A micro microwave discharge neutralizer and its working method

Abstract

The present invention belongs to the field of aerospace electric propulsion, and relates to a miniature microwave discharge neutralizer, including a shell, in which a joint cover plate, a top plate, a bottom plate and a hole plate connected in sequence are arranged, and the cavity formed by the top plate, the bottom plate and the hole plate includes a discharge cavity and a magnet placement cavity; there is a cavity area between the joint cover plate and the top plate, and the cavity area serves as a pressure equalizing chamber; the magnet placement cavity is arranged outside the discharge cavity, an antenna is arranged in the discharge cavity, and a magnetic array structure is arranged in the magnet placement cavity; the magnetic array structure is formed by a circular array of multiple Halbach magnetic strips, and each Halbach magnetic strip is spliced ​​by multiple magnetic block structures. The risk of high-temperature demagnetization is avoided from the root, the life of the neutralizer is increased, and the neutralizer is allowed to carry higher microwave power. The composition of the Halbach magnetic strip can be flexibly designed, and the working range can be changed by replacing the Halbach magnetic strip, covering a wider working range, reducing product costs and improving the applicable scenarios of the neutralizer.

Description

Technical Field

[0001] The present invention belongs to the field of aerospace electric propulsion, and in particular relates to a miniature microwave discharge neutralizer and a working method thereof. Background Art

[0002] The working principle of the microwave discharge neutralizer is as follows: microwaves are fed into the antenna in the discharge cavity, electrons are heated through the electron cyclotron resonance mechanism, high-energy electrons ionize neutral gas to produce plasma, and electron beams are emitted under the combined action of the static magnetic field and the external (virtual) anode.

[0003] The existing microwave discharge neutralizers mainly include: Figure 1 The μ10 and μ1 microwave discharge neutralizer systems shown are equipped with neutralizers, as well as Figure 2 The 10cm and 2cm microwave discharge neutralizer systems shown are equipped with neutralizers. The structures of these existing technologies all install permanent magnets inside the discharge cavity to construct a magnetic field, and use soft magnetic or hard magnetic materials to constrain the morphology of the electron cyclotron resonance zone. However, this approach will cause the permanent magnets, soft magnetic materials and hard magnetic materials to directly contact the plasma of several hundred degrees Celsius, and the vacuum environment is difficult to dissipate heat, which will face a severe risk of high-temperature demagnetization. If the material demagnetizes, the magnetic field configuration of the microwave discharge neutralizer will be destroyed, and the deformed electron cyclotron resonance zone will find it difficult to achieve the designed function, eventually leading to the failure of the neutralizer. In order to minimize the risk of demagnetization, existing technologies usually strictly limit the input microwave power, but the price that comes with it is that it is difficult to maximize the performance of the neutralizer. Summary of the Invention

[0004] The object of the present invention is to provide a miniature microwave discharge neutralizer and a working method thereof, which solve the problems of short life and low power limit of existing microwave discharge neutralizers caused by the risk of high-temperature demagnetization.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention discloses a micro microwave discharge neutralizer, comprising a housing, wherein a joint cover plate, a top plate, a bottom plate and a hole plate are sequentially connected in the housing, and a cavity formed by the top plate, the bottom plate and the hole plate comprises a discharge cavity and a magnet placement cavity;

[0007] There is a cavity area between the joint cover plate and the top plate, which serves as a pressure equalizing chamber;

[0008] The magnet placement cavity is arranged outside the discharge cavity, an antenna is arranged in the discharge cavity, and a magnetic array structure is arranged in the magnet placement cavity;

[0009] The magnetic array structure is composed of a circular array of multiple Halbach magnetic strips, and each Halbach magnetic strip is composed of multiple magnetic block structures.

[0010] Furthermore, the antenna is connected with a microwave connector; a transmitting hole is opened in the center of the orifice plate;

[0011] A plurality of vent holes are prefabricated on the top plate, and the pressure equalizing chamber is connected with the discharge cavity through the vent holes.

[0012] Furthermore, the diameter of the discharge chamber is less than or equal to 2.5 cm.

