A method for acquiring the generated posture of field-emission electrons in a microwave electron gun

Abstract

The present invention discloses a method for acquiring the generated posture of field-emission electrons in a microwave electron gun, belonging to the technical field of electronic components. The positioning method comprises: measuring the actual target posture of the field-emission electrons on a fluorescent screen; the field-emission electrons are generated and emitted inside the microwave electron gun, and are focused and projected onto the fluorescent screen via a preset magnetic field path; establishing a mapping relationship between the initial possible postures of the field-emission electrons generated inside the microwave electron gun and the target reference posture when they arrive at the fluorescent screen; using each of the initial possible postures of the field-emission electrons and the mapping relationship, obtaining the target reference posture of each field-emission electron when it arrives at the fluorescent screen; and selecting the most accurate generated posture of the field-emission electrons from multiple initial possible postures, thereby accurately determining the specific position and emission phase of the field-emission current when it is generated inside the microwave electron gun.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic components, and more specifically, relates to a method for acquiring the generated posture of field-emission electrons in a microwave electron gun. Background Art

[0002] With the continuous development of electron accelerator technology, the requirements for electron beam quality are constantly increasing. As a highly efficient electron source, microwave electron guns (RF guns) produce electron bunches with the advantages of short bunch length and low emittance. Therefore, they are widely used in electron accelerator-based devices such as ultrafast electron diffraction (UED), ultrafast electron imaging (UEM), and free electron lasers (FEL).

[0003] Currently, field emission current measurements in electron accelerators are typically performed using beam current measurement elements such as Faraday cups, integrating beam current transformers, or phosphor screens. Measurements using Faraday cups and integrating beam current transformers can determine the intensity of the field emission current from the element, while measurements using phosphor screens can determine the positional distribution of the field emission electron bunch at the measurement location. These measurement methods can directly determine the intensity and distribution of the field emission current at the measurement location, reflecting the overall state of the field emission current. However, due to the uncertainty of the location of rough or contaminated areas on the metal surface, the locations where strong field emission currents are generated are random, and the field emission current characteristics vary from emission location to emission location. Therefore, all field emission currents cannot be simply analyzed together.

[0004] In summary, traditional measurement methods are mainly used to qualitatively determine whether the field emission current is serious. The information obtained about the field emission current is limited, and it is impossible to determine where the field emission current specifically comes from inside the microwave electron gun, making it difficult to conduct in-depth research on it. Ultimately, it is impossible to correctly evaluate the operating status of the cathode, microwave electron gun, and even the entire accelerator structure. Summary of the Invention

[0005] In response to the above-mentioned defects or improvement needs of the prior art, the present invention provides a method for obtaining the generation posture of field-emission electrons in a microwave electron gun. The purpose of the method is to solve the technical problem that the prior art cannot accurately obtain the specific generation posture of field-emission electrons in a microwave electron gun.

[0006] To achieve the above object, according to one aspect of the present invention, a method for acquiring the generated pose of field-emission electrons in a microwave electron gun is provided, comprising:

[0007] S1: Measuring the actual target position of field-emission electrons on the fluorescent screen; the actual target position includes an actual radial position and an actual rotation angle; the field-emission electrons are generated and emitted inside a microwave electron gun, and are focused and projected onto the fluorescent screen via a preset magnetic field path;

[0008] S2: establishing a mapping relationship between an initial possible pose of field-emission electrons generated in the microwave electron gun and a target reference pose when the electrons reach the fluorescent screen; the initial possible pose includes an initial radial position and an initial emission phase; the target reference pose includes a reference radial position and a reference rotation angle;

[0009] S3: using each of the initial possible postures of the field-emission electrons and the mapping relationship, obtaining a target reference posture of each of the field-emission electrons when it reaches the fluorescent screen;

[0010] S4: Selecting from the multiple initial possible postures the one having the smallest difference between the target reference posture and the target actual posture as the generated posture of the field emission electron.

[0011] In one embodiment, the mapping relationship includes: a first sub-mapping relationship and a second sub-mapping relationship;

[0012] The first sub-mapping relationship represents the relationship between the actual radial position r1 and the initial radial position r0, the initial transmission phase the relationship between;

[0013] The second sub-mapping relationship represents the actual rotation angle θ L With the initial radial position r0, initial emission phase The relationship between them.

