A pulse mode multi-peak field built-in antenna radio frequency high-current negative hydrogen ion source

Abstract

The present invention discloses a pulse mode multi-peak field built-in antenna type radio frequency high-current negative hydrogen ion source, comprising: an ion source built-in radio frequency antenna, a radio frequency antenna upper cover, an inner cavity, an outer cavity, a permanent magnet array located between the inner cavity and the outer cavity, an ion source extraction structure, and an ion source composite structure filter field located at the bottom of the permanent magnet array and the ion source extraction structure. The characteristics are: the ion source built-in radio frequency antenna is an enamel-coated built-in radio frequency antenna capable of achieving a potential-free plasma sheath; the composite structure filter field is a composite structure filter field in which a magnetic field is superimposed at the highest point of the filter field to filter fast electrons; the ion source extraction structure is an ion source extraction structure that extracts a negative hydrogen current intensity greater than 100mA under a high voltage of 60kV. The present invention achieves high-yield extraction of negative hydrogen ions and solves the bottleneck problems encountered in high-yield extraction, such as the relatively short life of the built-in antenna, the limited space for generating negative hydrogen ions, and the relatively small magnetic field of the multi-peak field virtual filter field.

Description

Technical Field

[0001] The present invention belongs to the technical field of radio frequency ion sources, and in particular relates to a pulse mode multi-peak field built-in antenna type radio frequency high-current negative hydrogen ion source. Background Art

[0002] Ion source technology is a key component of cyclotron accelerators. An ion source is a device that ionizes neutral atoms or molecules and extracts an ion beam from them. As the source of the beam, the ion source determines beam quality and directly impacts cyclotron performance.

[0003] The high-current negative hydrogen radio frequency ion source is a high-yield, high-current ion source that has been widely demanded in recent years. Its extraction current is above 100mA. Compared with the low-yield, low-current ion sources in the existing technology, the difficulties in achieving a high-yield, high-current ion source are:

[0004] One of the difficulties is the contradiction between high-yield extraction and the relatively short lifespan of the internal antenna. High-yield extraction first requires high power efficiency of the ion source's RF antenna (the ion source's RF antenna is used to generate a vortex electric field. Residual electrons in a vacuum collide with hydrogen molecules or atoms under the acceleration of the ion source's RF antenna electric field to produce negative hydrogen ions). To address the low power utilization efficiency and weak extraction flux of traditional external-antenna RF ion sources, those skilled in the art have attempted to replace them with internal-antenna RF ion sources. This is because the internal antenna is in direct contact with the plasma, resulting in high power feed efficiency and a strong extraction flux. However, this direct contact with the plasma also creates a plasma sheath: any charged object in direct contact with the plasma will generate a sheath. The sheath is the dynamic inflow and outflow of particles. This dynamic sheath constantly impacts the antenna, shortening its lifespan. External coils, on the other hand, do not generate a sheath because they do not contact the plasma.

[0005] The second difficulty is that the high yield extraction and the limited space for the generation of negative hydrogen ions are in conflict. Existing technologies such as Patent No. 201020700147.9, Patent Name: Magnet Structure for Generating Virtual Filtering Magnetic Field, can only generate negative hydrogen ions in the cavity (1) without any other generation methods, such as its attached Figure 1 As shown, the plasma electrode (located at the end of the chamber, immediately adjacent to the chamber) has no angled entrance, and its inlet and outlet are vertically perpendicular. Therefore, negative hydrogen ions are generated in the body, not the surface. To increase output, the feed power must be increased, which in turn increases material and manufacturing costs. Without increasing costs, the ion source's output will be limited to its current level and cannot be increased further.

[0006] The third difficulty is the conflict between high yield and the relatively small magnetic field of the multi-peak virtual filter field in existing technologies. One reason for the small virtual filter field is that the highest peak of the filter field is not within the cavity. Existing technologies, such as Patent No. 201020700147.9, titled "Magnet Structure for Generating a Virtual Filter Magnetic Field," have a virtual filter magnetic field located within the cavity, but the highest point of its magnetic field intensity is located outside the cavity, on the lower surface of the plasma electrode in the extraction region. (The virtual filtering magnetic field is used to filter out fast electrons and retain 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 turn negative hydrogen ions into H atoms again). Since filtering out electrons depends on the magnetic field strength of the area (the magnetic field changes direction from vertical to horizontal, thereby intercepting the fast electrons moving vertically downward), when the highest point of the magnetic field strength is not in the cavity, the block electrons filtered out are not sufficient, and some fast electrons enter the extraction area due to inadequate filtering. Since the negative hydrogen ions in the extraction area are doped with fast electrons, the fast electrons will destroy some of the negative hydrogen ions, causing the negative hydrogen ions in the extraction area to return to their initial state, resulting in a decrease in the yield of negative hydrogen ions in the extraction area. The second reason why the virtual filtering field is relatively small is: the latest theoretical research shows that high temperature The H- yield produced by the interaction between the excited H2* and the 0.5eV slow electrons is higher, rather than the previously believed 1eV. This requires further increasing the magnetic field strength to filter out the 1eV electrons. The existing virtual filtering field is designed based on filtering out 1eV electrons. Compared with 0.5eV electrons and 1eV electrons, 1eV electrons can still destroy the negative hydrogen ions in the extraction area. Therefore, the virtual filtering field magnetic field based on filtering 1eV in the existing technology appears to be relatively small; the third reason for the small virtual filtering field magnetic field is: due to the use of built-in coils, the feed power efficiency is high, and the energy of the high-energy electrons generated is higher. The higher energy of high-energy electrons requires higher magnetic field strength, and the maximum value of the virtual filtering field magnetic field strength of the ion source in the existing technology is relatively low, and the highest point is not located in the area inside the cavity but in the extraction area, so the virtual filtering field magnetic field in the cavity appears to be relatively small.

[0007] The fourth difficulty is the contradiction between high yield and space charge effect. High-yield extraction means that a large amount of plasma is generated in the extraction area of ​​the ion source. When a large amount of plasma is extracted, the space charge effect will be very significant, making the beam emittance larger and the divergence larger. The plasma sheath affects and determines the shape of the plasma emission surface, which places higher requirements on the extraction structure. When the spacing, angular size, thickness of the extraction end, shape of the extraction electrode, thickness and shape of the ground level in the extraction structure are not properly designed, the plasma sheath will affect the shape of the emission surface: the emission surface shape is divergent or over-focused. When the emission surface shape is divergent, the divergent beam will hit the pipe receiving the beam at the application end. When the emission surface shape is over-focused, the beam will still diverge in the subsequent path, which is also undesirable. Summary of the Invention

[0008] In response to the problems existing in the prior art, the present invention proposes a pulse mode multi-peak field built-in antenna type radio frequency high-current negative hydrogen ion source, aiming to solve the contradiction between the yield extraction of the prior art high-current negative hydrogen multi-peak field radio frequency ion source and the relatively short life of the built-in antenna, the contradiction between high yield extraction and the limited space for negative hydrogen ion generation, the contradiction between high yield and the small magnetic field of the prior art multi-peak field virtual filter field, and the contradiction between high yield and space charge effect.

