A proton, hydride ion, hydrogen atom three-charge state beam extraction device

Abstract

The application discloses a kind of proton, negative hydrogen ion, hydrogen atom three charge state beam extraction device, its characteristics are: in the trajectory of beam acceleration to extraction energy, there is proton, negative hydrogen ion, hydrogen atom three charge state beam extraction device;The three charge state or double-charge state beam extraction device is equipped with stripping target and / or electrostatic deflection plate combined by different thickness and different position stripping film, the different position stripping film is used to adjust the proportion of each component beam online, the different thickness refers to according to the demand of multi-charge state beam extraction, stripping film is set to different thickness;The different position refers to on the trajectory of beam extraction, the front and back position of the multiple stripping films is different and the radial position is different between each other.The application solves the problem that the prior art can only extract single-charge state beam, and can only adjust the total flow intensity of each charge state beam online, but cannot adjust the flow intensity of each charge state beam respectively.

Description

Technical Field

[0001] This invention belongs to the field of cyclotron technology, and particularly relates to a device for extracting a beam of protons, negative hydrogen ions and hydrogen atoms in a triple-charged state. Background Technology

[0002] A cyclotron is a circular accelerator in which charged particles cyclone along a closed orbit. The particles are repeatedly accelerated by a periodically oscillating electric field acting on the acceleration gap. Because cyclotrons can reuse high-frequency electric fields for acceleration, they can accelerate particles to higher energies at a relatively low cost, leading to their widespread application in nuclear physics research, aerospace, weaponry, isotope production, cancer treatment, and industrial irradiation. Due to their small footprint, low cost, high reliability, ease of maintenance, and wide range of applications, numerous commercial and industrial cyclotrons were developed internationally in the last century.

[0003] In many applications, most do not have special requirements for the electrical properties of the extracted beam. However, with the development of scientific research, some applications have put forward new requirements for the beam's electrical properties: not only must multiple states of charge be provided simultaneously in a single application, but the beam intensity of each charge state must also be flexibly adjustable online. Providing multiple states of charge simultaneously in a single application means that, in addition to providing a conventional proton beam, a negative hydrogen ion beam and / or a hydrogen atom beam must also be provided simultaneously.

[0004] The difficulty in providing multiple states of charge simultaneously is that if the electrostatic deflection extraction method is used, only one of the proton beam or the negative hydrogen ion beam can be extracted; similarly, if the stripping membrane extraction method is used, the negative hydrogen ion beam cannot be extracted.

[0005] The difficulty in adjusting the various charge quantities online lies in the fact that each extraction device can only extract a beam of one charge state. Therefore, the current intensity of a single charge state cannot be adjusted by distributing the total current among the various charge states. To adjust the current intensity of a single type of beam online, the injection current intensity must be adjusted. Even assuming that the same extraction device can simultaneously extract beams of multiple charge states, when adjusting the current intensity of each charge state using this method of adjusting the injection current intensity, only the total current intensity of the various charge states can be adjusted online; the current intensity of each individual charge state cannot be adjusted separately. Summary of the Invention

[0006] This invention addresses the problems of existing technologies by proton, negative hydrogen ion, and hydrogen atom three-charge beam extraction device. The purpose is to solve the problem that existing extraction devices can only extract beams of one charge state and can only adjust the total current intensity of each charge state beam online, but cannot adjust the current intensity of each charge state beam separately.

[0007] To solve its technical problems, the present invention proposes the following technical solutions:

[0008] A proton, negative hydrogen ion, and hydrogen atom triple-charged beam extraction device is characterized by the following features: a proton, negative hydrogen ion, and hydrogen atom triple-charged beam extraction device is arranged along the trajectory of the beam accelerated to the extraction energy; each triple-charged or dual-charged beam extraction device is equipped with a stripping target and / or an electrostatic deflection plate composed of stripping films of different thicknesses and positions; the stripping films at different positions are used to adjust the proportion of each component beam in real time; the different thicknesses refer to setting the stripping films to different thicknesses according to the requirements of multi-charged beam extraction; the different positions refer to the different front-to-back positions and radial positions of the multiple stripping films along the beam extraction trajectory.