[0014] In one embodiment, the first sub-mapping relationship is related to the transmission matrix M, M=M L M sol M rf ;

[0015] Among them, M L represents the transmission matrix of the field-emission electrons from the preset magnetic field outlet to the phosphor screen, M sol represents the transmission matrix of the field-emission electrons on the preset magnetic field path, M rf It represents the transmission matrix of the field-emission electrons in the microwave electron gun.

[0016] In one embodiment, the mapping relationship is: a mapping relationship between an initial possible posture of the field-emission electrons generated by the microwave electron gun, a magnetic field intensity on the preset magnetic field path, and a target reference posture corresponding to the posture when the electrons reach the fluorescent screen.

[0017] In one embodiment, the mapping relationship includes: a third sub-mapping relationship and a fourth sub-mapping relationship;

[0018] The third sub-mapping relationship represents the relationship between the actual radial position r1 and the initial radial position r0 and the initial transmission phase The relationship between the magnetic field strength B on the preset magnetic field path;

[0019] The fourth sub-mapping relationship represents the actual rotation angle θ L With the initial radial position r0, initial emission phase The relationship between the magnetic field strength B on the preset magnetic field path.

[0020] In one embodiment, the third sub-mapping relationship is related to the transmission matrix M, M=M L M sol M rf ;

[0021] Among them, M L represents the transmission matrix of the field-emission electrons from the preset magnetic field outlet to the phosphor screen, M sol represents the transmission matrix of the field-emission electrons on the preset magnetic field path, M rf It represents the transmission matrix of the field-emission electrons in the microwave electron gun.

[0022] In one embodiment, the S2 includes: obtaining a mapping relationship between the initial possible posture of the field-emission electron and the target reference posture based on a particle tracking simulation program in a computer language.

[0023] According to another aspect of the present invention, a device for acquiring a generated posture of field-emission electrons in a microwave electron gun is provided, comprising:

[0024] A measurement module is configured to measure the actual target position of field-emission electrons on a fluorescent screen; the actual target position includes an actual radial position and an actual rotation angle; the field-emission electrons are generated and emitted inside a microwave electron gun, and are focused and projected onto the fluorescent screen via a preset magnetic field path;

[0025] An establishing module, configured to establish a mapping relationship between an initial possible pose of field-emission electrons generated in the microwave electron gun and a target reference pose when the electrons reach the fluorescent screen; the initial possible pose includes an initial radial position and an initial emission phase; the target reference pose includes a reference radial position and a reference rotation angle;

[0026] a calculation module, configured to obtain a target reference pose of each field-emission electron when it reaches the fluorescent screen by using each of the possible initial poses of the field-emission electron and the mapping relationship;

[0027] A determination module is used to select, from the multiple initial possible postures, the one corresponding to the smallest difference between the target reference posture and the target actual posture as the generated posture of the field emission electron.

[0028] According to another aspect of the present invention, a system for acquiring the generated posture of field-emission electrons in a microwave electron gun is provided, comprising: a microwave electron gun, a solenoid, a fluorescent screen, a memory, and a processor;

[0029] The microwave electron gun is used to generate field-emission electrons and emit them through the muzzle;

[0030] The solenoid, when the internal coil thereof is energized, generates a preset magnetic field path at the outlet of the microwave electron gun, wherein the preset magnetic field path is used to focus and project the field-emitted electrons with a preset focusing intensity;

[0031] A drift section having a preset distance between the fluorescent screen and the preset magnetic field path is provided, and the field-emission electrons focused and projected by the preset magnetic field path arrive at the fluorescent screen via the drift section;

[0032] The memory stores a computer program;

[0033] When the processor executes the computer program, the steps of the above positioning method are implemented.

[0034] According to another aspect of the present invention, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps of the above-mentioned positioning method are implemented.

