Self-neutralization microwave ion thruster and working method thereof

Abstract

The invention belongs to the technical field of aerospace propulsion, and relates to a self-neutralization microwave ion thruster and a working method thereof. The thruster comprises a discharge cavity A and a discharge cavity B which are communicated through a cavity connecting channel, the discharge cavity A, a microwave connector and a positive charge particle leading-out system form a discharge chamber A, and the discharge cavity B, the microwave connector and a negative charge particle leading-out system form a discharge chamber B in a surrounding mode. No permanent magnet is arranged on one side of the cavity connecting channel of the discharge cavity, the magnetic pole directions of magnetic fields provided by the two permanent magnet arrays are opposite, and communicated magnetic induction lines are formed in the cavity connecting channel. The magnetic induction lines communicated between the two discharge cavities guide the charged particles to move, so that the plasmas in the two discharge cavities are communicated, charge exchange is carried out, quasi-electric neutrality is maintained, and internal conditions are provided for plume neutralization at the downstream of the thruster. By applying direct-current bias voltage, the positive charge particle extraction system extracts positive charge particles, the negative charge particle extraction system extracts negative charge particles, and plume neutralization is achieved.

Description

Technical Field

[0001] The invention belongs to the field of aerospace propulsion technology, and in particular relates to a self-neutralizing microwave ion thruster and a working method thereof. Background Art

[0002] Microwave ion thrusters are a type of aerospace thrusters, with the characteristics of simple structure, high specific impulse, and high efficiency. Its working principle is: permanent magnets construct magnetic mirrors to confine electrons, and through the electron cyclotron resonance mechanism, microwave energy fed into the discharge chamber by antennas is used to heat electrons, high-energy electrons ionize neutral gases to produce plasma, and the grid system accelerates the ions to produce thrust.

[0003] At present, the plume self-neutralization technology of ion thrusters is mainly based on grid modulation, and is divided into two types: ion-ion thrusters and self-neutralizing radio frequency ion thrusters. The former applies a square wave voltage on the grid to allow positive and negative ions to be alternately extracted through the same grid or extracted separately through different grids; the latter applies a radio frequency voltage on the grid to extract ions through the same grid using the DC self-bias effect, and at the same time extracts electrons when the electron sheath collapses in each cycle, thereby achieving self-neutralization of the ion beam.

[0004] However, these two self-neutralization schemes face development bottlenecks. Ion-ion thrusters face application problems. On the one hand, the asymmetric magnetic field formed by the magnetic filtration device causes electron drift, which reduces the magnetic field's restraining force on electrons and increases thruster losses. On the other hand, in order to make the positive and negative ion beams equal in size, a complex grid voltage control system needs to be added, reducing the thruster's reliability. The mechanism for establishing a bias voltage between the screen grid and the acceleration grid of the self-neutralization RF ion thruster is complex, and it is currently impossible to achieve high voltage amplitude output and flexible control, which limits the thruster's performance improvement and continuous thrust adjustment capabilities.

[0005] In summary, the self-neutralization technology of gate modulation has development bottlenecks and application problems. It is necessary to develop a self-neutralization technology with a new working mode. Summary of the invention

[0006] The purpose of the present invention is to provide a self-neutralizing microwave ion thruster and a working method thereof, to provide a new technical solution for the self-neutralization of ion thruster plumes, and to solve the problem of excessive power demand of the power supply in the self-neutralization technology based on the gate voltage waveform modulation method.

[0007] The present invention is achieved through the following technical solutions:

[0008] The present invention discloses a self-neutralizing microwave ion thruster, comprising a microwave plasma source A, a microwave plasma source B and a cavity connecting channel;

[0009] The microwave plasma source A comprises a discharge cavity A, a permanent magnet array A, a microwave connector A and a positively charged particle extraction system, wherein the discharge cavity A, the microwave connector A and the positively charged particle extraction system surround a discharge chamber A; the permanent magnet array A is installed outside the discharge cavity A;

[0010] The microwave plasma source B includes a discharge cavity B, a permanent magnet array B, a microwave connector B and a negative charge particle extraction system. The discharge cavity B, the microwave connector B and the negative charge particle extraction system surround a discharge chamber B. The permanent magnet array B is installed outside the discharge cavity B.

