Beam spot adjustment method and electron accelerator

Abstract

The application discloses a kind of beam spot adjusting method and electron accelerator, the electron accelerator includes a anode potential adjusting device and an electron extraction device, the hot cathode of the electron accelerator is located on the electron extraction device, the beam spot adjusting method includes: obtaining the accelerating tube physical parameter of electron accelerator;According to the beam waist position of accelerating tube physical parameter calculation electron bunch;According to the control quantity of anode potential adjusting device obtained by beam waist position;The beam spot size of accelerating tube outlet is adjusted using the control quantity.The application can obtain the extraction electric field distribution, achieve the purpose of controlling beam envelope, so that the electron bunch safely reaches the outlet of electron accelerator, while controlling the potential difference between cathode and anode, realizing the dynamic adjustment of accelerator extraction port beam spot size within a certain range.

Description

Technical Field

[0001] This invention relates to a beam spot adjustment method and an electron accelerator. Background Technology

[0002] High-voltage electron accelerators are designed to accelerate electrons. They inject electrons emitted from an electron gun into an accelerating tube. Under the acceleration of the high-intensity electric field inside the accelerating tube, the electrons quickly approach the speed of light, and their energy quickly reaches hundreds of kilovolts, megavolts, or even tens or hundreds of megaelectron volts, thus forming a high-energy electron beam to irradiate and process objects; or they can rotate a target to generate X-rays to irradiate and process large objects or high-density products.

[0003] Without scanning magnet beam expansion, the electron beam spot size at the accelerator tube exit of existing electron accelerators is fixed. This limits the application of such accelerators to a narrow range of processing and production environments. Furthermore, to ensure the safe arrival of all electron beams at the accelerator exit, high-voltage accelerators of different energies impose different requirements on the electric field distribution within the accelerator. Once the accelerator structure is determined, it can only accommodate electron beam extraction within a limited energy range. Summary of the Invention

[0004] The technical problem to be solved by this invention is to overcome the shortcomings of existing electron accelerators, such as fixed beam spot size at the accelerator tube exit, limited energy adjustment range, and relatively limited application fields, making them unsuitable for various processing and production environments. This invention provides a beam spot adjustment method and an electron accelerator that can acquire the extracted electric field distribution to control the beam envelope, thereby ensuring the safe arrival of the electron beam at the electron accelerator exit. Simultaneously, by controlling the potential difference between the anode and cathode, the beam spot size at the accelerator exit can be dynamically adjusted within a certain range.

[0005] The present invention solves the above-mentioned technical problems through the following technical solution:

[0006] A method for beam spot adjustment in an electron accelerator, characterized in that the electron accelerator includes an anode potential adjustment device and an electron extraction device, the hot cathode of the electron accelerator is disposed on the electron extraction device, and the beam spot adjustment method includes:

[0007] Obtain the physical parameters of the accelerating tube of the electron accelerator;

[0008] Calculate the beam waist position of the electron beam based on the physical parameters of the accelerator tube;

[0009] The control quantity of the anode potential adjustment device is obtained based on the waist position;

[0010] The beam spot size at the accelerator tube outlet is adjusted using the control quantity.

[0011] Preferably, the physical parameters of the accelerating tube include a first parameter of the electric field force acting on the electron beam bunch in the beam defocusing region and a first axial distance of the electron beam bunch, and the calculation of the beam waist position of the electron beam bunch based on the physical parameters of the accelerating tube includes:

[0012] The first axial velocity and the first radial velocity of the electron beam cluster are calculated using the first parameter and the first axial distance.

[0013] The transverse defocusing data of the electron beam cluster is obtained based on the first axial velocity and the first radial velocity;

[0014] The waist position is obtained using lateral defocus data.

[0015] Preferably, the first parameter includes a first force and a first angle, wherein the first force is the value of the electric field force exerted on the electron beam cluster in the beam defocusing region, and the first angle is the angle between the direction of the electric field force exerted on the electron beam cluster in the beam defocusing region and the axis of the electrode sheet.

[0016] The first axial velocity is ,in As the first force, The first axial distance, For electronic quality;

[0017] The first radial velocity is ,in This is the first included angle.