[0009] The present invention proposes the following technical solutions to solve the technical problems:

[0010] A pulse mode multi-peak field built-in antenna type radio frequency high-current negative hydrogen ion source 1, which comprises, from top to bottom and from outside to inside: an ion source built-in radio frequency antenna 2, an ion source built-in radio frequency antenna upper cover plate 1-1, an ion source inner cavity 1-2, an ion source outer cavity 1-3, a permanent magnet array 3 located between the ion source inner cavity 1-2 and the ion source outer cavity 1-3, an ion source extraction structure 4, an ion source composite structure filtration field located at the bottom of the permanent magnet array and the ion source extraction structure, the ion source composite structure filtration field consisting of a filtering magnet array 3-1 and an attracting magnet 4-3 of the ion source extraction structure; the ion source built-in The RF antenna 2 is externally connected to a dual-frequency drive system, which is connected to the built-in RF antenna 2 located on the upper cover via an impedance matching and isolation system, and its RF power is coupled to the ion source cavity 1-2 through the built-in RF antenna 2; the ion source built-in RF antenna 2 is used to generate a vortex electric field, so that the free electrons remaining in the air collide with the hydrogen gas introduced into the ion source under the action of the electric field to generate negative hydrogen ions; the permanent magnet array 3 is used to provide a confining magnetic field for the ion source cavity 1-2; the ion source composite structure filter field is used to form a transverse magnetic field to filter fast electrons and filter slow electrons respectively;

[0011] Its characteristics are: the built-in radio frequency antenna 2 of the ion source is a built-in radio frequency antenna with an enamel coating that can achieve potential-free plasma sheath; the composite structure filter field is a composite structure filter field in which a magnetic field is superimposed at the highest point of the filter field to filter fast electrons; the ion source extraction structure 4 is an ion source extraction structure that extracts a negative hydrogen current intensity higher than 100mA under a high voltage of 60kV.

[0012] Furthermore, the ion source built-in RF antenna 2 is a built-in RF antenna with an enamel coating that can achieve potential-free plasma sheath. Specifically, the ion source built-in RF antenna 2 has 2.5-3.5 turns, an average winding diameter of 58 mm, a leg spacing of the straight parts at both ends of the coil is 25 mm, and the height of the spiral winding part of the coil is 40 mm-50 mm; the coating of the ion source built-in RF antenna 2 is an enamel structure. When the enamel structure simultaneously meets the conditions of a coating thickness of 0.6-0.7 mm, a relative dielectric constant of less than 30, and a coating resistivity greater than 45,000 Ω.cm, the plasma sheath is close to potential-free; the glaze of the enamel structure includes the following substances in parts by mass: 95-105 parts of base glaze, 4-8 parts of clay, 1-5 parts of quartz, 0.1-0.8 parts of urea, 0.1-0.5 parts of nitrite, and 45-55 parts of water.

[0013] Furthermore, the enamel structure is an enamel structure from which metal oxides used for coloring are removed, so as to reduce the relative dielectric constant of the coating; and the dielectric breakdown strength of the enamel structure exceeds 3 kV / mm.

[0014] Furthermore, the composite structure filter field is a composite structure filter field that superimposes a magnetic field at the highest point of the filter magnetic field to filter fast electrons. Specifically, the composite structure filter field includes a filter magnet array 3-1 at the bottom of the permanent magnet array arranged between the cylindrical ion source inner cavity 1-2 of the multi-peak field negative hydrogen ion source and the ion source outer cavity 1-3, and an ion source extraction structure attracting magnet 4-3 arranged at the bottom of the ion source cavity below the filter magnet array 3-1; 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, so that the fast electrons are fully filtered out before reaching the extraction structure, and the filter magnetic field is distributed axially. The thickness is moderate; the extraction structure attraction magnet 4-3 is used to form a superimposed magnetic field with the filtering magnet array 3-1 at the highest field strength to filter out the fast electrons before the plasma electrode 4-1; the extraction structure attraction magnet 4-3 is also used to filter out the 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 radial magnet arrays arranged from the top layer to the bottom layer at intervals along the circumferential direction, and the tangential magnet array at the bottom layer of the permanent magnet array 3, and the tangential magnet array at the bottom layer is to retain only the tangential magnets at the bottom layer and remove the tangential magnet array above the bottom layer of the permanent magnet array 3.

[0015] Furthermore, the filtering magnet array 3-1 is provided with a configuration in which the two opposing radial magnets at the bottom layer of the permanent magnet array 3 are replaced with radial magnets b1 with reversed polarity, and tangential magnets b2 and b3 of the same polarity are added on both sides of the radial magnets b1 after the polarity is reversed, and the distance between the radial magnets b1, b2, and b3 and the bottom surface is raised to 8 mm; 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 last layer of radial magnets and tangential magnets is used to form a multi-peak field for confining plasma.

[0016] Furthermore, the thickness of the filtering magnetic field in the axial distribution is moderate, specifically: the thickness of the filtering magnetic field in the axial distribution is about 50 mm.

[0017] Furthermore, the ion source extraction structure 4 is used to form a superimposed magnetic field with the filtering magnet array 3-1 at the highest field strength to filter out fast electrons before the plasma electrode. Specifically, the ion source extraction structure 4 includes a plasma electrode 4-1, an attracting pole 4-2, and an attracting pole magnet 4-3. Two pairs of upper and lower oppositely arranged figure-eight attracting pole magnets 4-3 with a 45-degree inclination are embedded in the middle of the attracting pole 4-2. The upper pair of oppositely arranged figure-eight attracting pole magnets 4-3 with a 45-degree inclination have a magnetic field component in one direction that is consistent with the filtering magnetic field direction of the filtering magnet array 3-1, and the two magnetic fields are superimposed together, thereby forming a superimposed magnetic field for filtering fast electrons; the upper pair of oppositely arranged figure-eight attracting pole magnets 4-3 with a 45-degree inclination have a magnetic field component in another direction that is used to deflect slow electrons in the negative hydrogen beam to the attraction baffle, thereby realizing the separation of electrons and negative hydrogen ions.

[0018] Furthermore, the axial distance between the suction electrode 4-2 and the plasma electrode 4-1 is 3.5 mm, the thickness of the suction electrode is 15 mm (3*5 mm), and two pairs of 3*5*25 mm permanent magnets are embedded in the middle.

[0019] Furthermore, the ion source extraction structure 4 is an ion source extraction structure that extracts a negative hydrogen current intensity higher than 100mA under a high voltage of 60kV, specifically: the ion source extraction structure 4 is provided with a plasma electrode 4-1, an attracting electrode 4-2, an attracting electrode magnet 4-3, an attracting level baffle 4-4, a plasma electrode fixing part 4-5, an attracting electrode fixing part 4-6, and a grounding level 4-7, which are arranged in sequence along the axial direction at the bottom of the ion source cavity; the plasma electrode 4-1 is used to receive particles to be extracted and allow the particles to pass through the middle opening, and the entrance side of the opening is provided with an angled inclined surface, the upper surface of the angled inclined surface is coated with a boron-doped diamond film, and the angled inclined surface is used for the surface generation of negative hydrogen ions; the The suction level 4-2 is used to improve the envelope shape of the negative hydrogen ion extraction so that the envelope shape neither diverges nor contracts. The suction level 4-2 has a sharp corner extending toward the lower surface of the plasma electrode; the suction pole magnet 4-3 is used to guide the trajectory of the negative hydrogen ion extraction into a straight trajectory and deflect the electrons in the negative hydrogen beam to the suction level baffle; the suction pole magnet 4-3 is arranged in two layers in the middle of the suction pole 4-2, each layer being a pair of permanent magnets inclined to each other; the ground electrode is used to form a voltage field for the extraction of negative hydrogen ions with the plasma electrode; wherein the electrodes are separated by an insulator, and an adjustable suction level voltage is applied between the suction pole 4-2 and the plasma electrode 4-1 to adjust the beam distribution.

[0020] Furthermore, the pole magnet 4-3 is divided into two layers, upper and lower, arranged in the middle of the pole magnet 4-2, and each layer is a pair of permanent magnets tilted to each other, specifically: the pair of permanent magnets in the upper layer are in an eight-shaped shape, each at a 45-degree angle to the plasma electrode plane, and the pair of permanent magnets in the lower layer are in an inverted eight-shaped shape, and each at a 45-degree angle to the plasma electrode plane. The magnetic field direction of the pair of permanent magnets in the lower layer is opposite to that of the pair of permanent magnets in the upper layer. The pair of permanent magnets in the lower layer with opposite magnetic field directions are used to correct the extraction direction of negative hydrogen ions.

