CN117703701A - External discharge Hall thruster adopting planar cusped magnetic field design - Google Patents

Abstract

The invention provides an external discharge Hall thruster adopting a planar cusped magnetic field design, which comprises a thruster structure body, an outer ring magnet, a thruster ceramic wall surface, an additional anode, an outer magnet, a magnetic screen, an anode, a ceramic structure body, an inner magnet, a short insulating pad, an M2 flat washer, an M2 elastic washer, an M2 nut, a long insulating pad, an M3 flat washer, an M3 elastic washer and an M3 nut. According to the invention, the permanent magnet is added on the outer side of the additional anode to form a new magnetic mirror field to restrict electrons, so that the current of the additional anode is reduced; by adjusting the magnetic field near the surface of the anode, the positive gradient magnetic field on the surface of the anode weakens the bombardment heating of electrons during the working of the anode, and improves the phenomena of heating of the thruster and demagnetization of the permanent magnet; the insulation between the anode and the additional anode is increased, and the service life and reliability of the thruster are improved.

Description

External discharge Hall thruster adopting planar cusped magnetic field design

Technical Field

The invention belongs to the technical field of space electric propulsion, and particularly relates to an external discharge Hall thruster adopting a planar cusped magnetic field design.

Background

With the rise of commercial aerospace and the reduction of satellite transmission cost, the world is lifted with the tide of microsatellite networking. The need for accurate control of microsatellites has placed new demands on the miniaturization and low power of the electrical thrusters commonly used on satellites. The Hall electric thruster has the advantages of simple structure, no space charge effect, higher specific impulse than chemical propulsion, larger thrust density than the ion thruster, longer service life and the like, and is widely applied to the attitude and orbit control of a spacecraft at present, thereby becoming an important research object for the miniaturization and low-power design of the electric thruster.

Conventional hall thrusters, including steady state plasma thrusters (Stationary Plasma Thruster, SPT), anode layer thrusters (Anode Layer Thruster, ALT), etc., are structured with discharge channels composed of ceramic or metal. When the thruster is miniaturized, the surface-to-surface ratio of the discharge channel is increased, so that the erosion of plasma to the channel wall surface is aggravated, the service life of the thruster is reduced, and the service life of the thruster becomes a key problem to be overcome in the hall thruster miniaturized design.

The external discharge Hall thruster without the design of the discharge channel is a solution for solving the problem of corrosion of the wall surface of the Hall thruster and prolonging the service life of the thruster. However, because the discharge channel is not limited, the beam divergence angle of the thruster is larger than that of the traditional Hall thruster, which not only causes larger non-axial thrust loss, but also creates challenges for the safe operation of instruments and equipment at other parts on the satellite. Meanwhile, when the thruster selects larger working medium flow, the oscillation of the thruster is aggravated, and the normal operation of the satellite is threatened. To solve the above problems, us prinston proposed a solution to add an additional anode outside the hall thruster anode and by demonstrating its effect on the suppression of oscillations and on reducing the beam divergence angle. The additional anode applies positive voltage outside the anode, so that positive potential at the beam edge is improved, a certain compression effect is achieved on the ion beam, and the beam divergence angle of the thruster is reduced. Meanwhile, experiments also find that the additional anode can reduce the oscillation of the anode. Additional anodic effects the invention is not discussed in any great detail in document [1]. However, a certain current is generated on the additional anode, which increases the load of the satellite power supply and defeats the purpose of low power design of the thruster. Meanwhile, metal atoms sputtered from the anode can be deposited on the wall surfaces of the anode and the additional anode of the thruster in a back flow manner, and when the metal atoms are deposited to a certain thickness, the anode and the additional anode can be conducted, so that the thruster is short-circuited, and the control of the thruster and the safe operation of a satellite are not facilitated. Therefore, comprehensive optimization of the external discharge Hall thruster should be carried out, the additional anode current is reduced, and the working reliability of the thruster is improved.

