A magnetic array structure and a large-aperture microwave discharge ion source containing the same

Abstract

The present invention belongs to the field of space electric propulsion, and relates to a magnetic array structure of a large-caliber microwave discharge ion source, including multiple tile-shaped Halbach magnets; the magnetic field enhancement direction of each tile-shaped Halbach magnet is pointed at the center of the distribution circle at an angle, and multiple tile-shaped Halbach permanent magnets are evenly distributed on the circumference in a trumpet shape. An easy ionization condition is formed at the narrow mouth of the trumpet, and a magnetic field gradient pointing to the open mouth of the trumpet is generated. The magnetic field gradient drift can be used to induce plasma migration to the downstream of the trumpet, thereby increasing the plasma density downstream of the discharge chamber. The trumpet-shaped distributed tile-shaped Halbach permanent magnets can provide discharge conditions for microwaves in a wider frequency range, and realize the general use of industrial microwave sources and customized microwave sources. The microwave ion source structure innovation is carried out around the improved magnetic array structure, and a large-caliber microwave discharge ion source is developed, which implements the unique advantages of the magnetic array without the risk of high-temperature demagnetization, higher carrying power, and better performance.

Description

Technical Field

[0001] The present invention belongs to the field of space electric propulsion in aerospace propulsion technology or the field of etching in industrial processing technology, and specifically relates to a magnetic array structure and a large-caliber microwave discharge ion source containing the same. Background Art

[0002] The working principle of the microwave discharge ion source is as follows: microwaves are fed into the discharge chamber through the antenna, permanent magnets build magnetic mirrors to confine electrons, electron cyclotron resonance mechanism is used to heat electrons, high-energy electrons ionize neutral gas to produce plasma, and the grid system accelerates ions to eject to produce ion beams. When used for etching, it is called an ion source, and when used for aerospace propulsion, it is called an ion thruster.

[0003] In the aerospace field, there are three common microwave ion sources with apertures of 10cm, 5cm and 2cm, where the aperture is defined as the inner diameter of the discharge chamber. In the field of etching, the existing microwave discharge ion sources with apertures of 2cm, 8.5cm, 12cm and 16cm are available at home and abroad. An analysis of the above microwave ion sources shows that the current mature microwave discharge ion sources all use bar magnets or ring magnets, and in order to achieve complex magnetic field configurations, magnets or soft magnetic materials are inevitably in direct contact with the plasma, which poses a serious risk of high-temperature demagnetization, restricting the upper limit of plasma density and power.

[0004] In response to the above situation, a magnetic array structure suitable for small-aperture microwave discharge ion sources has been developed. The structure of the Halbach magnetic array has been introduced into the microwave discharge ion source, and the permanent magnet has been placed outside the plasma, completely avoiding the risk of high-temperature demagnetization of permanent magnets and soft magnetic materials, and further improving the performance of the ion source.

[0005] However, due to the upper limit of the performance of permanent magnets, this method is only applicable to small-aperture microwave discharge ion sources and is difficult to replicate on large-aperture ion sources. Since the magnetic array requires multiple magnetic strips to be spliced ​​in a specified direction, the strong magnetic force of neodymium iron boron magnets is difficult to splice because of the strong attraction between each other; while the medium magnetic force of samarium cobalt magnets and the small magnetic force of ferrite magnets have limited coercive force. When the ion source aperture is enlarged, the ECR zone that can be provided (for a typical 2.45GHz microwave, the ECR zone is the isoline of magnetic induction intensity of 0.0875T) is too far from the antenna, and the performance is poor.

[0006] In summary, it is necessary to improve the large-aperture microwave discharge ion source so that the advanced concept of magnetic array structure can also be used in the large-aperture microwave discharge ion source to improve the performance of the ion source. Summary of the invention

[0007] The purpose of the present invention is to provide a magnetic array structure and a large-caliber microwave discharge ion source containing the same, so as to solve the problems that the conventional microwave discharge ion source cannot be universally used and the magnetic array cannot be enlarged.