[0021] Furthermore, the opening angle of the middle of the plasma electrode 4-1 is 45°, the thickness is 4 mm, the aperture is 16 mm, and there is a 1 mm*1 mm groove, and its voltage to ground is 60 kV.

[0022] Furthermore, the axial distance between the suction electrode 4-2 and the plasma electrode 4-1 is 3.5mm, the thickness is 15mm (3*5mm), and two pairs of 3*5*25mm permanent magnets are embedded in the middle; its first aperture is 12mm, the axial distance between the sharp corner and the plasma electrode is 1mm, and the aperture at the protruding point of the sharp corner is 17mm; the second aperture is 15mm; the third aperture is 16mm, which is a rounded corner, and its voltage to ground is 47-50kV, that is, the suction voltage between the plasma electrode and the suction stage is 10-13kV.

[0023] Furthermore, the thickness of the ground electrode is 5 mm, and the axial distance from the absorption electrode is 13.5 mm.

[0024] Advantages and effects of the present invention

[0025] 1. The present invention provides a built-in radio frequency antenna with an enamel coating for a radio frequency negative hydrogen ion source. Based on the working principle of the radio frequency ion source, the present invention meets the technical requirements of isolating the built-in radio frequency antenna from the potential difference with the plasma, insulating the coils and between the antenna and the inner cavity to prevent breakdown, and extending the working life. This effectively solves the problem of plasma back-bombardment of the antenna and increases the service life of the radio frequency antenna.

[0026] 2. The present invention achieves a potential-free plasma sheath by simultaneously configuring an antenna structure and an enamel structure that meet the requirements for coating thickness, relative dielectric constant, coating resistivity, and the mass composition ratios of the enamel glaze, thereby fundamentally resolving the problem of plasma bombardment antennas. Currently, the few coatings that meet these requirements for antenna coatings are mostly ceramic structures, which are expensive, complex to manufacture, brittle, and have poor adhesion to metals. The coating employed in the present invention, however, is a commonly used enamel coating that is low in cost, simple to manufacture, and durable, with excellent adhesion, impact resistance, and thermal shock resistance. Furthermore, the enamel structure employed in the present invention, originally used for water heater inner tanks, not only meets the aforementioned coating requirements but also possesses strong water resistance, i.e., low porosity, which perfectly meets the requirements for antenna coatings and greatly facilitates the creation of a vacuum environment within the ion source.

[0027] 3. The present invention achieves the replacement of ceramic coating with enamel coating by setting the number of antenna coils to 2.5-3.5, the average coil diameter to 58 mm, and the enamel structure simultaneously meeting the requirements of a coating thickness of 0.6-0.7 mm, a relative dielectric constant of less than 30, and a coating resistivity greater than 45,000 Ω.cm. In addition, the enamel structure comprises a glaze material comprising 95-105 parts by weight of base glaze, 4-8 parts of clay, 1-5 parts of quartz, 0.1-0.8 parts of urea, 0.1-0.5 parts of nitrite, and 45-55 parts of water. This significantly reduces costs: for a built-in RF antenna of the same specifications, the cost of using ceramic coating would be tens of thousands of yuan, while using enamel coating would be hundreds of yuan, a 100-fold difference, reducing the cost to one percent of the original cost.

[0028] 4. The technical solution provided by the present invention designs an ion source multi-peak field magnet structure layout with a grade-attracting magnet that can generate a virtual filtering field. It can not only well confine the plasma in the RF ion source, but also form a virtual filtering magnetic field that can well filter fast electrons with moderate lateral strength and thickness.

[0029] 5. The present invention designs a multi-peak field for confining plasma and raises the filtering field so that its highest point is just before the extraction structure, so that the fast electrons on the surface of the plasma electrode are filtered out in time and do not enter the extraction area. As a result, the negative hydrogen ions generated on the surface will not be destroyed by the fast electrons, thereby improving the yield.

[0030] 6. The present invention designs the thickness of the plasma electrode and the distance between the attracting electrode and the plasma electrode so that the magnetic field generated by the attracting electrode magnet can be superimposed on the filtering magnetic field on the upper surface of the plasma or near the upper surface. The superimposed filtering magnetic field has an increased field strength and can filter out not only 0.5eV fast electrons, but also 1eV fast electrons, thereby increasing the yield of negative hydrogen ions generated in the body and on the surface.

[0031] 7. This invention addresses the technical requirements for high-current negative hydrogen multi-peak field radiofrequency ion source high-voltage extraction and high-current extraction. It solves the problem of extracting negative hydrogen currents exceeding 100mA at 60kV, improves the quality of the ion source's extracted beam, and thus enhances accelerator performance. This current intensity reaches leading domestic standards.

[0032] 8. The present invention aims at the technical requirements of high-current negative hydrogen multi-peak field radio frequency ion source high-voltage extraction and high-current extraction. By adding an inclined surface on the plasma electrode of the extraction structure, the negative hydrogen ions are transformed from body generation to body generation + surface generation, thereby increasing the yield and solving the problem of extracting a negative hydrogen current intensity higher than 100mA at a high voltage of 60kV.

[0033] 9. The present invention designs the thickness of the suction electrode and the axial distance between the suction electrode and the plasma electrode to be minimum under the conditions of cooling and avoiding breakdown, so that the suction electrode magnetic field can be superimposed on the highest point of the filtering magnetic field on the upper surface of the plasma electrode, thereby improving the output. The current intensity index reaches the domestic leading level.

[0034] 10. The present invention designs the tip of the absorption pole so that the tip is 1 mm away from the plasma electrode, which effectively improves the divergence of the beam emission surface caused by the space charge effect and makes the beam emission surface closer to a straight line. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the negative hydrogen ion source device of the present invention;

[0036] Figure 2 This is a schematic diagram of the built-in radio frequency antenna of the ion source of the present invention;

[0037] Figure 2a This is a schematic diagram of the plasma sheath approaching potential-free state when the coating thickness, dielectric constant, and resistivity of the built-in antenna of the present invention meet certain conditions;

[0038] Figure 2b This is a schematic diagram of realizing potential-free plasma sheath in the present invention;

[0039] Figure 3a This is a cross-sectional view of a multi-peak field magnet in a multi-peak field negative hydrogen ion source in the prior art;

[0040] Figure 3b This is a top view of the multi-peak field magnet in the prior art multi-peak field negative hydrogen ion source; a is the radial magnet array, b is the tangential magnet array;

[0041] Figure 3c A cross-sectional view of the filtering magnet array within the multi-peak field negative hydrogen ion source of the present invention;

[0042] Figure 3dA top view of the filter magnet array within the multi-peak field negative hydrogen ion source of the present invention;

[0043] Figure 4a It is a cross-sectional view of the extraction structure of the ion source of the present invention;

[0044] Figure 4b The figure shows the structure and dimensions of the ion source of the present invention;

[0045] Figure 4c Schematic diagram of the superimposed magnetic field of the multi-peak field negative hydrogen ion source composite structure filtering field of the present invention;

[0046] Figure 4d This is a schematic diagram of the 120mA ion simulation beam envelope drawn out by the ion source extraction structure of the present invention.

