High intensity filtered magnetic field composite for radio frequency ion source

Abstract

The application discloses a high-intensity filtering magnetic field composite structure for a radio frequency ion source, which is composed of a filtering magnet array of the bottom layer of a permanent magnet array and an ion source extraction structure anode magnet arranged below the filtering magnet array; the permanent magnet array is arranged between a multi-peak field negative hydrogen ion source cylindrical ion source inner cavity and an ion source outer cavity; the filtering magnet array is used for adjusting the position with the highest filtering field strength to be in front of a plasma electrode, so that fast electrons are filtered out sufficiently before reaching the ion source extraction structure; the ion source extraction structure anode magnet is used for forming a superimposed magnetic field at the position with the highest field strength and the filtering magnet array, so as to filter out the fast electrons before the plasma electrode; the application raises the filtering field to make the highest position of the filtering field just be in front of the extraction structure, so that the fast electrons on the upper surface of the plasma electrode are filtered out in time, and thus the negative hydrogen ions generated by the surface are not damaged by the fast electrons, and the yield is improved.

Description

Technical Field

[0001] This invention belongs to the field of cyclotron technology, and particularly relates to a high-intensity filtering magnetic field composite structure for radio frequency ion sources. Background Technology

[0002] In cyclotrons, ion source technology is a key technology. An ion source is a device that ionizes neutral atoms or molecules and extracts an ion beam from them. The ion source is the source of the beam, determines the beam quality, and directly affects the performance of the cyclotron.

[0003] High-current negative hydrogen radio frequency ion sources are a type of high-yield, high-current ion source that has been widely in demand in recent years, with extraction current exceeding 100 mA. Compared with existing low-yield, low-current ion sources, the difficulty in achieving high-yield, high-current ion sources lies in:

[0004] The high yield and the relatively small magnetic field of the virtual filtering field in existing technologies contradict each other. One reason for the small magnetic field of the virtual filtering field in existing technologies is that the highest peak of the filtering field is not inside the cavity. For example, in patent number 201020700147.9, patent title: Magnet Structure for Generating Virtual Filtering Magnetic Field, the virtual filtering magnetic field is located inside the cavity, but the highest point of the filtering magnetic field strength is located on the lower surface of the plasma electrode in the lead-out area outside the cavity. (The virtual filtering magnetic field is used to filter out fast electrons while retaining slow electrons. The purpose of filtering out fast electrons is to prevent the negative hydrogen ions generated in the cavity from being destroyed by fast electrons: slow electrons and excited H atoms produce negative hydrogen ions, and fast electrons will cause the negative hydrogen ions to revert back to H atoms.) Since filtering out fast electrons depends on the strength of the filtering magnetic field in this region, when the highest point of the filtering magnetic field is not in the cavity, the number of fast electrons filtered out is insufficient. As a result, some fast electrons enter the extraction region due to inadequate filtering. Since the negative hydrogen ions in the extraction region are doped with fast electrons, the fast electrons will destroy some of the negative hydrogen ions, causing the negative hydrogen ions in the extraction region to revert to their initial state, resulting in a reduction in the yield of negative hydrogen ions in the extraction region. The second reason why the virtual filtering magnetic field in the existing technology is too small is that the latest theoretical research shows that the high-temperature excited state of H2* and 0.5 eV... The H- yield generated by the slow electron interaction is higher than the previously thought 1 eV. This requires a further increase in magnetic field strength to filter out even 1 eV electrons. However, the existing virtual filtering field magnetic field is designed to filter out 1 eV electrons. Compared to 1 eV electrons, 0.5 eV electrons can still destroy the negative hydrogen ions in the extraction region. Therefore, the existing virtual filtering field magnetic field based on filtering 1 eV is too small. The third reason for the small virtual filtering field magnetic field is that, due to the use of built-in coils, a higher feed power efficiency results in higher energy of the generated high-energy electrons. Higher energy high-energy electrons require a higher magnetic field strength. However, the maximum value of the virtual filtering field magnetic field strength in the existing ion source is low, and the highest point is not located in the cavity but in the extraction region. Therefore, the virtual filtering field magnetic field inside the cavity appears to be too small. Summary of the Invention

[0005] This invention addresses the problems existing in the prior art by proposing a high-intensity filtering magnetic field composite structure for radio frequency ion sources. The aim is to resolve the contradiction between the high yield of existing technologies and the relatively small magnetic field of the virtual filtering field in the multi-peak field of existing technologies.