[0035] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0036] (1) The present invention provides a method for obtaining the generation posture of field emission electrons in a microwave electron gun, by establishing a mapping relationship between the initial possible posture of the field emission electrons generated in the microwave electron gun and the target reference posture when they arrive at the fluorescent screen; using each of the initial possible postures of the field emission electrons and the mapping relationship, the target reference posture of each of the field emission electrons when they arrive at the fluorescent screen is obtained; and the most accurate generation posture of the field emission electrons is selected from multiple initial possible postures, so that the specific position and emission phase of the field emission current when it is generated in the microwave electron gun can be accurately determined.

[0037] (2) The method for obtaining the generated posture of the field-emission electrons in the microwave electron gun provided by this solution, wherein the first sub-mapping relationship represents the relationship between the actual radial position r1 and the initial radial position r0, the initial emission phase The relationship between the second sub-mapping relationship represents the actual rotation angle θ L With the initial radial position r0, initial emission phase In this solution, the first sub-mapping relationship and the second sub-mapping relationship are constructed separately, which can simplify the calculation process of establishing the mapping relationship, thereby reducing the execution difficulty and calculation complexity of the entire algorithm.

[0038] (3) This solution provides a method for obtaining the generated pose of field-emission electrons in a microwave electron gun. This method uses a transfer matrix to characterize the mapping relationship between the target reference position and the initial possible position of the electron on the fluorescent screen. Combined with the final position distribution characteristics of the field-emission electrons, the initial possible pose can be determined. This calculation method compensates for the relatively one-sided results obtained by traditional measurement methods and solves the problem that field-emission current is difficult to measure correctly due to the randomness of its emission position. Furthermore, compared with using a particle tracking program, the use of a transfer matrix can significantly reduce the calculation time while ensuring the required accuracy.

[0039] (4) The method for obtaining the generated posture of field-emission electrons in a microwave electron gun provided by this solution is as follows: the mapping relationship is the mapping relationship between the initial possible posture of the field-emission electrons generated by the microwave electron gun, the magnetic field intensity on the preset magnetic field path, and the target reference posture corresponding to the fluorescent screen. The influence of the magnetic field intensity B on the target reference posture is taken into account, which can improve the accuracy of the entire algorithm. Furthermore, the current intensity of the preset magnetic field path can be adjusted to change the focusing intensity of the preset magnetic field path on the field-emission electrons, and the actual target posture of the field-emission electrons on the fluorescent screen can be obtained accordingly; each of the initial possible postures of the field-emission electrons, the magnetic field intensity, and the mapping relationship can be used to determine the corresponding target reference posture, and then the multiple initial possible postures corresponding to each magnetic field intensity are compared with the target reference posture to find the most accurate generated posture of the field-emission electrons.

[0040] (5) The method for obtaining the generated posture of the electromagnetically emitted electrons in the microwave electron gun provided by this solution, wherein the third sub-mapping relationship represents the relationship between the actual radial position r1 and the initial radial position r0, the initial emission phase The relationship between the magnetic field strength B on the preset magnetic field path; the fourth sub-mapping relationship represents the actual rotation angle θ L With the initial radial position r0, initial emission phase The relationship between the magnetic field strength B on the preset magnetic field path; in this scheme, the first sub-mapping relationship and the second sub-mapping relationship are constructed respectively, while taking into account the influence of the magnetic field strength B on the target reference posture, which not only simplifies the calculation process of establishing the mapping relationship but also improves the positioning accuracy.

[0041] (6) The method for obtaining the generated posture of field-emission electrons in the microwave electron gun provided by this solution, wherein the first sub-mapping relationship is related to the transmission matrix M, M=M L M sol M rf Low computational complexity. The microwave electron gun transmission matrix mapping calculation can account for the influence of the solenoid magnetic field penetrating the microwave electron gun, and the solenoid transmission matrix mapping calculation can also account for the influence of higher-order magnetic field components on the transmission matrix calculation, ensuring the accuracy of the basic first and third sub-mapping relationships. Compared to using a particle tracing program, this method significantly reduces computation time while maintaining the required accuracy.

