Magnetic lens for an electron linear accelerator and method for structural optimization

Abstract

The application discloses a magnetic lens for an electronic linear accelerator and a structure optimization method, and the structure optimization method comprises the following steps: obtaining structure parameters of the magnetic lens; calculating a magnetic field intensity vector of the magnetic lens; obtaining a corresponding relationship between the structure parameters of the magnetic lens and the magnetic field intensity of the magnetic lens by using the magnetic field intensity vector; and optimizing the structure of the magnetic lens according to the corresponding relationship. The application can improve the maximum magnetic field of the magnetic lens, improve the focusing effect of the magnetic lens, reduce the size of an initial beam spot, provide a data basis for product research and development, and reduce the cost of product research and development.

Description

Technical Field

[0001] This invention relates to a magnetic lens for an electron linear accelerator and a method for optimizing its structure. 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] The compact and miniaturized 3MeV energy electron linear accelerator prototype can be used in a beam-guided target application scenario. By adjusting the magnetic field and electric field distribution in the electromagnetic lens, the focusing position and focusing diameter of the electron beam can be controlled.

[0004] Magnetic lens focusing of 3MeV energy electron beams can achieve electron beam focusing and has applications in various scenarios, such as X-ray emission from target shooting. It has been widely used in industrial non-destructive testing (CT / DR), medical radiotherapy, material irradiation modification, and scientific research on irradiation effects, and miniaturized equipment is rapidly becoming more common.

[0005] The maximum magnetic field that existing magnetic lenses can provide is around 1000 Gs, which cannot meet the usage requirements. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the defect that the maximum magnetic field provided by existing magnetic lenses is only about 1000 Gs, which cannot meet the application requirements. This invention provides a magnetic lens and structural optimization method for electron linear accelerators that can increase the maximum magnetic field of the magnetic lens, improve the focusing effect of the magnetic lens, reduce the size of the initial beam spot, provide a data basis for product development, and reduce product development costs.

[0007] The present invention solves the above-mentioned technical problems through the following technical solution:

[0008] A method for optimizing the structure of a magnetic lens, characterized in that the optimization method includes:

[0009] Obtain the structural parameters of the magnetic lens;

[0010] Calculate the magnetic field strength vector of the magnetic lens;

[0011] The relationship between the structural parameters of the magnetic lens and the magnetic field strength of the magnetic lens is obtained using the magnetic field strength vector.

[0012] The structure of the magnetic lens is optimized based on the above correspondence.

[0013] Preferably, the magnetic field strength vector is obtained through the formula Obtain, among which This represents the axial component of the magnetic field strength. The radial component of the magnetic field strength The thickness of the gap between the coil and the yoke. The number of coil turns. axial length Where is the coil radius, The average magnetic path length, The axis is the central symmetry axis of the magnetic lens. This represents the radial distance.

[0014] Preferably, obtaining the correspondence between the shape of the coil and the magnetic field strength of the magnetic lens using the magnetic field strength vector includes:

[0015] Obtain the total magnetic reluctance of the magnetic lens, wherein the total magnetic reluctance includes the air gap magnetic reluctance and the magnetic yoke magnetic reluctance;

[0016] Obtain the relationship between the total magnetic reluctance of the magnetic circuit and the magnetic field strength;

[0017] An optimization strategy for coil shape is obtained by utilizing the correspondence between the total magnetic reluctance of the magnetic circuit and the magnetic field strength.

[0018] Preferably, the optimization strategy includes setting the number of layers of the coil wound inside the magnetic lens and the number of turns per layer. The coil is a hollow square tube spirally wound inside the iron shell on the outside of the magnetic pole. One end of the coil is provided with a coolant inlet and the other end is provided with a coolant outlet.

[0019] Preferably, the total magnetic reluctance of the magnetic circuit is ,in For air gap reluctance, It is a radial air gap. , The permeability of free space, The cross-sectional area of ​​the air gap is... , axial length Where is the coil radius, For magnetic reluctance, ,in The average magnetic path length, , The relative permeability of the magnetic medium. For equivalent cross-sectional area, , The outer radius of the magnetic yoke is . Let be the inner radius of the magnetic yoke.