At present, no published literature is found to introduce a method for reducing the current of an additional anode and reducing the power consumption of the additional anode, and the work of optimizing a magnetic field near the anode of an externally placed Hall thruster is less, and no published related scientific research results are found. Similar approaches exist in other areas of electric propulsion for solutions that avoid a decrease in resistance between the insulating elements due to the coating:

1. an insulated enhanced gate system resistant to sputter contamination: the sputtering coating phenomenon of the screen grid and the acceleration grid of the radio frequency ion thruster can cause the resistance between the grids to be reduced and the grids to be ignited, so that the performance loss of the thruster is caused. For this phenomenon, wang Weizong, other molecular and smart et al, university of Beijing aviation, pointed out that increasing the surface area of the spacers between the gates,The area of the surface of the inter-gate spacer which is difficult to be covered by metal atoms is manufactured artificially, so that the probability of ignition phenomenon caused by resistance reduction between gates can be reduced ^[3] 。

2. Electric thruster with tangential field configuration: currently, there are thrusters that employ cusped magnetic fields to confine electrons to ionize, where the thrusters have walls with magnetic interfaces of the cusped magnetic fields perpendicular to the cylindrical walls, and where there are multiple magnetic interfaces in the passageway to form a multistage cusped magnetic field configuration. The anode is positioned at the bottom end of the channel, the cathode is positioned outside the inlet of the channel, and after electrons enter the channel from the cathode, the electrons are subjected to the action of electric field force and limited by magnetic mirror field (spirally vibrating back and forth), and radial magnetic induction line constraint (EXB drift) near the magnetic interface. The configuration of the cusped field magnetic field greatly prolongs the path of electrons reaching the anode, improves the ionization rate of the thruster and improves the comprehensive performance of the thruster. However, the purpose of the cusped field thruster of this type is to increase the confinement level of electrons in the passageway and to increase the ionization rate, by a design in which there is no additional anode in the passageway rather than in the plane, and by a significant difference from the present invention in terms of structure and implementation ^[2] 。

The additional anode is an anode that is outside the anode region, which is not the primary occurrence region of ionization, by the auxiliary property of the applied voltage that affects the beam current. Meanwhile, in the existing flat-plate type external discharge Hall thruster, the magnetic field near the anode is often in a negative gradient, so that the magnetic induction intensity on the surface of the anode is large, and the heating of the anode is not facilitated to be reduced. The defects of the existing external discharge Hall thruster technology with an additional anode are as follows:

1. the additional anode current that has been disclosed is relatively large compared to the current of the anode, and even exceeds the current of the anode under some conditions [1], see fig. 2a and 2b, while the voltage level at the additional anode is close to the voltage level at the anode, which means that the additional anode does not directly supply energy for ionization, but consumes a relatively large amount of energy. The reason why the additional anode generates a large current is that the radial magnetic field above is weak and the electrons are not sufficiently magnetized, and a large number of electrons are attracted by the additional anode to directly reach the additional anode. The radial magnetic field above the additional anode is reasonably enhanced, the magnetic shielding of the additional anode is facilitated, and the current of the additional anode is reduced.

2. The anode and the additional anode are easy to be conducted. In experiments, when the anode is made of stainless steel material which is not resistant to sputtering, atoms sputtered from the surface of the anode are extremely easy to deposit between the additional anode and the anode, a conductive metal film is formed, and the resistance between the two anodes is greatly reduced. In the working process of the thruster, the electric potentials of the anode and the additional anode are often different, so that a conductive path is formed between the anode and the additional anode, and the potential hazards of controlling the performance of the thruster and burying the safe operation of the satellite are large.