[0042] (7) This scheme provides a method for obtaining the generated posture of field-emission electrons in a microwave electron gun. The method uses a transmission matrix to characterize the mapping relationship between the target reference position of the electrons on the fluorescent screen, the electromagnetic intensity, and the initial possible position. The initial possible posture can be determined by combining the final position distribution characteristics and the electromagnetic intensity of the field-emission electrons. This calculation method makes up for the shortcomings of the relatively one-sided results obtained by traditional measurement methods and solves the problem that the field emission current is difficult to measure correctly due to the randomness of its emission position.

[0043] (8) The method for obtaining the generated posture of electrons emitted by field in a microwave electron gun provided in this scheme has extremely high requirements on the accuracy of the results compared to improving the calculation speed. When calculating the mapping relationship between the initial relevant information and the final position of the electron in any part, particle tracking simulation software can also be used for simulation to obtain more accurate results. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A schematic flow chart of a method for acquiring the generated posture of field-emission electrons in a microwave electron gun provided in Example 1 of the present invention;

[0045] Figure 2 A schematic diagram of a system for acquiring the generated posture of field-emission electrons in a microwave electron gun provided in Example 2 of the present invention;

[0046] Figure 3 Schematic diagram of the electric field distribution on the axis of the microwave electron gun and the magnetic field distribution on the axis of the solenoid provided in Example 1 of the present invention;

[0047] Figure 4 A comparison diagram of the radial position measurement value and the fitting result curve of the field emission electron end position provided in Example 1 of the present invention;

[0048] Figure 5 This is a comparison chart of the rotation angle measurement value of the final position of the field emission electron provided in Example 1 of the present invention and the fitting result curve. DETAILED DESCRIPTION

[0049] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0050] Example 1

[0051] like Figure 1 As shown, this embodiment provides a method for obtaining the generated posture of field emission electrons in a microwave electron gun, including the following steps: S1-S4. S1: Measuring the target actual posture of the field emission electrons on the fluorescent screen. The target actual posture includes the actual radial position and the actual rotation angle. The field emission electrons are generated and emitted inside the microwave electron gun, and are focused and projected onto the fluorescent screen through a preset magnetic field path. S2: Establishing a mapping relationship between the initial possible posture of the field emission electrons generated in the microwave electron gun and the target reference posture when they arrive at the fluorescent screen. The initial possible posture includes: an initial radial position and an initial emission phase. The target reference posture includes a reference radial position and a reference rotation angle. S3: Using each initial possible posture of the field emission electrons and the mapping relationship, obtain the target reference posture of each field emission electron when it arrives at the fluorescent screen. S4: Selecting the one with the smallest difference between the target reference posture and the target actual posture from multiple initial possible postures as the generated posture of the field emission electron.

[0052] As an optional implementation, the mapping relationship includes: a first sub-mapping relationship and a second sub-mapping relationship. The first sub-mapping relationship represents the relationship between the actual radial position r1 and the initial radial position r0, the initial transmission phase The second sub-mapping relationship represents the actual rotation angle θ LWith the initial radial position r0, initial emission phase The relationship between them.

[0053] As an optional implementation, the mapping relationship is: a mapping relationship between the initial possible posture of the field-emission electrons generated by the microwave electron gun, the magnetic field intensity on the preset magnetic field path, and the target reference posture corresponding to the arrival at the fluorescent screen.

[0054] As an optional implementation, the mapping relationship includes: a third sub-mapping relationship and a fourth sub-mapping relationship. The third sub-mapping relationship represents the relationship between the actual radial position r1 and the initial radial position r0, the initial transmission phase The relationship between the magnetic field strength B on the preset magnetic field path. The fourth sub-mapping relationship represents the actual rotation angle θ L With the initial radial position r0, initial emission phase The relationship between the magnetic field strength B along the preset magnetic field path.

[0055] As an optional implementation, S2 includes: obtaining a mapping relationship between an initial possible position of the field-emission electron and a target reference position based on a particle tracking simulation program in a computer language.

[0056] As an optional implementation, the first sub-mapping relationship and the third sub-mapping relationship are both related to the transmission matrix M, M=M L M sol M rf Among them, M L M represents the transmission matrix of field-emission electrons from the preset magnetic field outlet to the phosphor screen. sol It represents the transmission matrix of field-emission electrons on the preset magnetic field path, M rf Represents the transmission matrix of field-emission electrons in a microwave electron gun.