[0020] Preferably, obtaining the correspondence between the shape of the coil and the magnetic field strength of the magnetic lens using the magnetic field strength vector includes:

[0021] Obtain the total magnetic permeability of the magnetic circuit of the magnetic lens, wherein the total magnetic permeability is the ratio of the total magnetic flux to the total magnetomotive force;

[0022] Obtain the correspondence between the total magnetic permeability and the magnetic field strength of the magnetic circuit;

[0023] The optimization strategy for coil shape is obtained by utilizing the correspondence between the total magnetic permeability and magnetic field strength of the magnetic circuit;

[0024] Wherein, the total magnetic permeability of the magnetic circuit is , The total magnetic potential, For the total magnetic flux, The permeability of free space, The relative permeability of the magnetic medium. The total magnetic reluctance of the magnetic circuit. The cross-sectional area of ​​the air gap is... For equivalent cross-sectional area, The thickness of the gap between the coil and the yoke. Let be the average magnetic circuit length, if As we approach infinity, .

[0025] Preferably, in the paraxial region, the original unshielded axial magnetic field is: ,according to Get ,in, The total magnetic potential, Where is the coil radius, The axis is the central symmetry axis of the magnetic lens. Radial distance, The permeability of free space, The total magnetic permeability of the magnetic circuit;

[0026] The radial magnetic field when there is no shielding is ,according to Get .

[0027] Preferably, the structural optimization method includes:

[0028] Obtain the structural parameters of the optimized magnetic lens;

[0029] Calculate the magnetic field strength vector of the optimized magnetic lens;

[0030] The final optimized scheme for the magnetic lens is obtained by comparing the magnetic field strength vector results.

[0031] Preferably, the structural optimization method includes:

[0032] A magnetic lens of a target structure is obtained, and the size information of the target structure is calculated by inputting the corresponding relationship into artificial intelligence.

[0033] The target structure with size information is used as the optimized magnetic lens;

[0034] The number of layers of the coil wound inside the magnetic lens and the number of turns in each layer are calculated by comparing the magnetic field strength vector.

[0035] Output the number of layers and the number of turns per layer of the magnetic lens in the final optimized scheme, and output the size information of the magnetic lens structure in the final optimized scheme.

[0036] The present invention also provides a magnetic lens for an electron linear accelerator, characterized in that the magnetic lens includes a coil and an iron shell, the coil is disposed inside the iron shell, the coil is a hollow square tube spirally wound around the outside of a magnetic pole inside the iron shell, one end of the coil is provided with a coolant inlet and the other end is provided with a coolant outlet, and the number of layers and the number of turns per layer of the coil are preset values.

[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 increase the maximum magnetic field of a magnetic lens, improve the focusing effect of the magnetic lens, reduce the size of the initial beam spot, provide a data basis for product development, and reduce the cost of product development. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the structure of the magnetic lens in Embodiment 1 of the invention.

[0041] Figure 2 This is a schematic diagram illustrating the effect of the structural optimization method in Embodiment 1 of the invention.

[0042] Figure 3 This is another schematic diagram illustrating the effect of the structural optimization method in Embodiment 1 of the invention.

[0043] Figure 4 This is another schematic diagram illustrating the effect of the structural optimization method in Embodiment 1 of the invention.

[0044] Figure 5 This is another schematic diagram illustrating the effect of the structural optimization method in Embodiment 1 of the invention.

[0045] Figure 6 This is another schematic diagram illustrating the effect of the structural optimization method in Embodiment 1 of the invention.

[0046] Figure 7This is another schematic diagram illustrating the effect of the structural optimization method in Embodiment 1 of the invention. Detailed Implementation

[0047] 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.

[0048] Example 1

[0049] 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.

[0050] See Figures 1 to 7 This embodiment provides a 3MeV linear electron accelerator, which includes an accelerating tube, a magnetic lens, and a drift tube, with the magnetic lens and drift tube both located below the accelerating tube.

[0051] The magnetic lens includes a coil and an iron shell, with the coil disposed inside the iron shell to obtain the structural parameters of the magnetic lens.

[0052] The focusing ability of a magnetic lens mainly comes from the magnetic field it generates, and the coil current is the key factor that determines the strength of the magnetic field.

