A method of compressing the electron beam current divergence angle using a ring-shaped electron gun

Abstract

The present application relates to a method for compressing the divergence angle of electron beam by using a ring-shaped electron gun, which produces a peripheral ring-shaped electron beam by using a hollow ring-shaped cathode electron gun, and realizes effective control of the divergence angle of the electron beam by using the Coulomb repulsion of the inner electron beam, and can realize different compression amounts of the divergence angle by changing the current, energy and transmission distance of the outer electron beam.

Description

Technical Field

[0001] This invention relates to a method for compressing the divergence angle of an electron beam using a ring electron gun, belonging to the field of beam control for accelerator systems. Background Technology

[0002] Accelerators use electromagnetic fields to accelerate charged particles to a certain high speed, forming particle beams with certain characteristics such as energy, density, radius, and pulse width. They have wide applications in various fields such as industry, agriculture, medicine, and science and technology.

[0003] One of the important indicators of a particle beam is its divergence angle, which affects the transmission characteristics of particles, determines the beam spot radius at a certain location, and thus affects the beam density at that location, further influencing the irradiation effect under different applications.

[0004] Since the electron beam has a certain divergence angle after being generated in the accelerator, or may be amplified by certain beam optics or the space charge effect of the beam itself, certain measures need to be taken to reduce the beam divergence angle and improve the irradiation effect.

[0005] The most common method for compressing the divergence angle is to design an electromagnetic lens system. However, this method is generally applicable to a specific energy range, and requires redesign and reinstallation when the particle beam energy changes significantly. Therefore, this patent proposes a method for compressing the divergence angle of the electron beam using a ring-shaped electron gun. Furthermore, different divergence angle adjustment values ​​can be achieved by changing the current intensity, energy, and transmission distance of the ring-shaped particle beam, or by realizing specific divergence angle adjustment values ​​for electrons of different energies. Summary of the Invention

[0006] The technical problem solved by this invention is: to address the need for compressing the divergence angle of an electron beam, a method for compressing the divergence angle of an electron beam using a ring electron gun is proposed. By leveraging the Coulomb repulsion force of the outer ring electron beam on the inner electron beam, the divergence angle can be effectively controlled. Furthermore, different amounts of divergence angle compression can be achieved by changing the current intensity, energy, and transmission distance of the outer electron beam.

[0007] The technical solution adopted in this invention is as follows:

[0008] A method for constricting the divergence angle of an electron beam using a ring-shaped electron beam includes:

[0009] (1) Construct another coaxial peripheral annular electron beam along the electron beam transmission path;

[0010] (2) The phase space / divergence angle of the internal electron beam is controlled by the Coulomb force of the external annular electron beam.

[0011] Furthermore, when the internal electron beam enters the outer annular electron beam, it is distributed in the first and third quadrants of the x-x' and y-y' phase space, meaning that the electrons diverge outward from the beam axis.

[0012] Furthermore, the internal electron beam energy is lower than the outer ring electron beam energy.

[0013] Furthermore, the peripheral annular electron beam is generated by a hollow annular cathode electron gun.

[0014] Furthermore, the hollow inner diameter of the hollow annular cathode electron gun is close to the beam envelope, making the inner diameter of the outer annular electron beam close to the outer diameter of the inner electron beam.

[0015] Furthermore, the initial state of the peripheral annular electron beam is to converge toward the axis or be parallel, so as to avoid the rapid divergence of external electrons due to Coulomb force, thereby increasing the effective length of the outer electron beam on the inner electron beam.

[0016] Furthermore, the peripheral annular electron beam can be used to change the distance between the collecting electrodes of the hollow annular cathode electron gun as needed.

[0017] Furthermore, the peripheral annular electron beam current can be adjusted as needed to change the beam intensity and energy.

[0018] Furthermore, the control of the internal beam phase space / divergence angle by the Coulomb force of the internal electron beam through the outer annular electron beam specifically involves:

[0019] The electronic phase space at the current location is obtained by measurement or based on the simulation results from the previous level.

