Non-adiabatic plane emission electron gun applied to gyrotron

Abstract

The invention belongs to the technical field of millimeter wave sources, and particularly relates to a non-adiabatic plane emission electron gun applied to a gyrotron, which comprises a cathode assembly, an anode and a control electrode assembly, the cathode assembly is nested in the electrode manufacturing assembly and comprises an emitting surface for emitting electrons, and the emitting surface is of a plane structure; a radial hole is formed in the control electrode assembly; electrons are transmitted to the anode through the radial hole after being emitted from the emitting surface. The cathode assembly is arranged between the external control electrode and the internal control electrode, so that electron beams are only subjected to the action of axial electric field force in paths from a cathode emitting surface to an outlet of the control electrode, and the electron beams enter a heat insulation section in a linear track with higher quality. According to the electron gun, the current limitation of a traditional electron gun is broken through, and meanwhile good electron beam parameters are kept.

Description

Technical Field

[0001] The present invention belongs to the technical field of millimeter-wave sources, and specifically relates to a non-adiabatic planar emission electron gun applied to a gyrotron. Background Art

[0002] The technology gyrotron refers to a gyrotron that can output medium-power continuous waves in the millimeter-wave frequency bands such as 24 GHz and 28 GHz. The technology gyrotron has great advantages in millimeter-wave power applications. In the field of material processing, it can be used for ceramic sintering, metal powder composite sintering, deep geothermal drilling, etc.; in the chemical field, it can be used to excite millimeter-wave plasma to crack carbon dioxide, deposit coatings, grow diamonds, etc.; in the biological field, it can also be used for sterilization, tumor ablation, seed cultivation, etc. In addition, there are also many application scenarios in anti-stop weapons, energy transmission, etc. At present, the technology of using high-power continuous waves to interact with matter has been developed maturely in the low-frequency microwave band. However, in the millimeter-wave band, due to the lack of stable and economical high-power millimeter-wave sources, the development of this technology is relatively slow.

[0003] A gyrotron mainly consists of two important components, namely a resonant cavity and an electron gun. Among them, the working principle of the electron gun is to accelerate the electrons emitted from the cathode surface under the action of an accelerating voltage, and then modulate these electrons in an axially converging magnetic field. The electron beam that has been modulated and is in a specific state will enter the resonant cavity, where angular bunching occurs, that is, beam-wave interaction occurs, and then electromagnetic radiation is generated.

[0004] For the technology gyrotron, the two main obstacles are strong magnetic fields and high voltages. In terms of strong magnetic fields, taking the fundamental wave of the output electromagnetic wave frequency as an example, a 1 Tesla magnetic field can generate 28 GHz electromagnetic waves; when in the second harmonic, at the same magnetic field strength, the frequency of the output electromagnetic wave will double. Based on this characteristic, by using harmonics and combining with room-temperature magnets, the industrial use requirements can be met to a certain extent. However, in terms of high voltages, if the working voltage is directly reduced, two problems will arise. One is that the relativistic factor in the beam-wave interaction of the gyrotron will be reduced; the other is that due to the influence of the space charge effect, the quality of the electron beam will decline, ultimately resulting in a reduction in the working efficiency of the gyrotron. Therefore, the more common solution in this field is to significantly reduce the working current. However, this approach also has drawbacks. When the working current is reduced, with the reduction of the working voltage, the total input power of the gyrotron will be insufficient, thus unable to reach the power level required for industrial applications. Summary of the Invention

[0005] The object of the present invention is to provide a non-adiabatic planar emission electron gun applied to a gyrotron, which solves the problem that the maximum current that can be provided is too small after the operating voltage of a conventional magnetron injection electron gun is significantly reduced. This electron gun breaks the current limit of traditional electron guns while maintaining good electron beam parameters.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A non-adiabatic planar emission electron gun applied to a gyrotron, comprising a cathode assembly, an anode, and a control electrode assembly;

[0008] The cathode assembly is nested in the control electrode assembly and includes an emission surface for emitting electrons, and the emission surface is a planar structure;

[0009] The control electrode assembly is provided with radial holes; electrons are emitted from the emission surface and transmitted to the anode through the radial holes.

[0010] Further, the control electrode assembly includes an external control electrode and an internal control electrode disposed within the external control electrode. The end of the external control electrode and the internal control electrode close to the anode do not contact each other to form a radial hole.

[0011] Furthermore, the longitudinal section of the internal control electrode is a "T" - shaped structure, and the longitudinal section of the external control electrode is an inverted "L" - shaped structure.

