A hollow cathode magnetic shield structure for improving the performance of a rotating-field Hall thruster

Abstract

The application discloses a hollow cathode magnetic screen structure for improving performance of a Hall thruster, and relates to the technical field of space electric propulsion. The application sets the cathode magnetic screen of magnetic conductive material outside the hollow cathode, and reasonably assembles the cathode tube, the emitter, the heating wire, the insulating ceramic piece, the contact pole and the cathode base, so as to weaken the magnetic field intensity of the key area at the cathode outlet. The application reduces the magnetic field resistance in the electron movement process, further reduces the electron energy loss, and finally improves the efficiency of the thruster.

Description

Technical Field

[0001] This invention relates to the field of aerospace electric propulsion technology, and in particular to a hollow cathode magnetic screen structure for improving the performance of a Hall thruster. Background Technology

[0002] Hall thrusters, as the mainstream plasma electric propulsion device in the aerospace field, have been widely used in aerospace missions such as satellite attitude and orbit control, deep space exploration, and commercial constellation networking due to their core advantages of high specific impulse (1000-4000s), low propellant consumption (5-10 times lower than chemical propulsion), and long lifespan (design lifespan can reach thousands of hours). For example, the Chinese space station, the Fengyun series meteorological satellites, and the SMART-1 lunar probe are all equipped with Hall thrusters. They generate thrust by confining electrons with orthogonal electromagnetic fields to collide and ionize propellant, forming a high-speed plasma jet. This has become a key device for improving the mission endurance of spacecraft and reducing launch costs. With the rapid development of commercial aerospace and microsatellite formation flight, the demand for miniaturized, lightweight, and high-thrust-density thrusters for spacecraft is becoming increasingly urgent. Miniature Hall thrusters below kilowatt level need to be adapted to the payload limitations of microsatellites under 100kg, while meeting the performance requirements of formation coordination and rapid orbit changes, driving the evolution of Hall thrusters towards miniaturization (channel diameter ≤20mm).

[0003] However, traditional Hall thrusters face significant technical bottlenecks in miniaturization: on the one hand, miniaturization drastically reduces the internal magnetic field confinement space, disrupting the matching relationship between electron cyclotron radius and channel characteristic length, leading to increased electron escape and a significant decrease in ionization efficiency; on the other hand, the reduced channel size exacerbates wall effects, increasing the proportion of electrons conducted near the wall, resulting in insufficient thrust density and intensified wall sputtering corrosion, thus shortening thruster life. Furthermore, after miniaturization, the magnetic field gradient of traditional radial magnetic field configurations is difficult to maintain an optimized distribution, reducing the probability of electron collision ionization with propellant, further limiting the performance improvement of miniaturized thrusters. Against this backdrop, the tangential field Hall thruster, with its unique tangential magnetic field configuration, exhibits significant miniaturization applicability: the tangential magnetic field constructed by permanent magnets can still form a closed magnetic field confinement region within the miniaturized channel, effectively suppressing electron escape and improving ionization efficiency and thrust density; at the same time, the tangential magnetic field can optimize the electric field distribution within the channel, reduce energy loss caused by near-wall conduction, and enable the miniaturized thruster to maintain a high specific impulse and operational stability, becoming one of the core technical paths for the miniaturization development of Hall thrusters.

[0004] Although the Hall thruster effectively overcomes the miniaturization bottleneck of traditional structures, in actual operation, the magnetic field it generates still significantly interferes with the coupling process between the cathode and the thruster, leading to a decrease in thruster performance. It is important to clarify that the coupling between the cathode and the thruster is one of the core physical processes within the Hall thruster: under the combined effect of collision and magnetic fields, the movement of electrons emitted from the cathode towards the plume region and the anode is significantly hindered. Electrons must expend additional energy to overcome this resistance before entering the plume region to complete neutralization and enter the discharge channel to participate in ionization. This energy, which is not directly used for ion acceleration to generate thrust, becomes ineffectively lost. Therefore, cathode coupling loss has become a key energy loss mechanism in Hall thrusters, directly affecting the thruster's energy utilization efficiency.