[0008] The present invention is achieved through the following technical solutions:

[0009] A magnetic array structure of a large-caliber microwave discharge ion source, the magnetic array structure comprising a plurality of tile-type Halbach magnets;

[0010] The magnetic field enhancement direction of each tile-shaped Halbach magnet points to the center of the distribution circle at an angle, and multiple tile-shaped Halbach permanent magnets are evenly distributed on the circumference in a trumpet shape.

[0011] Furthermore, each tile-type Halbach magnet is composed of multiple-stage magnets, and the multiple-stage requirement is not less than three stages;

[0012] In terms of size, in two adjacent magnets, the lower base of the upper magnet and the upper base of the lower magnet are of the same length, and the lower base of the upper magnet is smaller than the lower base of the lower magnet;

[0013] The hypotenuses of the multi-polar magnets are collinear and have the same thickness; their heights are different and increase in sequence.

[0014] Furthermore, in the coercive force distribution, the coercive force of the upper-level magnet is greater than the coercive force of the lower-level magnet.

[0015] Further, the direction in which the first-stage magnet points toward the third-stage magnet is defined as the positive direction of the X-axis, and the direction in which the first-stage magnet is away from the discharge chamber is defined as the Z-axis direction;

[0016] Then in the magnetic pole direction, the N pole of the first-level magnet is magnetized along the positive direction of the Z axis, the N pole of the second-level magnet is magnetized along the positive direction of the X axis, and the N pole of the third-level magnet is magnetized along the negative direction of the Z axis;

[0017] If there are higher-level magnets, the N pole of the fourth-level magnet is magnetized along the negative direction of the X-axis, and the latter-level magnets are circulated with the first four-level magnets as a unit.

[0018] The present invention also discloses a large-caliber microwave discharge ion source including the magnetic array structure. The microwave discharge ion source includes a discharge chamber. The magnetic array structure is installed outside the discharge chamber. The diameter of the large-diameter end of the discharge chamber is greater than 3 cm.

[0019] Further, the microwave discharge ion source comprises a discharge cavity, a microwave connector, an antenna and a grid system;

[0020] The discharge cavity, microwave connector and grid system surround and form a discharge chamber;

[0021] An air inlet pipe is arranged at the side of the discharge cavity, and the air inlet pipe is arranged vertically to the microwave joint axially;

[0022] The discharge chamber is a trumpet-shaped structure; the grid system is installed at the large-diameter end of the discharge chamber, and the microwave connector is installed at the small-diameter end of the discharge chamber; the antenna is installed on the microwave connector and extends into the discharge chamber;

[0023] The magnetic array structure is installed outside the discharge chamber, and the magnetic array structure is clamped by a magnet fixing piece and a discharge cavity.

[0024] Further, the discharge cavity comprises a stepped shaft section, a horn section and a cylindrical section which are connected in sequence;

[0025] The magnetic array structure is arranged on the outer wall of the horn section; the microwave joint runs through the stepped shaft section, and the grid system is connected with the cylinder section by bolts.

[0026] Furthermore, the installation position of the intake pipe is located between two adjacent poles of the tile-shaped Halbach magnet.

[0027] Furthermore, a quartz plate is installed between the antenna and the microwave connector.

[0028] Furthermore, the distance between the outermost edge of the antenna and the electron cyclotron resonance region is controlled to be 2.5 mm to 3 mm.

[0029] Compared with the prior art, the present invention has the following beneficial technical effects:

[0030] The present invention discloses a magnetic array structure and a large-caliber microwave discharge ion source containing the same, wherein the large-caliber is reflected in the inner diameter of the discharge chamber of 3-10 cm. The magnetic array structure is composed of a plurality of tile-shaped Halbach magnets, which are evenly distributed on the circumference, and the magnetic field enhancement direction of each tile-shaped Halbach magnet points to the center of the distribution circle at a certain angle, forming an arrangement of tile-shaped Halbach permanent magnets with a specific trumpet-shaped distribution, forming an easy ionization condition at the trumpet narrow mouth, generating a magnetic field gradient pointing to the trumpet opening, and being able to use the magnetic field gradient drift to induce plasma migration to the trumpet opening (downstream), thereby increasing the plasma density downstream of the discharge chamber. The trumpet-shaped distributed tile-shaped Halbach permanent magnet can provide discharge conditions for microwaves in a wider frequency range, and can currently meet the discharge requirements of 2.45GHz to 4.2GHz microwaves, realizing the general use of industrial microwave sources and customized microwave sources. Through a number of improvement measures on the magnetic array of small-aperture microwave discharge ion source in the existing technology, it can be successfully used in large-aperture microwave discharge ion source, and the ion source structure innovation is carried out around the improved magnetic array, and a large-aperture microwave discharge ion source is developed, which implements the unique advantages of the magnetic array: no risk of high-temperature demagnetization, higher power carrying capacity and better performance.

