CN116528449A

CN116528449A - Pulse mode multi-peak field built-in antenna type radio frequency strong current negative hydrogen ion source

Info

Publication number: CN116528449A
Application number: CN202310396060.9A
Authority: CN
Inventors: 贾先禄; 农竹杰; 张贺; 丁傲轩; 李鹏展; 郑侠; 凌丽; 管锋平; 侯世刚
Original assignee: China Institute of Atomic of Energy
Current assignee: China Institute of Atomic of Energy
Priority date: 2023-04-13
Filing date: 2023-04-13
Publication date: 2023-08-01

Abstract

The invention discloses a pulse mode multi-peak field built-in antenna type radio frequency strong current negative hydrogen ion source, which comprises: the ion source built-in radio frequency antenna, radio frequency antenna upper cover plate, inner cavity, outer cavity, permanent magnet array between inner cavity and outer cavity, ion source extraction structure, ion source composite structure filtering field that is located this permanent magnet array bottom and ion source extraction structure, characteristics are: the built-in radio frequency antenna of the ion source is provided with an enamel coating and can realize no potential of a plasma sheath; the composite structure filtering field is a composite structure filtering field which is formed by superposing a magnetic field at the highest point of the filtering field so as to filter fast electrons; the ion source extraction structure is an ion source extraction structure which is used for extracting negative hydrogen flow with the voltage higher than 100mA under the high voltage of 60 kV. The invention realizes the high-yield extraction of negative hydrogen ions, and solves the bottleneck problems of relatively short service life of the built-in antenna, limited negative hydrogen ion generation space and small magnetic field of the multimodal field virtual filter field encountered by the high-yield extraction.

Description

Pulse mode multi-peak field built-in antenna type radio frequency strong current negative hydrogen ion source

Technical Field

The invention belongs to the technical field of radio frequency ion sources, and particularly relates to a pulse mode multi-peak field built-in antenna type radio frequency strong current negative hydrogen ion source.

Background

In cyclotrons, ion source technology is a critical technology, and an ion source is a device that ionizes neutral atoms or molecules and directs a beam of ions out of it. The ion source is the source of the beam, determines the beam quality, and also directly affects the performance of the cyclotron.

The high-yield Gao Liujiang ion source with the extraction flow intensity of more than 100mA is widely demanded in recent years, and compared with the low-yield low-flow high-intensity ion source in the prior art, the high-yield Gao Liujiang ion source has the implementation difficulty that:

one of the difficulties, high yield extraction and relatively short built-in antenna lifetime. The high-yield extraction requires high feed-in power efficiency of the ion source radio frequency antenna (the ion source radio frequency antenna is used for generating a vortex electric field, residual electrons in vacuum collide with hydrogen molecules or hydrogen atoms to generate negative hydrogen ions under the acceleration of the ion source radio frequency antenna electric field), in order to solve the problems of low power utilization efficiency, namely small extraction current of the traditional external antenna radio frequency ion source, the technical staff tries to replace the external antenna radio frequency ion source by adopting an internal antenna radio frequency ion source, because the internal antenna is directly contacted with plasma, the power feed-in efficiency is high, the extraction current is strong, but meanwhile, the internal antenna can generate a plasma sheath layer because the internal antenna is directly contacted with the plasma: any object directly contacts the plasma, and if the object is charged, a sheath layer is generated, the sheath layer is dynamic particle inflow and outflow, and the dynamic sheath layer continuously flows in and out to continuously strike the particles on the antenna, so that the service life of the antenna is shortened. The external coil does not contact the plasma, so that a sheath layer is not generated.

Two difficulties are contradicted by the limitations of high yield extraction and negative hydrogen ion generation space. The prior art is as follows: 201020700147.9, patent name: in the magnet structure for generating the virtual filtering magnetic field, the negative hydrogen ions can be generated only in the cavity (1) without other generation modes, as shown in figure 1, the inlet of the leading-out channel of the plasma electrode (the plasma electrode is arranged at the tail end of the cavity and is next to the cavity) has no opening angle, and the inlet and the outlet are vertical up and down, so that no negative hydrogen ions are generated, but only negative hydrogen ions are generated. If the cost is not increased, the yield of the ion source can be limited to the current yield and cannot be increased any more.

The three difficulties, high yield and small magnetic field of the prior art multi-peak field virtual filter field are contradictory. One of the reasons for the small magnetic field of the virtual filter field is that the peak of the filter field is not within the cavity. The prior art is as follows: 201020700147.9, patent name: a magnet structure for generating a virtual filtered magnetic field is provided, wherein the virtual filtered magnetic field is located inside a cavity, but the highest point of the magnetic field strength is located on the lower surface of a plasma electrode in an extraction area outside the cavity. (the virtual filtering magnetic field is used for filtering out fast electrons and reserving slow electrons, the purpose of filtering out fast electrons is that negative hydrogen ions generated in a cavity are not damaged by the fast electrons, slow electrons and excited H atoms generate negative hydrogen ions, the fast electrons can enable the negative hydrogen ions to be changed into H atoms again), the filtered electrons depend on the magnetic field strength of the area (the magnetic field changes direction, the vertical direction is changed into the horizontal direction, and therefore the fast electrons vertically downwards are intercepted), when the magnetic field strength is not in the cavity, the filtered block electrons are insufficient, a part of the fast electrons enter an extraction area due to insufficient filtering, and due to the fact that part of the fast electrons are doped in the negative hydrogen ions in the extraction area, the fast electrons can damage part of the negative hydrogen ions, the negative hydrogen ions in the extraction area are restored to an initial state, and the yield of the negative hydrogen ions in the extraction area is reduced; the second reason for the smaller virtual filtered field magnetic field is: recent theoretical studies show that the H2 of the high-temperature excited state interacts with 0.5eV of slow electrons to generate a higher H-yield, instead of 1eV, which is considered previously, and requires a further increase in the magnetic field strength to filter out 1eV of electrons, whereas the existing virtual filter field magnetic field is designed based on filtering out 1eV of electrons, 0.5eV of electrons still being able to destroy negative hydrogen ions in the extraction region compared with 1eV of electrons, so that the virtual filter field magnetic field based on filtering 1eV in the prior art appears smaller; the third reason why the virtual filtered field is smaller is: because the built-in coil is adopted, the energy of the high-energy electrons generated when the feed-in power efficiency is high is higher, the requirement on the magnetic field intensity is higher due to the higher energy of the high-energy electrons, the maximum value of the magnetic field intensity of the virtual filtering field of the ion source in the prior art is lower, and the highest position is not located in the cavity but located in the extraction area, so that the magnetic field of the virtual filtering field in the cavity is smaller.

Fourth, high yields and space charge effects are contradictory. The high yield extraction means that a large amount of plasmas are generated in an ion source extraction area, a large amount of plasmas are extracted, the space charge effect is quite remarkable, the beam emittance is larger, the divergence is larger, and the plasma sheath layer influences and determines the shape of a plasma emission surface, so that higher requirements are put on an extraction structure. When the space, the opening angle, the thickness of the leading-out end, the shape of the leading-out electrode, the thickness and the shape of the ground level and the like in the leading-out structure are improperly designed, the plasma sheath layer can influence the shape of the emitting surface: the emission surface is divergent or over-focused, when the emission surface is divergent, the divergent beam will strike the tube of the application end for receiving the beam, and when the emission surface is over-focused, the beam will diverge in the subsequent path, which is also undesirable.

Disclosure of Invention

Aiming at the problems existing in the prior art, the invention provides a pulse mode multi-peak field built-in antenna type radio frequency strong current negative hydrogen ion source, which aims to solve the problems that the contradiction between the yield extraction of the prior art strong current negative hydrogen multi-peak field radio frequency ion source and the relatively short service life of a built-in antenna, the contradiction between the limitation of the high yield extraction and the negative hydrogen ion generation space, the contradiction between the high yield and the small magnetic field of the prior art multi-peak field virtual filtering field, and the contradiction between the high yield and the space charge effect are solved.