[0018] Preferably, the physical parameters of the accelerating tube include a second parameter of the electric field force acting on the electron beam cluster in the beam focusing region and a second axial distance of the electron beam cluster. The calculation of the beam waist position of the electron beam cluster based on the physical parameters of the accelerating tube includes:

[0019] The second axial velocity and the second radial velocity of the electron beam cluster are calculated using the second parameter and the second axial distance.

[0020] The transverse focusing data of the electron beam is obtained based on the second axial velocity and the second radial velocity;

[0021] The waist position is obtained using lateral defocus data and lateral focus data.

[0022] Preferably, the second parameter includes a second force and a second angle, wherein the second force is the value of the electric field force exerted on the electron beam cluster in the beam focusing region, and the second angle is the angle between the direction of the electric field force exerted on the electron beam cluster at the electrode position and the axis of the electrode.

[0023] The second axial velocity is ,in The first axial velocity, The axial acceleration provided by the second force The time it takes for the electron beam cluster to travel at the distance along the second axis;

[0024] The second radial velocity is ,in First radial velocity, The radial acceleration provided for the second force.

[0025] Preferably, the physical parameters of the accelerating tube include a second axial distance and a second radial distance of the electron beam cluster under the influence of the electric field in the beam focusing region, and the calculation of the beam waist position of the electron beam cluster based on the physical parameters of the accelerating tube includes:

[0026] The time it takes for the electron bundle to return to the beam waist position is obtained based on the second radial distance and the second radial velocity;

[0027] The waist position is obtained using the duration, and the divergence angle of the electron bundle at the waist position is obtained using the axial velocity and the second radial velocity at the waist position.

[0028] The beam spot size at the accelerator tube exit is calculated using the aforementioned divergence angle and beam waist position.

[0029] The control parameters of the anode potential adjustment device are obtained by calculating the beam spot size.

[0030] Preferably, the duration is ,in The second radial distance, The second radial velocity;

[0031] The divergence angle is ,in Let be the axial velocity at the waist position. This is the second radial velocity.

[0032] Preferably, the electron extraction device includes a high-voltage cathode and a high-voltage anode. The accelerating tube includes a first electrode plate and a second electrode plate. The high-voltage cathode is connected to the negative high-voltage end of the electron accelerator. The hot cathode of the electron accelerator is disposed on the axis of the high-voltage cathode. The high-voltage anode is connected to the first electrode plate. The high-voltage cathode includes a first cylindrical tube. The top surface of the first cylindrical tube is coplanar with the electron emission surface. The high-voltage anode includes an integrally formed second cylindrical tube and an anode body. The diameter of the first cylindrical tube is larger than that of the second cylindrical tube. The second cylindrical tube is disposed inside the first cylindrical tube. The top aperture of the anode body is the same as that of the second cylindrical tube. The bottom of the anode body is connected to the first electrode plate, and the bottom aperture matches the beam aperture of the first electrode plate. The top aperture of the anode body is smaller than the bottom aperture.

[0033] Preferably, the anode potential adjustment device includes a rheostat and a hydraulic cylinder.

[0034] The rheostat is connected between the high-voltage cathode and the first electrode plate;

[0035] The hydraulic cylinder is connected to the hydraulic pump via a fluid delivery line, and the piston of the hydraulic cylinder is connected to the rheostat. The piston drives the rheostat to adjust the resistance value.

[0036] The present invention also provides an electron accelerator, wherein the beam spot size at the exit of the accelerator tube is adjusted using the beam spot adjustment method described above.

[0037] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0038] The positive and progressive effects of this invention are as follows:

[0039] This invention can obtain the output electric field distribution to control the beam envelope, thereby enabling the electron beam to safely reach the electron accelerator exit. At the same time, by controlling the potential difference between the anode and cathode, the size of the beam spot at the accelerator exit can be dynamically adjusted within a certain range. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the electron accelerator according to Embodiment 1 of the invention.

[0041] Figure 2 This is another structural schematic diagram of the electron accelerator of Embodiment 1 of the invention.

[0042] Figure 3 This is a schematic diagram of the anode potential adjustment device according to Embodiment 1 of the invention.

[0043] Figure 4 This is a schematic diagram of the electronic extraction device according to Embodiment 1 of the invention.

[0044] Figure 5 This is another schematic diagram of the electronic extraction device of Embodiment 1 of the invention.

