing of the electron beam.

[0047] In this embodiment, the center thickness d2 of the second anode hole 321 protruding toward the axial direction is equal to the wall thickness D2 of the second anode 32 .

[0048] In a specific embodiment, the end face of the anode head 312 on one side close to the cathode 1 is connected to the outer circle of the anode head 312 through a first transition surface 3121, and the end face of the anode head 312 on one side close to the cathode 1 is connected to the inner circle of the anode head 312 through a second transition surface 3122. The first transition surface 3121 and the second transition surface 3122 are both arc-shaped structures, and the connection between the first transition surface 3121 and the second transition surface 3122 is a smooth transition connection, so that the end face of the anode head 312 on one side close to the cathode 1 has a smooth arc-shaped structure, and there are no edges and corners on the electron beam entry side of the first anode hole 313, which can make the distribution of the magnetic field more uniform, so that the electron beam is subjected to uniform force, which is more conducive to the focusing of the electron beam.

[0049] In this embodiment, the distance d1 between the inner circle and the outer circle of the anode head 312 is equal to the thickness D1 of the anode plate 311 .

[0050] In a specific embodiment, the distance L1 between the end surface of the anode plate 311 close to the cathode 1 and the emission surface of the cathode 1 is inversely proportional to the magnitude of the electron beam current required by the electron gun to emit, that is, the greater the current required by the electron gun to generate the electron beam, the smaller the distance L1 between the anode plate 311 and the cathode 1. Similarly, the distance L2 between the end surface of the second anode 32 close to the first anode 31 and the emission surface of the cathode 1 is inversely proportional to the magnitude of the electron beam current required by the electron gun to emit, that is, the greater the current required by the electron gun to generate the electron beam, the smaller the distance L2 between the second anode 32 and the cathode 1. When designing an electron gun, the magnitude of the total current can be adjusted by adjusting the distance between each electrode.

[0051] In a specific embodiment, the focusing electrode 2 is disposed around the outer peripheral surface of the cathode 1 and extends to the anode head 312 . The focusing electrode 2 is used to focus the electron beam.

[0052] In one embodiment, the thickness d3 of the anode head 312 along the axial direction is equal to the thickness D1 of the anode plate 311 along the axial direction.

[0053] In the existing multi-electrode electron gun, the purpose of setting the second anode or multi-anode structure is to achieve the acceleration of the electron beam, which is grounded when in use, and the adjustment and focusing of the electron beam are completed by the first anode. In the terahertz traveling wave tube electron gun provided in this embodiment, the voltages applied to the first anode 31 and the second anode 32 are both positive, and the voltage of the first anode 31 is greater than the voltage of the second anode 32. The setting of the second anode 32 can increase the overall voltage of the anode 3 and reduce the influence of the thermal initial effect. In addition, the second anode 32 also realizes the function of a converging lens. According to the lens focusing formula, the focal length of the second anode lens is:

[0054]

[0055] Among them, f A2 is the central potential of the second anode, E3 is the electric field strength between the first anode 31 and the second anode 32, E3=U1-U2>0, E4 is the electric field strength between the second anode 32 and the tube shell 4, V zA2 is the center potential of the second anode hole.

[0056] In this embodiment, the second anode 32 is a converging lens, satisfying And the following conditions are met at the same time:

[0057] V zA2 >0

[0058] U1>U2

[0059] Therefore, after adding the second anode 32, the voltage relationship between the first anode 31 and the second anode 32 enables the second anode 32 to be used as a converging lens, thereby increasing the converging effect of the electron gun on the electron beam and further reducing the injection waist radius of the electron beam.

[0060] According to the principle of the electron gun, the influence of the thermal initial velocity effect on the electron beam can be reduced mainly by reducing the cathode temperature, increasing the anode voltage or reducing the radius of the cathode substrate. However, due to the limitation of the cathode material, the cathode temperature cannot be reduced to a lower level at present, and the radius of the cathode substrate is 1.1 mm, which can be reduced to 0.9 mm at most, and no further improvement can be made. It is known that the greater the anode voltage, the less the electron beam is affected by the thermal initial velocity effect. A single anode cannot increase the voltage, and is limited by the withstand voltage of the packaging porcelain and in order to avoid adverse effects on other properties of the electron gun, the variation range of the anode voltage should be controlled within 20%, which limits the reduction of the influence of the thermal initial velocity effect. In this embodiment, a second anode 32 is added on the basis of a single anode. First, the anode can have a higher voltage within the withstand voltage limit of the packaging porcelain, and secondly, the probability of adverse effects on other properties of the electron gun can be reduced, thereby reducing the influence of the thermal initial velocity effect on the electron beam, which is beneficial to electron beam bunching and long-distance transmission.