[0053] The magnetic field of an axisymmetric magnetic lens exhibits rotational symmetry and is most easily described using cylindrical coordinates (r, φ, z), where the z-axis is the central axis of symmetry of the magnetic lens, r is the radial distance, and φ is the circumferential angle. Due to the axisymmetry of the magnetic field, its magnetic field strength components depend only on r and z, with the circumferential component H... φ =0, radial component and axial component Satisfying the sourcelessness condition of Maxwell's equations ( , Vacuum permeability ( ), Where H is the relative permeability of the magnetic medium, and H is the magnetic field strength vector. An electromagnet is obtained through the formula... Calculating the magnetic flux density, it can be seen from the formula that the magnetic field strength will increase significantly when the coil current increases.

[0054] The core structural parameters of the shielded type include the air gap size (the thickness of the gap between the coil and the yoke). ), yoke parameters (material permeability) , inner radius Outer radius Axial length L, opening shape) and coil configuration (number of turns N, current I, coil radius R, axial length L). Air gap The air gap is the primary source of magnetic reluctance in the magnetic circuit; changes in its size directly alter the magnetic flux, thus affecting the magnetic field strength in the air gap region. The yoke's function is to confine the magnetic field and reduce leakage; its material's permeability, thickness, and opening shape influence the confinement effect and uniformity of the magnetic field distribution. The coil is the excitation source of the magnetic field; according to the Biot-Savart law, the number of turns, current, and geometry of the coil directly determine the excitation strength and distribution of the magnetic field. These three elements, coupled through magnetic circuit coupling, form a complex magnetic field distribution that collectively influences the focusing effect of the electron beam.

[0055] Based on the Biot-Savart law and magnetic circuit analysis, the axial direction of the magnetic field strength vector H, considering air gap and yoke parameters, is derived for a shielded axisymmetric magnetic lens. ) and radial ( ) Expanded form.

[0056] Total magnetic reluctance of the magnetic circuit Air gap magnetoresistance and magnetic reluctance of the yoke Series composition:

[0057] Air gap reluctance (radial air gap, ignoring edge effects): , (Air gap cross-sectional area).

[0058] Magnetic reluctance of the yoke (assuming the yoke is uniform and leakage flux is negligible): , (Average magnetic circuit length) (Equivalent cross-sectional area, which needs to be simplified according to the specific structure).

[0059] Total magnetic permeability of the magnetic circuit The ratio of total magnetomotive force NI to total magnetic flux Φ .

[0060] If the magnetic permeability of the yoke is extremely high ( →∞), then →0, at this time .

[0061] In the paraxial region (r≪R), the original unshielded axial magnetic field is: .

[0062] After considering the air gap and yoke, the magnetic field is compressed into the air gap, increasing the equivalent number of turns and improving magnetic field uniformity. (Corrected version) for: .

[0063] After unfolding: .

[0064] The radial magnetic field when there is no shielding is: .

[0065] After considering the air gap, the radial magnetic field is short-circuited by the yoke (high permeability materials attract magnetic field lines), therefore Significantly reduced. (Revised) for: .

[0066] like ≫ ,but: .

[0067] When the cross-sectional area of ​​the magnetic yoke Much larger than the air gap cross-sectional area hour, ≈0 (the magnetic field is completely axial).

[0068] Considering the air gap size g and the yoke parameters ( , After L), the expansion of the magnetic field strength vector H of the shielded axisymmetric magnetic lens is: .

[0069] The key parameters for optimizing the magnetic lens are obtained through the analysis of the above calculations.

[0070] For air gap size : Proportional to 1 / g, reducing the air gap can significantly enhance the axial magnetic field (improving focusing ability). It is proportional to g (after g is canceled out in the denominator), but in reality, due to the short-circuit effect of the magnetic yoke, It decays rapidly as g decreases.

[0071] Magnetic permeability of yoke : Almost unaffected Impact (because the magnetic field is mainly within the air gap). With 1 / Proportional to the magnetic field, a high permeability yoke can effectively suppress the radial magnetic field.

[0072] Geometric parameters of the yoke: cross-sectional area of ​​the yoke Increasing the size of the yoke can reduce its magnetic reluctance and further suppress [the magnetic field]. Extending the axial length L of the magnetic yoke can increase the air gap cross-sectional area. =2πRL, thus enhancing .

