Magnetic cage adjusting method and magnetic cage with increased magnetic conducting column hall thruster

Abstract

A kind of increase magnetic cage's magnetic column hall thrust and magnetic cage adjusting method, include inner magnetic pole, inner core, inner excitation coil, inner magnetic screen, anode, bottom plate, outer magnetic screen, permanent magnet structure, outer magnetic pole, discharge channel, outer excitation coil and outer magnetic column;Inner magnetic screen and outer magnetic screen are annular structure, inner core, inner magnetic screen, discharge channel and outer magnetic screen are annular structure, in turn away from axis and fixed on bottom plate, anode is arranged in discharge channel, the inner magnetic pole is fixed on inner core, outer magnetic column is uniformly arranged on bottom plate, outer magnetic pole is fixed on outer magnetic column, the outer magnetic pole is the plate-shaped structure with four straight edges, each straight edge edge is fixed with the permanent magnet structure opposite to the magnetic pole direction of outer excitation coil.This application has the advantages of reducing coupling pressure drop, improving voltage utilization, improving the discharge efficiency of thruster, while ensuring the life of cathode and thruster.

Description

Technical Field

[0001] This invention relates to Hall thrusters, and more specifically to a Hall thruster with an enlarged magnetic cage and a magnetic cage adjustment method. Background Technology

[0002] A Hall thruster is an electric propulsion device that uses an electromagnetic acceleration mechanism, primarily used in aerospace propulsion. The Hall thruster generates an orthogonal electromagnetic field within a discharge channel. Seed electrons enter the discharge channel from the cathode and are constrained by the magnetic field, undergoing Hall drift motion under the influence of the orthogonal electromagnetic field. Propellant is injected into the channel by a gas distributor at the bottom of the channel and ionizes upon collision with electrons, generating a large number of ions and electrons. These ions are accelerated and ejected by an axial electric field, generating thrust. Hall thrusters have advantages such as simple structure, high specific impulse, and high efficiency, which can extend satellite lifespan and increase payload rate. Currently, they are mainly used in on-orbit missions such as satellite attitude control, orbital maneuvers, position holding, and damping compensation for space stations.

[0003] Based on the excitation structure, Hall thrusters can be divided into two types: magnetic column thrusters and magnetic shield thrusters. Among them, the magnetic column thruster is lightweight and has a large heat dissipation area, and is widely used. The internal and external excitation currents of the magnetic column Hall thruster are in opposite directions, forming magnetic paths between the inner and outer magnetic poles and between the magnetic pole base plates, i.e., two magnetic mirror structures. The inner and outer magnetic mirrors squeeze each other, forming a magnetic interface in the magnetic field, a spatial curved surface structure, shaped like a cage. The thruster's plume is located inside the cage, and the magnetic field inside the cage has a significant influence on the constraint of the plume. Therefore, the cage-shaped region enclosed by the magnetic interface is called the magnetic cage, and the boundary of the magnetic cage is the magnetic interface. Usually, the boundary of the magnetic cage starts from the surface of the outer magnetic pole and extends to infinity in the axial and radial directions.

[0004] Studies have shown that for Hall thrusters with external cathodes and magnetic posts, if the cathode is located outside the magnetic cage, electrons entering the discharge channel need to cross the magnetic cage boundary, traversing more magnetic lines of force, resulting in a longer coupling path and a greater coupling voltage drop. This reduces voltage utilization and thruster discharge efficiency. Placing the cathode closer to the thruster, inside the magnetic cage, can alleviate these problems. However, placing the cathode closer to the thruster exacerbates the ion erosion effect on the cathode, reducing thruster lifespan. Therefore, it is necessary to increase the size of the magnetic cage to reduce coupling voltage, improve voltage utilization, enhance thruster discharge efficiency, and simultaneously ensure the lifespan of both the cathode and the thruster.

[0005] Patent document CN114320800A discloses a Hall thruster that uses a magnetic cage to constrain a plume and a method for adjusting the magnetic cage structure. It involves adding an additional coil to the outside of the outer magnetic source for excitation, so that the magnetic flux direction inside the inner magnetic source is opposite to that inside the outer magnetic source. The magnetic flux direction formed by the additional coil and the outer magnetic source for excitation is also opposite to that of the outer magnetic source. By adjusting the additional excitation ampere-turns of the additional coil, the tangent of the magnetic force line emitted by the outer magnetic source at the connection point with the additional coil structure is made to have an angle of not less than 90° with the axis of the Hall thruster. This achieves the purpose of converging the plume shape of the Hall thruster and reducing the degree of plume divergence. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention provides a Hall thruster with an enlarged magnetic cage and a method for adjusting the magnetic cage. The Hall thruster with an enlarged magnetic cage has a permanent magnet structure set at the straight edge of the outer magnetic pole. The magnetic cage is pushed outward and the outward extension trend of the magnetic cage boundary is stabilized. The angle between the magnetic cage and the thruster axis changes from the acute angle of the original structure to the obtuse angle after adjustment. This achieves the purpose of reducing coupling voltage drop, improving voltage utilization, and improving the discharge efficiency of the thruster.