[0013] Furthermore, the distance between the antenna and the electron cyclotron resonance region is adjusted to within 0.5 mm.

[0014] Furthermore, the magnetic array structure is composed of 6 Halbach magnetic strips arranged in a circular array outside the discharge cavity, and the magnetic field enhancement of each permanent magnet points to the center of the distribution circle where the ring is located.

[0015] Furthermore, each Halbach magnetic stripe adopts a three-magnetic block structure or a four-magnetic block structure.

[0016] Furthermore, the three-magnetic block structure consists of a front-stage magnetic block, a middle-stage magnetic block and a rear-stage magnetic block. When installed, the front-stage magnetic block is close to the microwave incident port, and the rear-stage magnetic block is close to the orifice plate;

[0017] The cross-sectional dimensions of the three magnets are the same. In terms of length, the front magnet is the smallest, the middle magnet is the second largest, and the rear magnet is the largest.

[0018] In terms of coercive force, the front magnetic block is the largest, the middle magnetic block is the second, and the rear magnetic block is the smallest;

[0019] The direction in which the front-stage magnetic block points to the rear-stage magnetic block is defined as the positive direction of the x-axis, and the direction in which the front-stage magnetic block is away from the discharge cavity is defined as the positive direction of the z-axis. Then, in the magnetization direction, the front-stage magnetic block is magnetized along the positive direction of the z-axis, away from the discharge cavity; the intermediate magnetic block is magnetized along the positive direction of the x-axis, and the microwave incident end points to the direction of the orifice plate; the rear-stage magnetic block is magnetized along the negative direction of the z-axis, pointing to the discharge cavity.

[0020] Furthermore, the four-magnetic block structure is composed of magnetic block No. 1, magnetic block No. 2, magnetic block No. 3 and magnetic block No. 4. When installed, magnetic block No. 1 is close to the microwave incident port and magnetic block No. 4 is close to the orifice plate;

[0021] The four magnets have the same cross-sectional dimensions, with magnet No. 1 being the larger in length and the other three being smaller.

[0022] In terms of coercive force, the No. 1 magnetic block has the largest coercive force, followed by the No. 4 magnetic block; the No. 2 and No. 3 magnetic blocks have smaller coercive forces;

[0023] In the magnetization direction, the direction in which magnet block No. 1 points to magnet block No. 4 is defined as the positive direction of the x-axis, and the direction in which magnet block No. 1 is away from the discharge cavity is defined as the positive direction of the z-axis. Then, in the magnetization direction, magnet block No. 1 is magnetized along the positive direction of the z-axis, away from the discharge cavity; magnet block No. 2 is magnetized along the positive direction of the x-axis, with the microwave incident end pointing toward the orifice plate; magnet block No. 3 is magnetized along the negative direction of the z-axis, pointing toward the discharge cavity; and magnet block No. 4 is magnetized along the negative direction of the x-axis.

[0024] Furthermore, the cross-sectional dimensions and total length of the four-magnetic block structure are the same as those of the three-magnetic block structure.

[0025] The present invention also discloses a working method of the micro microwave discharge neutralizer, which includes the following steps:

[0026] The working fluid gas enters the equalizing chamber and then flows into the discharge cavity after equalizing the pressure;

[0027] Microwaves are transmitted via a coaxial cable to a microwave connector and fed into a discharge cavity from an antenna. Microwave-induced discharge or microwave local electric field breakdown discharge generates initial electrons, which are confined by a magnetic field and move back and forth in a magnetic mirror. Relying on the resonance between 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.

[0028] After ignition, a large amount of plasma is generated inside the discharge chamber. The plasma migrates toward the orifice plate under the action of the magnetic field gradient. At this time, a positive voltage is applied to the external anode plate. Under the combined action of the static magnetic field and the electrostatic field, the ions are shielded at the orifice plate and electrons are emitted out of the orifice plate.