[0011] The discharge chamber A and the discharge chamber B are arranged axially in parallel, and the discharge chamber A and the discharge chamber B are connected through a cavity connecting channel;

[0012] A positively charged particle extraction system is used to extract positively charged particles and accelerate them to generate thrust;

[0013] The negatively charged particle extraction system is used to extract the negatively charged particles, and the negatively charged particles are neutralized with the positively charged particles extracted by the positively charged particle extraction system.

[0014] Furthermore, both discharge chamber A and discharge chamber B are trumpet-shaped structures;

[0015] The positive charge particle extraction system is installed at the wide end of the discharge chamber A, the negative charge particle extraction system is installed at the wide end of the discharge chamber B, the microwave connector A is installed at the narrow end of the discharge chamber A, and the microwave connector B is installed at the narrow end of the discharge chamber B; antennas are installed on both the microwave connector A and the microwave connector B;

[0016] An air inlet pipe arranged perpendicularly to the axial direction of the microwave joint A is provided on the side of the discharge cavity A; an air inlet pipe arranged perpendicularly to the axial direction of the microwave joint B is provided on the side of the discharge cavity B.

[0017] Further, the discharge chamber A and the discharge chamber B each include a stepped shaft section, a horn section and a cylindrical section connected in sequence;

[0018] The permanent magnet array A is arranged on the outer wall of the horn section of the discharge cavity A, and the permanent magnet array B is arranged on the outer wall of the horn section of the discharge cavity B; the microwave joint A runs through the stepped shaft section of the discharge cavity A, and the microwave joint B runs through the stepped shaft section of the discharge cavity B; the positive charge particle extraction system is bolted to the cylindrical section of the discharge cavity A, and the negative charge particle extraction system is bolted to the cylindrical section of the discharge cavity B.

[0019] Furthermore, openings are prefabricated on the sides of the horn sections of the discharge cavity A and the discharge cavity B, and the size of the openings is consistent with the external size of the cavity connecting channel, so as to be connected with the cavity connecting channel.

[0020] Furthermore, the cavity connecting channel is a trapezoidal square tube structure.

[0021] Furthermore, the length of the upper bottom side of the cavity connecting channel is greater than or equal to the sum of the radial widths of the cylindrical sections of the discharge cavity A and the discharge cavity B.

[0022] Furthermore, there is no permanent magnet on one side of the cavity connecting channel of the discharge cavity A, and there is no permanent magnet on one side of the cavity connecting channel of the discharge cavity B; the magnetic field poles provided by the permanent magnet array A and the permanent magnet array B are in opposite directions, so that connected magnetic flux lines are formed inside the cavity connecting channel.

[0023] Furthermore, the permanent magnet array A and the permanent magnet array B are composed of multiple tile-type Halbach magnets;

[0024] 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 outer wall of the discharge cavity in a trumpet shape;

[0025] Each tile-type Halbach magnet is composed of multiple-stage magnets, and the multi-stage requirement is not less than three;

[0026] 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;

[0027] The hypotenuses of the multi-level magnets are collinear and have the same thickness; their heights are different and increase in sequence;

[0028] In the coercive force distribution, the coercive force of the upper-level magnet is greater than or equal to the coercive force of the lower-level magnet.

[0029] 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 cavity is defined as the Z-axis direction;

[0030] Then, in the magnetic pole direction, the N pole of the first-level magnet of the permanent magnet array A 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; the N pole of the first-level magnet of the permanent magnet array B is magnetized along the negative direction of the Z axis, the N pole of the second-level magnet is magnetized along the negative direction of the X axis, and the N pole of the third-level magnet is magnetized along the positive direction of the Z axis;

[0031] If there are higher-order magnets, the N pole of the fourth-order magnet of permanent magnet array A is magnetized along the negative direction of the X-axis, and the N pole of the fourth-order magnet of permanent magnet array B is magnetized along the positive direction of the X-axis. The latter-order magnets are circulated with the first four-order magnets as a unit.

[0032] The present invention also discloses a working method of the self-neutralizing microwave ion thruster, comprising the following process:

[0033] The working fluid gas enters discharge chamber A and discharge chamber B respectively, and generates initial electrons 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. Relying on the microwave electric field and electron cyclotron resonance, the electrons continuously absorb microwave energy to become high-energy electrons, further ionize the gas, and generate and maintain plasma.