[0009] Furthermore, the proton, negative hydrogen ion, and hydrogen atom triple-charge beam extraction device includes a stripping target composed of stripping film A, stripping film B, and stripping film C, and an electrostatic deflection plate; the thickness of stripping film A is the thickness at which the hydrogen atom H current is highest when hydrogen atom H is extracted; the thickness of stripping film B and stripping film C is sufficient to extract proton H. + The proportion is over 99.9%; the stripping membrane B has a rectangular through hole in the middle, which is used to control the electrostatic deflection plate so that it is not bombarded by negative hydrogen ions when passing through it.

[0010] Furthermore, the stripping target composed of stripping membrane A, stripping membrane B, and stripping membrane C has a width greater than 150% of the beam spot size to ensure that the beam passes through the stripping membrane rather than through the support at the rear end of the stripping membrane. The radial positions of the inner sides of stripping membrane A and stripping membrane B are the same, and the proportion of the proton beam can be adjusted online by adjusting the radial position of stripping membrane C.

[0011] Furthermore, the proportion of the proton beam can be adjusted online by adjusting the radial position of the stripping membrane C. Specifically, the proportion of the proton beam is lowest when the inner radius of the stripping membrane C is greater than the outer radius of the small hole in the stripping membrane B.

[0012] Furthermore, the proportion of the proton beam can be adjusted online by adjusting the radial position of the stripping membrane C. Specifically, the smaller the inner radius of the stripping membrane C, the higher the proportion of the proton beam and the lower the proportion of the hydrogen atom beam and the negative hydrogen ion beam. When the inner radius of the stripping membrane C is smaller than the inner radius of the small hole in the stripping membrane B, only the proton beam is extracted.

[0013] Furthermore, the stripping target composed of stripping membrane A, stripping membrane B, and stripping membrane C allows for online adjustment of the proportion of hydrogen atom beams by adjusting the radial position of stripping membrane A.

[0014] Furthermore, the proportion of hydrogen atom beams can be adjusted online by adjusting the radial position of the stripping film A. Specifically, the proportion of hydrogen atom beams is highest when the inner radius of the stripping film A is smaller than the inner radius of the small hole in the stripping film B.

[0015] Furthermore, the proportion of hydrogen atom beams can be adjusted online by adjusting the radial position of the stripping membrane A. Specifically, the larger the inner radius of the stripping membrane A, the lower the proportion of hydrogen atom beams and the higher the proportions of proton beams and negative hydrogen ion beams. When the inner radius of the stripping membrane A is greater than the outer radius of the small hole in the stripping membrane B or the inner radius of the stripping membrane C, the proportion of hydrogen atom beams drops to 0.

[0016] Furthermore, by simultaneously adjusting the radial positions of the stripping membrane C and the stripping membrane A, the proportion of the three charge states in the beam can be adjusted online.

[0017] Furthermore, the inner radii of stripping membrane A and stripping membrane C cannot be less than the inner radius of stripping membrane B, in order to prevent stripping membranes A and C from stripping particles that have not reached the extraction energy region trajectory in areas where the inner radius of stripping membrane B is smaller.

[0018] Advantages and effects of the present invention

[0019] 1. This invention solves the problem that existing technologies can only extract beams of a single charge state and can only adjust the total current intensity of each charge state beam online, but cannot adjust the current intensity of each charge state beam separately, by installing a stripping target and / or an electrostatic deflection plate on the beam extraction trajectory, and by installing multiple stripping films of different thicknesses, longitudinal positions, and radial positions on the stripping target, thereby adjusting the proportion of each component beam in the online manner by adjusting the radial position of each stripping film.

[0020] 2. This invention cleverly utilizes the characteristic that the sum of the current intensities of various charge states after stripping (i.e., the total current intensity) is equal to the current intensity before stripping, solving the long-standing problem of adjusting the proportion of each component beam in online, which has been difficult for those skilled in the art. Because this invention sets multiple stripping films for multiple charge states on the beam extraction track instead of just one type of stripping film, when one of the stripping films reduces the current intensity passing through it due to adjusting its radial position and cannot extract 100% of the injected current intensity, the remaining current intensity will be "absorbed" by the stripping films of other charge states on the extraction track. The reason it is "absorbed" and will not merge into the next bundle of the current stripping film is that the remaining current intensity "has somewhere to go" rather than nowhere to go. Since it "has somewhere to go," it will not continue to rotate on the accelerator extraction track and will not merge into the next bundle of the current stripping film. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a proton, negative hydrogen ion, and hydrogen atom three-charge beam extraction device according to the present invention;