[0045] Figure 6 This is a schematic diagram illustrating the effect of the beam envelope evolution in Embodiment 1 of the invention.

[0046] Figure 7 This is another schematic diagram illustrating the effect of the beam envelope evolution in Embodiment 1 of the invention.

[0047] Figure 8 This is a flowchart of the beam spot adjustment method of Embodiment 1 of the invention.

[0048] Figure 9 This is a partial structural schematic diagram of the electron accelerator of Embodiment 1 of the invention.

[0049] Figure 10This is a schematic diagram illustrating the effect of the beam spot adjustment method in Embodiment 1 of the invention. Detailed Implementation

[0050] The present invention will be further illustrated by way of embodiments below, but the present invention is not limited to the scope of the embodiments described herein.

[0051] Example 1

[0052] In this embodiment, the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the present invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0053] See Figures 1 to 10 This embodiment provides an electron accelerator.

[0054] The electron accelerator includes an anode potential adjustment device and an electron extraction device, with the hot cathode of the electron accelerator disposed on the electron extraction device.

[0055] The anode potential adjustment device includes a rheostat and a hydraulic cylinder.

[0056] The rheostat is connected between the high-voltage cathode 11 and the first electrode plate 12, and the high-voltage cathode 11 is connected to the negative high-voltage terminal 13.

[0057] The hydraulic cylinder is connected to the hydraulic pump via a fluid delivery line, and the piston of the hydraulic cylinder is connected to the rheostat. The piston drives the rheostat to adjust the resistance value.

[0058] The electron extraction device includes a high-voltage cathode 11 and a high-voltage anode 12. The accelerating tube includes a first electrode plate 12 and a second electrode plate 14. The high-voltage cathode 11 is connected to the negative high-voltage end of the electron accelerator. The hot cathode 15 of the electron accelerator is located on the axis of the high-voltage cathode. The high-voltage anode is connected to the first electrode plate.

[0059] For rheostats, please refer to Figure 1 The conventional rheostat 21 is used, including terminals, slider 22, coil 23 and other components. The control module of the electron accelerator controls the hydraulic cylinder, which in turn causes the piston to move the slider to adjust the contact point between the slider and the coil, thereby changing the resistance value.

[0060] Further, see Figure 2The rheostat can also be a shift rheostat, which includes several anode resistors 32 and several reed switches 31. The first electrode plate is connected to the high voltage cathode 11 through all the anode resistors 32 connected in series. Two adjacent anode resistors are connected to the high voltage cathode through a reed switch 31. The piston is used to drive the opening and closing of each second reed switch.

[0061] See Figure 3 The rheostat includes two fixing parts 34, two circuit boards 35 and a rotating shaft 33. The rotating shaft is fixed between the two fixing parts. A magnet is provided on the outer surface of the rotating shaft. A reed switch 31 is arranged around the cylindrical outer surface of the rotating shaft and the reed contact point of the reed switch is aligned with the magnet in the axial position. One end of the rotating shaft is connected to the piston 37 through a rocker arm 36. The piston drives the rotating shaft to rotate.

[0062] The electron accelerator is used for:

[0063] Obtain the physical parameters of the accelerating tube of the electron accelerator;

[0064] Calculate the beam waist position of the electron beam based on the physical parameters of the accelerator tube;

[0065] The control quantity of the anode potential adjustment device is obtained based on the waist position;

[0066] The beam spot size at the accelerator tube outlet is adjusted using the control quantity.

[0067] The electron beam undergoes an acceleration process under the influence of the extraction structure and is specifically affected by its design. The beam initially encounters a lateral defocusing force, causing the beam spot to gradually expand. Subsequently, the electron beam is subjected to a lateral focusing force, gradually reducing its lateral velocity to zero, eventually accelerating and focusing towards the central axis. After passing through the extraction structure, the electron beam sequentially passes through a series of electrode plates, including the second and third electrodes, before finally reaching the extraction port.