[0012] Further, the cathode assembly further includes a first shaping cathode and a second shaping cathode, and the first shaping cathode and the second shaping cathode are located on both sides of the emitter.

[0013] Furthermore, the surfaces of the first shaping cathode and the second shaping cathode close to the anode are both inclined surface structures.

[0014] Furthermore, the inclination angles of the inclined surface structures of the first shaping cathode and the second shaping cathode are the same.

[0015] Further, the cathode assembly is insulated from the control electrode and the anode.

[0016] Further, the magnetic compression ratio of the magnetic field of the non-adiabatic planar emission electron gun applied to a gyrotron is 20 - 50.

[0017] In the present invention, the cathode assembly is divided into a first formed cathode, an emitter, and a second formed cathode. The surfaces of the first formed cathode and the second formed cathode on the side close to the anode are both inclined plane structures. In combination with the fact that the surface of the emitter on the side close to the anode is a flat plane structure and the magnetic compression ratio of the magnetic field is increased, that is, the magnetic field intensity is significantly reduced in the cathode region, so that electrons are emitted from the cathode surface in a straight line and move towards the resonant cavity of the gyrotron, that is, a non-adiabatic motion process. When the electrons pass through the control electrode and the cathode region, due to the presence of the transverse electric field component, the electron beam obtains transverse energy and enters the adiabatic magnetic field, and then starts the adiabatic process of the traditional electron gun.

[0018] In addition, different from the traditional gyrotron magnetron injection electron gun where the control electrode is only distributed outside the cathode, the cathode assembly of the present invention is nested inside the control electrode, that is, the cathode assembly is arranged between the external control electrode and the internal control electrode, so that in the path of the electron beam from the cathode emission surface to the control electrode outlet, it is only affected by the axial electric field force, so that the electron beam enters the adiabatic section with a higher-quality straight trajectory. On this basis, the electron beam then starts to participate in the modulation process to obtain a gyrotron electron beam with the required parameters.

[0019] In summary, it can be seen that the electron gun of the present invention breaks through the current limitation of the traditional electron gun while maintaining good electron beam parameters. Brief Description of the Drawings

[0020] Figure 1 Schematic diagram of the non-adiabatic planar emission electron gun structure of the embodiment;

[0021] Figure 2 Schematic diagram of the longitudinal sectional structure of the cathode and the control anode in the non-adiabatic planar emission electron gun of the embodiment;

[0022] Figure 3 Results of the electron trajectory of the non-adiabatic planar emission electron gun obtained by the 2D particle simulation software of the embodiment;

[0023] Figure 4 Results of the electron trajectory of the non-adiabatic planar emission electron gun obtained by the 3D particle simulation software of the embodiment;

[0024] Reference Signs:

[0025] 1-1 is the first formed electrode, 1-2 is the emitter, 1-3 is the second formed electrode, 2 is the external control electrode, 3 is the internal control electrode, and 4 is the anode. Detailed Embodiment

[0026] The present invention will be described in detail below in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] Due to the confinement of the small-orbit gyrotron electron beam in the waveguide by the space charge effect, it means that in a specific electron device or microwave system, electrons move in a small-orbit gyrotron manner to form an electron beam. When in the waveguide environment, the electrons in the electron beam will generate a space charge effect due to the charge interaction between electrons, thereby having a confinement effect on the movement and behavior of electrons. The formula for the limiting current that can be generated by a magnetron injection electron gun is:

[0028]

[0029] where γ 0 is the relativistic factor, β ∥0 is the longitudinal normalized velocity of the electron, and G(r i , r o , a) is the electron beam structure factor, which is related to the guiding radius of the electron beam and the waveguide radius.

[0030] It can be seen from formula (1) that the higher the voltage, the greater the limiting current, and the greater the transverse-to-longitudinal velocity ratio, the smaller the limiting current.

[0031] Based on the above theory, this embodiment provides a non-adiabatic planar emission electron gun structure. As Figure 1 and Figure 2 shown, the electron gun includes a cathode assembly, an anode 4, and a control electrode assembly. The cathode assembly is nested in the control electrode assembly and includes an emission surface 1-2 for emitting electrons, and the emission surface is a planar structure. The control electrode assembly is provided with radial holes; electrons are emitted from the emission surface and transmitted to the anode through the radial holes.