The invention provides the following technical scheme for solving the technical problems:

a pulsed mode multi-field built-in antenna type rf high current negative hydrogen ion source 1 comprising from top to bottom from outside to inside: the ion source comprises 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 positioned 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 filtering field positioned at the bottom layer of the permanent magnet array and the ion source extraction structure, wherein the ion source composite structure filtering field consists of a filtering magnet array 3-1 and a suction magnet 4-3 of the ion source extraction structure; the built-in radio frequency antenna 2 of the ion source is externally connected with a double-frequency driving system, and the double-frequency driving system is connected with the built-in radio frequency antenna 2 positioned on the upper cover plate through an impedance matching and isolating system and couples radio frequency power of the double-frequency driving system to the inner cavity 1-2 of the ion source through the built-in radio frequency antenna 2; the built-in radio frequency antenna 2 of the ion source is used for generating a vortex electric field, so that free electrons remained in the air collide with hydrogen introduced into the ion source under the action of the electric field to generate negative hydrogen ions; the permanent magnet array 3 is used for providing a constraint magnetic field of the cavity 1-2 in the ion source; the ion source composite structure filtering field is used for forming a transverse magnetic field respectively so as to filter fast electrons and slow electrons;

The method is characterized in that: the ion source built-in radio frequency antenna 2 is provided with an enamel coating and can realize no potential of a plasma sheath; the composite structure filtering field is a composite structure filtering field which is formed by superposing a magnetic field at the highest point of the filtering field so as to filter fast electrons; the ion source extraction structure 4 is an ion source extraction structure which can extract negative hydrogen flow higher than 100mA under high pressure of 60 kV.

Further, the ion source built-in radio frequency antenna 2 is a built-in radio frequency antenna with an enamel coating, which can realize no potential of a plasma sheath, and specifically comprises: the number of turns of the built-in radio frequency antenna of the ion source is 2.5-3.5, the average circle diameter of the built-in radio frequency antenna is 58mm, the leg spacing of the straight line parts at the two ends is 25mm, and the height of the spiral surrounding part of the coil is 40-50 mm; the coating of the radio frequency antenna 2 with the built-in ion source is of an enamel structure, and when the enamel structure simultaneously meets the conditions that the thickness of the coating is 0.6-0.7mm millimeter, the relative dielectric constant is less than 30 and the resistivity of the coating is more than 45000 Ω & cm, the plasma sheath layer approaches to no potential; the glaze of the enamel structure comprises 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 part of urea, 0.1-0.5 part of nitrous oxide and 45-55 parts of water.

Further, the enamel structure is an enamel structure from which a metal oxide for coloring is removed to reduce the relative dielectric constant of the coating; the dielectric breakdown strength of the enamel structure exceeds 3kV/mm.

Further, the composite structure filtering field is a composite structure filtering field for filtering fast electrons by superposing a magnetic field at the highest position of the filtering magnetic field, and specifically comprises the following steps: the composite structure filtering field comprises a filtering magnet array 3-1 arranged at the bottommost layer of a permanent magnet array between a cylindrical ion source inner cavity 1-2 and an ion source outer cavity 1-3 of the multi-peak field negative hydrogen ion source, and an ion source extraction structure pole-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 for adjusting the position of the highest position of the filtering magnetic field before the plasma electrode, so that fast electrons are sufficiently filtered before reaching the extraction structure, and the thickness of the filtering magnetic field distributed in the axial direction is moderate; the extraction structure pole attracting magnet 4-3 is used for forming a superimposed magnetic field with the filtering magnet array 3-1 at the highest field intensity to filter out fast electrons before the plasma electrode 4-1; the extraction structure attracting magnet 4-3 is also used for filtering slow electrons in negative hydrogen ions entering the ion source extraction structure 4 after the plasma electrode 4-1; the permanent magnet array 3 comprises radial magnet arrays which are distributed at intervals along the circumferential direction from the top layer to the bottom layer and tangential magnet arrays at the bottommost layer of the permanent magnet array 3, wherein the tangential magnet arrays at the bottommost layer not only remain tangential magnets at the bottommost layer, but also remove tangential magnet arrays above the bottommost layer of the permanent magnet array 3.

Further, the filter magnet array 3-1 is provided with a radial magnet b1 with reversed polarity which is replaced by two opposite radial magnets at the bottommost layer of the permanent magnet array 3, tangential magnets b2 and tangential magnets b3 with the same polarity are added at two sides of the radial magnet b1 with reversed polarity, and the distance between the radial magnet b1, the tangential magnets b2 and the tangential magnets b3 and the bottom surface is raised, so that the raised distance is 8mm; a tangential magnet b4 and a tangential magnet b5 of opposite polarities are added above the tangential magnets b2 and b3 to thin the filtering field, and the remaining radial magnets and tangential magnets of the last layer are used to form a multi-peak field confining the plasma.

Further, the thickness of the filtering magnetic field distributed in the axial direction is moderate, and the filtering magnetic field comprises the following specific components: the thickness of the axial distribution of the filtered magnetic field is about 50mm.

Further, the ion source extraction structure 4 is used for filtering fast electrons before the plasma electrode is filtered by forming a superimposed magnetic field with the highest field intensity and the filtering magnet array 3-1, and specifically comprises the following steps: the ion source extraction structure 4 comprises a plasma electrode 4-1, a suction electrode 4-2 and a suction magnet 4-3, wherein two pairs of suction magnets 4-3 which are arranged in a splayed shape and have a 45-degree inclination angle are embedded in the middle of the suction electrode 4-2, the pair of suction magnets 4-3 which are arranged in a splayed shape and have a 45-degree inclination angle and are arranged in a opposite way on the upper layer, the magnetic field component direction of each direction is consistent with the filtering magnetic field direction of the filtering magnet array 3-1, and the two magnetic fields are overlapped together, so that a stacked magnetic field for filtering fast electrons is formed; and a pair of opposite splayed pole-attracting magnets 4-3 with 45-degree inclined angles at the upper layer, wherein magnetic field components in the other directions of the magnets are used for deflecting slow electrons in negative hydrogen beam current to a pole-attracting baffle plate so as to realize separation of electrons and negative hydrogen ions.

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

Further, the ion source extraction structure 4 is an ion source extraction structure which extracts negative hydrogen flow with the voltage higher than 100mA under the high voltage of 60kV, and specifically comprises the following components: the ion source extraction structure 4 is provided with a plasma electrode 4-1, a suction electrode 4-2, a suction magnet 4-3, a suction baffle 4-4, a plasma electrode fixing piece 4-5, a suction electrode fixing piece 4-6 and a ground electrode 4-7 which are sequentially arranged at the bottom of the ion source cavity along the axial direction; the plasma electrode 4-1 is used for receiving particles to be extracted and allowing the particles to pass through the middle opening, an opening angle inclined plane is arranged at the inlet side of the opening, a boron-doped diamond film is plated on the upper surface of the opening angle inclined plane, and the opening angle inclined plane is used for generating negative hydrogen ions; the absorption stage 4-2 is used for improving the envelope shape of negative hydrogen ions led out, so that the envelope shape is neither divergent nor convergent, and the absorption stage 4-2 is provided with a sharp corner extending to the lower surface of the plasma electrode; the anode magnet 4-3 is used for guiding a track from which negative hydrogen ions are led out to be a linear track and deflecting electrons in the negative hydrogen beam to the anode baffle; the pole-attracting magnet 4-3 is divided into an upper layer and a lower layer which are arranged in the middle of the pole-attracting magnet 4-2, and each layer is a pair of permanent magnets which are inclined with each other; the ground level is used for forming a voltage field for leading out negative hydrogen ions with the plasma electrode; wherein the electrodes are separated by an insulator, and an adjustable pumping voltage is applied between the pumping electrode 4-2 and the plasma electrode 4-1 to adjust beam current distribution.