[0034] After ignition, a large amount of plasma is generated inside the discharge chamber A and the discharge chamber B, and under the action of the magnetic field, the plasma moves to the cavity connection channel, connecting the plasma in the discharge chamber A and the discharge chamber B, realizing charge exchange, so that the plasma inside the discharge chamber maintains quasi-electrical neutrality;

[0035] A positive voltage is applied to the positively charged particle extraction system, and a negative voltage is applied to the negatively charged particle extraction system. Under the action of electrostatics, the positively charged particles are extracted from the discharge chamber A, and the negatively charged particles are extracted from the discharge chamber B, and the plume self-neutralization is achieved downstream of the thruster.

[0036] Compared with the prior art, the present invention has the following beneficial technical effects:

[0037] The invention discloses a self-neutralizing microwave ion thruster, comprising a discharge cavity, a microwave joint, an antenna, a permanent magnet array, a positive charge particle extraction system and a negative charge particle extraction system; the discharge cavity comprises a discharge cavity A, a discharge cavity B and a cavity connection channel; the discharge cavity A, the microwave joint and the positive charge particle extraction system surround to form a discharge chamber A; the discharge cavity B, the microwave joint and the negative charge particle extraction system surround to form a discharge chamber B; the discharge cavity A and the discharge cavity B are arranged axially in parallel and welded together with the cavity connection channel to make the discharge chamber A and the discharge chamber B connected; the permanent magnet array is installed outside the discharge cavity, comprising the permanent magnet array A and the permanent magnet array B; by applying a DC bias voltage, the positive charge particle extraction system extracts positive charge particles, and the negative charge particle extraction system extracts negative charge particles, so as to realize plume neutralization.

[0038] Furthermore, the permanent magnet array A and the permanent magnet array B use tile-type Halbach magnets with opposite magnetic pole directions. The N pole of the permanent magnet array A points from the wide end of the discharge chamber A to the narrow end, and the N pole of the permanent magnet array B points from the narrow end of the discharge chamber B to the wide end. The number of permanent magnet arrays is adapted to the shape of the discharge cavity. There is no permanent magnet on one side of the cavity connection channel section, so that a connected magnetic flux line is formed inside the cavity connection channel. The connected magnetic flux lines between the discharge cavity A and the discharge cavity B can guide the movement of charged particles, so that the plasma in the discharge chamber A and the discharge chamber B are connected, and charge exchange can be performed to maintain quasi-electrical neutrality. By applying a DC bias voltage, the positive charge particle extraction system extracts positive charge particles, and the negative charge particle extraction system extracts negative charge particles, so as to achieve plume neutralization. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a structural diagram of a prototype of the self-neutralizing microwave ion thruster of the present invention;

[0040] Figure 2 A cross-sectional view of a prototype of a novel self-neutralizing microwave ion thruster provided in an embodiment;

[0041] Figure 3 This is a schematic diagram of the principle of a novel self-neutralizing microwave ion thruster provided in an embodiment of the present invention;

[0042] Figure 4 It is a schematic diagram of the structure of a single tile-type Halbach magnet; wherein, Figure (a) is a schematic diagram of the structure of a tile-type Halbach magnet in a permanent magnet array A; Figure (b) is a schematic diagram of the structure of a tile-type Halbach magnet in a permanent magnet array B;

[0043] Figure 5 The figure shows the magnetic field distribution formed by the permanent magnet array in the embodiment, where the white solid line is the electron cyclotron resonance region corresponding to the 2.45 GHz microwave; Figure (a) is a schematic diagram of the prototype cavity and the permanent magnet model; Figure (b) is an XZ section; Figure (c) is an XY section; Figure (d) is a YZ section;

[0044] Figure 6 This is an experimental image of the Xe working medium beam extraction from the self-neutralization microwave ion thruster in the embodiment;

[0045] Figure 7 : is a diagram of the potential distribution in the space downstream of the thruster when different voltages are applied to the screen grid A in the embodiment;

[0046] Figure 8 For Figure 1 The corresponding simulation diagram.