[0005] Currently, existing technologies mostly focus on optimizing the internal structure of the cross-field Hall thruster (such as channel size design and permanent magnet layout adjustment) or performance debugging under a single magnetic environment. There is no effective solution to the problem of interference of the strong magnetic field leaked by the thruster itself on the cathode electron conduction and coupling process. As a result, the cathode coupling loss of miniaturized cross-field Hall thrusters remains high, which seriously restricts the improvement of the overall performance of the thruster. Summary of the Invention

[0006] This invention proposes a hollow cathode magnetic screen structure for improving the performance of a Hall thruster. By setting a magnetically conductive cathode magnetic screen on the outside of the hollow cathode, and with the proper assembly of the cathode tube, emitter, heating wire, insulating ceramic parts, contact electrode and cathode base, the magnetic field strength in the key area of ​​the cathode outlet is weakened. This solves the problem that when the Hall thruster is working, the leakage magnetic field near the cathode interferes with electron conduction, resulting in large electron energy loss and poor thruster performance.

[0007] A hollow cathode magnetic screen structure for improving the performance of a Hall thruster in a cutting field includes a cathode tube, an insulating ceramic base, an insulating ceramic tube, a cathode magnetic screen, a heating wire, an emitter, a contact electrode, and a cathode base. The emitter is fixedly installed inside the top of the cathode tube by an interference fit. The heating wire is sleeved on the outside of the cathode tube corresponding to the position of the emitter. The insulating ceramic tube and the cathode magnetic screen are sleeved on the outside of the cathode tube from the inside out, and the extended surfaces at the bottom of both the insulating ceramic tube and the cathode magnetic screen are fixedly connected to the cathode base. The contact electrode is sleeved between the insulating ceramic tube and the cathode magnetic screen, and the extended surface at the bottom of the contact electrode is fixedly installed on the extended surface of the insulating ceramic tube. The insulating ceramic base is disposed between the cathode tube and the cathode base and is fixedly connected to the cathode base. The cathode magnetic screen is made of a magnetically conductive material.

[0008] Furthermore, the cathode tube, which carries the emitter, has an electron emission hole at its top, which guides the electrons generated by the emitter to be emitted directionally from the electron emission hole; An insulating ceramic base is used to achieve electrical insulation isolation between the cathode tube and the cathode base; An insulating ceramic tube is used to achieve electrical insulation isolation between the contact electrode and the cathode base; Cathode magnetic screens are used to weaken the magnetic field strength in the critical area of ​​the hollow cathode outlet, thereby reducing the magnetic field resistance to electron movement. The heating wire is used to heat the emitter to the operating temperature required for electron emission, thereby triggering electron emission. The emitter is used to generate and emit electrons required for the hollow cathode to function. The contact electrode is used to assist in the activation of the emitter and stabilize the electron emission state of the hollow cathode. The cathode base serves as the foundation for the overall structure, fixing the insulating ceramic base, insulating ceramic tube, and cathode magnetic screen.

[0009] Furthermore, the cathode magnetic screen is made of DT4C electrical pure iron and has a sleeve-type structure.

[0010] Furthermore, the cathode tube is made of tungsten metal.

[0011] Furthermore, the emitter is a cylindrical structure with a through hole at its core, made by impregnating a porous tungsten matrix with a barium oxide solution.

[0012] Furthermore, the distance between the cathode magnetic screen and the outer wall of the cathode tube is 1-2 mm, and the top of the cathode magnetic screen is flush with or 1-2 mm higher than the top of the contact electrode.

[0013] Furthermore, the heating wire is a spiral structure made of tungsten wire.

[0014] Furthermore, both the insulating ceramic base and the insulating ceramic tube are made of alumina ceramic.

[0015] Furthermore, the contact electrode is made of a nickel alloy.

[0016] Furthermore, the cathode base is made of stainless steel, and the surface of the cathode base has multiple mounting threaded holes for mounting and fixing the insulating ceramic base, insulating ceramic tube and cathode magnetic screen.

[0017] Compared with the prior art, the present invention achieves significant beneficial effects through the above technical solution: By setting a cathode magnetic screen of magnetically conductive material, the present invention can effectively weaken the magnetic field strength in the key area of ​​the hollow cathode outlet, reducing the magnetic field strength in the hollow cathode orifice area from 0.015~0.02T without a magnetic screen to below 0.005T, with a magnetic field weakening of more than 67%; at the same time, it can optimize the electron conduction path and reduce energy loss during electron movement. In the typical operating range of thruster total input power ≤90W, the total efficiency of thruster can be increased from 2.9%~8.5% without a magnetic screen to 5.5%~14.2%. Under the same power conditions, the relative improvement in total thruster efficiency is 3%~6%, effectively improving the poor performance problem of the Hall thruster caused by leakage magnetic field interference near the cathode, and significantly improving the energy utilization efficiency and practical value of the thruster. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a hollow cathode magnetic screen structure for improving the performance of a Hall thruster in a cutting field, according to the present invention. Figure 2 These are images of thruster discharge when the cathode has no magnetic shield structure. Figure 3 These are images of thruster discharge when the cathode has a magnetic shield structure. Figure 4 These are the three-dimensional magnetic field simulation results when the cathode has no magnetic screen structure; Figure 5 These are the simulation results of a three-dimensional magnetic field when the cathode has a magnetic shield structure; Figure 6 This is a comparison of thruster efficiency with and without a magnetic shield at the cathode.