[0031] The present invention is an improvement on a large-aperture microwave discharge ion source. In order to allow a magnetic array structure with better performance to be used on a large-aperture microwave discharge ion source, the present invention has made the following specific improvement measures:

[0032] ① The arrangement of the magnetic array is changed from the original cylindrical arrangement to a trumpet-shaped arrangement, so that the direction of magnetic field enhancement points to the center of the distribution circle at a certain angle.

[0033] For large-aperture microwave discharge ion sources, this improvement can bring advantages in magnetic field gradient and ECR zone (contour lines where the magnetic induction intensity is a certain value, for example, the ECR zone corresponding to 2.45GHz microwaves is the contour line of 0.0875T, and the ECR zone corresponding to 4.2GHz microwaves is the contour line of 0.15T). The first is the magnetic field gradient. For the original cylindrical arrangement, when the ion source aperture is small, the magnetic field gradient in its discharge chamber points from the microwave incident port to the gate, which facilitates the migration of plasma upstream of the gate. This has been explained in the previous patent. However, when the ion source aperture becomes larger, the magnetic field gradient at its axis no longer points to the gate, but to the axis, and the effect of driving the plasma will be greatly weakened. The second is the ECR zone. For the original cylindrical arrangement, when the ion source aperture becomes larger, the distance between the ECR zone and the antenna increases significantly, making it more difficult for electrons to obtain energy, and the difficulty of ignition increases significantly. These two problems will be solved by changing the arrangement of the magnetic array to a trumpet-shaped arrangement. For example Figure 4 As shown in the figure, the white arrow is the direction of the magnetic field gradient, and the black solid line is the ECR region corresponding to 2.45 GHz. Figure 4 The spherical area in the lower middle part is where the microwave antenna is located, which intuitively demonstrates the advantages brought by this improvement measure.

[0034] ②The single Halbach magnetic strip is changed from the original bar magnet to a tile-shaped magnet.

[0035] When the arrangement of the magnetic array was changed to a trumpet shape, the single Halbach magnetic strip was also changed to a tile-shaped magnet accordingly, which effectively improved the continuity of the ECR zone in the discharge chamber while making full use of the space, so that the microwave discharge ion source can adapt to a wider excitation frequency. Figure 4 As shown in the figure, the black solid line is the ECR area corresponding to 2.45GHz, and the white solid line is the ECR area corresponding to 2.45GHz. It can be observed that both ECR areas have a large enough coverage area and are close to the microwave antenna, which meets the normal working conditions of the microwave discharge ion source. Therefore, this improvement measure enables the microwave discharge ion source to adapt to microwave power sources between 2.45 and 4.2GHz, broadening the application scenarios.

[0036] The present invention also discloses a large-caliber microwave discharge ion source including the above-mentioned magnetic array structure. The original magnetic array installation method is a press-plug method. The magnetic array is fixed by the front and rear end covers of the coaxial structure and the discharge cavity. When installing, the magnet is forcibly inserted into the cavity in the middle of the coaxial structure, which is very easy to cause irreversible damage to the fragile permanent magnet. In addition, multiple Halbach magnetic strips will attract each other during installation. If the operation is improper, the magnets will collide and be damaged. The improved installation method is a buckling method. The magnetic strips are fixed by the magnet fixing parts and the discharge cavity. Each magnet is installed independently and has a corresponding card slot, so that the magnets will not be damaged due to improper operation during installation.

[0037] Furthermore, for the trumpet-shaped magnetic array structure, the installation position of the air inlet pipe is located between the second-stage magnet and the third-stage magnet of the Halbach magnetic strip. Horizontal air intake from this position will allow the gas just entering the discharge chamber to be immediately in an area that is easier to ionize, thereby reducing the difficulty of ignition of the large-caliber microwave discharge ion source.