[0073] In summary, reducing and increasing the yoke parameters Changing the N, I, and R of the coil will significantly affect the distribution of the magnetic field and the focusing performance.

[0074] Given that the actual magnetic lens has a large number of turns and a relatively small operating current, it briefly exceeds the rated current value during actual testing, causing the coil to overheat and become damaged, thus failing to meet normal usage requirements. In order to improve the magnetic field adjustment range and the reliability of use, a comprehensive analysis shows that the magnetic lens needs further optimization before it can be used normally.

[0075] As can be seen from the calculations of the embodiments of this application, the magnetic field can be increased by adjusting the coil structure, the magnetic yoke structure and the air gap structure. Due to the installation size limitation, the existing magnetic lens shell can only adjust the internal coil and magnetic yoke structure, replace the enameled wire or copper tube with a high current value, and adjust the air gap.

[0076] The coil is a hollow square tube spirally wound inside an iron shell on the outside of a magnetic pole. One end of the coil has a coolant inlet and the other end has a coolant outlet. The number of layers and the number of turns per layer of the coil are preset values.

[0077] With the same internal dimensions, increasing the size of the enameled wire reduces the number of turns, lengthens the coil, and limits the adjustable space of the outer casing. Furthermore, it lowers the magnetic field. According to calculations in the example, if a 6*6 copper tube is used, the current can reach up to 300A, the coil height increases to 99mm, and the outer diameter of the yoke and the inner diameter of the iron casing decrease. Calculations show that at 300A, the magnetic field can reach 3000Gs.

[0078] Using the algorithm described above, this embodiment provides a structural optimization method, including:

[0079] Obtain the structural parameters of the magnetic lens;

[0080] Calculate the magnetic field strength vector of the magnetic lens;

[0081] The relationship between the structural parameters of the magnetic lens and the magnetic field strength of the magnetic lens is obtained using the magnetic field strength vector.

[0082] The structure of the magnetic lens is optimized based on the above correspondence.

[0083] Wherein, the magnetic field strength vector is obtained through the formula Obtain, among which This represents the axial component of the magnetic field strength. The radial component of the magnetic field strength The thickness of the gap between the coil and the yoke. The number of coil turns. axial length Where is the coil radius, The average magnetic path length, The axis is the central symmetry axis of the magnetic lens. This represents the radial distance.

[0084] Specifically, obtaining the correspondence between the shape of the coil and the magnetic field strength of the magnetic lens using the magnetic field strength vector includes:

[0085] Obtain the total magnetic reluctance of the magnetic lens, wherein the total magnetic reluctance includes the air gap magnetic reluctance and the magnetic yoke magnetic reluctance;

[0086] Obtain the relationship between the total magnetic reluctance of the magnetic circuit and the magnetic field strength;

[0087] An optimization strategy for coil shape is obtained by utilizing the correspondence between the total magnetic reluctance of the magnetic circuit and the magnetic field strength.

[0088] The optimization strategy includes setting the number of layers of the coil wound inside the magnetic lens and the number of turns per layer. The coil is a hollow square tube spirally wound inside the iron shell on the outside of the magnetic pole. One end of the coil is provided with a coolant inlet and the other end is provided with a coolant outlet.

[0089] The total magnetic reluctance of the magnetic circuit is ,in For air gap reluctance, It is a radial air gap. , The permeability of free space, The cross-sectional area of ​​the air gap is... , axial length Where is the coil radius, For magnetic reluctance, ,in The average magnetic path length, , The relative permeability of the magnetic medium. For equivalent cross-sectional area, , The outer radius of the magnetic yoke is . Let be the inner radius of the magnetic yoke.

[0090] The step of obtaining the correspondence between the shape of the coil and the magnetic field strength of the magnetic lens using the magnetic field strength vector includes:

[0091] Obtain the total magnetic permeability of the magnetic circuit of the magnetic lens, wherein the total magnetic permeability is the ratio of the total magnetic flux to the total magnetomotive force;

[0092] Obtain the correspondence between the total magnetic permeability and the magnetic field strength of the magnetic circuit;

[0093] The optimization strategy for coil shape is obtained by utilizing the correspondence between the total magnetic permeability and magnetic field strength of the magnetic circuit;

[0094] Wherein, the total magnetic permeability of the magnetic circuit is , The total magnetic potential, For the total magnetic flux, The permeability of free space, The relative permeability of the magnetic medium. The total magnetic reluctance of the magnetic circuit. The cross-sectional area of ​​the air gap is... For equivalent cross-sectional area, The thickness of the gap between the coil and the yoke. Let be the average magnetic circuit length, if As we approach infinity, .