[0022] Figure 2 This is a curve showing the variation of each beam component with the thickness of the stripping film during the negative hydrogen ion beam stripping process of this invention;

[0023] Figure 3 This is the peeling membrane structure of the present invention;

[0024] Figure 4a This invention is a method for adjusting the proportion of proton beams;

[0025] Figure 4b This is the second method for adjusting the proton beam ratio according to the present invention;

[0026] Figure 4c This is the third method for adjusting the proton beam ratio in this invention;

[0027] Figure 5a This is a method for adjusting the proportion of hydrogen atom beams according to the present invention;

[0028] Figure 5b This is the second method for adjusting the proportion of hydrogen atom beams in this invention;

[0029] Figure 5c This is the third method for adjusting the proportion of hydrogen atom beams in this invention; Detailed Implementation

[0030] Design principle of the invention

[0031] 1. Target Structure Design. This invention installs three stripping films on the stripping target (conventional stripping targets have only one stripping film). These three stripping films have different thicknesses, different longitudinal positions, and different radial positions. The different thicknesses are selected according to the beam requirements; each thickness results in a different current intensity for each charge state beam after stripping. The sum of the current intensities of all charge states after stripping (i.e., the total current intensity) equals the current intensity before stripping. The different longitudinal positions mean that the three stripping films are positioned sequentially along the beam trajectory. The different radial positions mean that the three stripping films are positioned along the accelerator radius.

[0032] 2. The principle of how the composition of each beam changes with the thickness of the stripped film during the negative hydrogen ion beam stripping process. For example... Figure 2As shown, in this embodiment, negative hydrogen ions are injected from the central region of the accelerator. During the stripping process, as the thickness of the stripping film increases, electrons are stripped from the negative hydrogen ions. One or two electrons are stripped from each negative hydrogen ion. After stripping one electron, it becomes a hydrogen atom beam; after stripping two electrons, it becomes a proton beam. The proportion of hydrogen atoms in the beam reaches a peak as the stripping film thickness changes, then gradually decreases. This decrease is because the total number of negative hydrogen ions gradually decreases, thus reducing the number of hydrogen atoms generated. However, while the number of hydrogen atoms decreases, some hydrogen atoms will again lose one electron, becoming protons. The number of protons stripped from hydrogen atoms gradually increases. Simultaneously, protons rarely gain electrons to become hydrogen atoms (H) or negative hydrogen ions (H-). Therefore, once the stripping film reaches a certain thickness, the beam is completely stripped into a proton beam.

[0033] 3. Principles of Multiple Release Film Thickness Design. Based on... Figure 2 The thickness of the three release films was designed based on the principle that the proportion of each component in the beam varies with different release film thicknesses. Figure 2 As shown, the horizontal axis represents the thickness of the release film, and the vertical axis represents the beam current intensity. ① When the release film thickness is 6, the current intensity of hydrogen atoms is the highest, at 60, but at this time, the negative hydrogen ion H... - and proton H + The flux intensity is only about 20. When the peel film thickness is 6, the flux intensity of hydrogen atoms is equal to that of hydrogen ions (H). - and proton H + ① The current intensity is 3 times that of hydrogen atoms; ② As the thickness of the stripping film increases, the current intensity of hydrogen atoms and negative hydrogen ions gradually decreases. When the thickness of the stripping film reaches 40, the current intensity drops to 0, but at this time the current intensity of protons reaches the highest level of close to 99.

[0034] Utilizing the above characteristics, the thickness of the stripping film for generating hydrogen atoms is designed to be close to 6, and the thickness of the stripping film for generating protons is designed to be 40. In practical applications, the thickness of the stripping film for generating protons can be as thick as possible, so that the flux density approaches 99%. Figure 2 It can be seen that the current intensity of negative hydrogen ions is at its highest (100) when the thickness of the stripping membrane on the horizontal axis is 0. Therefore, the thickness of the negative hydrogen ion stripping membrane is designed to be 0, which means that no stripping membrane is needed. However, since the electrostatic deflection plate is not bombarded by negative hydrogen ions to avoid power loss when the negative hydrogen ions reach it, a stripping membrane specifically for negative hydrogen ions is still required. The center of this stripping membrane is a rectangular window, the size of which is calculated to control the diameter of the negative hydrogen ion clusters passing through the rectangular window. This diameter ensures that the clusters do not bombard the electrostatic deflection plate when passing through it.