[0057] Taking the calculation method of the mapping relationship using the transfer matrix as an example, assuming that the radial position of the initial emission position of the particle is r0 and the emission phase is The magnetic field strength at the center of the solenoid is B. The variable r0, B together determine the radial position r1 of the particle's final position and the rotation angle θ L , you can use the function and Represents the function of the radial position r1 of the particle's final position It can be obtained by calculating the matrix correlation of each particle in the transmission segment: and matrix M=M L M sol M rf related.

[0058] The mapping relationship of electrons in the microwave electron gun Mrf It can be determined by the following formula, which is applicable to the case where the magnetic field of the solenoid penetrates into the microwave electron gun. In an appropriate step size Δz, assuming that the electron moves from position i to position f within the step size inside the microwave electron gun, its transmission matrix ΔM rf It can be expressed as:

[0059]

[0060] The subscript i of the symbol represents the parameter corresponding to the electron at position i, and the subscript f represents the parameter corresponding to the electron at position f. E -1 It represents the transmission matrix corresponding to the step function type drop in electric field generated by the segment at position f, R rf represents the transmission matrix corresponding to the microwave magnetic field in the microwave electron gun, represents the transmission matrix corresponding to the longitudinal magnetic field in the microwave electron gun, R E = represents the transmission matrix corresponding to the step function type rising electric field generated by the electric field segmentation at position i. In the second line of the formula, γ and β represent the Lorentz factors of the particle, and γ′ can be expressed as γ′=dγ / dz=eE Z / mc 2 We get, where e represents the charge of the electron, E z is the amplitude of the longitudinal electric field component at that position, m is the rest mass of the electron, and c is the speed of light, from which we can get γ f =γ i +γ′Δz. p is the normalized particle momentum, i.e. p=βγ. In the matrix M dc In the equation, C = cos(Δθ L (z)), S = sin(Δθ L (z)), where the particle rotation angle is the Larmor angle Δθ L (z) = (b / γ′), where b = -eB z / 2mc.

[0061] Furthermore, the mapping relationship M of electrons in the microwave electron gun is rf The ΔM in each step of the microwave electron gun can be rf Multiply it and we get:

[0062] When the electron is in the solenoid part, the mapping relationship M within a step length L in the Larmor coordinate system is sol It can be determined by the following formula: Among them, K=B0 / 2Bρ, B0 is the magnetic induction intensity, and Bρ is the magnetic stiffness of the electron, that is, Bρ=mv / q.

[0063] Furthermore, when the radial position of the field-emission electron is large, if the magnetic induction intensity at that position is expressed by the solenoid intensity on the central axis, an error will occur. Therefore, when calculating the solenoid transmission matrix, B0 can be expanded, and K=B z (r) / 2Bρ:

[0064] When the electron is in the drift section, the mapping relationship M within a step length L L It can be determined by the following formula:

[0065] Function of the rotation angle of the particle's final position It is related to the size of the magnetic field that the particles pass through in the transmission section. Depending on whether the particles are still accelerating in the magnetic field, it can be calculated according to the following formula: γ, β represent the Lorentz factors of the particle, and the intermediate variable γ′ can be expressed by γ′=dγ / dz=eE Z / mc 2 So, b = -eB z / 2mc. p i0 and γ i0 Indicates the magnitude of the initial position momentum and the magnitude of the Lorentz factor, p(s i ) and γ(s i ) represents the momentum and Lorentz factor of the current position, Δs represents the longitudinal distance the electron moves; θ L =θ L (s1)+...+θ L (s N ).

[0066] Assume that the radial position of the initial emission of the particle is r0 and the emission phase is By changing the magnitude of the solenoid magnetic induction intensity B, a series of measurement values ​​can be obtained on the fluorescent screen at the end. The measurement values ​​can be decomposed into the radial position r1 of the particle's final position and the rotation angle θ according to the polar coordinate system. L Using the curve fitting method, we search for the most suitable r0. Make it a series of function values and The error with a series of measured values ​​is the smallest, and the r0 obtained at this time is The value of is the initial emission position and emission phase of the particle.