[0061] It should be noted that, in this embodiment, the effect of adding the second anode 32 on the injection waist radius of the electron beam is not only achieved by the electric field of the second anode 32 itself, but the electric field formed by all electrodes including the cathode 1, the first anode 31, the second anode 32, the focusing electrode 2, etc. together affects the motion state of the electron beam, so that the second anode 32 can be used as a converging lens, thereby reducing the injection waist radius of the electron beam and increasing the range. When designing an electron gun, the total current, the injection waist radius and the range of the electron beam can be adjusted by adjusting the voltage of each electrode, the geometric parameters of each electrode and the distance between each electrode.

[0062] Another embodiment of the present invention provides a method for using an electron gun for a terahertz traveling wave tube, the method comprising: applying a positive voltage to the first anode 31, the voltage value is U1, applying a positive voltage to the second anode 32, the voltage value is U2, and applying a negative voltage to the cathode 1;

[0063] Among them, U1>U2.

[0064] According to the lens focusing formula, the focal length of the second anode lens is:

[0065]

[0066] Among them, f A2 is the central potential of the second anode, E3 is the electric field strength between the first anode 31 and the second anode 32, E3=U1-U2>0, E4 is the electric field strength between the second anode 32 and the tube shell 4, V zA2 is the center potential of the second anode hole.

[0067] In this embodiment, the second anode 32 is a converging lens, satisfying And the following conditions are met at the same time:

[0068] V zA2 >0

[0069] U1>U2

[0070] Therefore, after adding the second anode 32, the voltage relationship between the first anode 31 and the second anode 32 enables the second anode 32 to be used as a converging lens, thereby increasing the converging effect of the electron gun on the electron beam and further reducing the injection waist radius of the electron beam.

[0071] The second anode 32 can not only increase the overall voltage of the anode 3 and reduce the influence of the thermal initial effect, but also be used as a converging lens, thereby increasing the converging effect of the electron gun on the electron beam and further reducing the injection waist radius of the electron beam.

[0072] In one embodiment, the voltage value U2 of the second anode 32 is ≠0, that is, the second anode 32 is not grounded when in use.

[0073] Another embodiment of the present invention provides a traveling wave tube, comprising the electron gun for the terahertz traveling wave tube and the tube shell 4 in the above embodiment, as shown in FIG. Figure 2 As shown, the tube shell 4 is located on a side of the second anode 32 away from the first anode 31 .

[0074] The embodiment of the present invention enhances the control of the motion state of the electron beam by adding the second anode 32, reduces the injection waist radius of the electron beam, and reduces the influence of the thermal initial velocity effect on the electron beam.

[0075] Computer Simulation Technology (CST) is used to simulate the prior art and compare it with the electron gun for the terahertz traveling wave tube provided in this embodiment. Figure 3 As shown, the horizontal axis at the lowest point is the range of the electron gun, and the vertical axis is the injection waist radius of the electron gun. The electron gun of the prior art can achieve an injection waist radius of 0.088 mm when the total current is 35 mA and the range is 10.7 mm; Figure 4As shown, the horizontal coordinate at the lowest point is the range of the electron gun, and the vertical coordinate is the injection waist radius of the electron gun. The terahertz traveling wave tube electron gun provided in this embodiment can achieve an electron injection range of 13.88mm and an electron injection waist radius of 0.082mm when the total current is the same (the total current is 35mA) and the focusing pole, cathode and first anode positions are the same as the prior art electron gun structure. Compared with the prior art electron gun, the range of the electron gun provided in the embodiment of the present invention is increased by 28.97%. It can be seen that the electron gun provided in the embodiment of the present invention can enhance the modulation effect on the electron beam, increase the modulation dimension of the electron beam motion trajectory, and can increase the electron injection range while reducing the electron beam injection waist radius.

[0076] The influence of thermal initial velocity effect on electron beam can be characterized by transverse velocity. Figure 5 As shown, the horizontal axis represents the travel position of the electron beam, and the vertical axis represents the lateral speed of the electron beam. The lateral speed of the electron beam of the electron gun of the prior art begins to increase again at the position of 8.9 mm. At this time, the lateral speed of the electron beam is 2*10 6 m / s; Figure 6 As shown, the horizontal axis represents the travel position of the electron beam, and the vertical axis represents the lateral speed of the electron beam. The lateral speed of the electron beam of the electron gun provided by the present invention begins to increase again at the position of 9.98 mm, and the lateral speed of the electron is 1.85*10 6 m / s. Comparison between the two shows that the lateral velocity of the electron gun provided by the embodiment of the present invention is reduced by 7.5%, and the subsequent increase in the lateral velocity of the electron beam is much smaller than the lateral velocity of the electron beam of the electron gun in the prior art. The lateral velocity region in the electron gun provided by the present invention is consistent, which has great advantages for focusing the magnetic field to control the bunching of the electron beam. Under the action of the focusing magnetic field, the electrons are not easy to diverge, and the electron focusing can be effectively controlled. It can be seen that the electron gun provided by the embodiment of the present invention can play a good role in regulating the lateral velocity of the electron beam, reduce the lateral velocity of the electron beam, and reduce the divergence of electrons, thereby achieving a higher flow rate of the electron gun.