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

[0030] The present invention discloses a miniature microwave discharge neutralizer, which uses a magnetic array structure to provide a magnetic field, moves the permanent magnet to the periphery of the discharge chamber, and does not require soft magnetic or hard magnetic materials in the discharge chamber. Through such an operation, the risk of high-temperature demagnetization can be avoided at the root, the life of the neutralizer can be improved, the neutralizer can be allowed to carry higher microwave power, and an axial emission magnetic field can be constructed to improve electron extraction performance. In addition, the structure of the Halbach magnetic strip can be flexibly designed. The present invention can change the working range by replacing only the Halbach magnetic strip while keeping other parts unchanged, covering a wider working range, reducing product costs and increasing the applicable scenarios of the neutralizer.

[0031] Furthermore, the magnetic array structure, composed of six permanent magnets, provides higher magnetic induction intensity than conventional bar magnets without sacrificing essential functional structures such as magnetic mirrors and magnetic traps. This allows for the free configuration of the electron cyclotron resonance region, resulting in a high-performance magnetic field configuration. This magnetic array structure is key to the present invention's ability to place permanent magnets outside the discharge chamber.

[0032] Furthermore, the magnetic field configuration inside the discharge chamber of the neutralizer has three significant features. First, the overall magnetic field gradient points from the microwave incident end to the orifice plate, which can induce the plasma to migrate to the magnetic trap position upstream of the orifice plate, thereby improving the electron extraction capability; second, the distance between the electron cyclotron resonance zone and the antenna can be adjusted within 0.5 mm, which can enhance the electron cyclotron resonance heating mechanism and improve the electron energy acquisition efficiency, thereby reducing the difficulty of neutralizer ignition and increasing the ionization efficiency; finally, there is an obvious electron emission zone near the orifice plate. There are significant magnetic lines of force along the axis outward in this area, which allow electrons to move directly outside the orifice plate along the magnetic lines of force, further improving the electron extraction capability.

[0033] Furthermore, the Halbach magnetic strip has two construction methods: three-block and four-block. The number, size, and coercive force relationship of the two construction methods are different. The main functional difference between the two is that the axial magnetic lines of force in the electron emission area of ​​the four-block magnetic strip are more concentrated, and the pulled electrons will be better focused in the emission hole of the aperture plate and drawn out, which can obtain a higher electron beam current, corresponding to a larger beam current working environment; while the axial magnetic lines of force in the electron emission area of ​​the three-block magnetic strip are more dispersed, and some electrons will collide with the aperture plate instead of being directly drawn out from the emission hole, so it corresponds to a smaller beam current working environment. In actual applications, the working range of the neutralizer can be switched by switching the magnetic blocks. The working range can be changed while other parts remain unchanged, reducing product costs and increasing the applicable scenarios of the neutralizer.

[0034] Furthermore, the cross-sectional dimensions and total length of the four-magnetic block structure are the same as those of the three-magnetic block design, so there is no need to modify the dimensions of the top plate and the bottom plate. It is more versatile and only requires replacing the magnetic block structure according to needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic diagram of the neutralizer structure used for conventional μ10 and 10cm microwave discharge neutralizer systems;

[0036] Figure 2 A schematic diagram of the neutralizer structure used for conventional μ1 and 2cm microwave discharge neutralizer systems;

[0037] Figure 3 This is an assembly diagram of a prototype of a small-caliber micro microwave discharge neutralizer disclosed in the present invention;

[0038] Figure 4 This is a cross-sectional view of a prototype of a small-caliber micro-microwave discharge neutralizer disclosed in the present invention;

[0039] Figure 5 The three views and isometric view of the magnetic array structure in the embodiment; Figure 5 (a) Main view, Figure 5(b) is a side view; Figure 5 (c) is a top view; Figure 5 (d) is the isometric view;

[0040] Figure 6 Schematic diagram of the Halbach magnetic stripe structure used in the embodiment; Figure 6 (a) is a schematic diagram of the Halbach magnetic stripe structure with three magnetic blocks. Figure 6 (b) is a schematic diagram of the Halbach magnetic stripe structure with four magnetic blocks;

[0041] Figure 7 The magnetic field distribution formed by the three-magnetic block magnetic array structure in the embodiment;

[0042] Figure 8 The magnetic field distribution formed by the four-magnetic-block magnetic array structure in the embodiment;

[0043] Figure 9 This is a photo of the beam extraction of the microwave discharge neutralizer prototype in the embodiment;

[0044] Figure 10 This is the volt-ampere characteristic curve of the microwave discharge neutralizer prototype in the embodiment.