[0067] The feasibility of this method is verified by simulating the actual measurement process through a particle tracking simulation program.

[0068] Assume that the radial position of the initial emission of field-emission electrons is r0 = 4 mm and the emission phase is Since the electric field in the microwave electron gun generally has a certain defocusing effect on the field emission current, the set electric field strength cannot be too large during measurement; however, in order to generate sufficient field emission current that can be detected by the fluorescent screen and to enable the field emission current to be transmitted to the next part after leaving the microwave electron gun, the set electric field strength cannot be too small. Therefore, when setting the electric field of the microwave electron gun, it is necessary to combine its structural characteristics and set the electric field strength of appropriate size for the position where the field emission current may be emitted. In order to enable the field emission current at this position to be transmitted to the final position fluorescent screen, the acceleration gradient of the cathode of the microwave electron gun is set to 40MV / m. The magnetic induction intensity B of the solenoid is set to a range of 0.035~0.045T, and a measurement is performed every 0.001T. At this time, based on the image information on the fluorescent screen, a series of radial positions r1 and rotation angles θ of the final electron position can be obtained. L Taking the least squares method as an example, by constructing the actual measured value and the function value and Error function, find the most suitable r0, The calculated value of makes the error function minimum.

[0069] By using the least squares method, we can get the value of r0 and r2 that minimize the error function. The value of the radial position r1 of the electron end position is compared with the function For comparison of calculated fitting curves, see Figure 4 The final position of the electron is rotated by an angle θ L The measurement value and use function For comparison of calculated fitting curves, see Figure 5 It can be seen that when the magnetic induction intensity B changes multiple times, the calculation results of each function can be consistent with the measurement results, and the calculation results obtained are highly accurate. In this embodiment, the radial position of the initial emission of field-emission electrons is set to r0 = 4mm and the emission phase is set to In this case, the radial position obtained by curve fitting is 4.04 mm, and the emission phase is 90.22°.

[0070] Overall, this method overcomes the shortcomings of traditional measurement methods, which often provide relatively limited information. Compared to traditional measurement methods, the method for measuring the source of field emission current within a microwave electron gun proposed in this invention reduces measurement error through curve fitting, enabling precise measurement of initial emission information such as the emission position and phase of field-emission electrons. The transfer matrix mapping calculation method employed in this invention significantly reduces calculation time while maintaining accuracy compared to particle tracking programs. Specifically, this method reduces calculation error by accounting for the influence of the solenoid magnetic field penetrating the microwave electron gun in the transfer matrix mapping calculation of the microwave electron gun, as well as the influence of nonlinear magnetic field components on the transfer matrix calculation in the transfer matrix mapping calculation of the solenoid portion. This method is suitable for situations where the radial position of the field emission current is large, and it also provides guidance for related transfer matrix-based measurement methods, such as thermal emittance measurement. Furthermore, the components configured in the measurement system for field emission current sources within a microwave electron gun provided in this invention are all essential components in common accelerator structures, reducing the cost of setting up the experimental platform, providing convenient and fast operation and high practicality.

[0071] Example 2

[0072] This embodiment provides a device for acquiring the generated pose of field-emission electrons in a microwave electron gun, comprising a measurement module, an establishment module, a calculation module, and a determination module. The measurement module is configured to measure the actual target pose of the field-emission electrons on a fluorescent screen. The target actual pose includes an actual radial position and an actual rotation angle. Field-emission electrons are generated and emitted within the microwave electron gun, and are focused and projected onto the fluorescent screen via a preset magnetic field path. The establishment module is configured to establish a mapping relationship between the initial possible poses of the field-emission electrons generated within the microwave electron gun and the target reference pose upon arrival at the fluorescent screen. The initial possible poses include an initial radial position and an initial emission phase. The target reference pose includes a reference radial position and a reference rotation angle. The calculation module is configured to use each initial possible pose of the field-emission electrons and the mapping relationship to obtain a target reference pose of each field-emission electron upon arrival at the fluorescent screen. The determination module is configured to select, from multiple initial possible poses, the one with the smallest difference between the target reference pose and the target actual pose as the generated pose of the field-emission electron.