[0035] Figure 2 This result applies to a specific beam energy. The required thickness varies with beam energy, and the maximum intensity of the hydrogen atom beam may also differ. For example, doubling the energy might change the thickness of the hydrogen atom beam peak from 6 to 12, while a proton 99 beam might require a thickness of 80, and so on. These are all calculable and fall under existing technology. Therefore, the thicknesses of 6 and 40 mentioned here are not universally applicable to all energies.

[0036] 4. Design Principle of Multiple Release Membrane Radial Positions. These positions include longitudinal and radial positions. The longitudinal positions have no fixed order and can be reversed because the thickness of the release membrane, not its position, determines the proportion of each component beam current; changing the position does not change the thickness. The radial positions of the release membranes are used to adjust the charge proportions between the various release membranes. The radial position of each release membrane must be determined according to its required proportion and cannot be arbitrarily reversed. This radial position is the distance from the inner side of the release membrane to the accelerator center point. Since the total length of the release membrane is fixed, the width of the release membrane varies depending on the radial distance from its inner side to the accelerator center point.

[0037] 5. Replace the method of adjusting the injection beam intensity with adjusting the radial positions of multiple release films. Adjusting the radial positions of multiple release films can change the proportion of various charges, but adjusting the radial position of a single release film cannot change the current intensity of a single type of charge; instead, the current intensity can only be changed by adjusting the injection beam intensity. Because the total current intensity remains constant from input to output, for extracting a single type of beam, even if the radial position of the stripping membrane C is changed (the radial distance inside the stripping membrane C increases and the width decreases), so that most of the beam is left behind and does not pass through the stripping membrane C to become protons, and only a few beams become protons, the remaining beams are not lost but continue to rotate in the accelerator and are merged into the next beam cluster. When the next beam cluster passes through the stripping membrane C, its current intensity is not only the current intensity injected from the injection port, but also the remaining current intensity that was not extracted last time and continues to rotate in the accelerator extraction track. As the number of superpositions increases, the remaining current intensity that continues to rotate in the accelerator extraction track includes the current intensity remaining from the previous N times, until the current intensity remaining from the previous N times plus the current current intensity passing through the stripping membrane C equals the 100% injected current intensity. Since the accelerator generates millions of beam clusters per second, the process of extracting a small portion of the injected current to 100% extraction is negligible. In other words, for extracting a beam in a single-charge state, although the radial position of the stripping membrane C is moved, the extracted beam current remains unchanged; 100% of the beam is still extracted. This is because the injected current is not lost; the remaining beam is added to the next beam cluster.

[0038] However, the situation changes when extracting a multi-charged beam: the remaining beam does not continue rotating on the accelerator extraction track, but is distributed to other stripping films at different radial positions. Because these other stripping films have different thicknesses than the current stripping film, beams with different proportions and different charge states are generated. The sum of the current intensities of these beams with different proportions and different charge states equals 100% of the total injection current. Therefore, in the case of extracting a multi-charged beam, the proportions of the multi-charged beams can be adjusted by adjusting the radial position of the stripping films. Furthermore, in the case of extracting a multi-charged beam, only the radial position can be adjusted, not the injection current. This is because when adjusting the current intensity of each charge state in the multi-charged beam using this method of adjusting the injection current intensity, only the total current intensity of each charge state beam can be adjusted online, not the current intensity of each individual charge state beam.

[0039] Based on the above principles, this invention designs a beam extraction device for a proton, negative hydrogen ion, and hydrogen atom triple charge state.

[0040] A device for extracting a beam of protons, negative hydrogen ions, and hydrogen atoms in a triple-charged state, such as Figure 1 As shown, its features are: a tri-charged beam extraction device consisting of protons 4, negative hydrogen ions 6, and hydrogen atoms 5 is arranged on the trajectory 3 where the beam is accelerated to the extracted energy; each of the tri-charged or dual-charged beam extraction devices is equipped with a stripping target 1 and / or an electrostatic deflection plate 2 composed of stripping films of different thicknesses and positions. The stripping films at different positions are used to adjust the proportion of each component beam online. The different thicknesses refer to setting the stripping films to different thicknesses according to the requirements of multi-charged beam extraction; the different positions refer to the different front-to-back positions and different radial positions of the multiple stripping films on the beam extraction trajectory.