[0047] Among them: 1. discharge cavity A; 2. positive charge particle extraction system; 3. cavity connection channel; 4. negative charge particle extraction system; 5. discharge cavity B; 6. discharge chamber B; 7. permanent magnet array B; 8. antenna; 9. microwave connector B; 10. air inlet pipe; 11. permanent magnet array A; 12. discharge chamber A; 13. magnet fixing part; 14. microwave connector A. 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 variants are intended to cover non-exclusive inclusion, so that a process, element, method, article or device that includes a series of elements includes not only those elements, but also includes other elements that are not explicitly listed, or also includes elements inherent to the process, element, method, article or device. In addition, the terms "horizontal" and "vertical" are based on the orientation and positional relationship of the devices or components shown in the drawings, and are only for the purpose of better describing the present invention, rather than requiring the devices, components or equipment shown to have this specific orientation, and therefore cannot be understood as limiting the present invention.

[0051] In view of the development bottleneck problem faced by the existing self-neutralization scheme of ion thrusters with gate voltage waveform modulation, the present invention proposes a self-neutralizing microwave ion thruster based on magnetic field control, designs two discharge chamber structures, and uses a specific permanent magnet array structure to form a connecting magnetic field in the cavity connecting channel 3 of the discharge cavity, guides the plasma in the two discharge chambers to be connected, maintains the quasi-electrical neutrality of the internal plasma, and uses the positive charge particle extraction system 2 and the negative charge particle extraction system 4 to respectively extract the positive charge particles and the negative charge particles to achieve plume neutralization.

[0052] The features and performances of the present invention are further described in detail below in conjunction with the embodiments.

[0053] The present invention discloses a self-neutralizing microwave ion thruster based on a magnetic field control method, the structure of which is as follows: Figure 1 , Figure 2 , Figure 3 and Figure 8 As shown. The discharge cavity A1, the discharge cavity B5 and the cavity connection channel 3 are welded together to form a main structure discharge cavity; the discharge cavity A1, the microwave joint A14 and the positive charge particle extraction system 2 surround to form a trumpet-shaped discharge chamber A12, the discharge cavity B5, the microwave joint B9 and the negative charge particle extraction system 4 surround to form a trumpet-shaped discharge chamber B6, and the discharge chamber A12 and the discharge chamber B6 are connected through the cavity connection channel 3.

[0054] Microwave connectors and antennas 8 are installed at the narrow ends of the discharge cavity A1 and the discharge cavity B5;

[0055] The discharge cavity A1 and the discharge cavity B5 are provided with an air inlet pipe 10 arranged perpendicular to the axial direction of the microwave joint. The two air inlet pipes 10 are arranged in parallel to facilitate connection with the gas supply device.

[0056] A positive charge particle extraction system 2 is installed at the wide end of the discharge cavity A1, and the positive charge particle extraction system 2 is composed of two metal grids (screen grid A, acceleration grid A) and an insulating fixture; a negative charge particle extraction system 4 is installed at the wide end of the discharge cavity B5, and the negative charge particle extraction system 4 is composed of two metal grids (screen grid B, acceleration grid B) and an insulating fixture;

[0057] There are a large number of concentric holes on the metal gate, and a specific electric field is formed by applying a DC voltage to accelerate and extract ions and electrons;

[0058] like Figure 3 As shown, the positively charged particle extraction system 2 applies a positive bias voltage to extract ions from the discharge chamber A12, and the negatively charged particle extraction system 4 applies a negative bias voltage to extract electrons from the discharge chamber B6 to achieve plume neutralization.

[0059] The periphery of the discharge cavity is a permanent magnet array fixed by a magnet fixing part 13 and the discharge cavity, which provides the required magnetic field conditions for ionization; the magnetic poles of the permanent magnet array A11 and the permanent magnet array B7 are arranged in opposite directions, and there is no permanent magnet array on the side close to the discharge cavity A1 and the discharge cavity B5, so that connected magnetic flux lines are formed in the cavity connecting channel 3, guiding the plasma in the discharge chamber A12 and the discharge chamber B6 to be connected, and maintaining the quasi-electrical neutrality of the internal plasma.

[0060] Preferably, Figure 2 As shown, the two discharge cavities have the same structure, both comprising a stepped shaft section, a horn section and a cylindrical section connected in sequence; the permanent magnet array is arranged on the outer wall of the horn section of the discharge cavity.

[0061] Specifically, the microwave joint runs through the stepped shaft section, and the positively charged particle extraction system 2 and the negatively charged particle extraction system 4 are bolted to the cylindrical section.

[0062] At the center of the narrow ends of the discharge cavities A1 and B5 is the antenna 8, which is threadedly connected to the inner conductor of the microwave connector and is used to emit microwaves into the discharge chamber A12 and the discharge chamber B6 respectively.