[0068] During this process, the electron beam spot size reaches its minimum at a specific location inside the accelerator, defined as the "beam waist." Due to the equidistant and gradient design of the accelerator electrode plates, the transverse electric field force experienced by the electron beam after the "beam waist" is almost zero. Therefore, the main factors determining the size of the exit beam envelope are the "beam waist" position and the scattering angle of the electron beam at the "beam waist." When the "beam waist" position is far from the hot cathode surface and the scattering angle of the electron beam at that position is small, the beam spot size at the exit will be small; conversely, the beam spot size will be large, or the beam spot may be too large, causing some electrons to be lost on the electrode plates. By reasonably adjusting the "beam waist" position and the beam scattering angle at that point, the beam spot size can be precisely controlled to ensure that the electron beam reaches the accelerator exit completely, and the beam spot size at the exit can be adjusted accordingly.

[0069] In this embodiment, for the target electron accelerator, by acquiring the physical parameters of the accelerator tube, such as the electric field strength at the center of the hot cathode and the electric field distance, the beam waist position of the electron beam can be calculated. After acquiring the beam waist position, the beam spot size at the accelerator tube outlet can be further calculated, and the correspondence between different anode-cathode potential differences and beam spot size can be calculated. Then, the beam spot size can be adjusted using the anode potential adjustment device to meet the needs of different processing scenarios.

[0070] The electron transport process in an accelerator can be simplified into three stages of lateral envelope change. In the first stage, the lateral defocusing force between the anode and cathode causes the beam envelope to gradually increase;

[0071] In the second stage, the lateral focusing force between the anode and the second electrode plate gradually reduces the lateral velocity of the electron beam to zero, and the electron beam begins to focus in the axial direction.

[0072] In the third stage, the electron beam is only affected by the longitudinal (axial) electric field, while the transverse (radial) electric field is almost zero. The electron beam continues to converge towards the axial direction and forms the "waist" point.

[0073] After passing through the "waist," the electron beam begins to defocus and accelerate, eventually reaching the accelerator exit. The electron beam has lower energies in the first and second stages; for ease of calculation, a non-relativistic approximation is used.

[0074] Phase 1 ( Assuming the electron beam cluster is a point at the center of the hot cathode, the beam propagation direction is the X-axis, the initial velocity of the electron beam is assumed to be zero, and the magnitude of the electric field experienced by the electrons is... (First force) and included angle are The electric field acting on the X-axis (the first angle between the electric field and the X-axis, i.e., the axis of the accelerator tube) and the projection of the distance acting on the X-axis. (First axial distance);

[0075] The physical parameters of the accelerating tube include a first parameter of the electric field force acting on the electron beam bunch in the beam defocusing region and a first axial distance of the electron beam bunch. The electron accelerator is also used for:

[0076] The first axial velocity and the first radial velocity of the electron beam cluster are calculated using the first parameter and the first axial distance.

[0077] The transverse defocusing data of the electron beam cluster is obtained based on the first axial velocity and the first radial velocity;

[0078] The waist position is obtained using lateral defocus data.

[0079] The beam defocusing region is the area between the hot cathode and the top of the high-voltage anode, specifically the area between the lower surface of the hot cathode and the upper half of the high-voltage anode.

[0080] The first parameter includes a first force and a first angle. The first force is the value of the electric field force exerted on the electron beam cluster in the beam defocusing region, and the first angle is the angle between the direction of the electric field force exerted on the electron beam cluster in the beam defocusing region and the axis of the electrode sheet.

[0081] The first axial velocity is ,in As the first force, The first axial distance, For electronic quality;

[0082] The first radial velocity is ,in This is the first included angle.

[0083] electron arrival Time required for location Radial reach of maximum position and the corresponding first axial velocity and first radial velocity They are respectively:

[0084] ; ; .

[0085] Because the longitudinal accelerating field of the electron beam is much higher than the transverse electric field, i.e., the angle between them is much greater. and Since both are relatively small, a smaller angle approximation is used. Therefore, we can conclude that:

[0086] .

[0087] Phase Two ( The magnitude of the electric field experienced by the electron is and the included angle is The lateral focusing electric field (with respect to the X-axis) acts on the projection of the effective distance in the X-direction. (Second axial distance);

[0088] The physical parameters of the accelerating tube include a second parameter of the electric field force acting on the electron beam in the beam focusing region and a second axial distance of the electron beam. The electron accelerator is used for:

[0089] The second axial velocity and the second radial velocity of the electron beam cluster are calculated using the second parameter and the second axial distance.