Further, the attracting magnet 4-3 is arranged in the middle of the attracting magnet 4-2 in an upper layer and a lower layer, and each layer is a pair of permanent magnets which are inclined with each other, specifically: the upper layer of the pair of permanent magnets is splayed, each of the pair of permanent magnets forms an inclined angle of 45 degrees with the plane of the plasma electrode, the lower layer of the pair of permanent magnets forms an inverted splayed, each of the pair of permanent magnets forms an inclined angle of 45 degrees with the plane of the plasma electrode, the magnetic field direction of the lower layer of the pair of permanent magnets is opposite to the magnetic field direction of the upper layer of the pair of permanent magnets, and the lower layer of the pair of permanent magnets with opposite magnetic field directions is used for correcting the extraction direction of negative hydrogen ions.

Further, the opening angle of the opening in the middle of the plasma electrode 4-1 is 45 degrees, the thickness is 4mm, the aperture is 16mm, and a 1mm x 1mm slot is arranged, and the voltage to ground is 60kV.

Further, the axial distance between the suction electrode 4-2 and the plasma electrode 4-1 is 3.5mm, the thickness is 15mm (3 x 5 mm), and two pairs of permanent magnets of 3 x 5 x 25mm are embedded in the middle; the first aperture is 12mm, the axial distance between the sharp corner and the plasma electrode is 1mm, and the aperture of the protruding part of the sharp corner is 17mm; the second aperture is 15mm; the third aperture is 16mm and is a round angle, the ground voltage is 47-50kV, namely the pumping voltage between the plasma electrode and the pumping stage is 10-13kV.

Further, the ground level is 5mm thick and is 13.5mm away from the sucker in the axial direction.

Advantageous effects of the invention

1. The invention provides a built-in radio frequency antenna with an enamel coating for a radio frequency negative hydrogen ion source, which is based on the working principle of the radio frequency ion source, and aims at the technical requirements that the built-in radio frequency antenna needs to isolate the potential difference between the built-in radio frequency antenna and plasma, the insulation between coils and between the antenna and an inner cavity needs to prevent breakdown, the service life is prolonged, and the like, so that the problem of the plasma back-bombing antenna is effectively solved, and the service life of the radio frequency antenna is prolonged.

2. According to the invention, by arranging the antenna structure and the enamel structure and simultaneously meeting the conditions of coating thickness, relative dielectric constant, coating resistivity and proportioning conditions of various mass components of the enamel glaze, the no-potential of a plasma sheath layer is realized, and the problem of a plasma back-bombing antenna is fundamentally solved. Most of the current used antenna coating can meet the requirements of the antenna coating, and has the advantages of ceramic structure, high price, complex manufacture, brittle material and poor adhesion with metal. The coating adopted by the invention is a common enamel coating, has low cost, is simple to manufacture, is firm in material, and has excellent adhesion, impact resistance and thermal shock resistance. Meanwhile, the enamel structure used by the invention is used for the inner container of the water heater, and has strong waterproof property under the condition of meeting the requirements of the coating, namely, the porosity of the material is lower, which is very in line with the requirements of the antenna coating, and is very beneficial to the formation of the vacuum environment in the ion source.

3. According to the invention, the number of turns of the antenna is 2.5-3.5, the average circle diameter is 58mm, the enamel structure simultaneously meets the requirements that the thickness of the coating is 0.6-0.7mm millimeter, the relative dielectric constant is less than 30, the resistivity of the coating is greater than 45000 Ω & cm, and the glaze of the enamel structure comprises, by mass, 95-105 parts of base glaze, 4-8 parts of clay, 1-5 parts of quartz, 0.1-0.8 part of urea, 0.1-0.5 part of nitrite and 45-55 parts of water, so that the enamel coating is used for replacing the ceramic coating, and the cost is greatly reduced: if the ceramic coating is tens of thousands yuan, and the enamel coating is hundreds of yuan, the difference is 100 times, and the cost is reduced to one percent.

4. According to the technical scheme provided by the invention, the multi-peak field magnet structure layout of the ion source with the attraction magnet capable of generating the virtual filtering field is designed, so that plasma can be well restrained in the radio frequency ion source, and a virtual filtering magnetic field capable of well filtering fast electrons, and having moderate transverse strength and thickness is formed.

5. According to the invention, by designing the multimodal field for confining the plasma and raising the filtering field to enable the highest position of the multimodal field to be just before the extraction structure, fast electrons on the upper surface of the plasma electrode are filtered in time and cannot enter the extraction area, so that negative hydrogen ions generated by the surface cannot be damaged by the fast electrons, and the yield is improved.

6. According to the invention, through designing the thickness of the plasma electrode and the distance between the attracting electrode and the plasma electrode, the magnetic field generated by the attracting magnet can be overlapped with the filtering magnetic field on the upper surface or near the upper surface of the plasma, and the overlapped filtering magnetic field can filter out 0.5eV fast electrons and 1eV fast electrons due to the improvement of the field intensity, so that the yield of negative hydrogen ions generated by the generation and the dough is improved.

7. Aiming at the technical requirements of high-voltage extraction and high-current extraction of the high-current negative hydrogen multimodal field radio frequency ion source, the invention solves the problem of extracting negative hydrogen current higher than 100mA at 60kV high voltage, improves the quality of extracted beam current of the ion source, and further improves the performance index of the accelerator. The flow strength index reaches the domestic leading level.

8. Aiming at the technical requirements of high-voltage extraction and high-current strong extraction of a high-current negative hydrogen multimodal field radio frequency ion source, the invention changes the generation of negative hydrogen ions from body generation to body generation plus surface generation by adding the inclined angle surface on the plasma electrode of the extraction structure, improves the yield, solves the problem of high negative hydrogen current of which the extraction voltage is higher than 100mA at the high voltage of 60kV,

9. according to the invention, through designing the thickness of the suction electrode and the axial distance between the suction electrode and the plasma electrode to take the minimum value under the conditions of cooling and avoiding breakdown, the suction electrode magnetic field can be overlapped with the highest point of the filtering magnetic field on the upper surface of the plasma electrode, the yield is improved, and the current strength index reaches the domestic leading level.

10. According to the invention, the suction pole sharp angle is designed to be 1mm away from the plasma electrode, so that the divergence condition of the beam emission surface caused by space charge effect is effectively improved, and the beam emission surface is more approximate to a straight line.

Drawings

FIG. 1 is a schematic diagram of a negative hydrogen ion source apparatus according to the present invention;

FIG. 2 is a schematic diagram of an RF antenna built in an ion source according to the present invention;

FIG. 2a is a schematic illustration of a plasma sheath approaching no potential when the thickness, dielectric constant, and resistivity of the coating of the internal antenna of the present invention satisfy certain conditions;

FIG. 2b is a schematic illustration of the implementation of the plasma sheath according to the present invention without potential;

FIG. 3a is a cross-sectional view of a multi-modal field magnet within a multi-modal field negative hydrogen ion source of the prior art;

FIG. 3b is a top view of a multi-modal field magnet within a multi-modal field negative hydrogen ion source of the prior art; wherein a is a radial magnet array and b is a tangential magnet array;

FIG. 3c is a cross-sectional view of a filter magnet array within a multi-modal field negative hydrogen ion source of the present invention;

FIG. 3d is a top view of an array of filter magnets within a multi-modal field negative hydrogen ion source of the present invention;

FIG. 4a is a cross-sectional view of an ion source extraction structure of the present invention;

FIG. 4b is a dimensional view of an ion source extraction structure of the present invention;

FIG. 4c is a schematic diagram of a filtered field superposition magnetic field of a multi-modal field negative hydrogen ion source composite structure of the present invention;

Fig. 4d is a schematic diagram of an envelope curve of a simulated beam current of 120mA extracted from the ion source extraction structure of the present invention.