[0006] The present invention adopts the following technical solution to solve its technical problem.

[0007] A high-intensity filtering magnetic field composite structure for a radio frequency ion source is characterized in that: the composite structure consists of a filter magnet array 3-1 at the bottom of a permanent magnet array 3, and an ion source extraction structure attracting magnet 4-3 arranged below the filter magnet array 3-1; the permanent magnet array 3 is arranged between the inner cavity 1-2 of the multi-peak field negative hydrogen ion source cylindrical ion source and the outer cavity 1-3 of the ion source; the filter magnet array 3-1 is used to adjust the position of the highest filtering field strength before the plasma electrode 4-1, so that fast electrons are fully filtered out before reaching the ion source extraction structure 4, and the thickness of the filtering magnetic field in the axial distribution is moderate; the ion... The source extraction structure attractor magnet 4-3 is used to form a superimposed magnetic field with the filter magnet array 3-1 at the highest field strength and filter out fast electrons before the plasma electrode 4-1; the ion source extraction structure attractor magnet 4-3 is also used to filter out slow electrons in the negative hydrogen ions entering the ion source extraction structure 4 after the plasma electrode 4-1; the permanent magnet array 3 includes a radial magnet array arranged at intervals along the circumferential direction from the top layer to the bottom layer, and a tangential magnet array at the bottom layer of the permanent magnet array 3. The bottom layer tangential magnet array is that only the bottom layer tangential magnet is retained, while the tangential magnet array above the bottom layer of the permanent magnet array (3) is removed.

[0008] Furthermore, the filter magnet array 3-1 is used to adjust the position of the highest field strength before the plasma electrode 4-1 so that fast electrons are fully filtered out before reaching the ion source extraction structure 4. Specifically, the filter magnet array 3-1 is provided to replace the two opposing radial magnets at the bottom layer of the permanent magnet array 3 with radial magnets b1 with reversed polarity, and to add tangential magnets b2 and b3 of the same polarity on both sides of the radial magnet b1 with reversed polarity, thereby raising the distance between the radial magnet b1, tangential magnet b2, tangential magnet b3 and the bottom surface, such that the raised distance is 8mm.

[0009] Furthermore, the thickness of the filtering magnetic field distributed axially is moderate, specifically: the thickness of the filtering magnetic field distributed axially is approximately 50 mm.

[0010] Furthermore, tangential magnets b4 and b5 of opposite polarities are added above the tangential magnets b2 and b3 to thin the filtering field, and the remaining radial and tangential magnets are used to form a multi-peak field confining the plasma.

[0011] Furthermore, the extraction structure is used to form a composite magnetic field with the filter magnet array b. Specifically, the ion source extraction structure 4 includes a plasma electrode 4-1, an absorber 4-2, and an absorber magnet 4-3. The absorber 4-2 has two pairs of oppositely arranged figure-eight 45-degree angled absorber magnets 4-3 embedded in the middle. The upper pair of oppositely arranged figure-eight 45-degree angled absorber magnets 4-3 each have a magnetic field component direction that is consistent with the filtering magnetic field direction of the filter magnet array 3-1, and the two magnetic fields are superimposed to form a superimposed magnetic field for filtering fast electrons.

[0012] Furthermore, the pair of opposing figure-eight 45-degree angled magnets 4-3 on the upper layer have their magnetic field components in another direction used to deflect slow electrons in the negative hydrogen beam to the magnet baffle, thereby achieving the separation of electrons and negative hydrogen ions.