3. In the existing flat-plate hall thruster, the commonly applied magnetic field configuration is negative gradient because the discharge area is located outside the end face of the magnetic pole. The configuration moves the region with the strongest magnetic field to the surface of the anode, so that electrons EXB near the anode drift more strongly, the potential gradient is larger, electrons are accelerated to bombard the surface of the anode under the action of larger potential difference, the thermal effect of the surface of the anode is stronger, and the demagnetization phenomenon of the permanent magnet near the anode and the ionization region is serious. However, the magnetic field post-loading technology for solving the problems is mostly applied to a hall thruster with a channel, such as a steady-state plasma thruster (Stationary Plasma Thruster, SPT), and no disclosed design is yet available for realizing the purpose of post-loading of the magnetic field of the external discharge hall thruster.

In summary, the existing external discharge hall thruster adopting the additional anode is easy to generate the problems of higher power of the additional anode, short circuit between the additional anode and the anode, demagnetization of the magnet caused by overheating of the thruster, and the like, which reflects that the existing external discharge plasma configuration also needs further optimization design. The invention can optimize the problems by innovatively changing the magnetic field configuration and the wall structure.

Reference is made to:

[1]Simmonds J,Raitses Y.Mitigation of breathing oscillations and focusing of the plume in a segmented electrode wall-less Hall thruster[J].Applied Physics Letters,2021,119(21).

[2]Hu P,Liu H,Mao W,et al.The effects of magnetic field in plume region on the performance of multi-cusped field thruster[J].Physics of Plasmas,2015,22(10).

related patent application:

[3] wang Weizong, a secondary molecule, li Yi, etc. an insulation enhanced grid system [ P ] resistant to sputtering pollution;

[4] wang Weizong, dong Yicheng, kong Weiyi, etc. A radio frequency ion thruster ionization chamber inner wall surface cleaning system and method [ P ]. Chinese patent application No. 202310886668.X.

Disclosure of Invention

In recent years, with the rise of international microsatellite networking surge, new requirements are being made on the miniaturization of satellite electric propulsion systems. It is under this wave that external discharge hall thrusters have been under considerable research in recent years, whereas external discharge hall thrusters employing an additional anode configuration have appeared later and have been under less research. Many problems in the field are not well solved and many potential technical difficulties are not found.

The permanent magnet is added on the outer side of the additional anode to form a new magnetic mirror field to restrict electrons, so that the current of the additional anode is reduced; by adjusting the magnetic field near the surface of the anode, the positive gradient magnetic field on the surface of the anode weakens the bombardment heating of electrons during the working of the anode, and improves the phenomena of heating of the thruster and demagnetization of the permanent magnet; the insulation between the anode and the additional anode is increased, and the service life and reliability of the thruster are improved.

The object of the present invention is to solve the following problems:

1. the problem of the external discharge hall thruster additional anode current of adopting the additional anode design, the consumption is great is solved.

2. The problem that an anode shielding magnetic ring attached to the outer ring of the thruster is difficult to process and easy to damage in installation is solved.

3. The problem that an external discharge Hall thruster anode adopting an additional anode design is easy to conduct and short-circuit is solved.

4. Solves the problems of serious electron bombardment anode and demagnetization of magnet caused by over strong heat effect of the thruster due to larger magnetic induction intensity near the anode.

Therefore, the invention provides the external discharge Hall thruster which adopts a planar cusp magnetic field, has an anode-to-anode insulation design and is loaded after the magnetic field on the surface of the anode. I.e. an external discharge hall thruster designed with a planar cusped magnetic field is used, as shown in fig. 3, 4a and 4 b.

The invention comprises a thruster structure 6, outer ring magnets 7 (32 are uniformly distributed in the circumferential direction), a thruster ceramic wall 8, an additional anode 9, an outer magnet 10, a magnetic screen 11, an anode 12, a ceramic structure 13, an inner magnet 14, a short insulating pad 15, an M2 flat washer 16, an M2 elastic washer 17, an M2 nut 18, a long insulating pad 19, an M3 flat washer 20, an M3 elastic washer 21 and an M3 nut 22.