[0077] In a specific example, the voltage of cathode 1 to ground is set to -20kV, the voltage of focusing electrode 2 to cathode 1 is set to 20V, the voltage U1 of first anode 31 is set to 1000V (voltage to ground), the voltage U2 of second anode 32 is set to 400V, the radius R1 of first anode hole 313 is 1.5mm, the radius R2 of second anode 321 is 1mm, the distance L1 from first anode plate 311 to cathode 1 is 6mm, and the distance L2 from second anode 32 to cathode 1 is 8mm. Through CST simulation calculation, it is obtained that Figure 7 As shown, the electron gun provided in this embodiment can achieve a total current of 35.45 mA, an electron injection distance of 10.71 mm, and an electron injection waist radius of 0.062 mm.

[0078] The electron gun, use method and traveling wave tube for a terahertz traveling wave tube provided in the embodiment of the present invention realize multi-dimensional control of the electron beam by adding a second anode and using the interaction between the first anode and the second anode so that the second anode can be used as a converging lens, thereby reducing the injection waist radius of the electron beam, thereby improving the electron flow rate of the electron beam in the traveling wave tube, reducing the influence of the thermal initial velocity effect on the electron beam, and enhancing the focusing ability of the electron beam.

[0079] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. An electron gun for a terahertz traveling wave tube, characterized in that: It includes a cathode, a focusing electrode, a first anode and a second anode which are coaxially arranged in sequence along the traveling direction of the electron beam; A cathode hole is provided at the center of the cathode; The second anode is located on a side of the first anode away from the cathode; The first anode comprises an anode plate and an anode head located at the center of the anode plate, wherein the anode head is opposite to the emission surface of the cathode; The first anode has a first anode hole for electron injection, the second anode has a second anode hole for electron injection, the first anode hole penetrates the anode plate and the anode head, and the first anode hole, the second anode hole and the cathode hole are coaxially arranged.

2. The electron gun for a terahertz traveling wave tube according to claim 1, characterized in that: The radius of the first anode hole is greater than the radius of the second anode hole.

3. The electron gun for a terahertz traveling wave tube according to claim 1, characterized in that: The hole wall of the second anode hole includes a first transition portion and a second transition portion respectively connected to the two side end surfaces of the second anode, the first transition portion and the second transition portion are both arc-shaped surfaces, and the connection between the first transition portion and the second transition portion is a smooth transition connection.

4. The electron gun for a terahertz traveling wave tube according to claim 1, characterized in that: The end face of the anode head close to the cathode and the outer circle of the anode head are connected through a first transition surface, and the end face of the anode head close to the cathode and the inner circle of the anode head are connected through a second transition surface. The first transition surface and the second transition surface are both arc-shaped structures, and the connection between the first transition surface and the second transition surface is a smooth transition connection.

5. The electron gun for a terahertz traveling wave tube according to claim 1, characterized in that: The distance between the anode plate and the cathode is inversely proportional to the magnitude of the current required by the electron gun to emit the electron beam. The greater the current required by the electron gun to emit the electron beam, the smaller the distance between the anode plate and the cathode.

6. The electron gun for a terahertz traveling wave tube according to claim 1, characterized in that: The focusing electrode is arranged around the outer peripheral surface of the cathode and extends to the anode head.

7. The electron gun for a terahertz traveling wave tube according to claim 1, characterized in that: The thickness of the anode head along the axial direction is equal to the thickness of the anode plate.

8. A method for using the electron gun for a terahertz traveling wave tube according to any one of claims 1 to 7, characterized in that: The method comprises: applying a positive voltage to a first anode, the voltage value is U1, applying a positive voltage to a second anode, the voltage value is U2, and applying a negative voltage to a cathode; Among them, U1>U2.

9. The method for using the electron gun for a terahertz traveling wave tube according to claim 8, characterized in that: The voltage value U2 of the second anode is ≠0.

10. A traveling wave tube, characterized in that: It comprises a tube shell and an electron gun for a terahertz traveling wave tube as claimed in any one of claims 1 to 7; The tube shell is located at a side of the second anode away from the first anode.

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