[0013] Furthermore, the axial distance between the absorber 4-2 and the plasma electrode 4-1 is 3.5 mm, the absorber thickness is 15 mm (3*5 mm), and two pairs of 3*5*25 mm permanent magnets are embedded in the middle.

[0014] Advantages and effects of the present invention

[0015] 1. This invention designs a multi-peak field to confine the plasma and raises the filter field so that its highest point is just before the extraction structure. This allows fast electrons on the surface of the plasma electrode to be filtered out in time and not enter the extraction region. As a result, the negative hydrogen ions generated on the surface are not destroyed by fast electrons, thus increasing the yield.

[0016] 2. By designing the thickness of the plasma electrode and the distance between the absorber and the plasma electrode, this invention enables the magnetic field generated by the absorber magnet to be superimposed on the filtering magnetic field on or near the upper surface of the plasma. Due to the increased field strength, the superimposed filtering magnetic field can not only filter out fast electrons of 0.5 eV, but also fast electrons of 1 eV, thereby increasing the yield of negative hydrogen ions generated in both the bulk and surface regions. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the negative hydrogen ion source device of the present invention;

[0018] Figure 2 This is a schematic diagram of the built-in radio frequency antenna of the ion source of the present invention;

[0019] Figure 2a This is a schematic diagram showing that when the thickness, dielectric constant, and resistivity of the built-in antenna coating of the present invention meet certain conditions, the plasma sheath approaches zero potential.

[0020] Figure 2bThis is a schematic diagram illustrating the realization of a plasma sheath without potential in this invention;

[0021] Figure 3a A cross-sectional view of a multi-peak field magnet within a conventional multi-peak field negative hydrogen ion source;

[0022] Figure 3b This is a top view of a multi-peak field magnet in a conventional multi-peak field negative hydrogen ion source; where a is a radial magnet array and b is a tangential magnet array.

[0023] Figure 3c This is a cross-sectional view of the filter magnet array within the multi-peak field negative hydrogen ion source of the present invention;

[0024] Figure 3d This is a top view of the filter magnet array inside the multi-peak field negative hydrogen ion source of the present invention;

[0025] Figure 4a This is a cross-sectional view of the ion source extraction structure of the present invention;

[0026] Figure 4b This is a dimensional diagram of the ion source extraction structure of the present invention;

[0027] Figure 4c This is a schematic diagram of the superimposed magnetic field of the filter field of the multi-peak field negative hydrogen ion source composite structure of the present invention;

[0028] Figure 4d This is a schematic diagram of the simulated 120mA ion beam envelope extracted by the ion source extraction structure of the present invention.

[0029] Figure 4e This is a schematic diagram of the reverse magnetic field of the lower layer of the ion source extraction structure of the present invention to correct the negative hydrogen ion extraction trajectory.

[0030] In the diagram: 1: Negative hydrogen ion source; 1-1: Top cover of the ion source's built-in radio frequency antenna; 1-2: Inner cavity of the ion source; 1-3: Outer cavity of the ion source; 2: Built-in radio frequency antenna of the ion source; 3: Permanent magnet array; 4: Ion source extraction structure; 3-1: Filter magnet array; 4: Ion source extraction structure; 4-1: Plasma electrode; 4-2: Adsorber; 4-3: Adsorber magnet; 4-4: Adsorber baffle; 4-5: Plasma electrode fixing component; 4-6: Adsorber fixing component; 4-7: Ground electrode. Detailed Implementation

[0031] Design principle of the invention

[0032] Design principle of high-yield, high-current negative ion source composite structure filter field:

[0033] ① Forming a multi-peak field for confining plasma: The multi-peak field magnet of this invention includes both radial and tangential magnets (the radial magnet has its polarity pointing in the radial direction, and the tangential magnet has its polarity pointing in the tangential direction of the circle), forming a confinement field for confining plasma. The bottom layer of the multi-peak field magnet is as follows: Figure 3c As shown, there are both radial and tangential magnets, while the five layers of magnets above the bottom layer only have radial magnets and no tangential magnets. The reason why the five layers of magnets above the bottom layer only have radial magnets is that, compared with the multi-peak field previously used for filament ion sources, the built-in antenna of the radio frequency ion source generates an alternating magnetic field pointing in the direction of the inner cavity axis while generating a vortex electric field to accelerate electron collisions with hydrogen molecules or hydrogen atoms. This magnetic field can largely achieve the confinement of electrons and plasma, that is, there is no need for excessively high multi-peak field strength.

[0034] ② Formation of a filtering field for high-energy electrons: For a multi-peak field negative hydrogen ion source, the plasma cavity of the ion source is divided into two parts from top to bottom: a high-temperature discharge cavity and a low-temperature ion extraction region. In the high-temperature discharge cavity, electrons remaining in the vacuum collide with hydrogen molecules or hydrogen atoms under the acceleration of the vortex electric field generated at the radio frequency antenna, producing high-energy excited-state H2*. The excited-state H2* interacts with slow electrons in the discharge cavity to produce H-, a reaction called dissociation adsorption reaction. However, H- can be destroyed by fast electrons. Thus, the high-temperature discharge cavity and the low-temperature ion extraction region are divided into two parts by a filtering magnetic field. The role of the filtering field is to ensure that slow electrons in the discharge cavity enter the extraction region to generate negative hydrogen ions, while preventing fast electrons from entering the extraction region and destroying the already formed negative hydrogen ions. It is a crucial part of the multi-peak field negative hydrogen ion source, and its structure directly affects the yield of negative hydrogen ions.

[0035] ③ This invention elevates the filter field so that its highest point is precisely before the extraction structure. The filter field of this invention is as follows: Figure 3c , 3d As shown, where Figure 3d This is a top view of the 3C after rotating it 90 degrees clockwise. Figure 3d The filtration field shown is a transverse filtration field. Figure 3c The filter field shown employs a configuration where the three bottom magnets are of the same polarity and arranged 180 degrees apart; that is, the other end of the magnet with polarity S is the other three magnets with polarity N. Figure 3d In the transverse filtering field, the N pole is on the right and the S pole is on the left, thus forming a transverse magnetic field pointing to the left. Since the transverse magnetic field is perpendicular to the vertical magnetic field, it can intercept fast electrons. Simultaneously, the newly designed extraction structure increases the surface generation of negative hydrogen ions. To prevent fast electrons from entering the extraction structure and disrupting the negative hydrogen ions generated on the extraction structure surface, it is necessary to... Figure 3d The filtration field is raised, the filtration field is raised as... Figure 3cAs shown in the diagram, the three magnetic poles in the middle are raised. According to calculations, this invention raises the three magnets 8mm above the bottom layer. At this time, the highest point of the filter field is exactly in front of the lead-out structure.

[0036] Raising the bottom three magnetic poles ensures that the filtering magnetic field is positioned just before the extraction structure. Figure 4a As shown, this refers to the area falling on or near the upper surface of the plasma electrode 4-1. In the prior art, because the distance between the three magnetic poles and the bottom surface is not increased, and because the field strength of the attracting magnet is greater than that of the three bottom magnets, the highest point of the superimposed filtering magnetic field falls on the lower surface of the plasma electrode. Therefore, the filtering magnetic field inside the cavity is not at its highest point, resulting in a weaker filtering magnetic field in the prior art.