[0047] Figure 4e Schematic diagram of the negative hydrogen ion extraction trajectory corrected by the reverse magnetic field of the lower polar magnet of the ion source extraction structure of the present invention;

[0048] In the figure: 1: negative hydrogen ion source; 1-1: upper cover of built-in radio frequency antenna of ion source; 1-2: inner cavity of ion source; 1-3: outer cavity of ion source; 2: built-in radio frequency antenna of 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: suction electrode; 4-3: suction electrode magnet; 4-4: suction level baffle; 4-5: plasma electrode fixing part; 4-6: suction electrode fixing part; 4-7: ground level. DETAILED DESCRIPTION

[0049] Design principle of the present invention

[0050] 1. Design of a high-yield, high-current negative hydrogen built-in RF antenna: ① The relationship between the coil structure design and the coil coating design: When an alternating current is passed through the coil to generate a vortex electric field for accelerating electrons, the antenna itself will generate a self-inductance voltage. According to research, the antenna self-inductance voltage must be maintained by the coating and the plasma sheath to maintain the potential, that is, the voltage of the antenna coating and the plasma sheath must jointly limit the self-inductance voltage. At the same time, a relatively low plasma sheath potential difference can reduce the sputtering of ions from the plasma on the antenna coating and increase the service life of the RF antenna. Therefore, it is hoped that the plasma sheath has no potential difference, the potential is limited to the coating, and breakdown between the antenna and the inner cavity is avoided. At this time, the design of the built-in RF antenna requires the structure of the built-in coil and the coating of the built-in coil. The structural design of the built-in coil determines the size of the self-inductance voltage. Only by predicting the size of the self-inductance voltage can breakdown be avoided, and the design of the built-in coil coating determines how to make the plasma sheath potential-free. ② Design of the Built-in RF Antenna: The design of the present invention's built-in antenna includes two aspects. First, the coil structure. Research has shown that in an inductively coupled plasma (ICP) RF ion source, the RF current flowing through the RF antenna induces an RF vortex electric field coaxial with the coil. This vortex electric field causes residual electrons in the cavity to perform a reciprocating cyclotron motion, colliding with gas molecules and ionizing them, ultimately generating plasma. When the RF frequency is selected, the magnitude of the vortex electric field depends solely on the coil's diameter and number of turns. Therefore, the primary parameters in antenna design are the loop diameter and number of turns. Specifically: the number of turns of the built-in RF antenna 2 of the ion source is 2.5-3.5 turns, the average diameter of the coil is 58mm, the leg spacing of the straight parts at both ends is 25mm, and the height of the spiral coil part is 40mm-50mm; second, the design of the coil coating: According to research, the impedance distribution of the plasma sheath and the insulating coating is capacitance and resistance in parallel. Referring to the numerical calculation model of fusion plasma and replacing the parameters with typical ion source parameters, and using numerical algorithms for calculation, it can be finally calculated that if the plasma sheath is to have no voltage distribution, it should meet the following requirements at the same time: the coating thickness is greater than 0.4mm, the relative dielectric constant is less than 30, the coating resistivity is greater than 45000Ω.cm, and the dielectric breakdown strength exceeds 3kV / mm. For most enamels, the ideal resistivity is about 10 14 Ω.cm, with an average dielectric breakdown strength of approximately 10kV / mm. After removing the metal oxide used for coloring, the relative dielectric constant is approximately 20. Furthermore, because the thermal effect of the RF field on the antenna is nearly uniform across the thickness, and the antenna is directly water-cooled, the impact of this thermal effect on the coating is negligible. This indicates that enamel can meet the requirements of RF antenna coatings, requiring only a certain porosity.

[0051] like Figure 2bAs shown, from left to right, there are four regions: the antenna, antenna coating, plasma sheath, and plasma. There are two lines above and below. When the upper line confines the potential within the antenna coating, there is almost no voltage difference in the plasma layer, which is called the sheath having no potential. Confining the potential within the antenna coating means that the highest point of voltage is within the antenna coating. When the highest point of voltage is in the plasma sheath, the plasma sheath has a potential. When the plasma sheath has a potential, the sheath is dynamically inflowing and outflowing particles. This dynamic inflow and outflow of particles into and out of the sheath constantly impacts the antenna, shortening the antenna's lifespan.

[0052] 2. Design of the composite structure filtration field of high-yield and high-current negative ion source;

[0053] ① Forming a multi-peak field for confining plasma: The multi-peak field magnet of the present invention includes both radial magnets and tangential magnets (the radial magnets have polarity pointing in the radial direction, and the tangential magnets have polarity pointing in the tangential direction of the circumference), forming a confinement field for confining plasma. Figure 3c As shown, there are both radial magnets and tangential magnets, while the five layers of magnets above the bottom layer only have radial magnets but 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 the filament ion source, the built-in antenna of the radio frequency ion source not only generates a vortex electric field for accelerating electrons to collide with hydrogen molecules or hydrogen atoms, but also generates an alternating magnetic field pointing to the axis of the inner cavity. This magnetic field can largely achieve confinement of electrons and plasma, that is, there is no need for an excessively high multi-peak field strength.

[0054] ② Forming a filtering field to filter high-energy electrons: For a multi-peak field negative hydrogen ion source, the ion source plasma chamber is divided from top to bottom into two parts: a high-temperature discharge chamber and a low-temperature ion extraction zone. In the high-temperature discharge chamber, electrons remaining in the vacuum are accelerated by the vortex electric field generated by the radio frequency antenna, where they collide with hydrogen molecules or atoms to produce high-energy excited H₂*. The excited H₂* interacts with slow electrons in the discharge chamber to produce H₁₀ in a reaction known as dissociative adsorption. However, H₁₀ is destroyed by fast electrons. Thus, the high-temperature discharge chamber and the low-temperature ion extraction zone are divided by the filtering magnetic field. The filtering field ensures that slow electrons in the discharge chamber enter the extraction zone to generate negative hydrogen ions, while preventing fast electrons from entering the extraction zone and destroying already formed negative hydrogen ions. This is a critical component of the multi-peak field negative hydrogen ion source, and its structure directly affects the yield of negative hydrogen ions.

[0055] ③ The present invention elevates the filtration field so that its highest point is just before the lead-out structure. Figure 3c 、 3d As shown, Figure 3d This is the top view after 3c is rotated 90 degrees clockwise. Figure 3d The filtration field shown is a transverse filtration field. Figure 3c The filtering field shown is that the three magnets at the bottom layer are magnets of the same polarity and are arranged 180 degrees relative to each other, that is, the other end of the same polarity S is 180 degrees away from the three magnets of 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. At the same time, the newly designed extraction structure increases the surface generation of negative hydrogen ions. In order to prevent fast electrons from entering the extraction structure and destroying the negative hydrogen ions generated on the extraction structure surface, it is necessary to Figure 3d The filtration field is raised, and the filtration field is raised as Figure 3c The middle magnetic poles 1, 2, and 3 are elevated as shown. After calculation, the present invention elevates the three magnets 8 mm above the bottom layer. At this time, the highest point of the filtration field is just before the lead-out structure.

[0056] After the three magnetic poles at the bottom layer are raised, the filtered magnetic field is just before the extraction structure, as shown in FIG. Figure 4a As shown, it falls on the upper surface of the plasma electrode 4-1 or in the area near the upper surface. Because the prior art does not raise the distance between the three magnetic poles and the bottom surface, and because the field strength of the attracting magnet is greater than the field strength of the three magnets on the bottom layer, the highest point of the superimposed filtered magnetic field falls on the lower surface of the plasma electrode. As a result, the filtered magnetic field within the cavity is not at its highest point, resulting in a weaker filtered magnetic field in the prior art.