[0045] Among them: 1. Air inlet pipe; 2. Connector cover; 3. Microwave connector; 4. Pressure equalizing chamber; 5. Top plate; 6. Bottom plate; 7. Magnetic array structure; 8. Antenna; 9. Discharge cavity; 10. Orifice plate. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the present invention more clear, the following is a further detailed description 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 intended to limit the present invention. That is, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments.

[0047] The components described and illustrated in the drawings and embodiments of the present invention may be arranged and designed in a variety of different 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. All other embodiments derived by those skilled in the art based on the drawings and embodiments of the present invention without inventive effort shall fall within the scope of protection of the present invention.

[0048] 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 apparatus 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 apparatus.

[0049] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0050] To address the short lifespan and low power limit faced by existing miniaturized microwave discharge neutralizers during miniaturization, the present invention provides a miniature microwave discharge neutralizer that utilizes a magnetic array structure 7 constructed with three or four magnetic blocks to provide a magnetic field. This allows permanent magnets to be positioned outside the discharge chamber 9, eliminating the need for soft or hard magnetic materials within the discharge chamber 9. The present invention is further described below with reference to the accompanying drawings.

[0051] The present invention discloses a small-caliber micro microwave discharge neutralizer, the structure of which is as follows: Figure 3 and Figure 4 As shown in the figure, from front to back, it is divided into three main areas: intake area, discharge area and extraction area.

[0052] The air intake area mainly includes the plenum chamber 4, the joint cover plate 2, the microwave joint 3, and the air intake pipe 1. The working medium enters the plenum chamber 4, which is surrounded by the joint cover plate 2 and the top plate 5, through the air intake pipe 1. After circulating in the plenum chamber 4, the working medium flows through the six inclined holes (i.e., vents) punched in the top plate 5 and flows into the discharge cavity 9 relatively evenly.

[0053] The discharge area mainly includes a discharge cavity 9, an antenna 8, a top plate 5, a bottom plate 6, and a magnetic array structure 7. The cavity formed by the top plate 5, the bottom plate 6, and the orifice plate 10 includes a discharge cavity 9 and a magnet placement cavity; the magnet placement cavity is arranged outside the discharge cavity 9, the antenna 8 is arranged in the discharge cavity 9, and the magnetic array structure 7 is arranged in the magnet placement cavity.

[0054] The discharge chamber 9 serves as the site for plasma generation. Due to the small-aperture characteristics of the present invention, its inner diameter should not exceed 2.5 cm. The antenna 8 serves as an important medium for transmitting microwave electromagnetic waves. Its diameter should be designed to be within 0.5 mm of the electron cyclotron resonance region. The shape of the antenna 8 is not limited, and both round-head and T-shaped shapes are applicable. The magnetic array structure 7 is placed outside the discharge chamber 9 and fixed by the top plate 5 and the bottom plate 6. It is configured by six Halbach magnetic strips. The directions of the enhanced magnetic fields of the magnetic strips all point to the axis of the discharge chamber 9. The magnetic strips have two available structures: three magnetic blocks and four magnetic blocks, corresponding to small beam and large beam working environments, respectively.

[0055] The extraction area mainly includes the orifice plate 10. The orifice plate 10 is a thin metal sheet with an electron emission hole in the center. It is fixed to the bottom surface of the base plate 6. The emission hole has a diameter of no more than 3mm. The external anode potential attracts electrons outside the hole to form an electron beam.

[0056] Next, the magnetic array is described in detail.