[0019] Among them, 1 is the cathode tube, 2 is the insulating ceramic base, 3 is the insulating ceramic tube, 4 is the cathode magnetic screen, 5 is the heating wire, 6 is the emitter, 7 is the contact electrode, and 8 is the cathode base. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Reference Figure 1As shown, a hollow cathode magnetic screen structure for improving the performance of a Hall thruster includes a cathode tube 1, an insulating ceramic base 2, an insulating ceramic tube 3, a cathode magnetic screen 4, a heating wire 5, an emitter 6, a contact electrode 7, and a cathode base 8. The emitter 6 is fixedly installed inside the top of the cathode tube 1 by an interference fit. The heating wire 5 is sleeved on the outside of the cathode tube 1 corresponding to the position of the emitter 6. The insulating ceramic tube 3 and the cathode magnetic screen 4 are sleeved on the outside of the cathode tube 1 from the inside to the outside, and the extended surfaces at the bottom of the insulating ceramic tube 3 and the cathode magnetic screen 4 are fixedly connected to the cathode base 8. The contact electrode 7 is sleeved between the insulating ceramic tube 3 and the cathode magnetic screen 4, and the extended surface at the bottom of the contact electrode 7 is fixedly installed on the extended surface of the insulating ceramic tube 3. The insulating ceramic base 2 is disposed between the cathode tube 1 and the cathode base 8 and is fixedly connected to the cathode base 8. The cathode magnetic screen 4 is made of a magnetically conductive material.

[0022] Specifically, this invention, through the rational assembly of cathode tube 1, insulating ceramic base 2, insulating ceramic tube 3, cathode magnetic screen 4, heating wire 5, emitter 6, contact electrode 7, and cathode base 8, and by placing the magnetically conductive cathode magnetic screen 4 outside the cathode tube 1, and in conjunction with the synergistic effect of each component, can effectively weaken the magnetic field strength in the key area of ​​the hollow cathode outlet, reducing the magnetic field strength in the hollow cathode orifice area from 0.015~0.02T without the magnetic screen to below 0.005T, a reduction of over 67%. This optimizes the electron conduction path and reduces energy loss during electron movement. Within the typical operating range of thruster total input power ≤90W, the total thruster efficiency can be increased from 2.9%~8.5% without the magnetic screen to 5.5%~14.2%, representing a relative increase of 3%~6% under the same power conditions. This effectively improves the poor performance problem of the Hall thruster caused by leakage magnetic field interference near the cathode, significantly enhancing the energy utilization efficiency and practical value of the thruster.

[0023] Furthermore, the cathode tube 1, which carries the emitter 6, has an electron emission hole at its top, which guides the electrons generated by the emitter 6 to be emitted directionally from the electron emission hole; The insulating ceramic base 2 is used to achieve electrical insulation isolation between the cathode tube 1 and the cathode base 8; The insulating ceramic tube 3 is used to achieve electrical insulation isolation between the contact electrode 7 and the cathode base 8; The cathode magnetic screen 4 is used to weaken the magnetic field strength in the key area of ​​the hollow cathode outlet and reduce the magnetic field resistance to electron movement. Heating wire 5 is used to heat the emitter 6 to the operating temperature required for electron emission, thereby triggering electron emission; Emitter 6 is used to generate and emit electrons required for the hollow cathode to operate; The contact electrode 7 is used to assist the emitter 6 in starting up and to stabilize the electron emission state of the hollow cathode; The cathode base 8 serves as the base for the overall structure, fixing the insulating ceramic base 2, the insulating ceramic tube 3, and the cathode magnetic screen 4.