[0038] Furthermore, for a small-aperture microwave discharge ion source, the input power is low, and the microwave connector will not work at a high power for a long time, so it is not easy to be damaged. However, for a large-aperture microwave discharge ion source, the higher input power makes the dielectric of the microwave connector (usually polytetrafluoroethylene) very easy to burn. In order to protect the dielectric of the microwave connector, a quartz plate is added between the antenna and the microwave connector. In this way, the plasma can be physically isolated from the dielectric, reducing the risk of burning and improving the power carrying capacity.

[0039] Through the above improvement measures, the magnetic array that was originally only used for small-aperture microwave discharge ion sources with an inner diameter of less than 3 cm in the discharge chamber can be applied to large-aperture microwave discharge ion sources with an inner diameter of more than 3 cm in the discharge chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A schematic diagram of a magnetic array structure suitable for a large-caliber microwave discharge ion source disclosed in the present invention;

[0041] Figure 2 This is a schematic diagram of the structure of a tile-type Halbach magnet, where the white arrow indicates the magnetization direction of the magnet;

[0042] Figure 3 3 are three views of the magnetic array structure in the embodiment, wherein the direction indicated by the black arrow is the direction of magnetic field enhancement; FIG. (a) is a front view of the magnetic array structure, FIG. (b) is a left view of the magnetic array structure, and FIG. (c) is a top view of the magnetic array structure;

[0043] Figure 4: is the magnetic field distribution formed by the magnetic array structure in the embodiment, wherein the black thick solid line is the electron cyclotron resonance region of 2.45 GHz, the white thick solid line is the electron cyclotron resonance region of 4.2 GHz, and the white arrow is the magnetic field gradient direction;

[0044] Figure 5 It is an assembly diagram of the large-caliber broadband microwave discharge ion source of the present invention;

[0045] Figure 6 A cross-sectional view of a prototype of a large-aperture broadband microwave discharge ion source applicable to the present invention;

[0046] Figure 7 Experimental images of Xe working fluid ignition and beam extraction in microwave discharge ion source.

[0047] Among them, 1. discharge cavity; 2. discharge chamber; 3. grid system; 4. air inlet pipe; 5. antenna; 6. quartz plate; 7. microwave connector; 8. tile-type Halbach magnet; 9. magnet fixing part. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the present invention more clear, the following is further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, not all embodiments.

[0049] The components described and shown in the drawings and embodiments of the present invention may be arranged and designed in various configurations. Therefore, the detailed description of the embodiments of the present invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely represents a selected embodiment of the present invention. Based on the drawings and embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0050] It should be noted that the terms "comprises", "includes" or any other variations are intended to cover non-exclusive inclusion, so that a process, element, method, article or equipment that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to the process, element, method, article or equipment.

[0051] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0052] The present invention mainly provides a magnetic array structure of a large-caliber microwave discharge ion source using an external permanent magnet. The diameter of the microwave discharge ion source suitable for the magnetic array structure should be greater than 3 cm, and the value is generally recommended to be 3-10 cm.

[0053] The present invention discloses a magnetic array structure suitable for a large-caliber microwave discharge ion source, which is composed of multiple tile-shaped Halbach magnets 8. The structure of a single tile-shaped Halbach magnet 8 is as follows: Figure 2 As shown, it includes multi-level magnets, which are required to be no less than three levels. Here, the most basic three-level magnet is taken as an example, including the first-level magnet, the second-level magnet and the third-level magnet. In terms of size, the lower base of the first-level magnet and the upper base of the second-level magnet are the same length; the lower base of the second-level magnet and the upper base of the third-level magnet are the same length; the hypotenuses of the three-level magnets are collinear, the magnet thickness is the same, and the height is different, which is in a sequentially increasing relationship. The same applies to higher-level magnets.

[0054] Specifically, the thickness refers to the dimension in the Z-axis direction, and the height refers to the dimension in the X-axis direction.