FIG. 4e is a schematic diagram of a negative hydrogen ion extraction trajectory corrected by the reverse magnetic field of the bottom layer attracting magnet of the ion source extraction structure of the present invention;

in the figure: 1: a negative hydrogen ion source; 1-1: an ion source built-in radio frequency antenna upper cover plate; 1-2: an ion source internal cavity; 1-3: an ion source outer cavity; 2: an ion source built-in radio frequency antenna; 3, permanent magnet array; 4, an ion source extraction structure; 3-1, filtering a magnet array; 4, an ion source extraction structure; 4-1, plasma electrode; 4-2, sucking poles; 4-3, a pole-attracting magnet; 4-4, a suction baffle; 4-5, plasma electrode fixing parts; 4-6, a suction pole fixing piece; 4-7, ground level.

Detailed Description

Principle of design of the invention

1. Design of high-yield strong-current negative-hydrogen built-in radio frequency antenna: (1) relationship between coil structure design and coil coating design: when alternating current is introduced into the coil to generate a vortex electric field for accelerating electrons, the antenna generates self-induced voltage. According to studies, it has been shown that the antenna self-induced voltage must be maintained at an electric potential by the coating and the plasma sheath, that is, it is required that the voltages of the antenna coating and the plasma sheath together limit the self-induced voltage. At the same time, the relatively low potential difference of the plasma sheath can reduce the sputtering of the antenna coating by ions from plasma and prolong the service life of the radio frequency antenna, so that the plasma sheath is hoped to have no potential difference, limit the potential in the coating and avoid breakdown between the antenna and the inner cavity. At this time, the design of the built-in radio frequency antenna requires the structure of the built-in coil and the coating of the built-in coil, wherein the structural design of the built-in coil determines the self-induced voltage and only predicts the self-induced voltage Breakdown is avoided and the design of the built-in coil coating determines how the plasma sheath is rendered potentiofree. (2) Design of a built-in radio frequency antenna: the design of the built-in antenna comprises two aspects, namely, the design of a first coil structure: according to researches, in an Inductively Coupled (ICP) radio frequency ion source, radio frequency current flowing through a radio frequency antenna generates a radio frequency vortex electric field coaxial with a coil, and residual electrons in a cavity do reciprocating type rotary motion under the action of the vortex electric field and collide with gas molecules to ionize the gas molecules, so that plasma is finally generated. When the radio frequency is selected, the magnitude of the swirling electric field is only related to the coil diameter and number of turns, so the main parameters of the antenna design are the antenna loop diameter and number of turns. The method comprises the following steps: the number of turns of the built-in radio frequency antenna of the ion source is 2.5-3.5, the average circle diameter of the built-in radio frequency antenna is 58mm, the leg spacing of the straight line parts at the two ends is 25mm, and the height of the spiral surrounding part of the coil is 40-50 mm; second, design of coil coating: according to the research, the impedance distribution of the plasma sheath layer and the insulating coating is parallel connection of capacitance and resistance, the fusion plasma numerical calculation model is referred, the parameters are replaced by typical ion source parameters, and the numerical algorithm is adopted for calculation, so that the plasma sheath layer has no voltage distribution, and finally, the requirements are simultaneously satisfied: the thickness of the coating is more than 0.4mm, the relative dielectric constant is less than 30, the resistivity of the coating is more than 45000 Ω & cm, and the dielectric breakdown strength is more than 3kV/mm. For most enamels, the ideal resistivity is about 10 ¹⁴ Omega cm, the average dielectric breakdown strength is about 10kV/mm, and the relative dielectric constant after removal of the metal oxide used for coloration is about 20. The thermal effect of the radio frequency field on the antenna is almost uniform in thickness, and the antenna is directly water-cooled, so that the influence of the thermal effect on the coating is negligible. The enamel material can meet the requirements of the radio frequency antenna coating, and only certain porosity is required to be met.

As shown in fig. 2b, from left to right, there are 4 areas, antenna coating, plasma sheath, plasma, 2 lines up and down, when the upper line limits the potential in the antenna coating, there is little potential difference in the voltage of the plasma layer, called sheath no potential; the potential is defined within the antenna coating, i.e., the highest point of the voltage is located within the antenna coating, and the plasma sheath is "potential" when the highest point of the voltage is at the plasma sheath. When the plasma sheath is provided with a potential, the dynamic sheath continuously flows in and out because the sheath is dynamic particles, and the particles are continuously beaten on the antenna, so that the service life of the antenna is shortened.

2. Designing a filtering field with a high yield and strong flow negative ion source composite structure;

(1) Forming a multi-peak field for confining the plasma: the multi-modal magnet of the present invention includes both radial and tangential magnets (the radial magnet being the one whose polarity is directed in a radial direction and the tangential magnet being the one whose polarity is directed in a circumferential tangential direction) to form a confinement field for confining the plasma. The reason that the bottom layer of the multi-mode field magnet is shown in fig. 3c, the radial magnet is also present, the tangential magnet is not present in the radial magnet, the tangential magnet is not present in the 5-layer magnet above the bottom layer, and the reason that the radial magnet is present in the 5-layer magnet above the bottom layer is that compared with the multi-mode field used in the filament ion source before, the built-in antenna of the rf ion source generates the vortex electric field for accelerating electrons to collide with hydrogen molecules or hydrogen atoms, and simultaneously generates the alternating magnetic field pointing to the axial direction of the inner cavity, and the magnetic field can realize restraint of electrons and plasmas to a great extent, namely, the multi-mode field strength is not required to be too high.

(2) Forming a filtering field for filtering high-energy electrons: for a multi-peak field negative hydrogen ion source, the ion source plasma cavity is divided into a high-temperature discharge cavity and a low-temperature ion extraction area from top to bottom. In the high-temperature discharge cavity, residual electrons in vacuum collide with hydrogen molecules or hydrogen atoms under the acceleration of a vortex electric field generated at the radio frequency antenna to generate H2 in a high-energy excited state. The excited state of H2 interacts with slow electrons in the discharge chamber to produce H-, a reaction known as dissociative adsorption. But H-is destroyed by fast electrons. The high temperature discharge cavity and the low temperature ion extraction area are divided into two parts by the filtering magnetic field, and the filtering magnetic field has the function of ensuring that slow electrons in the discharge cavity enter the extraction area so as to generate negative hydrogen ions, and simultaneously preventing fast electrons from entering the extraction area to destroy formed negative hydrogen ions. It is a key ring of multi-peak field negative hydrogen ion source, its structure directly affects the yield of negative hydrogen ions.

(3) The invention lifts the filter field so that its highest point is just before the extraction structure. The filter field of the present invention is shown in fig. 3c and 3d, wherein fig. 3d is a top view of the filter field after 90 degrees of rotation of 3c clockwise, and the filter field shown in fig. 3d is a transverse filter field. The filtering field shown in fig. 3c adopts the mode that 3 magnets at the bottom layer are homopolar magnets and are oppositely arranged at 180 degrees, namely: the other end of the same polarity S, 180 degrees, is 3 magnets with the polarity N; in the transverse filtering field of fig. 3d, the N pole is to the left at the right S pole, thereby forming a filtering field transverse magnetic field pointing to the left. Since the transverse magnetic field is perpendicular to the vertical magnetic field, fast electrons can be intercepted. Meanwhile, 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 damaging the negative hydrogen ions generated by the extraction structure surface, the filtering field of the figure 3d is required to be lifted, the lifting of the filtering field is shown as the lifting of 1, 2 and 3 magnetic poles in the middle of the figure 3c, and through calculation, 3 magnets are lifted to the bottom layer by 8mm, and at the moment, the highest position of the filtering field is just before the extraction structure.