[0024] Specifically, by clarifying the specific functions of each component, the cathode tube 1 effectively carries the emitter 6 and guides the electrons to be emitted in a directional manner. The insulating ceramic base 2 and the insulating ceramic tube 3 respectively achieve electrical insulation isolation between the cathode tube 1, the contact electrode 7 and the cathode base 8, avoiding electrical interference from affecting the normal operation of the components. The cathode magnetic screen 4 precisely weakens the magnetic field strength in the key area of ​​the hollow cathode outlet and reduces the magnetic field resistance of electron movement. The heating wire 5 can stably heat the emitter 6 to the working temperature required for electron emission to trigger electron emission. The emitter 6 continuously generates and emits electrons required for the operation of the hollow cathode. The contact electrode 7 assists the emitter 6 in starting and stabilizing the electron emission state. The cathode base 8 serves as the base of the overall structure to firmly fix each component. Each component performs its own function and works together to further optimize the electron conduction efficiency, reduce the ineffective loss of electron energy, and ensure the stable and reliable magnetic field weakening effect. At the same time, it ensures the working stability and assembly reliability of the overall structure, so as to steadily improve the overall efficiency of the thruster and effectively solve the performance degradation problem caused by leakage magnetic field interference near the cathode in the Hall thruster.

[0025] Furthermore, the cathode magnetic screen 4 is made of DT4C electrical pure iron and has a sleeve-type structure.

[0026] Specifically, this invention uses DT4C electrical pure iron as the material for the cathode magnetic screen 4, and sets the cathode magnetic screen 4 as a sleeve structure. DT4C electrical pure iron has excellent magnetic permeability, which can more efficiently adsorb the magnetic field leaked by the Hall thruster. With the sleeve structure, it can be tightly and completely fitted to the outside of the cathode tube 1, accurately covering the area where electrons are generated and emitted, including the emitter 6, the small hole at the top of the cathode tube 1, and the small hole at the top of the contact electrode 7. This further enhances the magnetic field weakening effect in the key area of ​​the hollow cathode outlet, ensuring that the magnetic field strength in the hollow cathode orifice area is stably reduced to 0. Below 0.005T, the magnetic field attenuation remains above 67%; at the same time, the sleeve structure facilitates a stable assembly with the cathode base 8, can fit tightly with the cathode tube 1 without affecting the normal operation of other components, avoids loose assembly leading to a decrease in magnetic field shielding effect, and thus more stably optimizes the electron conduction path, reduces energy loss during electron movement, and ensures that the total efficiency of the thruster is stably maintained at 5.5%~14.2% in the typical operating range of total input power ≤90W, further improving the energy utilization efficiency, working stability and overall assembly reliability of the thruster.

[0027] Furthermore, the cathode tube 1 is made of tungsten metal.

[0028] Specifically, tungsten metal is used as the material for the cathode tube 1. Tungsten metal has excellent high-temperature resistance and structural strength, which can adapt to the working environment of heating the emitter 6 to an electron emission temperature of 1000~1300K by the heating wire 5. This effectively prevents the cathode tube 1 from deforming or being damaged due to long-term exposure to high temperatures, ensuring that the cathode tube 1 can stably support the emitter 6 and ensuring the stability of the emitter 6 through interference fit. This prevents the emitter 6 from loosening and affecting the electron emission effect. At the same time, the strong structural stability of tungsten metal allows it to be firmly assembled with the insulating ceramic base 2, ensuring that the insulation and isolation effect between the cathode tube 1 and the cathode base 8 is not affected. This, in turn, works in conjunction with the cathode magnetic screen 4, heating wire 5, emitter 6, and other components to stably guide the directional emission of electrons generated by the emitter 6, ensuring the smoothness of the electron conduction path and further reducing electron energy loss.

[0029] Furthermore, the emitter 6 is a cylindrical structure with a through hole at its core, made by impregnating a porous tungsten substrate with a barium oxide solution.

[0030] Specifically, the emitter 6 is a cylindrical structure with a through hole at its core, made of a porous tungsten substrate impregnated with barium oxide solution. BaO-W possesses excellent electron emission performance and high-temperature resistance, making it suitable for working environments where the heating wire 5 heats the material to an electron emission temperature of 1000-1300K. It stably generates and emits electrons required for the operation of the hollow cathode, ensuring the continuity and stability of electron emission and providing a sufficient and stable source of electrons for electron conduction. The through hole structure at its core allows electrons to be emitted more smoothly from the emitter 6. Combined with the electron emission hole at the top of the cathode tube 1, it further optimizes the directional conduction path of electrons and reduces energy loss during the emission process. The cylindrical structure facilitates the stable fixation of the emitter 6 inside the cathode tube 1 through an interference fit, preventing loose assembly or displacement of the emitter 6 from affecting the electron emission effect. This ensures that the emitter 6 works in tandem with the cathode tube 1 and the heating wire 5. Combined with the magnetic field weakening effect of the cathode magnetic screen 4, it ensures that the magnetic field strength in the hollow cathode orifice area is stably reduced to below 0.005T.