[0055] In the distribution of coercive force, the coercive force of the first-level magnet is greater than that of the second-level magnet and greater than that of the third-level magnet, and the coercive force ranges from 600 to 700 kA / m. The direction in which the first-level magnet points to the third-level magnet is defined as the positive direction of the X-axis, and the direction in which the first-level magnet is away from the discharge chamber 2 is defined as the Z-axis direction. In the direction of the magnetic pole, the N pole of the first-level magnet is magnetized along the positive direction of the Z-axis, the N pole of the second-level magnet is magnetized along the positive direction of the X-axis, and the N pole of the third-level magnet is magnetized along the negative direction of the Z-axis.

[0056] If there are higher-order magnets, their magnetization directions continue in the arrangement of the traditional Halbach magnetic array. Specifically, the N pole of the fourth-order magnet is magnetized along the negative direction of the X-axis, and this is a cycle. The magnetization direction of the fifth-order magnet is the same as that of the first-order magnet, and the magnetization direction of the sixth-order magnet is the same as that of the second-order magnet, and so on. Figure 1 As shown, in this embodiment, there are specifically 8 magnetic strips. Considering that 8 strips are easier to do other subsequent processing, such as diagnosis, expansion, etc., the design of 8 magnetic strips was finally finalized. Of course, other numbers of strips can also be flexibly designed according to needs.

[0057] The magnetic array structure comprises eight Halbach magnets 8 arranged as follows: Figure 3 (a)-3(c) As shown in Figure 3. Eight Halbach permanent magnets are evenly distributed at 45° intervals on the circumference and arranged in a trumpet shape in space. The direction of magnetic field enhancement points to the center of the distribution circle at a certain angle, that is, Figure 3The direction indicated by the black arrow in (a) is specifically 45° in this embodiment. Among them, the magnetic field enhancement direction of Halbach magnet No. 1 is 45° and points to the center of the distribution circle; Halbach magnet No. 2 is rotated 45°; Halbach magnet No. 3 is rotated 90°; Halbach magnet No. 4 is rotated 135°; Halbach magnet No. 5 is rotated 180°; Halbach magnet No. 6 is rotated 225°; Halbach magnet No. 7 is rotated 270°; and Halbach magnet No. 8 is rotated 315°.

[0058] The 45° opening angle is not a specific value. In fact, it is only for the convenience of design and calculation and processing of various dimensions in the present invention. 45° is only used as a specific embodiment.

[0059] Depend on Figure 4 It can be seen that in the magnetic array composed of eight tile-shaped Halbach magnets 8, a magnetic field gradient with a specific direction is formed, that is, from the microwave incident port to the gate. The white arrow in the figure is the direction of the magnetic field gradient. This magnetic field gradient with a specific direction can regulate the drift direction of the plasma along the magnetic field gradient, so that the plasma moves according to the set magnetic field gradient. Figure 4 It can be seen that the magnetic array composed of eight tile-type Halbach magnets 8 meets the discharge requirements of 2.45 GHz to 4.2 GHz microwaves.

[0060] The present invention discloses a large-caliber broadband microwave discharge ion source, the structure of which is as follows: Figure 5 and Figure 6 As shown. The discharge cavity 1 is the core component, and the discharge chamber 2 is surrounded by the discharge cavity 1, the microwave connector 7 and the grid system 3; the discharge chamber 2 is the main place for the micro microwave ion thruster to generate plasma, and adopts a large-caliber design, the diameter of which should be greater than 3 cm and not greater than 10 cm, which can ensure that the magnetic array structure 11 can achieve the best effect.

[0061] In front of the discharge cavity 1, there are antenna 5, quartz plate 6, and microwave connector 7; in the center of the side of the discharge cavity 1, there is an air inlet pipe 4, and the air inlet pipe 4 and the microwave connector 7 are arranged axially vertically; behind the discharge cavity 1 is the grid system 3, which is fixed to the open end of the discharge cavity 1. The grid system 3 is composed of two metal grids (screen grid, acceleration grid) and insulating fixings. A large number of concentric circular holes are opened on the grid, and a specific electric field is formed by applying a DC voltage to accelerate and extract ions.

[0062] The magnetic array structure and the magnet fixing member 9 are located outside the discharge cavity 1 , wherein the magnetic array structure is clamped by the magnet fixing member 9 and the discharge cavity 1 .