Wherein the thruster structure 6 is made of cast aluminum alloy which is convenient for 3D printing and manufacturing; the outer ring magnet 7, the outer magnet 10 and the inner magnet 14 have a samarium cobalt ratio of 2:17, a samarium cobalt permanent magnet; the additional anode 9, 12 is made of stainless steel; the magnetic screen 11 is made of silicon steel; the ceramic wall surface 8 and the ceramic structure body 13 of the thruster are made of boron nitride ceramics; the short insulating pad 15 and the long insulating pad 19 are made of alumina ceramics; the M2 flat washer 16, the M2 elastic washer 17, the M2 nut 18, the M3 flat washer 20, the M3 elastic washer 21 and the M3 nut 22 are all commercial standard components. When the thruster is assembled, the outer magnet 10, the ceramic structure 13, the inner magnet 14, the magnetic screen 11, the 32 outer ring magnets 7 and the ceramic wall 8 of the thruster are assembled in sequence based on the thruster structure 6, and finally insulation and fixation of the additional anode 9 and the thruster structure 6 are ensured through the short insulation pad 15, the M2 flat washer, the M2 spring washer and the M2 nut, and insulation and fixation of the anode 12 and the thruster structure 6 assembly are ensured through the long insulation pad 19, the M3 flat washer, the M3 spring washer and the M3 nut. The specific assembly process is described at the end of the text.

At present, experimental phenomena and published documents obtained by carrying out performance test experiments of an external discharge Hall thruster with an additional anode can determine that the additional anode has a reducing effect on the divergence angle of the thruster and has an inhibiting effect on oscillation, which is the technical background of the invention. But directly at the edge of the thruster at the additional anode, the number density of working medium gas above the additional anode is lower, and the additional anode has smaller ionization contribution. But outside the additional anode, electrons need to cross over the additional anode along a magnetic induction line to reach an ionization region near the anode after being led out from the cathode, are attracted by the positive potential of the additional anode during movement, and do not participate in ionization and directly flow away from the additional anode, so that the current is larger and the additional power is higher. The addition of the outer ring magnet 7, with the addition of a magnetic mirror field outside the thruster, see fig. 5a, allows more electrons to be confined above the additional anode, reducing the additional anode current. Meanwhile, in order to facilitate processing, assembly and cost reduction, the thruster structure body 6 and the ceramic wall surface 8 are provided with corresponding circular grooves, and 32 cylinder outer ring magnets 7 are circumferentially fixed, as shown in fig. 6, 7 and 10, instead of adopting an integral magnetic ring.

Through adjusting the geometric parameters and the spatial arrangement of the permanent magnets, a magnetic screen design is adopted, so that a certain magnetic field rear loading phenomenon occurs in a near anode region, the maximum magnetic flux density is kept away from the anode by 2-4 mm while the magnetic flux density is at an EXB drifting level capable of effectively restraining electrons, as shown in fig. 5b, the position with a large electric field gradient can be pushed away from the anode, the electron bombardment is reduced, the heat is reduced, and the demagnetizing phenomenon of the permanent magnets is relieved. Due to the use of additional anodes and the configuration of the plate, there is a greater likelihood that metal atoms will deposit between the two anodes resulting in anode conduction due to the effects of anode ion sputtering, atomic deposition and wall surface. In the invention, two annular grooves are designed on the ceramic wall surface by combining the data of atomic free ranges at different positions, as shown in fig. 7c, the atomic deposition area and the difficulty degree are considered to be increased, and the conduction phenomenon between two anodes is improved.

Compared with the prior art, the invention has the following beneficial effects:

1. compared with an external discharge Hall thruster adopting an additional anode, the novel magnetic mirror field is formed to restrict electrons by adding the permanent magnet outside the additional anode, so that the cusp magnetic field which is concentrically distributed in a circular shape on a plane is formed, the additional anode current is reduced, the additional anode power is reduced, the anode power ratio of the anode power to ionization is improved, and the thruster efficiency is improved.

