MAGNETIC POLE STRUCTURE FOR HALL THRUSTER

Abstract

A magnetic pole structure for a Hall thruster is provided. The magnetic pole structure includes: multiple wide-envelope outer magnetic pole components, a magnetic bridge, a pagoda-shaped inner magnetic pole component, a top plate, and a bottom plate, where the multiple wide-envelope outer magnetic pole components are arranged on an outer edge of the Hall thruster, symmetrical about the pagoda-shaped inner magnetic pole component, and enclose a semi-open structure; the magnetic bridge is located between each of the wide-envelope outer magnetic pole components and the pagoda-shaped inner magnetic pole component; the bottom plate is attached to a bottom part of each of the wide-envelope outer magnetic pole components and a bottom part of the pagoda-shaped inner magnetic pole component; and the top plate is attached to an upper part of each of the wide-envelope outer magnetic pole components.

Claims

1. A magnetic pole structure for a Hall thruster, comprising: a plurality of wide-envelope outer magnetic pole components, a magnetic bridge, a pagoda-shaped inner magnetic pole component, a top plate, and a bottom plate, wherein the plurality of wide-envelope outer magnetic pole components are arranged on an outer edge of the Hall thruster and symmetrical about the pagoda-shaped inner magnetic pole component, and the plurality of wide-envelope outer magnetic pole components enclose a semi-open structure; the magnetic bridge is located between each of the plurality of wide-envelope outer magnetic pole components and the pagoda-shaped inner magnetic pole component, and is connected with a magnetic circuit formed by each of the plurality of wide-envelope outer magnetic pole components and the pagoda-shaped inner magnetic pole component; the bottom plate is attached to a bottom part of each of the plurality of wide-envelope outer magnetic pole components and a bottom part of the pagoda-shaped inner magnetic pole component; the top plate is attached to an upper part of each of the plurality of wide-envelope outer magnetic pole components, and the top plate is provided with a central through hole; and the magnetic bridge and the pagoda-shaped inner magnetic pole component are connected with an outer magnetic circuit through the central through hole; and the pagoda-shaped inner magnetic pole component is composed of a pagoda-shaped inner magnetic pole, an upper inner magnetic coil, and a lower inner magnetic coil; the pagoda-shaped inner magnetic pole comprises an upper part and a lower part, and the upper part has a diameter less than a diameter of the lower part; the upper part of the pagoda-shaped inner magnetic pole is wound by the upper inner magnetic coil; and the lower part of the pagoda-shaped inner magnetic pole is wound by the lower inner magnetic coil.

2. The magnetic pole structure according to claim 1, wherein the magnetic bridge is formed by welding an inner ring and an outer ring; a cavity is formed between the inner ring and the outer ring; the inner ring and the outer ring are provided with uniformly spaced pores; and the outer ring is connected with an outer gas tube.

3. The magnetic pole structure according to claim 1, wherein each of the plurality of wide-envelope outer magnetic pole components is composed of a wide-envelope outer magnetic pole and an outer magnetic coil; and the outer magnetic coil is wound on the wide-envelope outer magnetic pole.

4. The magnetic pole structure according to claim 1, wherein each of the plurality of wide-envelope outer magnetic pole components has a circumferential length of d, n wide-envelope outer magnetic pole components have a length of nd, and a circumference is of L, wherein 0.5≤nd/L≤0.7.

5. The magnetic pole structure according to claim 1, wherein the plurality of wide-envelope outer magnetic pole components are jointly enclosed by a metal mesh.

6. The magnetic pole structure according to claim 1, wherein a ceramic plate is provided between the magnetic bridge and the lower inner magnetic coil; and an inner outlet ceramic ring and an outer outlet ceramic ring are arranged on an upper part of the magnetic bridge.

7. The magnetic pole structure according to claim 2, wherein the magnetic bridge is made of a soft magnetic material.

8. The magnetic pole structure according to claim 7, wherein a working temperature of the magnetic bridge falls in a working temperature range of the soft magnetic material, and is less than 0.78 Tc (Tc refers to Curie temperature).

9. The magnetic pole structure according to claim 1, wherein the plurality of wide-envelope outer magnetic pole components and the magnetic bridge have a variety of shapes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Other features, objectives, and advantages of the present disclosure will become more apparent by reading the detailed description of non-limiting embodiments with reference to the following drawings.