[0095] In the paraxial region, the original unshielded axial magnetic field is: ,according to Get ,in, The total magnetic potential, Where is the coil radius, The axis is the central symmetry axis of the magnetic lens. Radial distance, The permeability of free space, The total magnetic permeability of the magnetic circuit;

[0096] The radial magnetic field when there is no shielding is ,according to Get .

[0097] The structural optimization method includes:

[0098] Obtain the structural parameters of the optimized magnetic lens;

[0099] Calculate the magnetic field strength vector of the optimized magnetic lens;

[0100] The final optimized scheme for the magnetic lens is obtained by comparing the magnetic field strength vector results.

[0101] The structural optimization method includes:

[0102] A magnetic lens of a target structure is obtained, and the size information of the target structure is calculated by inputting the corresponding relationship into artificial intelligence.

[0103] The target structure with size information is used as the optimized magnetic lens;

[0104] The number of layers of the coil wound inside the magnetic lens and the number of turns in each layer are calculated by comparing the magnetic field strength vector.

[0105] Output the number of layers and the number of turns per layer of the magnetic lens in the final optimized scheme, and output the size information of the magnetic lens structure in the final optimized scheme.

[0106] Using the optimization method of this application, it can be confirmed that:

[0107] See Figure 1 The coil is replaced with a 6*6 hollow square tube wound around the central axis of symmetry 101, specifically wound around the outer side of the magnetic pole 102. The coil position 100 is the coil coil, with 14 turns per layer, for a total of 6 layers, or 84 turns. The designed resistance is approximately 36mΩ. The coil width is 39.5mm and the height is 99mm. The air gap is changed, and the upper and lower magnetic yokes 103 are correspondingly thinned, with the outer radius shortened by 1mm on each side. The upper and lower covers of the magnetic lens are thinned by 4mm, and the inner radius of the outer shell is reduced by 2 mils. The excitation current adjustment range is 0~300A, and at 300A it can reach 3000Gs. The magnetic field is highly adjustable. For heat dissipation, water cooling is provided inside the square copper tube.

[0108] The above structural parameters can be confirmed using the optimization algorithm of this application. For example, the number of turns and the number of layers in each layer can be analyzed by artificial intelligence and verified using the optimization algorithm of this application, thus finally confirming the number of turns and the number of layers in the hollow square tube.

[0109] See Figure 2 , Figure 3 Under different air gaps, the highest local magnetic field value decreased from 10.3 to 8.93T compared with the left air gap of 1mm and the right air gap of 2mm and the left air gap of 0mm and the right air gap of 1mm.

[0110] Simulation predicts this scheme, namely Figure 3 The results of the parameterized scanning show that the peak magnetic field is 2660 Gs when the excitation current is 240 A, and the maximum beam diameter is 84 mm, which can meet the requirement of 60-80 mm beam diameter.

[0111] The optimized magnetic lens scheme was confirmed to meet the design requirements within a magnetic field range of 200~240A and 2600Gs. The magnetic field performance was simulated again by FEMM to assist in manufacturing.

[0112] The following two methods were used to locally refine the mesh, automatically defining it. Simulation calculations were performed with an excitation current Ic = 100A and an accuracy of 1e-08, generating a contour map of the magnetic flux density B as shown in the figure. This map displays the mesh distribution and includes mesh quantity calculations. Figure 4 (a) Basic grid: The maximum grid size of the coil is controlled within 8.8% of the radial dimension, with 31,000 grid cells. Figure 4 (b) Refine the mesh, with the maximum mesh size of the coil controlled within 2.35% of the radial dimension, and all boundaries refined to a maximum of 0.15mm. The mesh number is 191,000, which is a relative improvement of 6.16 times.