[0063] The horn sections of the discharge cavity A1 and the discharge cavity B5 are provided with openings on their sides, the size of which is consistent with the external size of the cavity connecting channel 3, and is used to fit tightly with the cavity connecting channel 3 and be connected by welding.

[0064] The cavity connecting channel 3 is a trapezoidal square tube structure, which is located outside the horn section of the discharge cavity and is closely close to the cylindrical section of the discharge cavity; the length of the upper bottom edge of the cavity connecting channel 3 is greater than or equal to the sum of the radial widths of the cylindrical sections of the discharge cavity A1 and the discharge cavity B5, so that the discharge cavity A1 is in contact with the cylindrical section of the discharge cavity B5.

[0065] Next, the permanent magnet array is described in detail.

[0066] The permanent magnet array designed in the present invention is adapted to the shape of the cavity, and includes a permanent magnet array A11 and a permanent magnet array B7, which are composed of multiple tile-shaped Halbach magnets. Figure 4 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.

[0067] Specifically, the thickness refers to the dimension in the Z-axis direction, and the height refers to the dimension in the X-axis direction.

[0068] In the coercive force distribution, the coercive force of the first-level magnet ≥ the coercive force of the second-level magnet ≥ the coercive force of the third-level magnet, and the coercive force range is 600-700 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. Then, in the magnetic pole direction, the N pole of the first-level magnet of the permanent magnet array A11 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; the N pole of the first-level magnet of the permanent magnet array B7 is magnetized along the negative direction of the Z-axis, the N pole of the second-level magnet is magnetized along the negative direction of the X-axis, and the N pole of the third-level magnet is magnetized along the positive direction of the Z-axis.

[0069] 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 of the permanent magnet array A11 is magnetized along the negative direction of the X-axis, which is a cycle, and 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; the N pole of the fourth-order magnet of the permanent magnet array B7 is magnetized along the positive direction of the X-axis, which is a cycle, and 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.

[0070] like Figure 5As shown in Figure (a), the permanent magnet array A11 and the permanent magnet array B7 in this embodiment respectively include 7 tile-type Halbach magnets. 7 are only one type in this embodiment, and other numbers can also be flexibly designed according to needs.

[0071] The 7 tile-shaped Halbach magnets of the permanent magnet array A11 are arranged in an octagonal array along the discharge cavity A1, and the directions of the magnet-enhanced magnetic field are all pointing to the axis of the discharge cavity A1; the 7 tile-shaped Halbach magnets of the permanent magnet array B7 are arranged in an octagonal array along the discharge cavity B5, and the directions of the magnet-enhanced magnetic field are all pointing to the axis of the discharge cavity B5. Among them, there is no permanent magnet at the place where the discharge cavity is connected to the cavity connection channel 3, so the permanent magnet array can form a connected magnetic flux line inside the cavity connection channel 3.

[0072] The magnetic field distribution formed by the permanent magnet array is as follows Figure 5 As shown, Figure 5 Figure (b) is the XZ section. Figure 5 Figure (c) is the XY section. Figure 5 Figure (d) is the YZ section. It can be seen that the magnetic field provided by the permanent magnet array can not only provide the magnetic field conditions required for ionization, but also form a connected magnetic field between the discharge cavity A1 and the discharge cavity B5, and there are connected magnetic flux lines in the cavity connection channel 3, which can guide the movement of charged particles, connect the plasma in the discharge chamber A12 and the discharge chamber B6, enable charge exchange, maintain quasi-electrical neutrality, and provide conditions for external plume neutralization.

[0073] The complete working process of the self-neutralizing microwave ion thruster of the present invention is as follows:

[0074] The working gas enters the discharge chamber A12 and the discharge chamber B6 from the inlet pipe 10, and the microwave is output by two microwave power supplies, transmitted to the microwave connector through two coaxial transmission lines, and fed into the discharge chamber A12 and the discharge chamber B6 from the antenna 8. The initial electrons are generated by microwave induced discharge or microwave local electric field breakdown discharge. These initial electrons are constrained by the magnetic field and reciprocate in the magnetic mirror; relying on the microwave electric field and electron cyclotron resonance, the electrons continuously absorb microwave energy to become high-energy electrons, further ionize the gas, generate and maintain plasma. After ignition, a large amount of plasma is generated inside the discharge chamber A12 and the discharge chamber B6, and under the action of the magnetic field, the plasma moves to the cavity connection channel 3, connecting the plasma in the discharge chamber A12 and the discharge chamber B6, realizing charge exchange, so that the plasma inside the discharge cavity maintains quasi-electric neutrality.