[0032] The control electrode assembly includes an external control electrode 2 and an internal control electrode 3 provided inside the external control electrode 2. One end of the external control electrode 2 and the internal control electrode 3 close to the anode 4 do not contact each other to form a radial hole. As Figure 2As shown, the longitudinal section of the internal control electrode 3 is a "T"-shaped structure, and the longitudinal section of the external control electrode 2 is an inverted "L"-shaped structure. The cathode assembly further includes a first formed cathode 1-1 and a second formed cathode 1-3, and the first formed cathode 1-1 and the second formed cathode 1-3 are located on both sides of the emitter 1-2. The surfaces of the first formed cathode 1-1 and the second formed cathode 1-3 close to the anode 4 are both inclined plane structures. The inclination angles of the inclined plane structures of the first formed cathode 1-1 are the same as those of the second formed cathode. The cathode assembly is insulated from the control electrode and the anode. The magnetic compression ratio of the magnetic field of the non-adiabatic planar electron gun applied to the gyrotron is 30, where the interaction magnetic field is 1.1T and the magnetic field in the gun region is 0.0367T. Electrons start to be emitted from the emission surface 1-2, and cooperate with the external control electrode 2 and the internal control electrode 3 to jointly regulate the electrostatic field distribution in the cathode region, so that the electrons are only affected by the longitudinal electrostatic field before the control electrode assembly.

[0033] In this embodiment, Magic particle simulation and CST particle simulation are respectively used to illustrate its effects. When the cathode voltage is -5000V, the voltages of the internal control electrode and the external control electrode are both -2500V, and the anode voltage is 0V, the Magic particle simulation results are as Figure 3 shown, and the CST particle simulation results are as Figure 4 shown. From Figure 3 and Figure 4 it can be seen that in Magic, the transverse-longitudinal ratio of the electron beam velocity is 1.46, and the velocity spread is 2%. In CST, the electron beam velocity ratio is 1.5, and the velocity spread is 1.5%. The calculation results show that the electron gun with this structure can generate an electron beam with excellent performance when approaching the space-limiting current.

[0034] Under the same conditions, that is, when the working voltage is 5kV and the required transverse-longitudinal ratio of the velocity is 1.5, with the structural parameters determined, the electron gun of this embodiment outputs a frequency of 30GHz, and the working mode is selected as TE0,1. At this time, the limiting current is 1.063A. While the working current of the traditional magnetron injection electron gun is usually only 0.1 - 0.2 times the limiting current, and it cannot exceed half of the limiting current.

[0035] Finally, it should be noted that the present invention aims to adopt a new type of magnetron injection electron gun and use a non-adiabatic emission method to achieve a higher excitation current under the same working voltage conditions; at the same time, make the electron beam reach a higher transverse-longitudinal ratio of the velocity and a lower degree of velocity spread. It is especially suitable for gyrotrons with a low-voltage working mode, but is not limited to the low-voltage working mode and is still applicable at normal working voltages.

Claims

1. A non-adiabatic planar emission electron gun for a gyrotron, characterized in that it comprises a cathode assembly, an anode assembly and a control electrode assembly; The cathode assembly is nested in the control electrode assembly, and includes an emission surface for emitting electrons, and the emission surface is a planar structure; The control electrode assembly is provided with radial holes; electrons are emitted from the emission surface and transmitted to the anode through the radial holes.

2. The non-adiabatic planar emission electron gun according to claim 1, characterized in that: The control electrode assembly comprises an external control electrode and an internal control electrode arranged inside the external control electrode. The external control electrode and the internal control electrode are not in contact with each other at one end close to the anode to form a radial hole.

3. The non-adiabatic planar emission electron gun according to claim 2, characterized in that: The longitudinal section of the inner control electrode is a "T"-shaped structure, and the longitudinal section of the outer control electrode is an inverted "L"-shaped structure.

4. The non-adiabatic planar emission electron gun according to claim 1, characterized in that: The cathode assembly further includes a first cathode and a second cathode. The first cathode and the second cathode are located at both sides of the emitter.

5. The non-adiabatic planar emission electron gun according to claim 4, characterized in that: The surfaces of the first cathode and the second cathode close to the anode are both inclined structures.

6. The non-adiabatic planar emission electron gun according to claim 5, characterized in that: The inclination angle of the first cathode-forming inclined surface structure is the same as the inclination angle of the second cathode-forming inclined surface structure.

7. The non-adiabatic planar emission electron gun according to claim 1, characterized in that: The cathode assembly is insulated from the control electrode assembly and the anode.

8. The non-adiabatic planar emission electron gun according to claim 1, characterized in that: The magnetic compression ratio of the magnetic field of the non-adiabatic planar emission electron gun applied to the gyrotron is 20-50.

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