[0090] The transverse focusing data of the electron beam is obtained based on the second axial velocity and the second radial velocity;

[0091] The waist position is obtained using lateral defocus data and lateral focus data.

[0092] The beam focusing region is the area between the bottom of the high-voltage anode and the second electrode plate, specifically the area between the lower half of the high-voltage anode and the second electrode plate.

[0093] The second parameter includes a second force and a second angle. The second force is the value of the electric field force exerted on the electron beam cluster in the beam focusing region, and the second angle is the angle between the direction of the electric field force exerted on the electron beam cluster at the electrode position and the axis of the electrode.

[0094] The second axial velocity is ,in The first axial velocity, The axial acceleration provided by the second force The time it takes for the electron beam cluster to travel at the distance along the second axis;

[0095] The second radial velocity is ,in First radial velocity, The radial acceleration provided for the second force.

[0096] The total time the electron beam spends in this region Lateral (radial) arrival position and the corresponding longitudinal (axial) velocity. and lateral speed They are respectively:

[0097] , ;

[0098] Therefore, we can conclude that:

[0099]

[0100]

[0101] Phase Three ( Electrons are subjected to a uniform axial accelerating electric field, and the electron beam is focused before reaching the "waist".

[0102] The physical parameters of the accelerating tube include the second axial distance and the second radial distance of the electron beam cluster under the influence of the electric field in the beam focusing region. The electron accelerator is also used for:

[0103] The time it takes for the electron bundle to return to the beam waist position is obtained based on the second radial distance and the second radial velocity;

[0104] The waist position is obtained using the duration, and the divergence angle of the electron bundle at the waist position is obtained using the axial velocity and the second radial velocity at the waist position.

[0105] The beam spot size at the accelerator tube exit is calculated using the aforementioned divergence angle and beam waist position.

[0106] The control parameters of the anode potential adjustment device are obtained by calculating the beam spot size.

[0107] This application can obtain the beam spot size corresponding to different anode potentials. For different processing requirements, different anode potentials can be adjusted to obtain different beam spot sizes. The control quantity is the adjustment quantity of the hydraulic cylinder.

[0108] The duration is ,in The second radial distance, The second radial velocity;

[0109] The divergence angle is ,in Let be the axial velocity at the waist position. This is the second radial velocity.

[0110] The electron moves at a constant velocity in the Y direction (radial direction). The electron beam is gradually accelerated to the target energy under the influence of a uniform accelerating field in the X direction (axial direction). Let the total time taken for the electron beam to travel from leaving the region encompassed by the second stage to returning to the "beam waist" point be... The final longitudinal velocity of the electron beam is And the scattering angle corresponding to the "waist" point is .

[0111] Increasing the voltage difference between the cathode and anode, that is, keeping all other variables constant, only increasing... Size (assuming it increases to the original size) times, After the first stage, the transverse offset of the electron remains unchanged, but the velocity components in the horizontal and vertical directions increase to their original values. The electron in the second stage experiences the same longitudinal acceleration, but its initial velocity is twice that of the original. times, after the same distance The required time is shorter. Since the acceleration is the same, the initial velocity increases, and consequently, the longitudinal velocity of the electron at the end of the second stage will increase. Because after focusing, the final transverse velocity of the electron will point towards the axis, i.e. Because the initial velocity is greater and the electron beam's travel time is shorter, the final lateral velocity of the electrons will decrease, while the lateral displacement of the electrons will increase. At the initial moment of the third stage, the initial lateral velocity of the electron beam decreases, resulting in a larger lateral displacement, while the longitudinal velocity increases. Therefore, the time required for the electron beam to return to the X-axis is longer. This will become larger, leading to an increase in the axial displacement of the electron beam at the "beam waist," and the corresponding scattering angle... The beam size will decrease. Therefore, increasing the voltage difference between the anode and cathode can effectively reduce the scattering angle of the electron beam at the "waist," making the beam propagate more parallel within the accelerator. Simultaneously, increasing the voltage difference can also lengthen the distance between the beam waist and the hot cathode surface, thereby reducing the beam envelope size within the accelerating tube and ensuring that all electron beams can safely pass through the accelerator. Furthermore, adjusting the voltage difference between the anode and cathode can also control the beam spot size at the accelerator exit, achieving precise beam control.