[0057] ④ Design principle of superimposed magnetic fields: The composite structure's superimposed magnetic fields enhance the filtration field and further improve yield: The attracting magnets 4-3 are arranged in two layers, upper and lower, between the attracting electrode 4-2. Each layer consists of a pair of mutually inclined permanent magnets. When the magnetic field direction of the upper pair of attracting magnets 4-3 aligns with the magnetic field direction of the filtering magnet array 3-1 within the cavity, one of the conditions for magnetic field superposition is met. The second condition for magnetic field superposition is to achieve the optimal superposition of the two magnetic fields. This optimal superposition depends on the thickness of the plasma electrode 4-1 and the axial distance between the attracting electrode 4-2 and the plasma electrode 4-1. The thicker the plasma electrode or the greater the axial distance between the attracting electrode 4-2 and the plasma electrode 4-1, the weaker the superposition of the two magnetic fields. At the same time, under the condition of a certain potential difference (the plasma electrode potential to ground is 60 kV, and the attracting electrode potential to ground is 47 kV), the greater the distance between the two electrodes, the less the electric field affects the shape of the plasma sheath. However, if the distance is too close, it is more likely to cause breakdown. Therefore, the present invention selects a compromise number: on the one hand, it is better to take into account the electric field, on the other hand, it is better to take into account the magnetic field, and it is also necessary to take into account that there will be no sparks due to the distance being too close. Therefore, the distance between the suction electrode 4-2 and the plasma electrode is selected to be 3.5mm.

[0058] 3. Design of the high-yield, high-current negative hydrogen ion source extraction structure: ① The generation of negative hydrogen ions on the inclined surface increases the yield. The present invention adds a 45-degree inclined surface at the entrance of the plasma electrode 4-1, so that negative hydrogen ions can be generated not only in the ion source cavity above the plasma electrode 4-1, but also on the current 45-degree inclined surface. The principle of the surface generating negative hydrogen ions is: when the residual electrons in the air collide with excited hydrogen atoms, in addition to fast electrons, slow electrons, and even negative hydrogen ions, a considerable number of positive hydrogen atoms will also be generated. When the positive hydrogen atoms hit the inclined surface coated with a specific coating, negative hydrogen ions will be generated. The prior art does not set an inclined surface on the plasma electrode, and the entrance of the plasma electrode has no "surface". Without a "surface", it cannot receive positive hydrogen atoms, and its negative hydrogen ions can only be generated in the cavity, so the yield is low. ② The design principle of the level extraction field: When a large amount of plasma is generated in the ion source cavity, the 60kV high voltage will extract the plasma. The extracted plasma will form a plasma sheath on the plasma electrode, thereby determining the shape of the plasma emission surface and changing the shape of the extracted beam. The present invention uses a level extraction field to affect the shape of the plasma sheath without changing the extraction energy, thereby improving the beam extraction state. ③ The design principle of the thickness of the plasma electrode 4-1: If the plasma electrode is too thick, and the level extraction voltage between the upper surface of the plasma electrode 4-1 and the level extraction 4-2 is too weak, the level extraction field cannot penetrate well into the emission hole, and the extraction ability is reduced. Therefore, in this design, without affecting the structural strength, the thickness of the plasma electrode 4-1 should be reduced as much as possible, and a suitable level extraction voltage should be selected. ④ Design principle of the sharp corner of the attractor 4-2: The attractor has a sharp corner extending outward, which can enhance the attractor field penetrating into the emission hole. At the same time, due to the space charge effect, the increase in the thickness of the attractor 4-2 and its axial distance from the plasma electrode 4-1 will increase the divergence angle. Therefore, in this design, the thickness of the attractor and its axial distance from the plasma electrode should be minimized under the conditions of cooling and avoiding breakdown. ⑤ Design principle of the magnet of the attractor 4-2: According to research, when negative hydrogen ions are extracted, a 100-fold electron beam (slow) will be extracted. Therefore, in this design, it is necessary to embed a suitable magnet in the attractor while meeting the size of the attractor 4-2 to deflect the electrons to the attractor baffle. ⑤ Design principle of the geoelectric stage 4-7: The aperture size has little effect on the performance of the extracted beam, but its aperture determines the beam radius that is ultimately injected into the accelerator.

[0059] Based on the above principles, the present invention designs a pulse mode multi-peak field built-in antenna type radio frequency high current negative hydrogen ion source 1;

[0060] A pulse mode multi-peak field built-in antenna type radio frequency high current negative hydrogen ion source 1, such as Figure 1As shown, it includes, from top to bottom and from outside to inside: an ion source built-in radio frequency antenna 2, an ion source built-in radio frequency antenna upper cover 1-1, an ion source inner cavity 1-2, an ion source outer cavity 1-3, a permanent magnet array 3 located between the ion source inner cavity 1-2 and the ion source outer cavity 1-3, an ion source extraction structure 4, an ion source composite structure filter field located at the bottom of the permanent magnet array and the ion source extraction structure, and the ion source composite structure filter field is composed of a filter magnet array 3-1 and an ion source extraction structure suction pole magnet 4-3; the ion source built-in radio frequency antenna 2 is externally connected to a dual-frequency driver The dual-frequency drive system is connected to the built-in radio frequency antenna 2 located on the upper cover via an impedance matching and isolation system, and its radio frequency power is coupled to the ion source cavity 1-2 through the built-in radio frequency antenna 2; the ion source built-in radio frequency antenna 2 is used to generate a vortex electric field, so that the free electrons remaining in the air collide with the hydrogen gas introduced into the ion source under the action of the electric field to generate negative hydrogen ions; the permanent magnet array 3 is used to provide a confining magnetic field in the ion source cavity 1-2; the ion source composite structure filter field is used to form a transverse magnetic field to filter fast electrons and filter slow electrons respectively;

[0061] It is characterized in that: the built-in radio frequency antenna 2 of the ion source is a built-in radio frequency antenna with an enamel coating that can achieve potential-free plasma sheath; the composite structure filter field is a composite structure filter field in which a magnetic field is superimposed at the highest point of the filter field to filter fast electrons; the ion source extraction structure 4 is an ion source extraction structure that extracts a negative hydrogen current intensity higher than 100mA under a high voltage of 60kV.

[0062] Furthermore, the ion source built-in radio frequency antenna 2 is as follows Figure 2 As shown, it is a built-in radio frequency antenna with an enamel coating that can achieve potential-free plasma sheath. Specifically, the ion source built-in radio frequency antenna 2 has 2.5-3.5 turns, an average winding diameter of 58 mm, a leg spacing of the straight parts at both ends of the coil is 25 mm, and the height of the spiral winding part of the coil is 40 mm-50 mm; the coating of the ion source built-in radio frequency antenna 2 is an enamel structure. When the enamel structure simultaneously meets the conditions of a coating thickness of 0.6-0.7 mm, a relative dielectric constant of less than 30, and a coating resistivity greater than 45000 Ω.cm, the plasma sheath is close to potential-free; the glaze of the enamel structure includes the following substances in parts by mass: 95-105 parts of base glaze, 4-8 parts of clay, 1-5 parts of quartz, 0.1-0.8 parts of urea, 0.1-0.5 parts of nitrite, and 45-55 parts of water.

[0063] Furthermore, the enamel structure is an enamel structure from which metal oxides used for coloring are removed, so as to reduce the relative dielectric constant of the coating; and the dielectric breakdown strength of the enamel structure exceeds 3 kV / mm.

[0064] Supplementary Note 1:

[0065] 1) If Figure 2b As shown, the ultimate goal of the present invention is to offset the self-inductance voltage in the internal coil by using the voltage of the antenna coating and the voltage of the plasma sheath. Since the voltage of the plasma sheath is desired to be essentially zero, the peak of the voltage must be cut off within the antenna coating. As shown in the figure, the peak of the upper line is essentially within the antenna coating. This requires the antenna coating to meet three conditions simultaneously: a coating thickness of 0.6-0.7 mm, a relative dielectric constant of less than 30, and a coating resistivity greater than 45,000 Ω.cm.