[0057] The magnetic array structure 7 designed by the present invention is configured by six Halbach magnetic strips, and the directions of the enhanced magnetic fields of the magnetic strips are all directed to the axis of the discharge chamber 9, such as Figure 5 (a) to Figure 5 As shown in (d), six Halbach magnetic strips are arranged in a circular array outside the discharge chamber 9, and the magnetic field enhancement of each Halbach magnetic strip points to the center of the distribution circle where the ring is located. Halbach magnetic strips have two available structures: three magnetic blocks and four magnetic blocks. Figure 6 shown.

[0058] Among them, the three-magnetic block structure consists of three magnetic blocks: front stage, middle stage and rear stage, such as Figure 6 As shown in (a). During installation, the front-stage magnet is closer to the microwave incident port, and the rear-stage magnet is closer to the orifice plate 10. The installation direction is very critical. If the installation direction is opposite, it is basically impossible to extract electrons. The three magnets have the same cross-sectional dimensions. In terms of length, the front-stage magnet is the smallest, the intermediate magnet is the second largest, and the rear-stage magnet is the largest. In terms of coercive force, the front-stage magnet is the largest, the intermediate magnet is the second largest, and the rear-stage magnet is the smallest, but the difference between the three is not large, all remaining in the range of 500-600kA / m. In terms of magnetization direction, the front-stage magnet is magnetized along the positive direction of the z-axis, away from the direction of the discharge cavity 9; the intermediate magnet is magnetized along the positive direction of the x-axis, with the microwave incident end pointing towards the direction of the orifice plate 10; and the rear-stage magnet is magnetized along the negative direction of the z-axis, pointing towards the direction of the discharge cavity 9.

[0059] The four-magnetic block structure consists of four magnetic blocks, No. 1, No. 2, No. 3 and No. 4, such as Figure 6 As shown in (b). During installation, magnet No. 1 is closer to the microwave incident port, and magnet No. 4 is closer to the orifice plate 10. The installation direction is also very strict. The four magnets have the same cross-sectional dimensions, but magnet No. 1 is larger in length, while magnets No. 2, 3, and 4 are smaller. In terms of coercive force, magnet No. 1 has the largest coercive force, followed by magnet No. 4, and the coercive forces of both are in the range of 500-800 kA / m; the coercive forces of magnets No. 2 and No. 3 are very small, in the range of 0-200 kA / m. In terms of magnetization direction, magnets No. 1, 2, and 3 are the same as the front-stage, middle-stage, and rear-stage magnets in the three-magnet structure, respectively, while the newly added magnet No. 4 is magnetized along the negative direction of the x-axis, that is, the direction in which the orifice plate 10 points to the microwave incident end.

[0060] More preferably, the cross-sectional dimensions and total length of the four-magnet structure are the same as those of the three-magnet structure, so there is no need to modify the dimensions of the top plate 5 and the bottom plate 6 .

[0061] The magnetic field configuration formed by the magnetic array structure 7 established by the three magnetic blocks is as follows: Figure 7 As shown, it can be seen that the emission area is large, and most of the magnetic lines of force are directed directly to the orifice plate 10. A considerable number of electrons will not be able to pass through the emission hole, but will directly bombard the orifice plate 10, so the electron beam is relatively smaller; and the magnetic field configuration formed by the magnetic array structure 7 established by the four magnetic blocks is as follows Figure 8 As shown, the emission area is relatively concentrated, and the magnetic lines of force all pass directly through the emission aperture. Electrons do not bombard the aperture plate 10, resulting in a relatively larger electron beam current. It can be seen that the four-magnetic block structure constrains the emission area by adding a new magnetic block, and maintains the front-end discharge structure basically unchanged by adjusting the size and coercive force of the magnetic block. This allows the present invention to switch the working range without replacing other parts, only the magnetic block structure.

[0062] like Figure 9 The image shown is a real-life image of the micro-microwave discharge neutralizer of the present invention in operation. Specifically, the image depicts the electron beam flow captured from the side of the neutralizer during operation. The luminous column in the image represents the electron beam flow. To the right of the electron beam flow is the location of the neutralizer's orifice plate 10, and to the left is the external anode plate.