[0041] Furthermore, such as Figure 1 , Figure 3 As shown, the proton, negative hydrogen ion, and hydrogen atom triple-charge beam extraction device includes a stripping target composed of stripping film A, stripping film B, and stripping film C, and an electrostatic deflection plate; the thickness of stripping film A is the thickness at which the hydrogen atom H current is highest when hydrogen atom H is extracted; the thickness of stripping film B and stripping film C is sufficient to extract proton H. + The proportion is over 99.9%; the stripping membrane B has a rectangular through hole in the middle, which is used to control the electrostatic deflection plate so that the electrostatic deflection plate is not bombarded by negative hydrogen ions 7 and 8 when the negative hydrogen ions pass through it.

[0042] Furthermore, the stripping target composed of stripping membrane A, stripping membrane B, and stripping membrane C has a width greater than 150% of the beam spot size to ensure that the beam passes through the stripping membrane rather than through the support at the rear end of the stripping membrane. The radial positions of the inner sides of stripping membrane A and stripping membrane B are the same, and the proportion of the proton beam can be adjusted online by adjusting the radial position of stripping membrane C.

[0043] Supplementary Explanation

[0044] Peeling membranes A, B, and C are respectively mounted on membrane frames. The membrane frames are connected to the peeling target. The radial back-and-forth movement of each membrane frame is controlled by a motor or other means, and their radial positions are fed back, so as to realize the online adjustment of the radial position of each peeling membrane.

[0045] Furthermore, such as Figure 4a As shown, the proportion of the proton beam can be adjusted online by adjusting the radial position of the stripping membrane C. Specifically, the proportion of the proton beam is lowest when the inner radius of the stripping membrane C is greater than the outer radius of the small hole in the stripping membrane B.

[0046] Furthermore, such as Figure 4c As shown, the proportion of the proton beam can be adjusted online by adjusting the radial position of the stripping membrane C. Specifically, the smaller the inner radius of the stripping membrane C, the higher the proportion of the proton beam and the lower the proportion of the hydrogen atom beam and the negative hydrogen ion beam. When the inner radius of the stripping membrane C is smaller than the inner radius of the small hole in the stripping membrane B, only the proton beam is extracted.

[0047] Furthermore, the stripping target composed of stripping membrane A, stripping membrane B, and stripping membrane C allows for online adjustment of the proportion of hydrogen atom beams by adjusting the radial position of stripping membrane A.

[0048] Furthermore, such as Figure 5a As shown, the proportion of hydrogen atom beams can be adjusted online by adjusting the radial position of the stripping film A. Specifically, the proportion of hydrogen atom beams is highest when the inner radius of the stripping film A is smaller than the inner radius of the small hole in the stripping film B.

[0049] Furthermore, such as Figure 5c As shown, the proportion of hydrogen atom beams can be adjusted online by adjusting the radial position of the stripping membrane A. Specifically, the larger the inner radius of the stripping membrane A, the lower the proportion of hydrogen atom beams and the higher the proportions of proton beams and negative hydrogen ion beams. When the inner radius of the stripping membrane A is greater than the outer radius of the small hole in the stripping membrane B or the inner radius of the stripping membrane C, the proportion of hydrogen atom beams drops to 0.

[0050] Furthermore, by simultaneously adjusting the radial positions of the stripping membrane C and the stripping membrane A, the proportion of the three charge states in the beam can be adjusted online.

[0051] Furthermore, the inner radii of stripping membrane A and stripping membrane C cannot be less than the inner radius of stripping membrane B, in order to prevent stripping membranes A and C from stripping particles that have not reached the extraction energy region trajectory in areas where the inner radius of stripping membrane B is smaller.