[0066] 2) Currently, most commonly used antenna coatings only address insulation and breakdown resistance, and do not meet the aforementioned antenna coating requirements. Therefore, they cannot fundamentally address the plasma bombardment antenna problem. The few currently used antenna coatings that meet the aforementioned antenna coating requirements are mostly ceramic structures, which are expensive, complex to manufacture, brittle, and have poor adhesion to metals. The coating used in the present invention is a commonly used enamel coating, which is low in cost, simple to manufacture, and made of a strong material. It also exhibits excellent adhesion, impact resistance, and thermal shock resistance. Furthermore, the enamel structure used in the present invention was originally used for water heater inner tanks. While meeting the aforementioned coating requirements, it also has strong water resistance, meaning the material has a low porosity, which fully meets the requirements for antenna coatings and is very conducive to the formation of a vacuum environment within the ion source.

[0067] Furthermore, the composite structure filter field is as follows Figure 3c As shown, it is a composite structure filtering field for superimposing a magnetic field at the highest point of the filtering magnetic field to filter fast electrons, specifically: the composite structure filtering field includes a filtering magnet array 3-1 at the bottom of the permanent magnet array arranged between the cylindrical ion source inner cavity 1-2 of the multi-peak field negative hydrogen ion source and the ion source outer cavity 1-3, and an ion source extraction structure attracting magnet 4-3 arranged at the bottom of the ion source cavity below the filtering magnet array 3-1; the filtering magnet array 3-1 is used to adjust the position of the highest point of the filtering magnetic field to be before the plasma electrode, so that the fast electrons are fully filtered out before reaching the extraction structure, and the thickness of the filtering magnetic field in the axial distribution is moderate; The extraction structure pole magnet 4-3 is used to form a superimposed magnetic field with the filtering magnet array 3-1 at the highest field strength to filter out fast electrons before the plasma electrode 4-1; the extraction structure pole 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 radial magnet arrays arranged from the top layer to the bottom layer along the circumferential direction, and the tangential magnet array at the bottom layer of the permanent magnet array 3. The tangential magnet array at the bottom layer is to only retain the tangential magnets at the bottom layer and remove the tangential magnet array above the bottom layer of the permanent magnet array 3.

[0068] Supplementary Note 2:

[0069] like Figure 4c As shown, the composite structure filtering field of the present invention filters out two types of electrons: fast electrons and slow electrons. The need to filter out slow electrons arises because after slow electrons combine with excited hydrogen atoms to produce negative hydrogen ions, a large number of slow electrons remain, mixed into the cluster of negative hydrogen ions, and enter the extraction structure. In order to prevent the slow electrons from being doped with the negative hydrogen ions, the slow electrons in the extraction structure must also be filtered out. The magnetic field components are arranged in an "eight" shape to generate magnetic field components, wherein the horizontal magnetic field component is used to filter out slow electrons. Although the direction of the slow electron filtering magnetic field here is the same as that of the fast electron filtering magnetic field, their physical locations are different. In the slow electron filtering magnetic field, because it is within the extraction structure, the fast electrons have already been filtered out before the extraction structure, that is, before the plasma electrode. Therefore, the filtering magnetic field here can only filter out slow electrons.

[0070] Furthermore, the filtering magnet array 3-1 is as follows Figure 3c As shown, the two opposing radial magnets at the bottom layer of the permanent magnet array 3 are replaced with radial magnets b1 with reversed polarity, and tangential magnets b2 and b3 of the same polarity are added on both sides of the reversed radial magnets b1. The distance between the radial magnets b1, b2, and b3 and the bottom surface is raised to 8 mm. Tangential magnets b4 and b5 of opposite polarity are added above the tangential magnets b2 and b3 to thin the filtering field. The remaining last layer of radial magnets and tangential magnets is used to form a multi-peak field for confining plasma.

[0071] Supplementary Note 3:

[0072] The difference between the present invention and the prior art is that the tangential magnets in the prior art penetrate from the upper layer to the lower layer, such as Figure 3a The figure shows a cross-sectional view of a multi-peak field magnet array of the prior art, while the present invention is as follows Figure 3c As shown, all tangential magnets above the bottom layer are removed, retaining only the radial magnets from the bottom to the top layer. This is because the reference document uses a filament as the electric field, while the present invention employs an internal RF antenna. When AC current is applied to the internal RF antenna, the magnetic field is oriented vertically. This vertical magnetic field already serves to constrain the beam to the axial centerline, so, relatively speaking, retaining the radial magnets is sufficient for the multi-peak magnetic field value.

[0073] Furthermore, the thickness of the filtering magnetic field in the axial distribution is moderate, specifically: the thickness of the filtering magnetic field in the axial distribution is about 50 mm.

[0074] Furthermore, if Figure 4cAs shown, the ion source extraction structure 4 is used to form a superimposed magnetic field with the filtering magnet array 3-1 at the highest point of the filtering magnetic field to filter out the fast electrons before the plasma electrode 4-1. Specifically, the ion source extraction structure 4 includes a plasma electrode 4-1, an attracting pole 4-2, and an attracting pole magnet 4-3. Two pairs of upper and lower oppositely arranged figure-eight attracting pole magnets 4-3 with a 45-degree inclination are embedded in the middle of the attracting pole 4-2. The upper pair of oppositely arranged figure-eight attracting pole magnets 4-3 with a 45-degree inclination have a magnetic field component in one direction that is consistent with the filtering magnetic field direction of the filtering magnet array 3-1, and the two magnetic fields are superimposed together, thereby forming a superimposed magnetic field for filtering fast electrons; the lower pair of oppositely arranged figure-eight attracting pole magnets 4-3 with a 45-degree inclination have a magnetic field component in another direction that is used to deflect slow electrons in the negative hydrogen beam to the suction baffle, thereby realizing the separation of electrons and negative hydrogen ions.

[0075] Supplementary Note 4:

[0076] The highest point of the filtration magnetic field is not indicated in the attached figures; it is roughly located on the upper surface of the plasma electrode or slightly above it. The 8mm elevation does not necessarily mean raising the highest point of the filtration magnetic field by 8mm. Rather, it shifts the highest point of the filtration magnetic field from below (near the lower surface) of the plasma electrode to above it, including the upper surface or the area near it. This elevation serves the purpose of intercepting fast electrons before they enter the extraction structure, preventing any negative hydrogen ions generated by the structure from being destroyed by the fast electrons in the extraction structure.

[0077] Furthermore, if Figure 4b As shown, the axial distance between the suction electrode 4-2 and the plasma electrode 4-1 is 3.5 mm, the suction electrode thickness is 15 mm (3*5 mm), and two pairs of 3*5*25 mm permanent magnets are embedded in the middle.

[0078] Furthermore, the ion source extraction structure 4 is as follows Figure 4aAs shown, it is an ion source extraction structure that extracts a negative hydrogen current intensity higher than 100mA under a high voltage of 60kV, specifically: the ion source extraction structure 4 is provided with a plasma electrode 4-1, an attracting electrode 4-2, an attracting electrode magnet 4-3, an attracting level baffle 4-4, a plasma electrode fixing part 4-5, an attracting electrode fixing part 4-6, and a grounding level 4-7, which are arranged in sequence along the axial direction at the bottom of the ion source cavity; the plasma electrode 4-1 is used to receive particles to be extracted and allow the particles to pass through the middle opening, and the upper side of the opening is provided with an angled inclined surface, the upper surface of the angled inclined surface is coated with a boron-doped diamond film, and the angled inclined surface is used for the surface generation of negative hydrogen ions; the attracting level 4-2 is used In order to improve the envelope shape of the negative hydrogen ion extraction so that the envelope shape neither diverges nor contracts, the suction level 4-2 has a sharp corner extending toward the lower surface of the plasma electrode; the said suction pole magnet 4-3 is used to guide the trajectory of the negative hydrogen ion extraction into a straight trajectory and deflect the electrons in the negative hydrogen beam to the suction level baffle; the suction pole magnet 4-3 is arranged in two layers in the middle of the suction pole 4-2, each layer is a pair of permanent magnets inclined to each other; the said ground electrode is used to form a voltage field for the extraction of negative hydrogen ions with the plasma electrode; wherein the electrodes are separated by an insulator, and an adjustable suction level voltage is applied between the suction pole 4-2 and the plasma electrode 4-1 to adjust the beam distribution.