The lifting of the bottom-most 3 pieces of pole is followed by a filtered magnetic field just before the extraction structure, as shown in fig. 4a, which is a region that falls at or near the upper surface of the plasma electrode 4-1. In the prior art, the distance between the 3 magnetic poles and the bottom surface is not raised, and the field intensity of the pole attracting magnet is larger than that of the bottom layer 3 magnetic poles, so that the highest point of the superposed filtering magnetic field falls on the lower surface of the plasma electrode, and the filtering magnetic field in the cavity is not the highest point of the filtering magnetic field, so that the filtering magnetic field in the prior art is weaker.

(4) Design principle of superimposed magnetic field: the superposed magnetic field of the composite structure enhances the filtering field and further improves the yield, wherein the pole-attracting magnet 4-3 is distributed in the middle of the pole-attracting magnet 4-2 in an upper layer and a lower layer, each layer is a pair of permanent magnets which are mutually inclined, and when the magnetic field direction of the upper layer of the pole-attracting magnet 4-3 is consistent with the magnetic field direction of the filtering magnet array 3-1 in the cavity, one of the magnetic field superposition conditions is satisfied; the second condition of the magnetic field superposition is that the superposition of the two magnetic fields is in the best superposition state, and the best superposition state of the two magnetic fields is determined depending on the thickness of the plasma electrode 4-1 and the axial distance from the attracting electrode 4-2 to the plasma electrode 4-1, when the thickness of the plasma electrode is thicker or the axial distance from the attracting electrode 4-2 to the plasma electrode 4-1 is longer, the two magnetic fields are weaker. Meanwhile, under the condition of a certain potential difference (60 kv of the plasma electrode to the ground potential and 47kv of the suction electrode to the ground potential), the longer the distance between the two electrodes is, the smaller the influence of an electric field on the shape of the plasma sheath is, but the shorter the distance is, the easier breakdown is caused. The present invention therefore selects a compromise number: on the one hand, the electric field is better, on the other hand, the magnetic field is better, and the ignition cannot be caused by too close distance, so that the distance between the suction electrode 4-2 and the plasma electrode is 3.5mm.

3. Design of a high-yield strong-current negative hydrogen ion source extraction structure: (1) the production of negative hydrogen ions at the inclined plane increases yield. According to the invention, the 45-degree inclined plane is additionally arranged at the inlet of the plasma electrode 4-1, so that negative hydrogen ions can be generated in the ion source cavity above the plasma electrode 4-1 and can also be generated on the current 45-degree inclined plane. The principle of negative hydrogen ion generation by the surface is as follows: when the residual electrons in the air collide with the excited hydrogen atoms, a considerable amount of positive hydrogen atoms are generated in addition to the fast electrons, slow electrons, and even negative hydrogen ions, and the positive hydrogen atoms strike the inclined surface coated with the specific coating layer to generate negative hydrogen ions. In the prior art, no inclined surface is arranged on the plasma electrode, the inlet of the plasma electrode has no surface, positive hydrogen atoms cannot be received without the surface, and negative hydrogen ions can only be generated in the cavity, so that the yield is low. (2) Design principle of suction field: when a large amount of plasmas are generated in the ion source cavity, at the moment, the plasmas are led out by 60kV high voltage, and the led-out plasmas form a plasma sheath layer on a plasma electrode, so that the shape of a plasma emission surface is determined, and the shape of an led-out beam is changed. The invention adopts the suction field to influence the shape of the plasma sheath layer on the premise of not changing the extraction energy, thereby improving the beam extraction state. (3) Design principle of plasma electrode 4-1 thickness: if the plasma electrode is too thick and the pumping voltage between the upper surface of the plasma electrode 4-1 and the pumping stage 4-2 is too weak, the pumping field cannot well penetrate into the emission hole, and the extraction capacity is reduced, so that in the design, the thickness of the plasma electrode 4-1 is reduced as much as possible and the proper pumping voltage is selected on the premise of not affecting the structural strength. (4) Design principle of suction electrode 4-2 sharp angle: the suction stage has sharp corners extending out, so that the suction stage field penetrating into the emission hole can be enhanced, and meanwhile, due to space charge effect, the thickness of the suction stage 4-2 and the axial distance between the suction stage and the plasma electrode 4-1 are increased to increase the scattering angle, so that the thickness of the suction stage and the axial distance between the suction stage and the plasma electrode in the design are minimum under the conditions of cooling and avoiding breakdown. (5) Design principle of magnet with suction pole 4-2: according to the research, 100 times of electron beam (slow) is extracted when negative hydrogen ions are extracted, so in the design, under the condition of meeting the 4-2 size of the absorption stage, a proper magnet is embedded in the absorption stage, and electrons are deflected to the absorption stage baffle plate. (5) Design principle of ground level 4-7: the aperture size has little effect on the performance of the extracted beam, but its aperture determines the beam radius of the final injection accelerator.

According to the principle, the invention designs a pulse mode multi-mode field built-in antenna type radio frequency strong current negative hydrogen ion source 1;

a pulsed mode multi-field internal antenna type rf high current negative hydrogen ion source 1, as shown in fig. 1, comprising from top to bottom, from outside to inside: the ion source comprises 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 positioned 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 filtering field positioned at the bottom layer of the permanent magnet array and the ion source extraction structure, wherein the ion source composite structure filtering field consists of a filtering magnet array 3-1 and a suction magnet 4-3 of the ion source extraction structure; the built-in radio frequency antenna 2 of the ion source is externally connected with a double-frequency driving system, and the double-frequency driving system is connected with the built-in radio frequency antenna 2 positioned on the upper cover plate through an impedance matching and isolating system and couples radio frequency power of the double-frequency driving system to the inner cavity 1-2 of the ion source through the built-in radio frequency antenna 2; the built-in radio frequency antenna 2 of the ion source is used for generating a vortex electric field, so that free electrons remained in the air collide with hydrogen introduced into the ion source under the action of the electric field to generate negative hydrogen ions; the permanent magnet array 3 is used for providing a constraint magnetic field of the cavity 1-2 in the ion source; the ion source composite structure filtering field is used for forming a transverse magnetic field respectively so as to filter fast electrons and slow electrons;

Further, as shown in fig. 2, the ion source built-in rf antenna 2 is a built-in rf antenna with an enamel coating, which can realize no potential of a plasma sheath, and specifically includes: the number of turns of the built-in radio frequency antenna of the ion source is 2.5-3.5, the average circle diameter of the built-in radio frequency antenna is 58mm, the leg spacing of the straight line parts at the two ends is 25mm, and the height of the spiral surrounding part of the coil is 40-50 mm; the coating of the radio frequency antenna 2 with the built-in ion source is of an enamel structure, and when the enamel structure simultaneously meets the conditions that the thickness of the coating is 0.6-0.7mm millimeter, the relative dielectric constant is less than 30 and the resistivity of the coating is more than 45000 Ω & cm, the plasma sheath layer approaches to no potential; the glaze of the enamel structure comprises 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 part of urea, 0.1-0.5 part of nitrous oxide and 45-55 parts of water.

Supplementary notes 1:

1) The final object of the invention is to cancel the self-induced voltage in the built-in coil by the voltage of the antenna coating and the voltage of the plasma sheath, as shown in fig. 2b, since it is desirable that the voltage of the plasma sheath is substantially zero, the highest point of the voltage is cut off in the antenna coating, and the highest point of the upper line is shown substantially in the antenna coating. This requires the antenna coating to meet 3 conditions simultaneously: the thickness of the coating is 0.6-0.7mm millimeter, the relative dielectric constant is less than 30, and the resistivity of the coating is more than 45000 Ω cm.