[0037] ④ Design principle of superimposed magnetic field: The superimposed magnetic field of the composite structure enhances the filtering field and further improves yield: The absorber magnets 4-3 are arranged in two layers in the middle of the absorber 4-2. Each layer consists of a pair of permanent magnets that are tilted to each other. When the magnetic field direction of the pair of absorber magnets 4-3 in the upper layer is consistent with the magnetic field direction of the filter magnet array 3-1 in the cavity, one of the conditions for magnetic field superposition is satisfied. The second condition for magnetic field superposition is to achieve the best superposition state of the two magnetic fields. The determination of the best superposition state of the two magnetic fields depends on the thickness of the plasma electrode 4-1 and the axial distance from the absorber 4-2 to the plasma electrode 4-1. When the thickness of the plasma electrode is thicker or the axial distance from the absorber 4-2 to the plasma electrode 4-1 is greater, the superposition of the two magnetic fields is weaker. At the same time, under the condition of a certain potential difference (the potential of the plasma electrode to ground is 60kV, and the potential of the absorber electrode to ground is 47kV), the farther the distance between the two electrodes, the smaller the influence of the electric field on the shape of the plasma sheath. However, if the distance is too close, it is easy to break down. Therefore, this invention chose a compromise: it takes into account both a good electric field and a good magnetic field, and also takes into account that it will not spark due to the close distance. Therefore, the distance between the absorber 4-2 and the plasma electrode was chosen to be 3.5 mm.

[0038] Based on the above-mentioned principles, this invention relates to a high-intensity filtering magnetic field composite structure for radio frequency ion sources.

[0039] A high-intensity filtering magnetic field composite structure for radio frequency ion sources, such as Figure 1 , Figure 3c , Figure 3d , Figure 4aAs shown, its characteristics are: the composite structure consists of a filter magnet array 3-1 at the bottom of the permanent magnet array 3, and an ion source extraction structure attracting magnet 4-3 arranged below the filter magnet array 3-1; the permanent magnet array 3 is arranged between the inner cavity 1-2 and the outer cavity 1-3 of the multi-peak field negative hydrogen ion source cylindrical ion source; the filter magnet array 3-1 is used to adjust the position of the highest point of the filter magnetic field before the plasma electrode 4-1, so that fast electrons are fully filtered out before reaching the ion source extraction structure 4, and the thickness of the filter magnetic field in the axial distribution is moderate; the ion source extraction structure attracting magnet 4-3... -3 is used to form a superimposed magnetic field with the filter magnet array 3-1 at the highest point of the filter magnetic field, and to filter out fast electrons before the plasma electrode 4-1; the ion source extraction structure attractor magnet 4-3 is also used to filter out slow electrons in the negative hydrogen ions entering the ion source extraction structure 4 after the plasma electrode 4-1; the permanent magnet array 3 includes a radial magnet array arranged at intervals along the circumferential direction from the top layer to the bottom layer, and a tangential magnet array at the bottom layer of the permanent magnet array 3. The bottom layer tangential magnet array is that only the bottom layer tangential magnet is retained, while the tangential magnet array above the bottom layer of the permanent magnet array 3 is removed.

[0040] Furthermore, such as Figure 3c As shown, the filter magnet array 3-1 is used to adjust the position of the highest field strength before the plasma electrode 4-1 so that fast electrons are fully filtered out before reaching the ion source extraction structure 4. Specifically, the filter magnet array 3-1 is provided with replacing the two opposing radial magnets at the bottom layer of the permanent magnet array 3 with radial magnets b1 with reversed polarity, and adding tangential magnets b2 and b3 of the same polarity on both sides of the radial magnet b1 after polarity reversal, raising the distance between the radial magnet b1, tangential magnet b2, tangential magnet b3 and the bottom surface, so that the raised distance is 8mm.

[0041] Supplementary Note 1:

[0042] The difference between this invention and the prior art is that the tangential magnet in the prior art penetrates from the upper layer to the lower layer, such as... Figure 3a The image shown is a cross-sectional view of a prior art multi-peak field magnet array, while the present invention... Figure 3c As shown, all tangential magnets above the bottom layer are removed, leaving only the radial magnets from the bottom to the top layer. This is because the prior art uses a filament as the electric field, while this invention uses a built-in radio frequency antenna. When alternating current is applied to the built-in radio frequency antenna, the magnetic field direction is vertical. The vertical magnetic field already serves to confine the beam to the axial centerline, so relatively speaking, retaining the radial magnets is sufficient for the multi-peak magnetic field value.