[0079] Supplementary Note 5:

[0080] The existing plasma electrode inlet has a trapezoidal shape with the short side at the top and the long side at the bottom, lacking a 45-degree inclination. The present invention places the long side at the top and the short side at the bottom, forming an angled inlet surface. This angled surface enables the second generation of negative hydrogen ions: the first generation occurs within the ion source chamber, and the second generation occurs on the surface. The surface generation condition is that positive hydrogen atoms react with the paraboronated diamond film on the surface to produce negative hydrogen ions. The first generation of negative hydrogen ions within the wall is caused by slow electrons and excited hydrogen atoms. Positive hydrogen atoms are generated when participating electrons in the air collide with the incoming hydrogen atoms, producing fast electrons, slow electrons, and even negative hydrogen ions and positive hydrogen atoms. Positive hydrogen atoms account for a significant proportion of these. Therefore, utilizing positive hydrogen atoms to generate negative hydrogen ions a second time is of great significance for increasing yield.

[0081] Furthermore, the polar magnet 4-3 is as follows Figure 4e As shown, it is divided into two layers, upper and lower, arranged in the middle of the suction electrode 4-2, and each layer is a pair of permanent magnets tilted to each other, specifically: the pair of permanent magnets in the upper layer are in an eight-shaped shape, each at a 45-degree angle to the plasma electrode plane, and the pair of permanent magnets in the lower layer are in an inverted eight-shaped shape, and each at a 45-degree angle to the plasma electrode plane. The magnetic field direction of the pair of permanent magnets in the lower layer is opposite to that of the pair of permanent magnets in the upper layer. The pair of permanent magnets in the lower layer with opposite magnetic field directions are used to correct the extraction direction of negative hydrogen ions.

[0082] Supplementary Note 6:

[0083] like Figure 4e As shown, the directions of the two upper-layer polar magnets are consistent with the direction of the filtering field, and the directions of the two lower-layer polar magnets are opposite to the direction of the filtering field. The negative hydrogen ions of the extraction structure will be deflected in one direction under the action of the upper-layer polar magnets. Since the directions of the lower-layer polar magnets and the upper-layer polar magnets are opposite, the deflected negative hydrogen ion beam trajectory will be deflected in the opposite direction, thereby realizing a linear beam trajectory.

[0084] Furthermore, the opening angle of the middle of the plasma electrode 4-1 is 45°, the thickness is 4 mm, the aperture is 16 mm, and there is a 1 mm*1 mm groove, and its voltage to ground is 60 kV.

[0085] Furthermore, if Figure 4b As shown, the axial distance between the suction electrode 4-2 and the plasma electrode 4-1 is 3.5mm, the thickness is 15mm (3*5mm), and two pairs of 3*5*25mm permanent magnets are embedded in the middle; its first aperture is 12mm, the axial distance between the sharp corner and the plasma electrode is 1mm, and the aperture at the protruding point of the sharp corner is 17mm; the second aperture is 15mm; the third aperture is 16mm, which is a rounded corner, and its voltage to ground is 47-50kV, that is, the suction voltage between the plasma electrode and the suction stage is 10-13kV.

[0086] Supplementary Note 7:

[0087] like Figure 4a As shown, the two sharp corners of the suction electrode 4-2 extend toward the plasma electrode 4-1 and are 1 mm apart from the plasma electrode. Under the condition of a constant voltage (the voltage of the plasma electrode 4-1 is 6 kV, and the suction electrode voltage is 4.7 kV), the closer the distance between the two electrodes, the more obvious the pressure difference, and the more obvious the pressure difference, the easier it is to adjust the shape of the beam envelope to a straight line. Figure 4d As shown, when the sharp corner of the absorber extends toward the plasma electrode, under the repulsive force of the electric field at the sharp corner, the shape of the beam envelope at the upper left corner changes from close to the plasma electrode to far away from the plasma electrode, improving the shape of the envelope at the sharp corner, making it easier for the envelope at the sharp corner to form a whole with the linear envelope behind it.

[0088] Furthermore, the thickness of the ground electrode is 5 mm, and the axial distance from the absorption electrode is 13.5 mm.

[0089] It should be emphasized that the above specific embodiments are merely explanations of the present invention and are not limitations of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the above embodiments as needed, 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 pulse mode multi-peak field built-in antenna type radio frequency high current negative hydrogen ion source (1), which comprises from top to bottom and from outside to inside: An ion source built-in radio frequency antenna (2), an ion source built-in radio frequency antenna upper cover (1-1), an ion source inner cavity (1-2), an ion source outer cavity (1-3), a permanent magnet array (3) located between the ion source inner cavity (1-2) and the ion source outer cavity (1-3), an ion source extraction structure (4), and an ion source composite structure filter field located at the bottom of the permanent magnet array and the ion source extraction structure, wherein the ion source composite structure filter field is composed of a filter magnet array (3-1) and an attracting pole magnet (4-3) of the ion source extraction structure; the ion source built-in radio frequency antenna (2) is externally connected to a dual-frequency drive system, The dual-frequency drive system is connected to a built-in radio frequency antenna (2) located on the upper cover plate via an impedance matching and isolation system, and its radio frequency power is coupled to the ion source inner cavity (1-2) through the built-in radio frequency antenna (2); the ion source built-in radio frequency antenna (2) is used to generate a vortex electric field, so that the free electrons remaining in the air collide with the hydrogen gas introduced into the ion source under the action of the electric field to generate negative hydrogen ions; the permanent magnet array (3) is used to provide a confining magnetic field for the ion source inner cavity (1-2); the ion source composite structure filter field is used to respectively form a transverse magnetic field to filter fast electrons and filter slow electrons; The invention is characterized in that: the ion source built-in radio frequency antenna (2) is a built-in radio frequency antenna with an enamel coating that can realize a potential-free plasma sheath; the composite structure filter field is a composite structure filter field in which a magnetic field is superimposed at the highest point of the filter field to filter fast electrons; the ion source extraction structure (4) is an ion source extraction structure that extracts a negative hydrogen current intensity higher than 100 mA under a high voltage of 60 kV; The filtering magnet array (3-1) is used to adjust the position of the highest field strength before the plasma electrode, so that fast electrons are fully filtered out before reaching the extraction structure, and the thickness of the filtering magnetic field in the axial distribution is moderate; the filtering magnet array (3-1) is provided with replacing the two opposite 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 tangential magnets (b3) of the same polarity on both sides of the radial magnets (b1) after the reversed polarity, and raising the distance between the radial magnets (b1), the tangential magnets (b2), and the tangential magnets (b3) and the bottom surface so that the raised distance is 8 mm; The ion source extraction structure (4) is used to form a superimposed magnetic field with the filtering magnet array (3-1) at the highest field strength point to filter out fast electrons before the plasma electrode. Specifically, the ion source extraction structure (4) includes a plasma electrode (4-1), an attracting pole (4-2), and an attracting pole magnet (4-3). Two pairs of upper and lower oppositely arranged figure-eight attracting pole magnets (4-3) with a 45-degree inclination are embedded in the middle of the attracting pole (4-2). The upper pair of oppositely arranged figure-eight attracting pole magnets (4-3) with a 45-degree inclination have a magnetic field component direction in one direction that is consistent with the filtering magnetic field direction of the filtering magnet array (3-1), and the two magnetic fields are superimposed together, thereby forming a superimposed magnetic field for filtering fast electrons. The axial distance between the suction electrode (4-2) and the plasma electrode (4-1) is 3.5 mm, and the thickness of the plasma electrode (4-1) is 4 mm. The plasma electrode (4-1) is used to receive particles to be drawn out and allow the particles to pass through the opening in the middle, and an angled inclined surface is provided on the inlet side of the opening, the upper surface of the angled inclined surface is coated with a boron-doped diamond film, and the angled inclined surface is used for the surface generation of negative hydrogen ions.