2) Most of the antenna coatings commonly used at present only consider the problem of insulation breakdown prevention, but do not meet the requirements of the antenna coatings, so that the problem of plasma detonation of the antenna cannot be fundamentally solved. Most of the current used antenna coating can meet the requirements of the antenna coating, and has the advantages of ceramic structure, high price, complex manufacture, brittle material and poor adhesion with metal. The coating adopted by the invention is a common enamel coating, has low cost, is simple to manufacture, is firm in material, and has excellent adhesion, impact resistance and thermal shock resistance. Meanwhile, the enamel structure used by the invention is used for the inner container of the water heater, and has strong waterproof property under the condition of meeting the requirements of the coating, namely, the porosity of the material is lower, which is very in line with the requirements of the antenna coating, and is very beneficial to the formation of the vacuum environment in the ion source.

Further, as shown in fig. 3c, the filtering field with a composite structure is a composite structure filtering field for filtering fast electrons by superposing a magnetic field at the highest position of the filtering magnetic field, and specifically comprises: the composite structure filtering field comprises a filtering magnet array 3-1 arranged at the bottommost layer of a permanent magnet array between a cylindrical ion source inner cavity 1-2 and an ion source outer cavity 1-3 of the multi-peak field negative hydrogen ion source, and an ion source extraction structure pole-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 for adjusting the position of the highest position of the filtering magnetic field before the plasma electrode, so that fast electrons are sufficiently filtered before reaching the extraction structure, and the thickness of the filtering magnetic field distributed in the axial direction is moderate; the extraction structure pole attracting magnet 4-3 is used for forming a superimposed magnetic field with the filtering magnet array 3-1 at the highest field intensity to filter out fast electrons before the plasma electrode 4-1; the extraction structure attracting magnet 4-3 is also used for filtering slow electrons in negative hydrogen ions entering the ion source extraction structure 4 after the plasma electrode 4-1; the permanent magnet array 3 comprises radial magnet arrays which are distributed at intervals along the circumferential direction from the top layer to the bottom layer and tangential magnet arrays at the bottommost layer of the permanent magnet array 3, wherein the tangential magnet arrays at the bottommost layer not only remain tangential magnets at the bottommost layer, but also remove tangential magnet arrays above the bottommost layer of the permanent magnet array 3.

Supplementary explanation 2:

as shown in fig. 4c, the composite structure filtering field of the present invention filters out two types of electrons: the requirement for filtering the slow electrons is that after the slow electrons are combined with the excited hydrogen atoms to generate negative hydrogen ions, a large amount of slow electrons are mixed into the beam group of the negative hydrogen ions to enter the extraction structure, so that the slow electrons in the extraction structure are filtered out so as not to be doped into the negative hydrogen ions. The attracting magnets are arranged in a splayed manner, so that they generate magnetic field components, wherein the horizontal magnetic field components are used for filtering out slow electrons. Although the slow electron filtering magnetic field direction and the fast electron filtering magnetic field direction are consistent, the physical location is different, and the slow electron filtering magnetic field is inside the extraction structure, and the fast electrons are filtered before the extraction structure, that is, before the plasma electrode, so that the filtering magnetic field only can filter the slow electrons.

Further, as shown in fig. 3c, the filter magnet array 3-1 is provided with a radial magnet b1 with reversed polarity, which is replaced by two opposite radial magnets at the bottom layer of the permanent magnet array 3, and tangential magnets b2 and b3 with the same polarity are added at two sides of the radial magnet b1 with reversed polarity, so that the distance between the radial magnet b1, the tangential magnet b2 and the tangential magnet b3 and the bottom surface is raised, and the raised distance is 8mm; a tangential magnet b4 and a tangential magnet b5 of opposite polarities are added above the tangential magnets b2 and b3 to thin the filtering field, and the remaining radial magnets and tangential magnets of the last layer are used to form a multi-peak field confining the plasma.

Supplementary notes 3:

the invention differs from the prior art in that: while the tangential magnets of the prior art are cut through the top to bottom layers, as shown in fig. 3a, which is a cross-sectional view of a prior art multi-peak field magnet array, the present invention is shown in fig. 3c with all tangential magnets above the bottom most layer removed, leaving only radial magnets from bottom to top. This is because the reference uses filaments as the electric field, whereas the present invention uses a built-in radio frequency antenna. When the built-in radio frequency antenna is powered on with alternating current, the magnetic field direction is vertical, and the magnetic field in the vertical direction has the function of restraining the beam current at the axial center line, so that the multi-peak magnetic field value is enough to keep the radial magnet relatively.

Further, as shown in fig. 4c, the ion source extraction structure 4 is configured to form a superimposed magnetic field with the filter magnet array 3-1 at the highest position of the filter magnetic field, and filter out fast electrons before the plasma electrode 4-1, specifically: the ion source extraction structure 4 comprises a plasma electrode 4-1, a suction electrode 4-2 and a suction magnet 4-3, wherein two pairs of suction magnets 4-3 which are arranged in a splayed shape and have a 45-degree inclination angle are embedded in the middle of the suction electrode 4-2, the pair of suction magnets 4-3 which are arranged in a splayed shape and have a 45-degree inclination angle and are arranged in a opposite way on the upper layer, the magnetic field component direction of each direction is consistent with the filtering magnetic field direction of the filtering magnet array 3-1, and the two magnetic fields are overlapped together, so that a stacked magnetic field for filtering fast electrons is formed; and a pair of opposite splayed pole-attracting magnets 4-3 with 45-degree inclined angles at the lower layer, wherein magnetic field components in the other directions of the magnets are used for deflecting slow electrons in the negative hydrogen beam to the pole-attracting baffle plate so as to separate electrons from negative hydrogen ions.

Supplementary explanation 4:

the highest point of the filtered magnetic field is not identified in the drawing, and is generally in the upper surface or slightly upward region of the upper surface of the plasma electrode. Raising by 8mm does not raise the highest point of the filtering magnetic field by 8mm, but rather by raising by 8mm, the highest point of the filtering magnetic field is changed from being below the plasma electrode (near the lower surface) to being above the plasma electrode, including the upper surface of the plasma electrode or the area near the upper surface, in the sense that: the fast electrons are intercepted before entering the extraction structure, so that the generated negative hydrogen ions entering the extraction structure are not destroyed by the fast electrons in the extraction structure.

Further, as shown in fig. 4b, the axial distance between the suction electrode 4-2 and the plasma electrode 4-1 is 3.5mm, the suction electrode thickness is 15mm (3×5 mm), and two pairs of permanent magnets of 3×5×25mm are embedded in the middle.

Further, as shown in fig. 4a, the ion source extraction structure 4 is an ion source extraction structure which extracts negative hydrogen current higher than 100mA at a high voltage of 60kV, specifically: the ion source extraction structure 4 is provided with a plasma electrode 4-1, a suction electrode 4-2, a suction magnet 4-3, a suction baffle 4-4, a plasma electrode fixing piece 4-5, a suction electrode fixing piece 4-6 and a ground electrode 4-7 which are sequentially arranged at the bottom of the ion source cavity along the axial direction; the plasma electrode 4-1 is used for receiving particles to be extracted and allowing the particles to pass through the middle opening, an opening angle inclined plane is arranged at the inlet side of the opening, a boron-doped diamond film is plated on the upper surface of the opening angle inclined plane, and the opening angle inclined plane is used for generating negative hydrogen ions; the absorption stage 4-2 is used for improving the envelope shape of negative hydrogen ions led out, so that the envelope shape is neither divergent nor convergent, and the absorption stage 4-2 is provided with a sharp corner extending to the lower surface of the plasma electrode; the anode magnet 4-3 is used for guiding a track from which negative hydrogen ions are led out to be a linear track and deflecting electrons in the negative hydrogen beam to the anode baffle; the pole-attracting magnet 4-3 is divided into an upper layer and a lower layer which are arranged in the middle of the pole-attracting magnet 4-2, and each layer is a pair of permanent magnets which are inclined with each other; the ground level is used for forming a voltage field for leading out negative hydrogen ions with the plasma electrode; wherein the electrodes are separated by an insulator, and an adjustable pumping voltage is applied between the pumping electrode 4-2 and the plasma electrode 4-1 to adjust beam current distribution.