[0075] A DC voltage is applied to the positive charge particle extraction system 2, the screen grid A carries a positive voltage, the acceleration grid A is grounded, and the voltage of the screen grid A is greater than the voltage of the acceleration grid A to form a positive high-voltage sheath, and the ions in the discharge chamber A12 are accelerated and extracted to generate an ion beam. A DC voltage is applied to the negative charge particle extraction system 4 and the discharge cavity, a negative voltage is applied to the discharge cavity, a negative voltage is applied to the screen grid B, the acceleration grid B is grounded, and the voltage of the screen grid B is less than the voltage of the acceleration grid B to form a negative high-voltage sheath, and the electrons in the discharge chamber B6 are extracted to generate an electron beam. The ion beam generated by the positive charge particle extraction system 2 and the electron beam generated by the negative charge particle extraction system 4 are neutralized to achieve plume self-neutralization.

[0076] This embodiment has produced a prototype and carried out relevant tests, such as Figure 6 Shown is the beam extraction image under Xe working fluid. The thruster can generate ion beam and electron beam at the same time.

[0077] like Figure 7 The potential distribution in the space downstream of the thruster when different voltages are applied to screen A. It can be observed that compared with the voltage applied on screen A, the potential in the space downstream of the thruster is significantly lower, which can achieve plume neutralization.

[0078] The present invention designs a discharge cavity with two cavity structures connected by a cavity connecting channel 3, forms connected magnetic flux lines in the cavity connecting channel 3 through the permanent magnet array A11 and the permanent magnet array B7, connects the plasma in the discharge chamber A12 and the plasma in the discharge chamber B6, and exchanges charges, so that the plasma inside the discharge cavity maintains electrical neutrality, and at the same time, the positive charge particle extraction system 2 extracts ions and the negative charge particle extraction system 4 extracts electrons, thereby achieving plume neutralization.

[0079] 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 self-neutralizing microwave ion thruster, characterized in that: It comprises a microwave plasma source A, a microwave plasma source B and a cavity connecting channel (3); The microwave plasma source A comprises a discharge cavity A (1), a permanent magnet array A (11), a microwave connector A (14) and a positively charged particle extraction system (2); the discharge cavity A (1), the microwave connector A (14) and the positively charged particle extraction system (2) surround a discharge chamber A (12); the permanent magnet array A (11) is installed outside the discharge cavity A (1); The microwave plasma source B comprises a discharge cavity B (5), a permanent magnet array B (7), a microwave connector B (9) and a negative charge particle extraction system (4); the discharge cavity B (5), the microwave connector B (9) and the negative charge particle extraction system (4) surround a discharge chamber B (6); the permanent magnet array B (7) is installed outside the discharge cavity B (5); The discharge cavity A (1) and the discharge cavity B (5) are arranged axially in parallel, and the discharge chamber A (12) and the discharge chamber B (6) are connected through a cavity connecting channel (3); A positively charged particle extraction system (2) is used to extract positively charged particles and accelerate them to generate thrust; The negatively charged particle extraction system (4) is used to extract the negatively charged particles, and the negatively charged particles are neutralized with the positively charged particles extracted by the positively charged particle extraction system (2).

2. The self-neutralizing microwave ion thruster according to claim 1, characterized in that: The discharge chamber A (12) and the discharge chamber B (6) are both trumpet-shaped structures; The positive charge particle extraction system (2) is installed at the wide end of the discharge chamber A (12), the negative charge particle extraction system (4) is installed at the wide end of the discharge chamber B (6), the microwave connector A (14) is installed at the narrow end of the discharge chamber A (12), and the microwave connector B (9) is installed at the narrow end of the discharge chamber B (6); the antenna (8) is installed on both the microwave connector A (14) and the microwave connector B (9); An air inlet pipe (10) is arranged on the side of the discharge cavity A (1) and is arranged perpendicularly to the axial direction of the microwave joint A (14); and an air inlet pipe (10) is arranged on the side of the discharge cavity B (5) and is arranged perpendicularly to the axial direction of the microwave joint B (9).