[0073] Example 3

[0074] like Figure 2As shown, this embodiment provides a system for acquiring the generated posture of field-emission electrons in a microwave electron gun, comprising: a microwave electron gun, a solenoid, a fluorescent screen, a memory, and a processor. The microwave electron gun is used to generate field-emission electrons and emit them through the muzzle. The solenoid, when its internal coil is energized, generates a preset magnetic field path at the outlet of the microwave electron gun, and the preset magnetic field path is used to focus and project the field-emission electrons with a preset focusing intensity. The fluorescent screen has a drift section with a preset spacing from the preset magnetic field path, and the field-emission electrons focused and projected by the preset magnetic field path arrive at the fluorescent screen through the drift section. The memory stores a computer program. When the processor executes the computer program, the steps of the above-mentioned positioning method are implemented.

[0075] In this system, the microwave electron gun is used to create a certain electric field to generate field emission current and accelerate the field emission current so that it can leave the microwave electron gun and be transmitted to the final position fluorescent screen. The solenoid is used to create a certain magnetic field to focus the field emission current. The focusing strength of the solenoid is determined by the intensity of the solenoid coil current, which is used to change the imaging position of the field emission electrons at the final position. For the schematic diagram of the electric field distribution on the axis of the microwave electron gun and the magnetic field distribution on the axis of the solenoid, please refer to Figure 3 , it can be seen that there is a certain overlap between the microwave electron gun electric field and the solenoid magnetic field. The transmission matrix used in this invention can calculate the mapping information of this overlapping portion in this case. The drift segment allows the focused field-emission electrons to be further transmitted, ultimately being received and imaged by the fluorescent screen at the final position. The components configured in the system are all essential components in the structure of a conventional electron accelerator. Therefore, using this system to measure field emission current can reduce the cost of setting up the experimental platform, is convenient and fast to operate, easy to implement, and has high practicality.

[0076] By adjusting the electric field strength within the microwave electron gun, field-emission electrons are induced to be generated from the cathode or other metal surface. These electrons are then accelerated by the microwave electron gun and transmitted to the detection terminal for observation. By adjusting the current intensity of the solenoid coil, the solenoid's focusing strength on the field-emission electrons is changed, thereby correspondingly obtaining a series of image information of the field-emission electrons on the detection phosphor screen. Furthermore, by appropriately adjusting the microwave electron gun's acceleration gradient and the solenoid's magnetic induction strength, field-emission current electron bunches from different emission positions can ultimately be imaged on the final position phosphor screen. This allows for comprehensive measurement and evaluation of all locations within the microwave electron gun and on the cathode surface that may produce strong field emission.

[0077] Example 4

[0078] This embodiment provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the above-mentioned positioning method are implemented.

[0079] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for obtaining the generated posture of field-emission electrons in a microwave electron gun, characterized in that: include: S1: Measure the actual position of the target on the fluorescent screen caused by field emission electrons; The actual position of the target includes an actual radial position and an actual rotation angle; The field-emission electrons are generated and emitted inside the microwave electron gun, and are focused and projected onto the fluorescent screen via a preset magnetic field path; S2: establishing a mapping relationship between an initial possible pose of field-emission electrons generated in the microwave electron gun and a target reference pose when the electrons reach the fluorescent screen; The initial possible pose includes: an initial radial position and an initial transmission phase; the target reference pose includes a reference radial position and a reference rotation angle; S3: using each of the initial possible postures of the field-emission electrons and the mapping relationship, obtaining a target reference posture of each of the field-emission electrons when it reaches the fluorescent screen; S4: Selecting from the multiple initial possible postures the one having the smallest difference between the target reference posture and the target actual posture as the generated posture of the field emission electron.

2. The method for obtaining the generation posture of field-emission electrons in a microwave electron gun according to claim 1, characterized in that: The mapping relationship includes: a first sub-mapping relationship and a second sub-mapping relationship; The first sub-mapping relationship represents the actual radial position r 1 and the initial radial position r 0. Initial emission phase φ The relationship between 0; The second sub-mapping relationship represents the actual rotation angle θ L With the initial radial position r 0. Initial emission phase φ The relationship between 0.