Supplementary explanation 5:

the invention forms an inlet inclined plane with the long side of the trapezoid under the upper short side, and the inclined plane with the entrance inclined 45 degrees, the inclined plane realizes the second generation of negative hydrogen ions, the first generation is generated in the ion source cavity, the second generation is generated on the surface, the condition of the generation on the surface is that positive hydrogen atoms react with the boron-doped diamond film on the surface to generate negative hydrogen ions, and the first generation of negative hydrogen ions in the wall is slow electrons and excited hydrogen atoms to generate negative hydrogen ions. Positive hydrogen atoms are generated because the electrons involved in the air collide with the hydrogen atoms that are introduced to produce fast electrons, slow electrons, and even negative hydrogen ions, positive hydrogen atoms. Wherein the positive hydrogen atoms account for a substantial proportion. Therefore, the second generation of negative hydrogen ions using positive hydrogen atoms is significant for improving yield.

Further, as shown in fig. 4e, the attracting magnet 4-3 is arranged in the middle of the attracting magnet 4-2 in two layers, wherein each layer is a pair of permanent magnets inclined to each other, specifically: the upper layer of the pair of permanent magnets is splayed, each of the pair of permanent magnets forms an inclined angle of 45 degrees with the plane of the plasma electrode, the lower layer of the pair of permanent magnets forms an inverted splayed, each of the pair of permanent magnets forms an inclined angle of 45 degrees with the plane of the plasma electrode, the magnetic field direction of the lower layer of the pair of permanent magnets is opposite to the magnetic field direction of the upper layer of the pair of permanent magnets, and the lower layer of the pair of permanent magnets with opposite magnetic field directions is used for correcting the extraction direction of negative hydrogen ions.

Supplementary notes 6:

as shown in fig. 4e, the directions of the two pole-attracting magnets at the upper layer are consistent with the direction of the filtering field, the directions of the two pole-attracting magnets at the lower layer are opposite to the direction of the filtering field, negative hydrogen ions of the extraction structure deflect in one direction under the action of the pole-attracting magnets at the upper layer, and the deflected negative hydrogen ion beam current track deflects in the opposite direction due to the opposite directions of the pole-attracting magnets at the lower layer and the pole-attracting magnets at the upper layer, so that the linear beam current track is realized.

Further, as shown in fig. 4b, the axial distance between the suction electrode 4-2 and the plasma electrode 4-1 is 3.5mm, the thickness is 15mm (3×5 mm), and two pairs of permanent magnets of 3×5×25mm are embedded in the middle; the first aperture is 12mm, the axial distance between the sharp corner and the plasma electrode is 1mm, and the aperture of the protruding part of the sharp corner is 17mm; the second aperture is 15mm; the third aperture is 16mm and is a round angle, the ground voltage is 47-50kV, namely the pumping voltage between the plasma electrode and the pumping stage is 10-13kV.

Supplementary notes 7:

as shown in fig. 4a, two sharp corners of the suction electrode 4-2 extend to the plasma electrode 4-1 and have a distance of 1mm from the plasma electrode, and under the condition of a certain voltage (the voltage of the plasma electrode 4-1 is 6kv, the suction electrode voltage is 4.7 kv), the pressure difference is obvious when the distance between the two electrodes is closer, and the shape of the beam envelope is more easily adjusted to be a straight line when the pressure difference is more obvious. After the sharp corner of the suction electrode extends to the plasma electrode, the shape of the envelope of the beam current at the upper left corner is changed from being close to the plasma electrode to being far away from the plasma electrode under the repulsive force of the sharp corner electric field, so that the shape of the envelope at the sharp corner is improved, and the envelope at the sharp corner is convenient to form a whole with the linear envelope at the back.

It should be emphasized that the above-described embodiments are merely illustrative of the invention, which is not limited thereto, and that modifications may be made by those skilled in the art, as desired, without creative contribution to the above-described embodiments, while remaining within the scope of the patent laws.

Claims

1. A pulsed mode multi-field built-in antenna type rf high current negative hydrogen ion source (1) comprising from top to bottom from outside to inside: the ion source comprises 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) positioned 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 filtering field positioned at the bottom layer of the permanent magnet array and the ion source extraction structure, wherein the ion source composite structure filtering field consists of a filtering magnet array (3-1) and a pole-absorbing magnet (4-3) of the ion source extraction structure; the ion source built-in radio frequency antenna (2) is externally connected with a double-frequency driving system, and the double-frequency driving system is connected with the built-in radio frequency antenna (2) positioned on the upper cover plate through an impedance matching and isolating system and couples radio frequency power of the built-in radio frequency antenna (2) to an inner cavity (1-2) of the ion source; the built-in radio frequency antenna (2) of the ion source is used for generating a vortex electric field, so that free electrons remained in the air collide with hydrogen introduced into the ion source under the action of the electric field to generate negative hydrogen ions; the permanent magnet array (3) is used for providing a constraint magnetic field of the cavity (1-2) in the ion source; the ion source composite structure filtering field is used for forming a transverse magnetic field respectively so as to filter fast electrons and slow electrons;

The method is characterized in that: the built-in radio frequency antenna (2) of the ion source is provided with an enamel coating and can realize no potential of a plasma sheath; the composite structure filtering field is a composite structure filtering field which is formed by superposing a magnetic field at the highest point of the filtering field so as to filter fast electrons; the ion source extraction structure (4) is an ion source extraction structure which is used for extracting negative hydrogen flow with the voltage higher than 100mA under the high voltage of 60 kV.

2. The pulsed mode multi-mode, multi-field, built-in antenna type rf high current negative hydrogen ion source of claim 1, wherein: the ion source built-in radio frequency antenna (2) is provided with an enamel coating and can realize no potential of a plasma sheath, and specifically comprises the following components: the number of turns of the built-in radio frequency antenna (2) of the ion source is 2.5-3.5, the average circle diameter of the turns is 58mm, the leg spacing of the straight line parts at the two ends is 25mm, and the height of the spiral surrounding part of the coil is 40-50 mm; the coating of the radio frequency antenna (2) with the built-in ion source is of an enamel structure, and when the enamel structure simultaneously meets the conditions that the thickness of the coating is 0.6-0.7mm millimeter, the relative dielectric constant is less than 30, and the resistivity of the coating is more than 45000 Ω & cm, the plasma sheath layer approaches to no potential; the glaze of the enamel structure comprises 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 part of urea, 0.1-0.5 part of nitrous oxide and 45-55 parts of water.

3. The pulsed mode multi-mode, multi-field, built-in antenna type rf high current negative hydrogen ion source of claim 2, wherein: the enamel structure is an enamel structure from which metal oxides used for coloring are removed, and is used for reducing the relative dielectric constant of the coating; the dielectric breakdown strength of the enamel structure exceeds 3kV/mm.