[0020] Based on the electron beam phase space and the phase space after the desired divergence angle is compressed, the flux intensity, electron energy and action distance of the annular electron beam are continuously simulated and optimized.

[0021] The specific design of the electron gun is realized based on the range of hollow inner diameter, electron energy, and electron beam intensity.

[0022] A hollow annular cathode electron gun is installed at a designated location, and a collector electrode is installed at a certain distance after the electron beam. The position of the collector electrode is adjustable.

[0023] By changing the cathode voltage and gate voltage of the ring electron gun, a ring electron beam with specified electron energy and electron beam current intensity can be emitted, thereby achieving the desired divergence angle control of the inner electron beam.

[0024] The advantages of this invention compared to the prior art are:

[0025] The present invention provides a method for compressing the divergence angle of an electron beam using a ring electron gun, which has some unique advantages compared with existing methods for compressing the divergence angle using electromagnetic lens groups.

[0026] (1) Changing the effective working length and spacing between electromagnetic lens groups is costly or relatively cumbersome, so it is generally suitable for a specific energy range. When the particle beam energy changes significantly, a redesign and reinstallation is required. Compared with electromagnetic lens elements, the present invention can easily change the effective length of the Coulomb force of the outer electron beam by changing the position of the collecting electrode, or change the magnitude of the Coulomb force by changing the energy and current intensity of the outer electron beam, thereby achieving different divergence angle adjustment values ​​of the inner electron beam or specific divergence angle adjustment values ​​of electron beams with different energies.

[0027] (2) The design of electromagnetic lens groups is quite complicated. Every time the electron beam energy is changed, the design needs to be redone. Moreover, since the influence of its various parameters on the divergence angle is nonlinear, the detailed design is very complex and requires a lot of intelligent optimization calculations. In contrast, the Coulomb field of the outer electron beam in the present invention is positively correlated with the current. The effective distance is the distance between the emitter and collector electrodes of the outer electron beam. Therefore, the design is simpler, and the optimal solution can be quickly found by experimenting with the bisection method of the effective distance, provided that the current meets the requirements. Attached Figure Description

[0028] Figure 1 This is a schematic cross-sectional view of the annular electron gun of the present invention;

[0029] Figure 2 This is a flowchart of the method for compressing the divergence angle of an electron beam using a ring electron gun according to the present invention. Detailed Implementation

[0030] This invention proposes a method for constricting the divergence angle of an electron beam using a ring-shaped electron beam, comprising the following steps:

[0031] (1) Construct another coaxial peripheral annular electron beam along the electron beam transmission path;

[0032] (2) The phase space / divergence angle of the internal electron beam is controlled by the Coulomb force of the external annular electron beam.

[0033] When the internal electron beam enters the outer annular electron beam, it is distributed in the first and third quadrants of the x-x' and y-y' phase space, that is, the electrons diverge outward from the beam axis.

[0034] The energy of the internal electron beam is lower than that of the outer ring electron beam.

[0035] like Figure 1 As shown, the outer annular electron beam is generated by a hollow annular cathode electron gun.

[0036] The hollow annular cathode electron gun has a hollow inner diameter that is close to the beam envelope, making the inner diameter of the outer annular electron beam close to the outer diameter of the inner electron beam.

[0037] The initial state of the peripheral annular electron beam is to converge toward the axis or be parallel, so as to avoid the rapid divergence of external electrons due to Coulomb force, thereby increasing the effective length of the outer electron beam on the inner electron beam.

[0038] The distance between the outer annular electron beam and the collecting electrode of the hollow annular cathode electron gun can be changed as needed.

[0039] The peripheral annular electron beam can be adjusted in terms of current intensity and energy as needed.

[0040] This invention can easily change the effective length of the Coulomb force of the outer electron beam by changing the position of the collecting electrode, or change the magnitude of the Coulomb force by changing the energy and current of the outer electron beam, thereby achieving different divergence angle adjustment values ​​for the inner electron beam or specific divergence angle adjustment values ​​for electron beams of different energies.