3. The method for obtaining the generation posture of field-emission electrons in a microwave electron gun according to claim 2, characterized in that: The first sub-mapping relationship and the transmission matrix M Related, M = M L M sol M rf ; in, M L represents the transmission matrix between the field-emission electrons from the preset magnetic field outlet to the fluorescent screen, M sol It indicates that the field emission electrons are transmitted in the preset magnetic field path. M rf It represents the transmission matrix of the field-emission electrons in the microwave electron gun.

4. The method for obtaining the generation posture of field-emission electrons in a microwave electron gun according to claim 1, wherein: The mapping relationship is: a mapping relationship between an initial possible posture of the field-emission electrons generated by the microwave electron gun, the magnetic field intensity on the preset magnetic field path, and a target reference posture corresponding to the posture when the electrons reach the fluorescent screen.

5. The method for obtaining the generation posture of field-emission electrons in a microwave electron gun according to claim 4, characterized in that: The mapping relationship includes: a third sub-mapping relationship and a fourth sub-mapping relationship; The third sub-mapping relationship represents the actual radial position r 1 and the initial radial position r 0. Initial emission phase φ 0. Magnetic field strength on the preset magnetic field path B the relationship between; The fourth sub-mapping relationship represents the actual rotation angle θ L With the initial radial position r 0. Initial emission phase φ 0. Magnetic field strength on the preset magnetic field path B The relationship between them.

6. The method for obtaining the generation posture of field-emission electrons in a microwave electron gun according to claim 5, characterized in that: The third sub-mapping relationship and the transmission matrix M Related, M = M L M sol M rf ; in, M L represents the transmission matrix between the field-emission electrons from the preset magnetic field outlet to the fluorescent screen, M sol It indicates that the field emission electrons are transmitted in the preset magnetic field path. M rf It represents the transmission matrix of the field-emission electrons in the microwave electron gun.

7. The method for obtaining the generation posture of field-emission electrons in a microwave electron gun according to claim 1, wherein: The S2 includes: obtaining a mapping relationship between the initial possible posture of the field-emission electron and the target reference posture based on a particle tracking simulation program in a computer language.

8. A device for acquiring the generated posture of field-emission electrons in a microwave electron gun, characterized in that: include: A measurement module is used to measure the actual target position of field-emission electrons on the fluorescent screen; The actual position of the target includes an actual radial position and an actual rotation angle; The field-emission electrons are generated and emitted inside the microwave electron gun, and are focused and projected onto the fluorescent screen via a preset magnetic field path; An establishing module, configured to establish a mapping relationship between an initial possible pose of field-emission electrons generated in the microwave electron gun and a target reference pose when the electrons reach the fluorescent screen; The initial possible pose includes: an initial radial position and an initial transmission phase; the target reference pose includes a reference radial position and a reference rotation angle; a calculation module, configured to obtain a target reference pose of each field-emission electron when it reaches the fluorescent screen by using each of the possible initial poses of the field-emission electron and the mapping relationship; A determination module is used to select, from the multiple initial possible postures, the one corresponding to the smallest difference between the target reference posture and the target actual posture as the generated posture of the field emission electron.

9. A system for acquiring the generated posture of field-emission electrons in a microwave electron gun, characterized in that: include: microwave electron gun, solenoid, phosphor screen, memory and processor; The microwave electron gun is used to generate field-emission electrons and emit them through the muzzle; The solenoid, when the internal coil thereof is energized, generates a preset magnetic field path at the outlet of the microwave electron gun, wherein the preset magnetic field path is used to focus and project the field-emitted electrons with a preset focusing intensity; A drift section having a preset distance between the fluorescent screen and the preset magnetic field path is provided, and the field-emission electrons focused and projected by the preset magnetic field path arrive at the fluorescent screen via the drift section; The memory stores a computer program; When the processor executes the computer program, the steps of the method for acquiring the generation posture of field-emission electrons in a microwave electron gun according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for acquiring the generation pose of field-emission electrons in a microwave electron gun according to any one of claims 1 to 7 are implemented.

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