[0063] like Figure 10 The figure shows the electron beam current-anode voltage curve of the micro microwave discharge neutralizer of the present invention, which is the working characteristic measured in the experiment. It can be observed that the neutralizer can draw an electron beam current of not less than 35mA at an external anode voltage of 100V under a microwave power of 7.5W, indicating excellent performance.

[0064] The complete working process of the small-caliber micro microwave discharge neutralizer of the present invention is as follows:

[0065] The working fluid enters the plenum chamber 4, formed by the connector cover 2 and the top plate 5, through the inlet pipe 1. After circulating in the plenum chamber 4, it flows through the vent holes in the top plate 5 and flows relatively evenly into the discharge chamber 9. After ventilation, microwave electromagnetic waves are transmitted from the power supply to the microwave connector 3 via a coaxial cable and incident on the discharge chamber 9 through the microwave antenna 8. Subsequently, microwave-induced discharge or microwave local electric field breakdown discharge generates initial electrons. These electrons are confined by magnetic mirrors and undergo reciprocating motion. During this reciprocating motion, they absorb energy from the electromagnetic waves as they pass through the electron cyclotron resonance region, forming high-energy electrons. These high-energy electrons collide with neutral particles, forming an electron avalanche and ultimately generating a high-density plasma. Induced by the magnetic field gradient, the plasma migrates toward the magnetic trap upstream of the orifice plate 10. At this point, a positive voltage is applied to the external anode plate. The static magnetic field and electrostatic fields act together to shield ions at the orifice plate 10, while electrons are emitted through the small holes in the orifice plate 10.

[0066] Throughout the entire operation, the neutralizer requires only one microwave power source, eliminating the need for a DC power source. Because the dimensions of antenna 8 and the electron cyclotron resonance region are specifically designed, with the distance between them kept within 0.5 mm, the present invention significantly reduces ignition time compared to existing technologies. After the gas enters discharge chamber 9, microwave power is applied and ignition occurs within one minute, resulting in a more stable ignition process.

[0067] The present invention uses a magnetic array structure 7 constructed with three or four magnetic blocks to provide a magnetic field, which can move the permanent magnet to the periphery of the discharge chamber 9, and no soft magnetic or hard magnetic material is required in the discharge chamber 9. Through such an operation, the risk of high-temperature demagnetization can be avoided at the root, the life of the neutralizer can be improved, the neutralizer can be allowed to carry higher microwave power, and an axial emission magnetic field can be constructed to improve the electron extraction performance. In addition, the present invention can change the working range while keeping other parts unchanged by replacing only the Halbach magnetic strip, covering a wider working range, reducing product costs and improving the applicable scenarios of the neutralizer.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the 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 by the scope of protection of the claims of the present invention.