[0112] To further verify the accuracy of the computational model, a three-dimensional CST simulation model of the high-voltage accelerator was established. The central electrode plates were designed with equal spacing and gradient. By scanning the potential difference between the anode and cathode from 12kV to 20kV in 2kV steps, the relationship between the beam envelope and the potential difference was observed.

[0113] Figure 6 The evolution of the beam envelope under different potential differences is shown. The electrode aperture is set to 17.5 mm, and electrons are lost when they collide with the electrode. When the voltage difference between the cathode and anode is less than 13 keV, the beam radius remains approximately 17.5 mm at the end of the accelerator, indicating that some electrons are lost when they hit the electrode. However, when the energy is 15 keV or higher, the beam radius gradually increases after passing the "beam waist" point, and all electrons reach the exit point. See [link to relevant documentation]. Figure 10 As the voltage difference between the anode and cathode increases, the "waist" electrical position moves away from the surface of the hot cathode. Figure 10 (Moving to the right from the center), and at the "waist" position, the rate of change of the beam spot size slows down significantly, and the simulation results are consistent with the theoretical derivation.

[0114] The electron extraction device includes a high-voltage cathode 11, a high-voltage anode 12, a first electrode plate, and a second electrode plate. The high-voltage cathode is connected to the negative high-voltage end of the electron accelerator. The hot cathode of the electron accelerator is located on the axis of the high-voltage cathode. The high-voltage anode is connected to the first electrode plate. The high-voltage cathode includes a first cylindrical tube, the top surface of which is coplanar with the electron emission surface. The high-voltage anode includes an integrally formed second cylindrical tube and an anode body. The diameter of the first cylindrical tube is larger than that of the second cylindrical tube. The second cylindrical tube is located inside the first cylindrical tube. The top aperture of the anode body is the same as that of the second cylindrical tube. The bottom of the anode body is connected to the first electrode plate, and the bottom aperture matches the beam aperture of the first electrode plate. The top aperture of the anode body is smaller than the bottom aperture.

[0115] While increasing the voltage difference between the anode and cathode can effectively reduce the size of the beam envelope, this voltage difference is limited by the breakdown voltage. In addition, the higher the voltage difference, the higher the requirements for the hardware, which greatly increases the overall manufacturing cost of the accelerator.

[0116] To address this issue, this application provides an anode cylinder with a flared opening at its lower end. The inner diameter of the flared opening matches the aperture of the electrode plate, and the anode cylinder and electrode plate are placed concentrically on the electrode plate. By appropriately setting the size of the flared opening, the contact area between the electric field lines and the anode cylinder can be increased, thereby weakening the lateral focusing force of the electric field.

[0117] Keeping other hardware unchanged, by designing a "horn-shaped" structure, the magnitude and direction of the force experienced by the electron beam in the first stage remain unchanged.

[0118] During the second-stage focusing of the electron beam, it can be approximated that the magnitude of the force and the electric field remain essentially constant, while the beam angle decreases, causing the electrons to take a longer time to return to the axial direction. Simultaneously, due to the smaller transverse focusing field, the transverse velocity of the electrons decreases after the second stage. Therefore, the flared structure can simultaneously increase the distance between the "beam waist" point and the hot cathode surface, and reduce the electron beam scattering angle at the "beam waist" point, thus controlling the beam envelope.

[0119] Figure 7 The diagram shows the evolution of the beam envelope for cylindrical and flared anodes with a potential difference of 11 keV. It can be seen that when the anode cylinder structure is enlarged to a flared shape, the "waist" position of the electron beam moves away from the hot cathode surface, and the rate of change of the beam spot size slows down significantly at the "waist" position, resulting in a significant technical effect.

[0120] In this embodiment, the shape of the flared opening increases uniformly or logarithmically. Using simulation software, the optimal shape parameters of the flared opening can be obtained, and a high-voltage anode that further expands the distance between the "waist" point and the hot cathode surface can be obtained. Specifically, the axial coordinate is set as the x-axis of the logarithmic function, and the radial coordinate is set as the y-axis of the logarithmic function to establish a logarithmic function. The coefficients of the logarithmic function are predicted by simulation software (parameter settings are obtained through the formula in this embodiment) and artificial intelligence, thereby obtaining the logarithmic function coefficients of the optimal shape.