[0113] Taking the local magnetic flux density B, limited to the range of 0.01~0.5T, the simulation results show that with a resistance of 34.08mΩ and an excitation current of Ic=100A, the voltage drop is 3.408V and the power is 340.8W. Compared with the design value of 36mΩ and voltage drop of 3.6V by the magnetic material manufacturer, the deviation is 5.3%, which is basically consistent. As shown in the figure, the magnetic field is lower closer to the center of the axis in the radial direction. Ignoring the abnormal increase in magnetic field distortion in the figure, the values ​​are compared with the radial near-center point r=10, z=-60. In Figure (a), B=962Gs, and in Figure (b), B=942Gs, with a deviation of 20Gs. Roughly compared with the theoretical value of 1066Gs, the deviation is within 10%.

[0114] Further optimization of the magnetic field simulation scheme is as follows: Figure 5 As shown, at 190A, the theoretical calculated value is 2057Gs, the simulated value is 2166Gs, and the simulated value is 2140Gs. The corresponding beam dynamics calculation shows that the beam spot can reach 42mm. At 240A, the theoretical calculated value is 2598Gs, the simulated value is 2736Gs, and the simulated value is 2660Gs. The corresponding beam dynamics calculation shows that the beam spot is 84mm. It is basically predicted that the design requirements can be achieved within the excitation current range of 210~240A.

[0115] The optimized scheme was confirmed through theoretical and simulation analysis. The magnetic lens was modified accordingly, with modifications made to the yoke and outer shell by the shell manufacturer, and the coil was rewound by the magnetic material manufacturer. To verify the discrepancy between the simulation data and the actual data, the settings in FEMM were adjusted to make the simulated resistance of 35.7mΩ close to the design value, taking into account the theoretical design resistance. Simulation was performed again, and the magnetic flux density B at the radial near-center point (r=6, z=-60) and point (r=8, z=-60) was taken. The magnetic flux density B at the shaft center point (r=0, z=-60) was estimated based on its linearity and compared with the actual test value after modification.

[0116] Only the magnetic field at the axial center and radial midpoint (Z=-60°) is analyzed. Theoretical calculations, simulations, and actual test values ​​are used, along with the error between the actual test values ​​and the simulation values. The results are summarized as follows: Figure 6 As shown.

[0117] The test was then retested using a chiller. The ambient temperature was 16℃, the humidity was 45%, the wire temperature was 24.3℃, and the wire, water, and internal cavity temperatures were 24.3℃, 24.3℃, and 27℃, respectively. The test was conducted according to the established test plan, but at 200A, the wire, water, and internal cavity temperatures were 72℃, 38.9℃, and 81.5℃, respectively, and the power supply display showed a power of 14.23KW, so the test was stopped.

[0118] Only the magnetic field at the axial center and radial midpoint (Z=-60°) is analyzed. Theoretical calculations, simulations, and actual test values ​​are used, along with the error between the actual test values ​​and the simulation values. The results are summarized as follows: Figure 7 As shown.

[0119] Due to the different testing environments (ordinary water circulation and chiller water circulation), the results of the two tests with the same current showed slight deviations. Overall, the error between simulation and actual measurement was controlled within 13%, except for 13% for 40A. Moreover, the larger the current, the smaller the deviation between simulation and actual measurement, with an error of ±2%. Because the optimized magnetic lens has a large magnetic field adjustment range, the excitation current can be finely adjusted to meet the set magnetic field requirements. The simulation data was deemed valid, and it is expected that the beam dynamics predicted by the simulation can achieve the design goals.

[0120] 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 optimizing the structure of a magnetic lens, characterized in that, The structural optimization method includes: Obtain the structural parameters of the magnetic lens; Calculate the magnetic field strength vector of the magnetic lens; The relationship between the structural parameters of the magnetic lens and the magnetic field strength of the magnetic lens is obtained using the magnetic field strength vector. The structure of the magnetic lens is optimized based on the above correspondence.

2. The method for optimizing the structure of a magnetic lens as described in claim 1, characterized in that, The magnetic field strength vector is expressed by the formula Obtain, among which This represents the axial component of the magnetic field strength. The radial component of the magnetic field strength The thickness of the gap between the coil and the yoke. The number of coil turns. axial length Where is the coil radius, The average magnetic path length, The axis is the central symmetry axis of the magnetic lens. This represents the radial distance.