[0031] Furthermore, the distance between the cathode magnetic screen 4 and the outer wall of the cathode tube 1 is 1-2 mm, and the top of the cathode magnetic screen 4 is flush with or 1-2 mm higher than the top of the contact electrode 7.

[0032] Specifically, in this invention, a cathode magnetic screen 4 is fitted over the contact electrode 7, with a distance of 1-2 mm between the cathode magnetic screen 4 and the outer wall of the contact electrode 7. Simultaneously, the top of the cathode magnetic screen 4 is flush with or 1-2 mm higher than the small hole at the top of the contact electrode 7. This distance serves two purposes: firstly, it provides electrical insulation: the contact electrode 7 is ignited with a 100V ignition voltage and maintains a 10-20V operating voltage during stable operation; the spacing prevents electrical short circuits between the magnetic screen and the energized contact electrode 7. Secondly, it provides thermal insulation: the emitter 6 operates at a temperature of 1000-1300K, and the contact electrode 7 heats up due to radiation; the spacing prevents the magnetic screen from losing its magnetic permeability due to excessive temperature, ensuring stable magnetic shielding. The top of the cathode magnetic screen 4 can completely cover the entire area of ​​electron generation and extraction of the emitter 6 and the small hole at the top of the contact electrode 7, ensuring that the magnetic field in the key area of ​​electron extraction of the hollow cathode is comprehensively and efficiently weakened, ensuring that the magnetic field strength in the hollow cathode orifice area is stably reduced to below 0.005T, and the magnetic field weakening is maintained at more than 67%, thereby optimizing the electron conduction path and reducing energy loss during electron movement; at the same time, the reasonable spacing and top position facilitate the stable assembly of the cathode magnetic screen 4 and the cathode base 8, avoiding positional deviations during assembly that would reduce the magnetic field shielding effect, and ensuring that the electrons generated by the emitter 6 can be smoothly and directionally emitted.

[0033] Furthermore, the heating wire 5 is a spiral structure made of tungsten wire.

[0034] Specifically, the present invention sets the heating wire 5 as a spiral structure made of tungsten wire. Tungsten wire has excellent high temperature resistance and can adapt to the working requirements of heating the emitter 6 to the electron emission temperature of 1000~1300K. It is not easy to melt or be damaged during long-term operation, ensuring the reliability and service life of the heating wire 5. The spiral structure can be tightly and evenly wrapped around the outside of the cathode tube 1 near the emitter 6, so that the heat generated by the heating wire 5 can be evenly transferred to the emitter 6, avoiding damage to the emitter 6 or unstable electron emission due to uneven local heating. This ensures that the emitter 6 can stably reach the temperature required for electron emission, continuously generate and emit electrons, and provide a stable electron source for electron conduction. At the same time, the spiral structure is easy to assemble and fix on the outside of the cathode tube 1, and will not interfere with other components such as the cathode magnetic screen 4 and the insulating ceramic tube 3.

[0035] Furthermore, both the insulating ceramic base 2 and the insulating ceramic tube 3 are made of alumina ceramic.

[0036] Specifically, the present invention uses alumina ceramic for both the insulating ceramic base 2 and the insulating ceramic tube 3. Alumina ceramic has excellent high-temperature resistance and excellent electrical insulation properties, which can perfectly adapt to the high-temperature working environment of the heating wire 5 heating the emitter 6 in the present invention, from 1000 to 1300K. It will not deform or be damaged due to high temperature, effectively ensuring the structural stability and service life of the insulating ceramic base 2 and the insulating ceramic tube 3. At the same time, the excellent electrical insulation properties allow the insulating ceramic base 2 to better achieve electrical isolation between the cathode tube 1 and the cathode base 8, avoiding electrical interference affecting the normal operation of the cathode tube 1 and the directional conduction of electrons. It also allows the insulating ceramic tube 3 to stably achieve electrical isolation between the contact electrode 7 and the cathode base 8, preventing leakage, short circuits and other problems, and ensuring the stable electrical performance between the components. In addition, the alumina ceramic material has a robust structure and is easy to process, making it easy to assemble with the cathode tube 1, cathode base 8 and other components. It will not interfere with other components such as the cathode magnetic screen 4 and the heating wire 5, and can better cooperate with the components to ensure the weakening effect of the cathode magnetic screen 4 on the magnetic field, ensuring a smooth electron conduction path and reducing electron energy loss.