[0063] The original installation method of the magnetic array is a compression method. The magnetic array is fixed by the front and rear end covers of the coaxial structure and the discharge cavity 1. During installation, the magnet is forcibly inserted into the cavity in the middle of the coaxial structure, which can easily cause irreversible damage to the fragile permanent magnet. In addition, multiple Halbach magnetic strips will attract each other during installation. Improper operation may cause the magnets to collide and break. The improved installation method is a buckling method. Each magnet is installed independently and has a corresponding card slot, so the magnet will not be damaged due to improper operation during installation. The specific operation method is that the magnetic strip is fixed by the magnet fixing part 9 and the discharge cavity 1, such as Figure 5 As shown, during installation, the tile-shaped magnet is first fixed in the slot of the magnet fixing member 9, and then the two are fixed together on the surface of the discharge cavity 1 by screws.

[0064] The installation position of the air intake pipe 4 is changed from the original end air intake to the side air intake, such as Figure 6 As shown. For the trumpet-shaped magnetic array structure, the installation position of the intake pipe 4 is located between the secondary magnet and the tertiary magnet of the Halbach magnetic strip, as shown in FIG. Figure 6 As shown. Figure 4 It can be observed from the magnetic field structure that horizontal gas intake from this position will allow the gas just flowing into the discharge chamber 2 to be immediately in an area that is easier to ionize, thereby reducing the difficulty of ignition of the large-aperture microwave discharge ion source.

[0065] Preferably, Figure 6 As shown, the discharge cavity 1 includes a stepped shaft section, a horn section and a cylindrical section connected in sequence; the magnetic array structure is arranged on the outer wall of the horn section, and the taper of the outer wall of the horn section is 45°, which can ensure that the magnetic field enhancement direction of each tile-type Halbach magnet 8 of the magnetic array structure points to the center of the distribution circle at an angle of 45°.

[0066] Specifically, the microwave joint 7 runs through the stepped shaft section, and the grid system 3 is bolted to the cylindrical section.

[0067] At the center of the narrow end of the discharge cavity 1 is an antenna 5 , which is connected to the inner conductor of the microwave connector 7 through threads and is used to emit microwaves into the discharge chamber 2 .

[0068] Antenna 5 is an important component for ignition of micro microwave ion thruster. Its size has been specially designed to match the electron cyclotron resonance region. The final effect is that the distance between the outermost edge of antenna 5 and the electron cyclotron resonance region can be controlled within 2.5mm to 3mm, which can maximize the success rate of ignition of micro microwave ion thruster and meet the discharge requirements of microwave frequency range of 2.45GHz to 4.2GHz. On the basis of achieving controllable distance, the round-head shape of antenna 5 can achieve good results.

[0069] Working process:

[0070] The working fluid gas flows into the discharge chamber 2 from the air inlet pipe 4; the microwave is transmitted by the coaxial line to the microwave connector 7 and fed into the discharge chamber 2 from the antenna 5, and initial electrons are generated by microwave induced discharge or microwave local electric field breakdown discharge. These electrons are constrained by the magnetic field and make reciprocating motion in the magnetic mirror; relying on the resonance of the microwave electric field and the electron cyclotron frequency, the electrons continuously gain energy and become high-energy electrons, further ionizing the gas to generate and maintain plasma. After ignition, a large amount of plasma is generated inside the discharge chamber 2. At this time, a voltage is applied to the grid system 3, the screen grid has a positive voltage, and the acceleration grid has a negative voltage, forming a high-voltage sheath to accelerate and extract the ions to generate an ion beam. A prototype has been produced for this embodiment, and relevant tests have been carried out. The test pictures are shown in the figure. Figure 7 As shown, the left picture is a picture taken directly facing the grid when the ion source is ignited, and the right picture is a picture of the extracted ion beam.