[0024] FIG. 1 is a three-dimensional view of a special magnetic pole structure for a Hall thruster;

[0025] FIG. 2 is a sectional view of the special magnetic pole structure for a Hall thruster;

[0026] FIG. 3 shows a distribution of pores in an inner ring of a magnetic bridge;

[0027] FIG. 4 is a top view of the special magnetic pole structure for a Hall thruster;

[0028] FIGS. 5A-5D show different shapes of the magnetic bridge;

[0029] FIG. 6 is a two-dimensional sectional view of the special magnetic pole structure for a Hall thruster;

[0030] FIG. 7 is a sectional view of a wide-envelope round-diamond-shaped outer magnetic pole;

[0031] FIG. 8 is a three-dimensional diagram showing a flow direction of magnetic conductivity of the special magnetic pole structure for a Hall thruster;

[0032] FIG. 9 shows the wide-envelope outer magnetic poles with different shapes;

[0033] FIG. 10 is an exterior view of a magnetic pole structure for a Hall thruster with four wide-envelope round-diamond-shaped outer magnetic poles;

[0034] FIG. 11 shows a comparison of radial magnetic induction intensities of the special magnetic pole structure and a traditional magnetic circuit structure for a Hall thruster; and

[0035] FIG. 12 shows a comparison of circumferential magnetic field uniformity of the special magnetic pole structure and the traditional magnetic circuit structure for a Hall thruster.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] The present disclosure is described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art further understand the present disclosure, but will not limit the present disclosure in any way. It should be noted that several variations and improvements can also be made by a person of ordinary skill in the art without departing from the conception of the present disclosure. These all fall within the protection scope of the present disclosure.

[0037] As shown in FIGS. 1 to 4, a special magnetic pole structure for a Hall thruster includes: wide-envelope outer magnetic pole components 1, magnetic bridge 2, pagoda-shaped inner magnetic pole component 3, top plate 4, and bottom plate 7. The wide-envelope outer magnetic pole components 1 enclose a semi-open structure. Metal mesh 12 is provided outside the wide-envelope outer magnetic pole components 1 to shield plasma. Inner outlet ceramic ring 5 and outer outlet ceramic ring 6 form an outlet space and are arranged on an upper part of the magnetic bridge 2. The pagoda-shaped inner magnetic component 3 is located on a central axis of the Hall thruster and adopts a variable-section structure with a thin top end and a thick bottom end. Upper inner magnetic coil 10 is wound on an upper part of pagoda-shaped inner magnetic pole 15 and has a small number of turns due to a space limit by the magnetic bridge. Lower inner magnetic coil 11 is wound at a lower part of the pagoda-shaped inner magnetic pole, and has a large number of turns. On the one hand, the thick lower part increases the area of magnetic conductivity, so as to make up for the insufficient magnetic conductivity in the upper part and optimize the magnetic conductivity. On the other hand, more turns wound at the lower part can significantly reduce the excitation current, reduce the magnetic loss of the Hall thruster, effectively reduce the thermal load, and improve the efficiency of the Hall thruster on the premise that the ampere-turns remain unchanged. Meanwhile, the lower part serves as a load-bearing part to support the magnetic bridge 2 (anode). With the increase in the area of magnetic conductivity, the load-bearing area increases correspondingly, thus improving the resistance of the Hall thruster to impact.

[0038] The magnetic bridge is composed of inner ring 16 and outer ring 17. Either or both of the two rings can be made of a soft magnetic material as required. The magnetic bridge is located between the inner and outer magnetic poles. A magnetic circuit is provided with a magnetic leakage gap between the magnetic bridge and the inner and outer magnetic poles and finally forms a closed loop. A required magnetic field is formed in a channel of a discharge chamber to restrict the movement of electrons and accelerate the ion ejection to form a thrust. A cavity is formed between the inner ring 16 and the outer ring 17. Pores are uniformly distributed on the inner ring 16. A gas is introduced into the cavity by a gas tube. After buffering and uniform distribution, the gas enters a discharge channel formed by the magnetic bridge 2 through the small holes. Insulating ceramic plate 13 is located between the lower inner magnetic coil 11 and the magnetic bridge 2 (anode) and plays an insulating role. The magnetic bridge is in direct contact with a discharge working zone. Through the reasonable thermal design, the working temperature of the magnetic bridge is in a working range of the soft magnetic material, that is, less than 0.78 Tc (Tc refers to Curie temperature). Therefore, the Hall thruster can work normally without affecting the normal magnetic conductivity of the magnetic bridge.