[0037] Furthermore, the contact electrode 7 is made of a nickel alloy.

[0038] Specifically, the present invention uses a nickel alloy for the contact electrode 7. Nickel alloy has excellent high temperature resistance and suitable conductivity, which can be adapted to the high temperature working environment of 1000~1300K for heating the emitter 6 by the heating wire 5 in the present invention. It is not easy to oxidize, deform or be damaged during long-term operation, effectively ensuring the structural stability and service life of the contact electrode 7. At the same time, the suitable conductivity allows the contact electrode 7 to better assist the emitter 6 in starting, quickly respond to and stabilize the electron emission state of the hollow cathode, avoid problems such as fluctuation and interruption of electron emission, and ensure that the electrons generated by the emitter 6 can be continuously and stably emitted in a directional manner. Combined with the electron guiding effect of the cathode tube 1 and the magnetic field weakening effect of the cathode magnetic screen 4, the electron conduction path is optimized and the electron energy loss is reduced.

[0039] Furthermore, the cathode base 8 is made of stainless steel, and the surface of the cathode base 8 has multiple mounting threaded holes for mounting and fixing the insulating ceramic base 2, the insulating ceramic tube 3 and the cathode magnetic screen 4.

[0040] Specifically, the cathode base 8 of this invention is made of stainless steel, and multiple threaded holes are provided on its surface for mounting and fixing the insulating ceramic base 2, the insulating ceramic tube 3, and the cathode magnetic screen 4. Stainless steel has excellent high temperature resistance, corrosion resistance, and strong structural strength, which can adapt to the high-temperature working environment of 1000~1300K for heating the emitter 6 by the heating wire 5 in this invention. It is not prone to deformation, rust, or damage during long-term operation, effectively ensuring the structural stability and service life of the cathode base 8 as the base of the overall structure. At the same time, the multiple threaded holes enable precise positioning and stable assembly of the insulating ceramic base 2, the insulating ceramic tube 3, and the cathode magnetic screen 4, ensuring accurate installation and tight connection of each component. This avoids displacement of components due to loose assembly, thereby preventing problems such as the cathode magnetic screen 4 failing to accurately cover the critical electron emission area where the emitter 6 is located, and the insulating ceramic base 2 and the insulating ceramic tube 3 failing to effectively achieve electrical isolation. The stable assembly also ensures that the components work together, allowing the cathode magnetic screen 4 to stably exert its magnetic field weakening effect.

[0041] The assembly steps of this invention are as follows: The hollow cathode magnetic shield structure of this embodiment is assembled according to the following steps: 1. Press the emitter 6 into the inside of the top of the cathode tube 1, ensuring that the top of the emitter 6 is flush with the top of the cathode tube 1 after assembly; 2. The heating wire 5 is spirally wound around the outside of the cathode tube 1 in the area near the emitter 6; 3. Fix the insulating ceramic base 2 to the cathode base 8 with bolts. Insert the cathode tube 1 into the mounting hole of the insulating ceramic base 2 and fix it with the lock nut. 4. Secure the contact electrode 7 and the insulating ceramic tube 3 to the mounting position of the cathode base 8 using bolts; 5. Fit the cathode magnetic screen 4 onto the outside of the contact electrode 7, making the top of the cathode magnetic screen 4 flush with the small hole at the top of the contact electrode 7. Fix the cathode magnetic screen to the cathode bottom 8 with three bolts evenly distributed around the circumference to complete the overall assembly. 6. Connect the assembled hollow cathode to the Hall thruster via a flange. The distance between the cathode magnetic screen 4 and the discharge channel outlet of the thruster should be controlled within a reasonable range to ensure that electrons are directionally conducted to the discharge channel.

[0042] The working process and effects of this invention: When the Hall thruster is activated, the tangential magnetic field generated by its permanent magnet leaks outward, forming a strong magnetic field environment near the cathode (the magnetic field strength in the orifice area is 0.015-0.02T without a magnetic screen). At this time, the cathode magnetic screen 4, through its high magnetic permeability, adsorbs the leaked magnetic field into the interior of the magnetic screen body, reducing the magnetic field strength in the hollow cathode orifice area (key area for electron emission) to below 0.005T, with a magnetic field attenuation of more than 67% (simulation results are shown in Figures 4 and 5).