[0121] See Figure 8 Using the aforementioned electron accelerator and computing terminal, this embodiment also provides a beam spot adjustment method comprising:

[0122] Step 100: Obtain the physical parameters of the electron accelerator tube;

[0123] Step 101: Calculate the beam waist position of the electron beam based on the physical parameters of the accelerating tube;

[0124] Step 102: Obtain the control quantity of the anode potential adjustment device based on the waist position;

[0125] Step 103: Adjust the beam spot size at the accelerator tube outlet using the control quantity.

[0126] The physical parameters of the accelerating tube include a first parameter of the electric field force acting on the electron beam cluster in the beam defocusing region and a first axial distance of the electron beam cluster. Step 101 includes:

[0127] Step 1011: Calculate the first axial velocity and the first radial velocity of the electron beam using the first parameter and the first axial distance;

[0128] Step 1012: Obtain the lateral defocusing data of the electron beam cluster based on the first axial velocity and the first radial velocity;

[0129] Step 1013: Obtain the waist position using lateral defocus data.

[0130] The first parameter includes a first force and a first angle. The first force is the value of the electric field force exerted on the electron beam cluster in the beam defocusing region, and the first angle is the angle between the direction of the electric field force exerted on the electron beam cluster in the beam defocusing region and the axis of the electrode sheet.

[0131] The first axial velocity is ,in As the first force, The first axial distance, For electronic quality;

[0132] The first radial velocity is ,in This is the first included angle.

[0133] The physical parameters of the accelerating tube include a second parameter of the electric field force acting on the electron beam cluster in the beam focusing region and a second axial distance of the electron beam cluster. Step 1013 includes:

[0134] Step 10131: Calculate the second axial velocity and second radial velocity of the electron beam using the second parameter and the second axial distance;

[0135] Step 10132: Obtain the transverse focusing data (radial focusing data) of the electron beam cluster based on the second axial velocity and the second radial velocity.

[0136] The waist position is obtained using lateral defocus data and lateral focus data.

[0137] The second parameter includes a second force and a second angle. The second force is the value of the electric field force exerted on the electron beam cluster in the beam focusing region, and the second angle is the angle between the direction of the electric field force exerted on the electron beam cluster at the electrode position and the axis of the electrode.

[0138] The second axial velocity is ,in The first axial velocity, The axial acceleration provided by the second force The time it takes for the electron beam cluster to travel at the distance along the second axis;

[0139] The second radial velocity is ,in First radial velocity, The radial acceleration provided for the second force.

[0140] The physical parameters of the accelerating tube include the second axial distance and the second radial distance of the electron beam cluster under the electric field force in the beam focusing region. Step 101 further includes:

[0141] Step 1014: Obtain the time it takes for the electron beam to return to the beam waist position based on the second radial distance and the second radial velocity;

[0142] Step 1015: Obtain the waist position using the duration, and obtain the divergence angle of the electron bundle at the waist position using the axial velocity and the second radial velocity at the waist position.

[0143] Step 103 includes:

[0144] The beam spot size at the accelerator tube exit is calculated using the aforementioned divergence angle and beam waist position.

[0145] The control parameters of the anode potential adjustment device are obtained by calculating the beam spot size.

[0146] In step 1014, the duration is... ,in The second radial distance, The second radial velocity;

[0147] Specifically, in step 1015, the divergence angle is... ,in Let be the axial velocity at the waist position. This is the second radial velocity.