[0039] Specifically, as shown in FIG. 7, a preferred embodiment of the present disclosure provides a special magnetic pole structure. Compared with the discrete magnetic cylinders and annular magnetic pole structure of a traditional Hall thruster, the special magnetic pole structure of the present disclosure adopts wide-envelope outer magnetic poles 8. The wide-envelope outer magnetic poles extend outside the Hall thruster, achieving uniform distribution of the magnetic field and uniform ionization in the discharge channel, thus improving the efficiency of the Hall thruster. The magnetic bridge 2 is made of a magnetic conductive material and also serves as a magnetic shield. Compared with the traditional Hall thruster, a width of the magnetic bridge 2 is slightly larger than a width of the outlet ceramic, and the magnetic bridge 2 is shallower. In this way, a steep magnetic field configuration is formed, leading to a steep gradient of radial magnetic induction intensity, thus improving the acceleration performance and specific impulse of the Hall thruster.

[0040] More specifically, as shown in FIGS. 8 to 10, the wide-envelope outer magnetic pole components 1 are formed by winding outer magnetic coils 9 outside the wide-envelope outer magnetic poles 8, respectively. The wide-envelope outer magnetic pole components are uniformly distributed on the outer edge of the Hall thruster, fixed on the bottom plate 7, and are pressed by the top plate 4. The wide-envelope outer magnetic pole components 1 each have a circumferential length of d. That is, n wide-envelope outer magnetic pole components have a length of nd, and a circumference is of L, where 0.5≤nd/L≤0.7. The wide-envelope magnetic poles 8 feature a uniform distribution of the magnetic field, which makes a gas medium uniformly ionized in the discharge channel, thus improving the performance of the Hall thruster. In addition, the wide-envelope magnetic poles form an effective heat dissipation window. The wide-envelope outer magnetic poles 8 can have different shapes, such as a round diamond, arch, triangle, plane, and trapezoid.

[0041] As shown in FIGS. 5A-5D, the rings of the magnetic bridge can have different shapes, such as double-L shape, chamfer U shape, arc U shape, and taper, to adapt to different spatial constraints in the Hall thruster.

[0042] FIG. 6 shows a flow direction of the magnetic conductivity of the special magnetic pole structure for the Hall thruster. It can be seen from the figure that the magnetic circuit is divided into a left branch and a right branch. Each branch starts from the wide-envelope outer magnetic pole 1, flows through the magnetic bridge 2, and forms magnetic leakage at the outlet. The two branches converge at the central pagoda-shaped inner magnetic pole 3 and flow to the bottom plate 7. Finally, the left and right branches flow back to the top plate 4 from the two wide-envelope outer magnetic poles 1.

[0043] FIG. 11 shows a comparison of radial magnetic induction intensities of the special magnetic pole structure and the traditional magnetic circuit structure for the Hall thruster. It can be seen from the figure that the magnetic field gradient of the special magnetic pole structure is steeper, reaching 41 Gs/mm, while the magnetic field gradient of the traditional magnetic circuit structure is only 13 Gs/mm. In addition, compared with the traditional magnetic circuit structure, the maximum radial magnetic induction intensity of the special magnetic pole structure increases from 230 Gs to 270 Gs, the radial magnetic induction intensity of the anode decreases from 25 Gs to 5 Gs, the outlet position of the discharge chamber moves from 32.5 mm to 15 mm, and the length of the acceleration zone is compressed from 25 mm to 3 mm. With this magnetic field configuration, a plume divergence angle decreases by 55%, from 90° to 40°, the specific impulse performance of the Hall thruster increases by 35%, and the efficiency of the Hall thruster increases by 20%.

[0044] As shown in FIG. 12, the special magnetic pole structure improves the distribution uniformity of the magnetic field. A circumferential fluctuation of the magnetic field of the traditional magnetic circuit is 8%, while the circumferential fluctuation of the magnetic field of the special magnetic pole structure decreases by an order of magnitude, only 4‰. The distribution uniformity of the magnetic field of the special magnetic pole structure is improved, which makes the ionization in the discharge channel of the Hall thruster more uniform, thus improving the performance of the Hall thruster. In addition, the special magnetic pole structure also greatly reduces the influence of magnetic field bump on the thrust output, and significantly reduces the thrust vector eccentricity.

[0045] In the description of the present application, it needs to be understood the orientation or positional relationships indicated by terms, such as “up”, “down”, “front”, “rear”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, and “outside”, are based on the orientation or positional relationship shown in the drawings, are merely for facilitating the description of the present application and simplifying the description, rather than indicating or implying that an apparatus or element referred to must have a particular orientation or be constructed and operated in a particular orientation, and therefore will not be interpreted as limiting the present application.

[0046] The specific embodiments of the present disclosure are described above. It should be understood that the present disclosure is not limited to the above specific implementations, and a person skilled in the art can make various variations or modifications within the scope of the claims without affecting the essence of the present disclosure. The embodiments in the present disclosure and features in the embodiments may be freely combined with each other in a non-conflicting manner.