[0043] Furthermore, the thickness of the filtering magnetic field distributed axially is moderate, specifically: the thickness of the filtering magnetic field distributed axially is approximately 50 mm.

[0044] Furthermore, such as Figure 3c As shown, tangential magnets b4 and b5 of opposite polarities are added above the tangential magnets b2 and b3 to thin the filtering field, and the remaining radial and tangential magnets are used to form a multi-peak field confining the plasma.

[0045] Furthermore, such as Figure 4a As shown, the ion source extraction structure is used to form a composite magnetic field with the filter magnet array 3-1. Specifically, the ion source extraction structure 4 includes a plasma electrode 4-1, an absorber electrode 4-2, and an absorber magnet 4-3. The absorber electrode 4-2 has two pairs of oppositely arranged figure-eight 45-degree angled absorber magnets 4-3 embedded in the middle. The upper pair of oppositely arranged figure-eight 45-degree angled absorber magnets 4-3 each have a magnetic field component direction that is consistent with the filtering magnetic field direction of the filter magnet array 3-1, and the two magnetic fields are superimposed to form a superimposed magnetic field for filtering fast electrons.

[0046] Supplementary Note 2:

[0047] The highest point of the filtering magnetic field is not marked in the attached diagram. It is roughly located on the upper surface of the plasma electrode or in the area slightly above it. Raising it by 8 mm does not mean raising the highest point of the filtering magnetic field by 8 mm, but rather that by raising it by 8 mm, the highest point of the filtering magnetic field changes from below (near the lower surface) of the plasma electrode to above the plasma electrode, including the upper surface of the plasma electrode or the area near the upper surface. The significance of this is to intercept fast electrons before they enter the extraction structure, ensuring that the already generated negative hydrogen ions entering the extraction structure are not destroyed by the fast electrons in the extraction structure.

[0048] Furthermore, such as Figure 4c As shown, the lower layer has a pair of opposite figure-eight 45-degree tilting magnets 4-3. The magnetic field component in the other direction of each magnet is used to deflect the slow electrons in the negative hydrogen beam to the magnet baffle, thereby achieving the separation of electrons and negative hydrogen ions.

[0049] Supplementary Note 3:

[0050] like Figure 4cAs shown, the composite structure filter field of this invention aims to filter out two types of electrons: fast electrons and slow electrons. The need to filter slow electrons arises because after slow electrons combine with excited hydrogen atoms to generate negative hydrogen ions, a large number of slow electrons remain and mix into the negative hydrogen ion clusters, entering the extraction structure. To prevent slow electrons from doping into the negative hydrogen ions, it is necessary to filter out the slow electrons in the extraction structure as well. Therefore, the attracting magnets are arranged in a V-shape to generate a magnetic field component, with the horizontal magnetic field component used to filter out slow electrons. Although the direction of the slow electron filtering magnetic field is the same as that of the fast electron filtering magnetic field, their physical locations are different. At the slow electron filtering magnetic field, because it is inside the extraction structure, while fast electrons have already been filtered out before the extraction structure, i.e., before the plasma electrode, the filtering magnetic field at this location can only filter slow electrons.

[0051] Furthermore, such as Figure 4b As shown, the axial distance between the absorber 4-2 and the plasma electrode 4-1 is 3.5 mm, the absorber thickness is 15 mm (3*5 mm), and two pairs of 3*5*25 mm permanent magnets are embedded in the middle.