[0043] After the heating wire 5 is energized and heats the emitter 6 to a set temperature, the electrons emitted by the emitter 6 experience a significant reduction in Lorentz force in the low magnetic field environment of the aperture region, forming a directional "electron bridge" (discharge image as shown). Figure 3 As shown), it efficiently enters the thruster discharge channel to participate in ionization; compared to the condition without a magnetic shield (such as... Figure 2 The external halo phenomenon shown indicates a significant improvement in electron conduction efficiency.

[0044] The total efficiency of the thruster was obtained through actual measurement and calculation using a thrust measurement device (results are shown below). Figure 6 As shown, within the thrust input power range of 30-90W, after configuring the magnetic screen structure of this embodiment, the total thrust efficiency increases from 2.9%-8.5% to 5.5%-14.2%, which is an efficiency increase of 3%-6% at the same power.

[0045] A schematic diagram of the hollow cathode structure described in this invention is shown below. Figure 1 As shown in the image, the discharge images of the Hall thruster with and without a magnetic screen at the cathode are shown in the image. Figure 2 , Figure 3 As shown: When the magnetic shielding structure described in this invention is configured on the cathode, a bright light path (known in the industry as the "electron bridge") pointing from the cathode to the thruster can be clearly observed. This phenomenon directly proves that the electrons emitted from the cathode form a clear directional conduction path, enabling them to efficiently enter the thruster and participate in the discharge process. Furthermore, the resistance to electron conduction along this path is significantly reduced. However, when the cathode is not configured with a magnetic shielding structure, the aforementioned "electron bridge" phenomenon is not observed. Instead, a distinct halo forms outside the thruster. This halo originates from the magnetic field binding the electrons outside the thruster, causing some propellant to undergo ineffective ionization outside the thruster. This further confirms the technical defects of disordered electron conduction and severe energy loss without magnetic shielding, and also highlights the key role of the magnetic shielding structure of this invention in optimizing the electron conduction path and reducing ineffective losses.

[0046] To further quantify the magnetic field shielding effect of the magnetic shielding structure of this invention, the external magnetic field strength and distribution characteristics of the tangential field Hall thruster under two operating conditions—without and with a magnetic shield at the cathode—were simulated and analyzed using three-dimensional simulation software. The simulation results are as follows: Figure 4 , Figure 5As shown in the figure. Simulation data shows that when the cathode is not equipped with a magnetic shielding structure, the magnetic field strength in the hollow cathode aperture region (the key region for electron emission) is 0.015~0.02T. Since the electrons emitted by the cathode need to exit from the aperture region and be conducted to the thruster, the magnetic field strength in this region directly determines the electron emission velocity and conduction resistance, making it a core critical region affecting the electron conduction efficiency of the cathode. When the cathode is equipped with the magnetic shielding structure described in this invention, the magnetic field strength in the hollow cathode aperture region significantly decreases to below 0.005T, with a reduction of more than 67%. This simulation result corroborates the aforementioned discharge experiment phenomena, clearly demonstrating that the magnetic shielding structure described in this invention can specifically weaken the leakage magnetic field strength in the key region of the cathode, providing a magnetic field environment guarantee for low-resistance directional electron conduction, further solidifying the effectiveness and feasibility of the technical solution of this invention.

[0047] To visually demonstrate the effect of the magnetic shielding structure of this invention on improving the core performance of the thruster, thrust data of the Hall thruster under different input power were measured using a dedicated thrust measurement device. The overall thruster efficiency was calculated based on thrust, input power, and propellant flow rate. The measured results are as follows: Figure 6 As shown in the figure. Data indicates that within the typical operating range of a thruster with a total input power ≤ 90W, the total thruster efficiency is only 2.9%~8.5% without a magnetic shielding structure; however, after configuring the magnetic shielding structure described in this invention, the total thruster efficiency increases to 5.5%~14.2%, representing a relative improvement of 3%~6% under the same power conditions. This experimental result directly confirms the complete technical logic of magnetic field shielding → optimized electron conduction → reduced energy loss → improved performance. It clearly demonstrates that the magnetic shielding structure described in this invention not only effectively improves the magnetic field environment near the cathode but also translates into a substantial improvement in the total thruster efficiency. This solves the problem of low efficiency caused by magnetic field interference in miniaturized Hall thrusters and other electric thrusters, significantly enhancing the practical value and competitiveness of the propulsion system.