4. The pulsed mode multi-mode, multi-field, built-in antenna type rf high current negative hydrogen ion source of claim 1, wherein: the composite structure filtering field is a composite structure filtering field for filtering fast electrons by superposing a magnetic field at the highest field intensity, and specifically comprises the following components: the composite structure filtering field comprises a filtering magnet array (3-1) arranged at the bottommost layer of a permanent magnet array between a cylindrical inner cavity and an outer cavity of the multi-peak field negative hydrogen ion source, and an ion source extraction structure pole-attracting magnet (4-3) arranged at the bottom of an ion source cavity below the filtering magnet array (3-1); the filtering magnet array (3-1) is used for adjusting the position of the highest field intensity before the plasma electrode, so that fast electrons are sufficiently filtered before reaching the extraction structure, and the thickness of the filtering magnetic field distributed in the axial direction is moderate; the extraction structure pole attracting magnet (4-3) is used for filtering out fast electrons before the plasma electrode (4-1) at the position with highest field intensity and the filtering magnet array (3-1) form a superimposed magnetic field; the extraction structure attracting magnet (4-3) is also used for filtering slow electrons in negative hydrogen ions entering the ion source extraction structure (4) after the plasma electrode (4-1); the permanent magnet array (3) comprises radial magnet arrays which are distributed at intervals along the circumferential direction from the top layer to the bottom layer, tangential magnet arrays at the bottommost layer of the permanent magnet array (3), and tangential magnet arrays above the bottommost layer of the permanent magnet array (3) are removed.

5. The pulsed, multi-mode, field, built-in antenna, rf, high current negative hydrogen ion source of claim 4, wherein: the filter magnet array (3-1) is provided with a radial magnet (b 1) with reversed polarity which is used for replacing two opposite radial magnets at the bottommost layer of the permanent magnet array (3), tangential magnets (b 2) and tangential magnets (b 3) with the same polarity are added at two sides of the radial magnet (b 1) with reversed polarity, and the distance between the radial magnet (b 1), the tangential magnets (b 2) and the tangential magnets (b 3) and the bottom surface is raised, so that the raised distance is 8mm; and adding tangential magnets (b 4) and tangential magnets (b 5) with opposite polarities above the tangential magnets (b 2) and (b 3) to thin the filtering field, wherein the rest radial magnets and tangential magnets of the last layer are used for forming a multimodal field for confining plasma.

6. The pulsed, multi-mode, field, built-in antenna, rf, high current negative hydrogen ion source of claim 4, wherein: the thickness of the filtering magnetic field in axial distribution is moderate, and the filtering magnetic field is specifically: the thickness of the axial distribution of the filtered magnetic field is about 50mm.

7. The pulsed, multi-mode, field, built-in antenna, rf, high current negative hydrogen ion source of claim 4, wherein: the ion source extraction structure (4) is used for filtering fast electrons before plasma electrodes are filtered by forming a superimposed magnetic field at the highest field intensity and the filtering magnet array (3-1), and specifically comprises the following components: the ion source extraction structure (4) comprises a plasma electrode (4-1), a suction electrode (4-2) and a suction magnet (4-3), wherein the suction magnet (4-3) with a splayed 45-degree inclination angle is embedded in the middle of the suction electrode (4-2), and the suction magnet (4-3) with a splayed 45-degree inclination angle is arranged in the upper layer in a pair, wherein the directions of magnetic field components of the suction magnet and the suction magnet are consistent with the directions of filtering magnetic fields of the filtering magnet array (3-1), and the two magnetic fields are overlapped together, so that a stacked magnetic field for filtering fast electrons is formed; and a pair of opposite splayed pole-attracting magnets (4-3) with 45-degree inclined angles at the upper layer, wherein magnetic field components in the other directions of the magnets are used for deflecting slow electrons in the negative hydrogen beam to the pole-attracting baffle plate so as to separate electrons from negative hydrogen ions.

8. The pulsed, multi-mode, field, built-in antenna, rf, high current negative hydrogen ion source of claim 7, wherein: the axial distance between the suction electrode (4-2) and the plasma electrode (4-1) is 3.5mm, the suction electrode thickness is 15mm (3 x 5 mm), and two pairs of permanent magnets with the thickness of 3 x 5 x 25mm are embedded in the middle.

9. The pulsed mode multi-mode, multi-field, built-in antenna type rf high current negative hydrogen ion source of claim 1, wherein: the ion source extraction structure (4) is an ion source extraction structure which extracts negative hydrogen flow with the voltage higher than 100mA under the high voltage of 60kV, and specifically comprises the following components: the ion source extraction structure (4) is provided with a plasma electrode (4-1), a suction electrode (4-2), a suction magnet (4-3), a suction baffle (4-4), a plasma electrode fixing piece (4-5), a suction electrode fixing piece (4-6) and a ground electrode (4-7) which are sequentially arranged at the bottom of the ion source cavity along the axial direction; the plasma electrode (4-1) is used for receiving particles to be extracted and allowing the particles to pass through the middle opening, an opening angle inclined plane is arranged at the inlet side of the opening, a boron-doped diamond film is plated on the upper surface of the opening angle inclined plane, and the opening angle inclined plane is used for generating negative hydrogen ions; the absorption stage (4-2) is used for improving the envelope shape of negative hydrogen ion extraction, so that the envelope shape is neither divergent nor convergent, and the absorption stage (4-2) is provided with a sharp angle extending to the lower surface of the plasma electrode; the anode attracting magnet (4-3) is used for guiding a track from which negative hydrogen ions are led out to be a linear track and deflecting electrons in the negative hydrogen beam to the anode baffle; the suction magnet (4-3) is arranged in the middle of the suction magnet (4-2) in an upper layer and a lower layer, and each layer is a pair of permanent magnets which are inclined with each other; the ground level is used for forming a voltage field for leading out negative hydrogen ions with the plasma electrode; wherein the electrodes are separated by an insulator, and an adjustable pumping voltage is added between the pumping electrode (4-2) and the plasma electrode (4-1) to adjust beam current distribution.

10. The pulsed, multi-mode, field, internal antenna, rf, high current negative hydrogen ion source of claim 9, wherein: the attracting magnet (4-3) is distributed in the middle of the attracting magnet (4-2) in an upper layer and a lower layer, and each layer is a pair of permanent magnets which incline mutually, specifically: the upper layer of the pair of permanent magnets is splayed, each of the pair of permanent magnets forms an inclined angle of 45 degrees with the plane of the plasma electrode, the lower layer of the pair of permanent magnets forms an inverted splayed, each of the pair of permanent magnets forms an inclined angle of 45 degrees with the plane of the plasma electrode, the magnetic field direction of the lower layer of the pair of permanent magnets is opposite to the magnetic field direction of the upper layer of the pair of permanent magnets, and the lower layer of the pair of permanent magnets with opposite magnetic field directions is used for correcting the extraction direction of negative hydrogen ions.

11. The pulsed, multi-mode, field, internal antenna, rf, high current negative hydrogen ion source of claim 9, wherein: the opening angle of the opening in the middle of the plasma electrode (4-1) is 45 degrees, the thickness is 4mm, the aperture is 16mm, and a 1 mm-1 mm groove is formed, and the voltage to ground is 60kV.

12. The pulsed, multi-mode, field, internal antenna, rf, high current negative hydrogen ion source of claim 9, wherein: the axial distance between the suction electrode (4-2) and the plasma electrode (4-1) is 3.5mm, the thickness is 15mm (3 x 5 mm), and two pairs of permanent magnets with the thickness of 3 x 5 x 25mm are embedded in the middle; the first aperture is 12mm, the axial distance between the sharp corner and the plasma electrode is 1mm, and the aperture of the protruding part of the sharp corner is 17mm; the second aperture is 15mm; the third aperture is 16mm and is a round angle, the ground voltage is 47-50kV, namely the pumping voltage between the plasma electrode and the pumping stage is 10-13kV.

13. The pulsed, multi-mode, field, internal antenna, rf, high current negative hydrogen ion source of claim 9, wherein: the thickness of the ground level is 5mm, and the axial distance between the ground level and the suction electrode is 13.5mm.