3. The self-neutralizing microwave ion thruster according to claim 1, characterized in that: The discharge chamber A (1) and the discharge chamber B (5) both include a stepped shaft section, a horn section and a cylindrical section which are connected in sequence; A permanent magnet array A (11) is arranged on the outer wall of the horn section of the discharge cavity A (1), and a permanent magnet array B (7) is arranged on the outer wall of the horn section of the discharge cavity B (5); a microwave connector A (14) runs through the stepped shaft section of the discharge cavity A (1), and a microwave connector B (9) runs through the stepped shaft section of the discharge cavity B (5); a positive charge particle extraction system (2) is bolted to the cylindrical section of the discharge cavity A (1), and a negative charge particle extraction system (4) is bolted to the cylindrical section of the discharge cavity B (5).

4. The self-neutralizing microwave ion thruster according to claim 3, characterized in that: The horn sections of the discharge cavity A (1) and the discharge cavity B (5) are both prefabricated with openings, the size of the openings being consistent with the external size of the cavity connection channel (3) and being used for communicating with the cavity connection channel (3).

5. The self-neutralizing microwave ion thruster according to claim 1, characterized in that: The cavity connecting channel (3) is a trapezoidal square tube structure.

6. The self-neutralizing microwave ion thruster according to claim 5, characterized in that: The length of the upper bottom side of the cavity connecting channel (3) is greater than or equal to the sum of the radial widths of the cylindrical sections of the discharge cavity A (1) and the discharge cavity B (5).

7. The self-neutralizing microwave ion thruster according to claim 1, characterized in that: There is no permanent magnet on one side of the cavity connecting channel (3) of the discharge cavity A (1), and there is no permanent magnet on one side of the cavity connecting channel (3) of the discharge cavity B (5); The magnetic fields provided by the permanent magnet array A (11) and the permanent magnet array B (7) have opposite magnetic pole directions, so that interconnected magnetic flux lines are formed inside the cavity connecting channel (3).

8. The self-neutralizing microwave ion thruster according to claim 1, characterized in that: The permanent magnet array A (11) and the permanent magnet array B (7) are composed of multiple Halbach magnets. 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 outer wall of the discharge cavity in a trumpet shape; Each tile-type Halbach magnet is composed of multiple-stage magnets, and the multi-stage requirement is not less than three; 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; In the coercive force distribution, the coercive force of the upper-level magnet is greater than or equal to the coercive force of the lower-level magnet.

9. The self-neutralizing microwave ion thruster according to claim 1, characterized in that: 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 cavity is defined as the Z-axis direction; Then, in the magnetic pole direction, the N pole of the first-level magnet of the permanent magnet array A (11) 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; the N pole of the first-level magnet of the permanent magnet array B (7) is magnetized along the negative direction of the Z axis, the N pole of the second-level magnet is magnetized along the negative direction of the X axis, and the N pole of the third-level magnet is magnetized along the positive direction of the Z axis; If there are higher-order magnets, the N pole of the fourth-order magnet of permanent magnet array A (11) is magnetized along the negative direction of the X-axis, and the N pole of the fourth-order magnet of permanent magnet array B (7) is magnetized along the positive direction of the X-axis. The latter-order magnets are circulated with the first four-order magnets as a unit.

10. The operating method of the self-neutralizing microwave ion thruster according to any one of claims 1 to 9, characterized in that: The process includes: The working fluid gas enters the discharge chamber A (12) and the discharge chamber B (6) respectively, and generates initial electrons 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. Relying on the microwave electric field and electron cyclotron resonance, the electrons continuously absorb microwave energy to become high-energy electrons, further ionize the gas, and generate and maintain plasma. After ignition, a large amount of plasma is generated inside the discharge cavity A (1) and the discharge cavity B (5), and under the action of the magnetic field, the plasma moves to the cavity connecting channel (3), connecting the plasma in the discharge chamber A (12) and the plasma in the discharge chamber B (6), realizing charge exchange, so that the plasma inside the discharge cavity maintains quasi-electrical neutrality; A positive voltage is applied to the positively charged particle extraction system (2), and a negative voltage is applied to the negatively charged particle extraction system (4). Under the action of electrostatics, positively charged particles are extracted from the discharge chamber A (12), and negatively charged particles are extracted from the discharge chamber B (6), and plume self-neutralization is achieved downstream of the thruster.

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