3. The method for optimizing the structure of a magnetic lens as described in claim 1, characterized in that, The step of obtaining the correspondence between the shape of the coil and the magnetic field strength of the magnetic lens using the magnetic field strength vector includes: Obtain the total magnetic reluctance of the magnetic lens, wherein the total magnetic reluctance includes the air gap magnetic reluctance and the magnetic yoke magnetic reluctance; Obtain the relationship between the total magnetic reluctance of the magnetic circuit and the magnetic field strength; An optimization strategy for coil shape is obtained by utilizing the correspondence between the total magnetic reluctance of the magnetic circuit and the magnetic field strength.

4. The method for optimizing the structure of a magnetic lens as described in claim 3, characterized in that, The optimization strategy includes setting the number of layers of the coil wound inside the magnetic lens and the number of turns per layer. The coil is a hollow square tube spirally wound inside the iron shell on the outside of the magnetic pole. One end of the coil is provided with a coolant inlet and the other end is provided with a coolant outlet.

5. The method for optimizing the structure of a magnetic lens as described in claim 3, characterized in that, The total magnetic reluctance of the magnetic circuit is ,in For air gap reluctance, It is a radial air gap. , The permeability of free space, The cross-sectional area of ​​the air gap is... , axial length Where is the coil radius, For magnetic reluctance of the yoke, ,in The average magnetic path length, , The relative permeability of the magnetic medium. For equivalent cross-sectional area, , The outer radius of the magnetic yoke is . Let be the inner radius of the magnetic yoke.

6. The method for optimizing the structure of a magnetic lens as described in claim 1, characterized in that, The step of obtaining the correspondence between the shape of the coil and the magnetic field strength of the magnetic lens using the magnetic field strength vector includes: Obtain the total magnetic permeability of the magnetic circuit of the magnetic lens, wherein the total magnetic permeability is the ratio of the total magnetic flux to the total magnetomotive force; Obtain the correspondence between the total magnetic permeability and the magnetic field strength of the magnetic circuit; The optimization strategy for coil shape is obtained by utilizing the correspondence between the total magnetic permeability and magnetic field strength of the magnetic circuit; Wherein, the total magnetic permeability of the magnetic circuit is , The total magnetic potential, For the total magnetic flux, The permeability of free space, The relative permeability of the magnetic medium. The total magnetic reluctance of the magnetic circuit. The cross-sectional area of ​​the air gap is... For equivalent cross-sectional area, The thickness of the gap between the coil and the yoke. Let be the average magnetic circuit length, if As we approach infinity, .

7. The method for optimizing the structure of a magnetic lens as described in claim 6, characterized in that, In the paraxial region, the original unshielded axial magnetic field is: ,according to Get ,in, The total magnetic potential, Where is the coil radius, The axis is the central symmetry axis of the magnetic lens. Radial distance, The permeability of free space, The total magnetic permeability of the magnetic circuit; The radial magnetic field when there is no shielding is ,according to Get .

8. The method for optimizing the structure of a magnetic lens as described in claim 1, characterized in that, The structural optimization method includes: Obtain the structural parameters of the optimized magnetic lens; Calculate the magnetic field strength vector of the optimized magnetic lens; The final optimized scheme for the magnetic lens is obtained by comparing the magnetic field strength vector results.

9. The method for optimizing the structure of a magnetic lens as described in claim 8, characterized in that, The structural optimization method includes: A magnetic lens of a target structure is obtained, and the size information of the target structure is calculated by inputting the correspondence into artificial intelligence. The target structure with size information is used as the optimized magnetic lens; The number of layers of the coil wound inside the magnetic lens and the number of turns in each layer are calculated by comparing the magnetic field strength vector. Output the number of layers and the number of turns per layer of the magnetic lens in the final optimized scheme, and output the size information of the magnetic lens structure in the final optimized scheme.

10. A magnetic lens for an electron linear accelerator, characterized in that, The magnetic lens includes a coil and an iron shell. The coil is located inside the iron shell and is a hollow square tube spirally wound around the outside of the magnetic pole inside the iron shell. One end of the coil is provided with a coolant inlet and the other end is provided with a coolant outlet. The number of layers and the number of turns per layer of the coil are preset values.

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