[0071] The present invention plays the role of constructing a magnetic field structure from the outside so that only the antenna 5 structure exists in the discharge chamber 2. Under the condition of ensuring the confinement of electrons and maintaining efficient discharge, it plays the role of preventing the magnet from being demagnetized by high temperature or erosion, and further improving the service life. At the same time, the horn-shaped magnetic array structure design not only meets the microwave broadband discharge requirements, but also meets the transmission conditions of right-handed circularly polarized waves in magnetic plasma, which can ensure that electrons are continuously heated, reduce microwave reflection, and further improve energy utilization efficiency.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A magnetic array structure of a large-aperture microwave discharge ion source, characterized in that: The magnetic array structure comprises a plurality of Halbach magnets (8); The magnetic field enhancement direction of each tile-shaped Halbach magnet (8) points to the center of the distribution circle at an angle, and multiple tile-shaped Halbach permanent magnets are evenly distributed on the circumference to form a trumpet shape; The magnetic array structure meets the discharge requirements of 2.45GHz to 4.2GHz microwaves; Each tile-type Halbach magnet (8) is composed of a multi-stage magnet, and the multi-stage requirement is not less than three stages; In terms of size, in two adjacent magnets, the lower base of the upper magnet and the upper base of the lower magnet are of the same length, and the lower base of the upper magnet is smaller than the lower base of the lower magnet; The hypotenuses of the multi-level magnets are collinear and have the same thickness; their heights are different and increase in sequence; The direction in which the first-stage magnet points toward the third-stage magnet is defined as the positive direction of the X-axis, and the direction in which the first-stage magnet moves away from the discharge chamber (2) is defined as the direction of the Z-axis; Then in the magnetic pole direction, the N pole of the first-level magnet is magnetized along the positive direction of the Z axis, the N pole of the second-level magnet is magnetized along the positive direction of the X axis, and the N pole of the third-level magnet is magnetized along the negative direction of the Z axis; If there are higher-level magnets, the N pole of the fourth-level magnet is magnetized along the negative direction of the X-axis, and the latter-level magnets are circulated with the first four-level magnets as a unit.

2. The magnetic array structure of the large-aperture microwave discharge ion source according to claim 1, characterized in that: In the coercive force distribution, the coercive force of the upper-level magnet is greater than that of the lower-level magnet; The coercive force ranges from 600 to 700 kA / m.

3. A large-aperture microwave discharge ion source comprising the magnetic array structure according to claim 1 or 2, characterized in that: The microwave discharge ion source comprises a discharge chamber (2), a magnetic array structure is installed outside the discharge chamber (2), and the diameter of the large diameter end of the discharge chamber (2) is greater than 3 cm.

4. The large-aperture microwave discharge ion source according to claim 3, characterized in that: The microwave discharge ion source comprises a discharge cavity (1), a microwave connector (7), an antenna (5) and a grid system (3); The discharge cavity (1), the microwave connector (7) and the grid system (3) surround and form a discharge chamber (2); An air inlet pipe (4) is provided on the side of the discharge cavity (1), and the air inlet pipe (4) and the microwave connector (7) are arranged axially and vertically; The discharge chamber (2) is a horn-shaped structure; the grid system (3) is installed at the large-diameter end of the discharge chamber (2), and the microwave connector (7) is installed at the small-diameter end of the discharge chamber (2); the antenna (5) is installed on the microwave connector (7) and extends into the discharge chamber (2); The magnetic array structure is installed outside the discharge chamber (2), and the magnetic array structure is clamped by a magnet fixing piece (9) and the discharge cavity (1).

5. The large-aperture microwave discharge ion source according to claim 4, characterized in that: The discharge chamber (1) comprises a stepped shaft section, a horn section and a cylindrical section which are connected in sequence; The magnetic array structure is arranged on the outer wall of the horn section; the microwave joint (7) runs through the stepped shaft section, and the grid system (3) is bolted to the cylindrical section.

6. The large-aperture microwave discharge ion source according to claim 4, characterized in that: The installation position of the air intake pipe (4) is located between two adjacent magnets of the tile-shaped Halbach magnet (8).

7. The large-aperture microwave discharge ion source according to claim 4, characterized in that: A quartz plate (6) is installed between the antenna (5) and the microwave connector (7).

8. The large-aperture microwave discharge ion source according to claim 4, characterized in that: The distance between the outermost edge of the antenna (5) and the electron cyclotron resonance region is controlled to be 2.5 mm to 3 mm.

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