[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 high-intensity filtered magnetic field composite structure for a radio frequency ion source, characterized by: The composite structure consists of a filter magnet array (3-1) at the bottom of a permanent magnet array (3), and an ion source extraction structure attractor magnet (4-3) arranged below the filter magnet array (3-1); the permanent magnet array (3) is arranged between the inner cavity (1-2) and the outer cavity (1-3) of the multi-peak field negative hydrogen ion source cylindrical ion source; the filter magnet array (3-1) is used to adjust the position of the highest filtering field strength before the plasma electrode (4-1), so that fast electrons are fully filtered out before reaching the ion source extraction structure (4), and the thickness of the filtering magnetic field in the axial distribution is moderate; the ion source extraction structure attractor magnet (4-1) 3) Used to form a superimposed magnetic field with the filter magnet array (3-1) at the highest field strength and filter out fast electrons before the plasma electrode (4-1); the ion source extraction structure attractor magnet (4-3) is also used to filter out slow electrons in the negative hydrogen ions entering the ion source extraction structure (4) after the plasma electrode (4-1); the permanent magnet array (3) includes a radial magnet array arranged at intervals along the circumferential direction from the top layer to the bottom layer, and a tangential magnet array at the bottom layer of the permanent magnet array (3), wherein the bottom layer tangential magnet array is one that retains only the bottom layer tangential magnets and removes the tangential magnet arrays above the bottom layer of the permanent magnet array (3).

2. The high-strength filtered magnetic field composite structure for a radio frequency ion source of claim 1, wherein: The filter magnet array (3-1) is used to adjust the position of the highest field strength before the plasma electrode (4-1) so that fast electrons are fully filtered out before reaching the ion source extraction structure (4). Specifically, the filter magnet array (3-1) is provided to replace the two opposing radial magnets at the bottom layer of the permanent magnet array (3) with radial magnets (b1) with reversed polarity, and to add tangential magnets (b2) and tangential magnets (b3) of the same polarity on both sides of the radial magnets (b1) with reversed polarity, thereby raising the distance between the radial magnets (b1), tangential magnets (b2), tangential magnets (b3) and the bottom surface, such that the raised distance is 8mm.

3. The high-strength filtered magnetic field composite structure for a radio frequency ion source of claim 2, wherein: The thickness of the filtering magnetic field distributed axially is moderate, specifically: the thickness of the filtering magnetic field distributed axially is approximately 50 mm.

4. The high-strength filtered magnetic field composite structure for a radio frequency ion source of claim 1, wherein: Tangential magnets (b4) and (b5) of opposite polarity are added above the tangential magnets (b2) and (b3) to thin the filtering field, and the remaining radial and tangential magnets are used to form a multi-peak field confining the plasma.

5. The magnet structure for generating a virtual filtered magnetic field according to claim 1, wherein: The extraction structure is used to form a composite magnetic field with the filter magnet array b. Specifically, the ion source extraction structure (4) includes a plasma electrode (4-1), an absorber (4-2), and an absorber magnet (4-3). The absorber (4-2) has two pairs of oppositely arranged figure-eight 45-degree angled absorber magnets (4-3) embedded in the middle. The pair of oppositely arranged figure-eight 45-degree angled absorber magnets (4-3) in the upper layer have magnetic field components in one direction that are consistent with the direction of the filter magnetic field of the filter magnet array (3-1), and the two magnetic fields are superimposed to form a superimposed magnetic field for filtering fast electrons.

6. The magnet structure for generating a virtual filtered magnetic field according to claim 5, wherein: The upper layer of a pair of opposite splayed 45 degree angle of the absorbing magnet (4-3), their respective other direction magnetic field component for the slow electron beam of negative hydrogen deflection to the absorbing baffle, the realization of electron and negative hydrogen ion separation.

7. The magnet structure for generating a virtual filtered magnetic field according to claim 5, wherein: The distance between the absorbing electrode (4-2) and the plasma electrode (4-1) is 3.5 mm, the thickness of the absorbing electrode is 15 mm (3*5 mm), and two pairs of 3*5*25 mm permanent magnets are embedded in the middle.

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