[0048] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A hollow cathode magnetic screen structure for improving the performance of a Hall thruster, characterized in that, The assembly includes a cathode tube (1), an insulating ceramic base (2), an insulating ceramic tube (3), a cathode magnetic screen (4), a heating wire (5), an emitter (6), a contact electrode (7), and a cathode base (8). The emitter (6) is fixedly installed inside the top of the cathode tube (1) by an interference fit. The heating wire (5) is sleeved on the outside of the cathode tube (1) corresponding to the position of the emitter (6). The insulating ceramic tube (3) and the cathode magnetic screen (4) are sleeved on the outside of the cathode tube (1) from the inside to the outside, and the extended surfaces of the bottom of the insulating ceramic tube (3) and the cathode magnetic screen (4) are fixedly connected to the cathode base (8). The contact electrode (7) is sleeved between the insulating ceramic tube (3) and the cathode magnetic screen (4), and the extended surface of the bottom of the contact electrode (7) is fixedly installed on the extended surface of the insulating ceramic tube (3). The insulating ceramic base (2) is disposed between the cathode tube (1) and the cathode base (8) and is fixedly connected to the cathode base (8). The cathode magnetic screen (4) is made of a magnetically conductive material.

2. The hollow cathode magnetic screen structure for improving the performance of a Hall thruster in a cutting field, as described in claim 1, is characterized in that, The cathode tube (1) is used to carry the emitter (6), and an electron emission hole is opened at the top to guide the electrons generated by the emitter (6) to be emitted directionally from the electron emission hole; An insulating ceramic base (2) is used to achieve electrical insulation isolation between the cathode tube (1) and the cathode base (8); An insulating ceramic tube (3) is used to achieve electrical insulation isolation between the contact electrode (7) and the cathode base (8); Cathode magnetic screen (4) is used to weaken the magnetic field strength in the key area of ​​the hollow cathode outlet and reduce the magnetic field resistance to electron movement. Heating wire (5) is used to heat the emitter (6) to the operating temperature required for electron emission, thereby triggering electron emission; The emitter (6) is used to generate and emit electrons required for the hollow cathode to operate; The contact electrode (7) is used to assist the emitter (6) in starting and stabilize the electron emission state of the hollow cathode; The cathode base (8) is used as the base of the overall structure to fix the insulating ceramic base (2), the insulating ceramic tube (3) and the cathode magnetic screen (4).

3. The hollow cathode magnetic screen structure for improving the performance of a Hall thruster in a slit field, as described in claim 2, is characterized in that... The cathode magnetic screen (4) is made of DT4C electrical pure iron and has a sleeve structure.

4. The hollow cathode magnetic screen structure for improving the performance of a Hall thruster in a cutting field according to claim 2, characterized in that, The cathode tube (1) is made of tungsten metal.

5. The hollow cathode magnetic screen structure for improving the performance of a Hall thruster in a cutting field according to claim 2, characterized in that, The emitter (6) is a cylindrical structure with a through hole at its core, made by impregnating a porous tungsten matrix with a barium oxide solution.

6. The hollow cathode magnetic screen structure for improving the performance of a Hall thruster in a cutting field, as described in any one of claims 2, 3, or 4, is characterized in that... The distance between the cathode magnetic screen (4) and the outer wall of the cathode tube (1) is 1-2 mm, and the top of the cathode magnetic screen (4) is flush with or 1-2 mm higher than the top of the contact electrode (7).

7. The hollow cathode magnetic screen structure for improving the performance of a Hall thruster in a scissor field according to claim 2, characterized in that, The heating wire (5) is a spiral structure made of tungsten wire.

8. The hollow cathode magnetic screen structure for improving the performance of a Hall thruster in a scissor field according to claim 2, characterized in that, The insulating ceramic base (2) and the insulating ceramic tube (3) are both made of alumina ceramic.

9. The hollow cathode magnetic screen structure for improving the performance of a Hall thruster in a slit field, as described in claim 2, is characterized in that... The contact electrode (7) is made of nickel alloy.

10. The hollow cathode magnetic screen structure for improving the performance of a Hall thruster in a scissor field according to claim 2, characterized in that, The cathode base (8) is made of stainless steel. Multiple mounting threaded holes are provided on the surface of the cathode base (8) for the installation and fixing of the insulating ceramic base (2), the insulating ceramic tube (3) and the cathode magnetic screen (4).

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