2. Compared with the existing external discharge Hall thruster, a positive gradient configuration is formed on the surface of the anode, and the electric field gradient on the surface of the anode is weakened. The effect of rear loading is innovatively realized in the external discharge Hall thruster, the degree of electron bombardment on the surface of the anode is reduced, the heating of the thruster is reduced, and the demagnetization phenomenon of the permanent magnet is improved.

3. By adopting the design of the insulation groove, the insulation between the anode and the additional anode is increased, the conduction between the two anodes is prevented, and the service life and the reliability of the thruster are improved.

4. The invention adopts the design of replacing the whole magnetic ring with small magnets which are circumferentially arranged, is convenient for processing and assembly, and reduces the cost.

5. The invention is helpful for improving the overall performance of the external discharge Hall thruster and promoting the progress of engineering and practical application.

Drawings

Fig. 1 is a schematic cross-sectional view of a sputter-resistant insulated enhanced gate system.

Fig. 2a is a block diagram of a cusped field thruster.

Fig. 2b is the extracted beam of the cusped field thruster.

Fig. 3 is a schematic diagram of an external discharge hall thruster employing cusped magnetic fields.

Fig. 4a is a cross-sectional view of an assembled schematic.

Fig. 4b is a side bottom view of the assembled schematic.

Fig. 5a is a cross-sectional view of the magnetic field distribution over the anode of the present invention.

Fig. 5b is a graph of the above-anode magnetic flux density pattern of the above-anode magnetic field distribution of the present invention.

Fig. 6a is a side, upper view of the thruster structure.

Fig. 6b is a side down view of the thruster structure.

Fig. 7a is a side top view of a schematic of a ceramic wall.

Fig. 7b is a side down view of a schematic of a ceramic wall.

Fig. 7c is a cross-sectional view of a schematic of a ceramic wall.

Fig. 8 is an anode axial side view.

Fig. 9 is an additional anode axial side view.

Fig. 10 is an exploded view of the thruster.

Fig. 11 is a mating relationship of long and short insulation pads in a thruster.

Fig. 12 is an axial side view of a ceramic structure.

Fig. 13 is a graph of the power ratio of a thruster designed according to the present invention versus an additional anode of a thruster not designed according to the present invention.

The reference numerals in the figures are illustrated as follows:

bowl-shaped accelerating grid 1, inter-grid insulator 2 and screen grid 3

Sputter-resistant insulation trench 5 thruster structure 6 of accelerator gate exhaust hole 4

Outer ring magnet 7 (32) ceramic wall surface 8 of thruster

Magnetic screen 11 with external magnet 10 attached to anode 9

Anode 12 ceramic structure 13 internal magnet 14

Short insulation pad 15 M2 flat gasket 16 M2 elastic gasket 17

M2 nut 18 long insulation pad 19 M3 flat washer 20

M3 elastic washer 21 M3 nut

Detailed Description

The invention has more adjustable electrical parameters, wherein the selection of anode voltage and additional anode is more critical. For the choice of the anode voltage of the disclosed miniaturized Hall thruster and the combination of experimental measurement, the thrust of the 'mN' level is considered to be realized, and the anode voltage can be changed between 150 and 400V within the range of 2-10 sccm of xenon flow. The additional anode voltage is not easy to be excessively selected, and can be selected in a range of 100-300V which is lower than the anode voltage. The choice of cathode parameters is not within the scope of the present discussion.

The installation process of the invention comprises the following steps:

when assembling the thruster, based on the thruster structure 6, firstly placing the outer magnet 10 and the ceramic structure 13 in a cylindrical cavity in the center of the thruster structure 6 (see fig. 6) according to the assembly relation shown in fig. 4a (omitting the internal details of the anode 12), and paying attention to that the holes on the ceramic structure 13 should be aligned with the holes on the thruster structure 6; placing the inner magnet 14 in the central recess of the ceramic structure (see fig. 12); then the magnetic screen 11 is put between the inner magnet and the outer magnet to be in close contact with the ceramic structure 13; placing 32 outer ring magnets 7 into slots of a thruster structure body 6 in sequence, and pressing a magnetic screen 11, an outer magnet 10 and 32 outer ring magnets 2 by using a ceramic wall surface 8 of the thruster, wherein the holes (see fig. 7) formed on the ceramic wall surface 8 are aligned with corresponding holes formed on the thruster structure body 6 and the ceramic structure body 13, and the 32 outer ring magnets are introduced into the slots formed on the lower side of the ceramic wall surface 8 in the circumferential direction (see fig. 7 b); finally, the pins of the anode 12 and the additional anode 4 pass through the corresponding holes on the ceramic wall surface 8, the ceramic structure body 13 and the thruster structure body 6, the anode 12 is provided with two pins (see fig. 8), and insulation and fixation are ensured through two long insulation pads 19, an M3 flat washer 20, an M3 elastic washer 21 and an M3 nut 22. Two pins (see fig. 9) of the additional anode 9 pass through two short insulating pads 15, an M2 flat washer 16, an M2 elastic washer 17 and an M2 nut 18, wherein the matching relationship of the long and short insulating pads is shown in fig. 11, the longer pin of the anode is hollow and is used for connecting a gas circuit, and the other pin of the anode is used for connecting a circuit. Both pins of the additional anode are connected with another power supply, and the circuit design is not in the scope of the invention. The overall thruster assembly is shown in fig. 10.

The ground experiment operation flow of the invention is as follows:

assembling the thruster according to the sequence, connecting a circuit of the thruster anode 12 and the additional anode 9, connecting a gas circuit on a long pin of the anode 12, vacuumizing, introducing the thruster anode 12, applying positive voltage to a given value by the main anode 12, opening the cathode, igniting the thruster, applying positive voltage to the given value by the additional anode 9, closing the power supply of the additional anode 9, closing the cathode, closing the power supply of the anode 12, closing the gas circuit of the anode 12, breaking the vacuum chamber, disassembling the circuit and the gas circuit of the thruster, and properly storing the thruster.

The positive voltage phase on the anode 12, the additional anode 9 of the present invention refers to a commonly generated positive voltage with respect to the thruster circuitry, the design of which is outside the scope of the present discussion.

Typical working conditions of the invention are as follows:

when the anode voltage is 250V, the flow is 6sccm, the additional anode voltage is 200V, and the cathode flow is 4sccm, the main anode current is about 0.5A, the additional anode current can be kept below 50mA and is smaller than the current of the additional anode (in the order of 100 mA) when the outer ring magnet 2 is not added, and the proportion of the power consumed by the additional anode in the total power is reduced. The ratio of additional anode power to total power (anode power + additional anode power) at different additional anode voltages results are shown in fig. 13.

In the design of the present invention, the additional anode is positively biased, so it can be used as an anode. If the additional anode voltage is changed to be adjustable, the working condition adjusting range of the thruster can be increased, and the robustness of the adjusting control of the thruster can be improved.

In particular, reference may be made to the method of patent application [4], which innovatively cleans the metallic coating in an external discharge hall thruster. If negative voltage is applied to the additional anode, negative voltage is applied to a coating area which is in contact with the additional anode, positively charged ions are attracted to and impact on the coating area, the sputtering degree of the wall base material is reasonably regulated and controlled, the coating of the wall is possibly eliminated to a certain extent, and the service life of the thruster is prolonged.

The design of the magnetic field of the thruster can be further improved by combining experiments, and the magnets with higher remanence and higher temperature resistance can be changed by combining the development and progress of science and technology, so that the rationality and reliability of the design of the magnetic field of the thruster are improved.