[0041] like Figure 2 As shown, the specific process of using a ring particle beam to compress the electron beam divergence angle is as follows:

[0042] Design a hollow annular cathode electron gun with a hollow inner diameter close to the beam envelope;

[0043] The electronic phase space at the current location is obtained by measurement or based on the simulation results from the previous level.

[0044] Based on the electron beam phase space and the phase space after the desired divergence angle is compressed, the flux intensity, electron energy and action distance of the annular electron beam are continuously simulated and optimized.

[0045] The specific design of the electron gun is realized based on the range of hollow inner diameter, electron energy, and electron beam intensity.

[0046] A hollow annular cathode electron gun is installed at a designated location, and a collector electrode is installed at a certain distance after the electron beam. The position of the collector electrode is adjustable.

[0047] By changing the cathode voltage and gate voltage of the ring electron gun, a ring electron beam with specified electron energy and electron beam current intensity can be emitted, thereby achieving the desired divergence angle control of the inner electron beam.

[0048] The Coulomb field of the outer electron beam in this invention is positively correlated with the current. The effective distance is the distance between the emitter and collector electrodes of the outer electron beam. Therefore, the design is relatively simple, and the optimal solution can be quickly found by experimenting with the binary method of the effective distance, provided that the current meets the requirements.

[0049] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for constricting the divergence angle of an electron beam using a ring-shaped electron beam, characterized in that... include: Construct another coaxial peripheral annular electron beam along the electron beam transmission path; The phase space / divergence angle of the internal electron beam is controlled by the Coulomb force of the internal electron beam through the outer annular electron beam. When the internal electron beam enters the outer annular electron beam, it is distributed in , The first and third quadrants of the phase space, i.e., electrons diverge outward from the beam axis; The energy of the internal electron beam is lower than that of the outer ring electron beam. The control of the internal beam phase space / divergence angle by using the Coulomb force of the outer annular electron beam to control the internal electron beam specifically involves: The electronic phase space at the current location is obtained by measurement or based on the simulation results from the previous level. Based on the electron beam phase space and the phase space after the desired divergence angle is compressed, the flux intensity, electron energy and action distance of the annular electron beam are continuously simulated and optimized. The specific design of the electron gun is realized based on the range of hollow inner diameter, electron energy, and electron beam intensity. A hollow annular cathode electron gun is installed at a designated location, and a collector electrode is installed at a certain distance after the electron beam. The position of the collector electrode is adjustable. By changing the cathode voltage and gate voltage of the ring electron gun, a ring electron beam with specified electron energy and electron beam current intensity can be emitted, thereby achieving the desired divergence angle control of the inner electron beam.

2. The method for compressing the divergence angle of an electron beam using a ring electron gun according to claim 1, characterized in that: The outer annular electron beam is generated by a hollow annular cathode electron gun.

3. The method for compressing the divergence angle of an electron beam using a ring electron gun according to claim 2, characterized in that: The hollow annular cathode electron gun has a hollow inner diameter that is close to the beam envelope, making the inner diameter of the outer annular electron beam close to the outer diameter of the inner electron beam.

4. The method for compressing the divergence angle of an electron beam using a ring electron gun according to claim 2, characterized in that: The initial state of the peripheral annular electron beam is to converge toward the axis or be parallel, so as to avoid the rapid divergence of external electrons due to Coulomb force, thereby increasing the effective length of the outer electron beam on the inner electron beam.

5. The method for compressing the divergence angle of an electron beam using a ring electron gun according to claim 2, characterized in that: The distance between the outer annular electron beam and the collecting electrode of the hollow annular cathode electron gun can be changed as needed.

6. The method for compressing the divergence angle of an electron beam using a ring electron gun according to claim 2, characterized in that: The peripheral annular electron beam can be adjusted in terms of current intensity and energy as needed.

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