[0148] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A method for beam spot adjustment in an electron accelerator, characterized in that, The electron accelerator includes an anode potential adjustment device and an electron extraction device, wherein the hot cathode of the electron accelerator is disposed on the electron extraction device, and the beam spot adjustment method includes: Obtain the physical parameters of the accelerating tube of the electron accelerator; Calculate the beam waist position of the electron beam based on the physical parameters of the accelerator tube; The control quantity of the anode potential adjustment device is obtained based on the waist position; The beam spot size at the accelerator tube outlet is adjusted using the aforementioned control quantity; The physical parameters of the accelerating tube include a first parameter of the electric field force acting on the electron beam bunch in the beam defocusing region and a first axial distance of the electron beam bunch. The calculation of the beam waist position of the electron beam bunch based on the physical parameters of the accelerating tube includes: The first axial velocity and the first radial velocity of the electron beam cluster are calculated using the first parameter and the first axial distance. The transverse defocusing data of the electron beam cluster is obtained based on the first axial velocity and the first radial velocity; The first parameter includes a first force and a first angle. The first force is the value of the electric field force exerted on the electron beam cluster in the beam defocusing region, and the first angle is the angle between the direction of the electric field force exerted on the electron beam cluster in the beam defocusing region and the axis of the electrode sheet. The first axial velocity is ,in As the first force, The first axial distance, For electronic quality; The first radial velocity is ,in The first included angle; The physical parameters of the accelerating tube include a second parameter of the electric field force acting on the electron beam bunch in the beam focusing region and a second axial distance of the electron beam bunch. The calculation of the beam waist position of the electron beam bunch based on the physical parameters of the accelerating tube includes: The second axial velocity and the second radial velocity of the electron beam cluster are calculated using the second parameter and the second axial distance. The transverse focusing data of the electron beam is obtained based on the second axial velocity and the second radial velocity; The waist position is obtained using lateral defocus data and lateral focus data; The second parameter includes a second force and a second angle. The second force is the value of the electric field force exerted on the electron beam cluster in the beam focusing region, and the second angle is the angle between the direction of the electric field force exerted on the electron beam cluster at the electrode position and the axis of the electrode. The second axial velocity is ,in The first axial velocity, The axial acceleration provided by the second force The time it takes for the electron beam cluster to travel at the distance along the second axis; The second radial velocity is ,in First radial velocity, The radial acceleration provided for the second force.

2. The beam spot adjustment method for an electron accelerator as described in claim 1, characterized in that, The physical parameters of the accelerating tube include the second axial distance and the second radial distance of the electron beam cluster under the electric field force in the beam focusing region. The calculation of the beam waist position of the electron beam cluster based on the physical parameters of the accelerating tube includes: The time it takes for the electron bundle to return to the beam waist position is obtained based on the second radial distance and the second radial velocity; The waist position is obtained using the duration, and the divergence angle of the electron bundle at the waist position is obtained using the axial velocity and the second radial velocity at the waist position. The beam spot size at the accelerator tube exit is calculated using the aforementioned divergence angle and beam waist position. The control parameters of the anode potential adjustment device are obtained by calculating the beam spot size.

3. The beam spot adjustment method for an electron accelerator as described in claim 2, characterized in that, The duration is ,in The second radial distance, The second radial velocity; The divergence angle is ,in The axial velocity is at the waist position.

4. The beam spot adjustment method for an electron accelerator as described in claim 1, characterized in that, The electron extraction device includes a high-voltage cathode and a high-voltage anode. The accelerating tube includes a first electrode plate and a second electrode plate. The high-voltage cathode is connected to the negative high-voltage end of the electron accelerator. The hot cathode of the electron accelerator is located on the axis of the high-voltage cathode. The high-voltage anode is connected to the first electrode plate. The high-voltage cathode includes a first cylindrical tube. The top surface of the first cylindrical tube is coplanar with the electron emission surface. The high-voltage anode includes an integrally formed second cylindrical tube and an anode body. The diameter of the first cylindrical tube is larger than that of the second cylindrical tube. The second cylindrical tube is located inside the first cylindrical tube. The top aperture of the anode body is the same as that of the second cylindrical tube. The bottom of the anode body is connected to the first electrode plate, and the bottom aperture matches the beam aperture of the first electrode plate. The top aperture of the anode body is smaller than the bottom aperture.

5. The beam spot adjustment method for an electron accelerator as described in claim 4, characterized in that, The anode potential adjustment device includes a rheostat and a hydraulic cylinder. The rheostat is connected between the high-voltage cathode and the first electrode plate; The hydraulic cylinder is connected to the hydraulic pump via a fluid delivery line, and the piston of the hydraulic cylinder is connected to the rheostat. The piston drives the rheostat to adjust the resistance value.

6. An electron accelerator, characterized in that, The electron accelerator adjusts the beam spot size at the accelerator tube outlet using the beam spot adjustment method as described in any one of claims 1 to 5.

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