Claims (10)

1. An external discharge Hall thruster adopting a planar cusped magnetic field design, which is characterized in that: the novel high-voltage power generation device comprises a thruster structure body, an outer ring magnet, a thruster ceramic wall surface, an additional anode, an outer magnet, a magnetic screen, an anode, a ceramic structure body, an inner magnet, a short insulating pad, an M2 flat washer, an M2 elastic washer, an M2 nut, a long insulating pad, an M3 flat washer, an M3 elastic washer and an M3 nut; the outer magnet, the ceramic structure, the inner magnet, the magnetic screen, the 32 outer ring magnets and the ceramic wall surface of the thruster are assembled in sequence based on the thruster structure, and finally insulation and fixation of an additional anode and the thruster structure are ensured through a short insulation pad, an M2 flat washer, an M2 spring washer and an M2 nut, and insulation and fixation of the anode and the thruster structure assembly are ensured through a long insulation pad, an M3 flat washer, an M3 spring washer and an M3 nut.

2. An external discharge hall thruster designed with a planar cusped magnetic field according to claim 1, wherein: the thruster structure body is made of cast aluminum alloy which is convenient for 3D printing and manufacturing; outer ring magnet, outer magnet, interior magnet are 2 by samarium cobalt ratio: 17, a samarium cobalt permanent magnet; the additional anode and the anode are made of stainless steel; the magnetic screen is made of silicon steel; the ceramic wall surface and the ceramic structure body of the thruster are made of boron nitride ceramics; the short insulating pad and the long insulating pad are made of alumina ceramics.

3. An external discharge hall thruster according to claim 1 or 2, designed with a planar cusped magnetic field, characterized in that: corresponding circular grooves are formed on the ceramic wall surfaces of the thruster structure body and the thruster, and the cylindrical outer ring magnets are circumferentially fixed instead of an integral magnetic ring.

4. An external discharge hall thruster designed with a planar cusped magnetic field according to claim 3, wherein: the outer magnet and the ceramic structure body are placed in a cylindrical cavity in the center of the thruster structure body, and the holes formed in the ceramic structure body are aligned with the holes in the thruster structure body.

5. An external discharge hall thruster designed with a planar cusped magnetic field according to claim 1, wherein: placing the inner magnet in a central groove of the ceramic structure body; then the magnetic screen is placed between the inner magnet and the outer magnet and is tightly contacted with the ceramic structure body.

6. An external discharge hall thruster designed with a planar cusped magnetic field according to claim 1, wherein: the 32 outer ring magnets are sequentially placed into grooves of the thruster structure body, the ceramic wall surface of the thruster is utilized to compress the magnetic screen, the outer magnets and the 32 outer ring magnets, the holes formed in the ceramic wall surface are aligned with the corresponding holes in the thruster structure body and the ceramic structure body, and the 32 outer ring magnets are required to enter the grooves formed in the circumferential direction of the lower side of the ceramic wall surface.

7. An external discharge hall thruster designed with a planar cusped magnetic field according to claim 1, wherein: the anode and pins of the additional anode penetrate through corresponding holes in the ceramic wall surface, the ceramic structure body and the thruster structure body, and the anode is provided with two pins, and insulation and fixation are ensured through two long insulation pads, an M3 flat washer, an M3 elastic washer and an M3 nut.

8. An external discharge hall thruster according to claim 1 or 7, designed with a planar cusped magnetic field, characterized in that: two pins of the additional anode pass through two short insulating pads, an M2 flat washer, an M2 elastic washer and an M2 nut; the anode is hollow and is used for connecting with a gas circuit, and the other pin of the anode is used for connecting with a circuit; the two pins of the additional anode are connected with the other power supply.

9. The external discharge hall thruster of claim 8, wherein the planar cusped magnetic field design is characterized by: the positive bias voltage is applied to the additional anode, which can be used as the anode; the positive voltage phase on the anode, the additional anode, both refer to a positive voltage generated in common with respect to the thruster circuit.

10. An external discharge hall thruster according to claim 1 or 5 or 6 or 7 or 9, designed with a planar cusped magnetic field, characterized in that: the anode voltage varies between 150 and 400V within the range of 2 to 10sccm of xenon flow; the additional anode voltage is selected to be in the range of 100-300V.