Claims

1. A micro microwave discharge neutralizer, characterized in that: The invention comprises a shell, wherein a joint cover plate (2), a top plate (5), a bottom plate (6) and a hole plate (10) which are connected in sequence are arranged in the shell, and a cavity formed by the top plate (5), the bottom plate (6) and the hole plate (10) comprises a discharge cavity (9) and a magnet placement cavity; There is a cavity area between the joint cover plate (2) and the top plate (5), and the cavity area serves as a pressure equalizing chamber (4); The magnet placement cavity is arranged outside the discharge cavity (9), an antenna (8) is arranged in the discharge cavity (9), and a magnetic array structure (7) is arranged in the magnet placement cavity; The magnetic array structure (7) is formed by a circular array of multiple Halbach magnetic strips, and each Halbach magnetic strip is formed by splicing multiple magnetic block structures; Each Halbach magnetic strip adopts a three-magnetic block structure or a four-magnetic block structure; The three-magnetic block structure is composed of a front-stage magnetic block, a middle-stage magnetic block and a rear-stage magnetic block. When installed, the front-stage magnetic block is close to the microwave incident port, and the rear-stage magnetic block is close to the orifice plate (10); The cross-sectional dimensions of the three magnets are the same. The front magnet is the smallest in length, followed by the middle magnet, and the rear magnet is the largest. In terms of coercive force, the front magnetic block is the largest, the middle magnetic block is the second, and the rear magnetic block is the smallest; The direction in which the front-stage magnetic block points to the rear-stage magnetic block is defined as the positive direction of the x-axis, and the direction in which the front-stage magnetic block is away from the discharge cavity (9) is defined as the positive direction of the z-axis. Then, in the magnetization direction, the front-stage magnetic block is magnetized along the positive direction of the z-axis, away from the discharge cavity (9); the intermediate magnetic block is magnetized along the positive direction of the x-axis, with the microwave incident end pointing in the direction of the orifice plate (10); and the rear-stage magnetic block is magnetized along the negative direction of the z-axis, pointing in the direction of the discharge cavity (9); The four-magnetic block structure is composed of a No. 1 magnetic block, a No. 2 magnetic block, a No. 3 magnetic block and a No. 4 magnetic block. When installed, the No. 1 magnetic block is close to the microwave incident port, and the No. 4 magnetic block is close to the orifice plate (10); The cross-sectional dimensions of the four magnets are the same, with magnet No. 1 being larger in length and the other three being smaller; In terms of the magnitude of coercive force, the No. 1 magnetic block has the largest coercive force, followed by the No. 4 magnetic block; the No. 2 and No. 3 magnetic blocks have smaller coercive forces; In the magnetization direction, the direction in which the No. 1 magnet blocks point to the No. 4 magnet blocks is defined as the positive direction of the x-axis, and the direction in which the No. 1 magnet blocks are away from the discharge cavity (9) is defined as the positive direction of the z-axis. Then, in the magnetization direction, the No. 1 magnet blocks are magnetized along the positive direction of the z-axis, away from the discharge cavity (9); the No. 2 magnet blocks are magnetized along the positive direction of the x-axis, with the microwave incident end pointing in the direction of the orifice plate (10); the No. 3 magnet blocks are magnetized along the negative direction of the z-axis, pointing in the direction of the discharge cavity (9); and the No. 4 magnet blocks are magnetized along the negative direction of the x-axis.

2. A micro microwave discharge neutralizer according to claim 1, characterized in that: The antenna (8) is connected to a microwave connector (3); a transmitting hole is opened at the center of the orifice plate (10); A plurality of vent holes are prefabricated on the top plate (5), and the pressure equalizing chamber (4) is connected to the discharge chamber (9) through the vent holes.

3. A micro microwave discharge neutralizer according to claim 1, characterized in that: The diameter of the discharge chamber (9) is less than or equal to 2.5 cm.

4. A micro microwave discharge neutralizer according to claim 1, characterized in that: The distance between the antenna (8) and the electron cyclotron resonance region is adjusted to within 0.5 mm.

5. A micro microwave discharge neutralizer according to claim 1, characterized in that: The magnetic array structure (7) is composed of 6 Halbach magnetic strips arranged in a circular array outside the discharge cavity (9), and the magnetic field enhancement of each permanent magnet points to the center of the distribution circle where the circular ring is located.

6. A micro microwave discharge neutralizer according to claim 1, characterized in that: The cross-sectional dimensions and total length of the four-magnetic block structure are the same as those of the three-magnetic block structure.

7. The working method of the micro microwave discharge neutralizer according to any one of claims 1 to 6, characterized in that: The process includes: The working fluid gas enters the pressure equalizing chamber (4) and flows into the discharge chamber (9) after pressure equalization; The microwave is transmitted from the coaxial line to the microwave connector (3) and fed from the antenna (8) into the discharge cavity (9), whereby initial electrons are generated through microwave induced discharge or microwave local electric field breakdown discharge. The initial electrons are confined by the magnetic field and reciprocate in the magnetic mirror. By virtue of the resonance between 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 (9), and the plasma migrates toward the vicinity of the orifice plate (10) under the action of the magnetic field gradient; at this time, a positive voltage is applied to the external anode plate, and under the combined action of the static magnetic field and the electrostatic field, ions are shielded at the orifice plate (10), and electrons are emitted from the orifice plate (10).

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