[0052] It should be emphasized that the above specific embodiments are merely explanations of the present invention and are not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to the above embodiments without contributing any inventive step, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A proton, negative hydride ion, hydrogen atom tri-charge state beam extraction device, characterized by: On the trajectory of the beam accelerated to the extraction energy, a proton, negative hydrogen ion and hydrogen atom three-charge-state beam extraction device is arranged; the three-charge-state or double-charge-state beam extraction device is provided with a stripping target composed of stripping films with different thicknesses and different positions and / or electrostatic deflection plates, the different positions of the stripping films are used for online adjustment of the proportion of each component beam, the different thicknesses refer to that the stripping films are arranged with different thicknesses according to the requirements of multi-charge-state beam extraction, and the different positions refer to that the positions of the plurality of stripping films are different in front and back and different in radial position on the trajectory of the beam extraction. The proton, hydride ion, hydrogen atom three-charge-state beam extraction device comprises a stripping target composed of stripping films A, B and C, and an electrostatic deflection plate; the thickness of the stripping film A is the thickness at which the hydrogen atom H flow intensity is the highest when the hydrogen atom H is extracted; the thicknesses of the stripping films B and C are thick enough to make the extracted proton H + account for more than 99.9%; the stripping film B is provided with a rectangular through hole in the middle, and the rectangular through hole is used to control the electrostatic deflection plate from being bombarded by the hydride ions when the hydride ions pass through the electrostatic deflection plate.

2. The apparatus of claim 1, wherein: the apparatus is configured to produce a beam of protons, negative hydride ions, and hydrogen atoms in a triply-charged state. The stripping target composed of the stripping film A, the stripping film B and the stripping film C, the width of the stripping film A, the stripping film B and the stripping film C is greater than 150% of the beam spot size to ensure that the beam passes through the stripping film and not the rear support of the stripping film, the radial positions of the inside of the stripping film A and the stripping film B are the same, and the proportion of the proton beam is adjusted online by adjusting the radial position of the stripping film C.

3. The apparatus of claim 2, wherein: the magnetic field is configured to provide a magnetic field gradient in the direction of the beam axis; and the magnetic field gradient is configured to provide a magnetic field gradient of at least 0.1 T / cm in the direction of the beam axis. The proportion of the proton beam is adjusted online by adjusting the radial position of the stripping film C, specifically, when the inside radius of the stripping film C is greater than the outside radius of the small hole of the stripping film B, the proportion of the proton beam is the lowest.

4. The proton, negative hydrogen ion, and hydrogen atom triple-charge beam extraction device according to claim 2, characterized in that: The proportion of the proton beam is adjusted online by adjusting the radial position of the stripping film C, specifically, the smaller the inside radius of the stripping film C, the higher the proportion of the proton beam, and the lower the proportion of the hydrogen atom beam and the negative hydrogen ion beam, when the inside radius of the stripping film C is smaller than the inside radius of the small hole of the stripping film B, only the proton beam is extracted.

5. The apparatus of claim 1, wherein: the apparatus is configured to produce a beam of protons, negative hydride ions, and hydrogen atoms in a triply-charged state. The stripping target composed of the stripping film A, the stripping film B and the stripping film C adjusts the proportion of the hydrogen atom beam online by adjusting the radial position of the stripping film A.

6. The apparatus of claim 5, wherein: The proportion of the hydrogen atom beam is adjusted online by adjusting the radial position of the stripping film A, specifically, when the inside radius of the stripping film A is smaller than the inside radius of the small hole of the stripping film B, the proportion of the hydrogen atom beam is the highest.

7. The apparatus of claim 5, wherein: the magnetic field is configured to provide a magnetic field gradient in the direction of the beam axis. The proportion of the hydrogen atom beam is adjusted online by adjusting the radial position of the stripping film A, specifically, the larger the inside radius of the stripping film A, the lower the proportion of the hydrogen atom beam, and the higher the proportion of the proton beam and the negative hydrogen ion beam, when the inside radius of the stripping film A is greater than the outside radius of the small hole of the stripping film B or the inside radius of the stripping film C, the proportion of the hydrogen atom beam is reduced to 0.

8. The apparatus of claim 5, wherein: the magnetic field is configured to provide a magnetic field gradient in the direction of the beam axis. Simultaneous adjustment of the radial positions of the stripping film C and the stripping film A can realize online adjustment of the proportions of the three-charge-state beams.

9. The apparatus of claim 5, wherein: the magnetic field is configured to provide a magnetic field gradient in the direction of the beam axis. The inside radii of the stripping film A and the stripping film C cannot be smaller than the inside radius of the stripping film B, so as to prevent the stripping film A and C from stripping particles on the trajectory of the extraction energy zone which have not reached the extraction energy zone.

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