2. The pulse mode multi-peak field internal antenna type radio frequency high current negative hydrogen ion source according to claim 1, characterized in that: The ion source built-in radio frequency antenna (2) is a built-in radio frequency antenna with an enamel coating that can achieve a plasma sheath without potential, specifically: the ion source built-in radio frequency antenna (2) has 2.5-3.5 turns, an average winding diameter of the turns is 58 mm, the leg spacing of the straight parts at both ends is 25 mm, and the height of the spiral winding part of the coil is 40 mm-50 mm; the coating of the ion source built-in radio frequency antenna (2) is an enamel structure, when the enamel structure simultaneously meets the conditions of a coating thickness of 0.6-0.7 mm, a relative dielectric constant of less than 30, and a coating resistivity of greater than 45000 Ω.cm, the plasma sheath is close to being without potential; the glaze of the enamel structure includes the following substances in parts by mass: 95-105 parts of base glaze, 4-8 parts of clay, 1-5 parts of quartz, 0.1-0.8 parts of urea, 0.1-0.5 parts of nitrite, and 45-55 parts of water.

3. The pulse mode multi-peak field internal antenna type radio frequency high current negative hydrogen ion source according to claim 2, characterized in that: The enamel structure is an enamel structure from which metal oxide used for coloring is removed, so as to reduce the relative dielectric constant of the coating; the dielectric breakdown strength of the enamel structure exceeds 3 kV / mm.

4. The pulse mode multi-peak field internal antenna type radio frequency high current negative hydrogen ion source according to claim 1, characterized in that: The composite structure filtering field is a composite structure filtering field that superimposes a magnetic field at the highest field strength to filter fast electrons, specifically: the composite structure filtering field includes a filtering magnet array (3-1) at the bottom layer of the permanent magnet array arranged between the cylindrical inner cavity and the outer cavity of the multi-peak field negative hydrogen ion source, and an ion source extraction structure attracting magnet (4-3) arranged at the bottom of the ion source cavity below the filtering magnet array (3-1); the extraction structure attracting magnet (4-3) is used to form a superimposed magnetic field with the filtering magnet array (3-1) at the highest field strength to filter out fast electrons before the plasma electrode (4-1); the extraction structure attracting 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), and a tangential magnet array above the bottom layer of the permanent magnet array (3) is removed.

5. The pulse mode multi-peak field internal antenna type radio frequency high current negative hydrogen ion source according to claim 4, characterized in that: Tangential magnets (b4) and (b5) of opposite polarity are added above the tangential magnets (b2) and (b3) to thin the filtering field. The remaining last layer of radial magnets and tangential magnets are used to form a multi-peak field for confining plasma.

6. The pulse mode multi-peak field internal antenna type radio frequency high current negative hydrogen ion source according to claim 4, characterized in that: The thickness of the filtering magnetic field in the axial distribution is moderate, specifically: the thickness of the filtering magnetic field in the axial distribution is 50 mm.

7. The pulse mode multi-peak field internal antenna type radio frequency high current negative hydrogen ion source according to claim 4, characterized in that: The upper layer comprises a pair of oppositely arranged figure-eight magnets (4-3) with a 45-degree inclination angle. The magnetic field components in the other direction of each magnet are used to deflect slow electrons in the negative hydrogen beam to the magnet baffle, thereby achieving separation of electrons and negative hydrogen ions.

8. The pulse mode multi-peak field internal antenna type radio frequency high current negative hydrogen ion source according to claim 7, characterized in that: The thickness of the attracting pole is 15 mm, and two pairs of 3*5*25 mm permanent magnets are embedded in the middle.

9. The pulse mode multi-peak field internal antenna type radio frequency high current negative hydrogen ion source according to claim 1, characterized in that: The ion source extraction structure (4) is an ion source extraction structure that extracts a negative hydrogen current intensity higher than 100 mA under a high voltage of 60 kV. Specifically, the ion source extraction structure (4) is provided with a plasma electrode (4-1), an attracting electrode (4-2), an attracting electrode magnet (4-3), an attracting electrode baffle (4-4), a plasma electrode fixing member (4-5), an attracting electrode fixing member (4-6), and a grounding electrode (4-7) arranged in sequence along the axial direction at the bottom of the ion source cavity; the attracting electrode (4-2) is used to improve the envelope shape of the negative hydrogen ion extraction, so that the envelope shape is neither divergent nor contracted, and the attracting electrode (4-2) is used to improve the envelope shape of the negative hydrogen ion extraction, so that the envelope shape is neither divergent nor contracted. -2) with a pointed corner extending toward the lower surface of the plasma electrode; the said attracting pole magnet (4-3) is used to guide the trajectory of the negative hydrogen ion extraction into a straight trajectory and deflect the electrons in the negative hydrogen beam to the attracting pole baffle; the attracting pole magnet (4-3) is divided into two layers, upper and lower, arranged in the middle of the attracting pole (4-2), and each layer is a pair of permanent magnets inclined to each other; the said ground electrode is used to form a voltage field for the extraction of negative hydrogen ions with the plasma electrode; wherein, the electrodes are separated by an insulator, and an adjustable attracting pole voltage is applied between the attracting pole (4-2) and the plasma electrode (4-1) to adjust the beam distribution.

10. The pulse mode multi-peak field internal antenna type radio frequency high current negative hydrogen ion source according to claim 9, characterized in that: The pole magnet (4-3) is divided into two layers, upper and lower, arranged in the middle of the pole magnet (4-2). Each layer is a pair of permanent magnets tilted to each other. Specifically, the pair of permanent magnets in the upper layer are in an eight-shaped shape, each tilted at 45 degrees to the plasma electrode plane, and the pair of permanent magnets in the lower layer are in an inverted eight-shaped shape, each tilted at 45 degrees to the plasma electrode plane. The magnetic field direction of the pair of permanent magnets in the lower layer is opposite to the magnetic field direction of the pair of permanent magnets in the upper layer. The pair of permanent magnets in the lower layer with opposite magnetic field directions are used to correct the extraction direction of negative hydrogen ions.

11. The pulse mode multi-peak field internal antenna type radio frequency high current negative hydrogen ion source according to claim 9, characterized in that: The opening angle of the plasma electrode (4-1) in the middle is 45°, the aperture is 16 mm, and there is a 1 mm*1 mm groove. The voltage to ground is 60 kV.

12. The pulse mode multi-peak field internal antenna type radio frequency high current negative hydrogen ion source according to claim 9, characterized in that: The axial distance between the suction electrode (4-2) and the plasma electrode (4-1) is 3.5 mm, the thickness is 15 mm, and two pairs of 3*5*25 mm permanent magnets are embedded in the middle; its first aperture is 12 mm, the axial distance between the sharp corner and the plasma electrode is 1 mm, and the aperture where the sharp corner extends is 17 mm; the second aperture is 15 mm; the third aperture is 16 mm, with rounded corners, and its voltage to ground is 47-50 kV, that is, the suction voltage between the plasma electrode and the suction electrode is 10-13 kV.

13. The pulse mode multi-peak field internal antenna type radio frequency high current negative hydrogen ion source according to claim 9, characterized in that: The thickness of the ground electrode (4-7) is 5 mm, and the axial distance from the absorption electrode is 13.5 mm.

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