[0007] A Hall thruster with an enlarged magnetic cage includes an inner magnetic pole, an inner iron core, an inner excitation coil, an inner magnetic screen, an anode, a base plate, an outer magnetic screen, a permanent magnet structure, an outer magnetic pole, a discharge channel, an outer excitation coil, and an outer magnetic column. Both the inner and outer magnetic screens are annular structures. The inner iron core, inner magnetic screen, discharge channel, and outer magnetic screen are also annular structures, sequentially positioned away from the axis and fixed to the base plate. An anode is disposed within the discharge channel. The inner magnetic pole is fixed to the inner iron core. The outer magnetic columns are evenly distributed on the base plate, and the outer magnetic poles are fixed to the outer magnetic columns. The outer magnetic pole is a plate-like structure with four straight edges. A permanent magnet structure opposite in direction to the magnetic pole of the outer excitation coil is fixed to each straight edge. This allows for adjustment of the initial position and angle of the magnetic cage at the edge of the outer magnetic pole, as well as the angle between the magnetic cage and the outlet plane of the Hall thruster after the magnetic cage's extension trend stabilizes, thereby enlarging the magnetic cage.

[0008] A method for adjusting the magnetic cage structure using a Hall thruster with an enlarged magnetic cage guide column is proposed. By adding a magnetic field to the permanent magnet structure, the magnetic field near the magnetic cage is distorted, the starting point of the magnetic cage is moved from the upper surface of the outer magnetic pole to the lower surface, the initial angle between the magnetic cage and the thruster is increased from an acute angle to an obtuse angle, the magnetic cage is pushed outward radially, and the angle between the magnetic cage and the thruster axis is increased after the extension trend stabilizes.

[0009] The advantages of this invention compared to the prior art are:

[0010] This invention involves setting a permanent magnet structure at the straight edge of the outer magnetic pole, pushing the magnetic cage outward, and increasing the angle between the magnetic cage boundary and the thruster axis after the outward extension trend of the magnetic cage is stabilized. By adjusting the design parameters of the permanent magnet (such as axial dimensions, shape, and assembly method), it is beneficial to regulate the degree of magnetic cage enlargement. By adding a permanent magnet structure and adjustment method, it has the advantages of reducing coupling voltage drop, improving voltage utilization, improving thruster discharge efficiency, and ensuring the lifespan of the cathode and thruster.

[0011] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments: Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the Hall thruster with a magnetic guide column for increasing the magnetic cage according to the present invention;

[0013] Figure 2 This is a main cross-sectional view and working principle schematic diagram of the Hall thruster with enlarged magnetic cage of the present invention.

[0014] Figure 3 This is a schematic diagram showing the arrangement of the external magnetic column and the external excitation coil of the present invention;

[0015] Figure 4 This is a schematic diagram of a traditional magnetic column Hall thruster without a permanent magnet structure in Example 4;

[0016] Figure 5 This is a schematic diagram of the Hall thruster with the first permanent magnet structure set in Example 4;

[0017] Figure 6 This is a schematic diagram showing the axial dimension of the first permanent magnet structure in Example 4 extending upstream of the thruster channel;

[0018] Figure 7 This is a schematic diagram showing the axial dimension of the first permanent magnet structure in Example 4 extending downstream of the thruster channel;

[0019] Figure 8 A partially enlarged view showing the axial dimension of the first type of permanent magnet structure extending upstream of the thruster channel;

[0020] Figure 9 A partially enlarged view showing the axial dimension of the first permanent magnet structure extending downstream of the thruster channel;

[0021] Figure 10 This diagram shows the relationship between the second type of external magnetic pole and the permanent magnet structure assembly.

[0022] Figure 11 A schematic diagram of the assembly of the third type of external magnetic pole and permanent magnet structure;

[0023] Figure 12 This diagram illustrates the radial displacement effect of permanent magnets with different configurations on the outer magnetic poles on the magnetic cage.

[0024] Figure 13 The diagram shows the magnetic field strength distribution along the centerline of the Hall thruster channel before and after the permanent magnets are installed.

[0025] Wherein: 1-inner magnetic pole, 2-inner iron core, 3-inner excitation coil, 4-inner magnetic screen, 5-anode, 6-base plate, 7-outer magnetic screen, 8-permanent magnet structure, 9-outer magnetic pole, 10-discharge channel, 11-outer excitation coil, 12-outer magnetic column. Detailed Implementation

[0026] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. Unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning understood by those skilled in the art.

[0027] First Implementation Method

[0028] Example 1: Based on the current external cathode Hall thruster with magnetic column, if the cathode is located outside the magnetic cage, electrons need to cross the magnetic cage boundary and traverse more magnetic lines of force to enter the discharge channel. This results in a longer coupling path and a greater coupling voltage drop, thus reducing voltage utilization and thruster discharge efficiency. Placing the cathode closer to the thruster inside the magnetic cage can alleviate the above problems. However, placing the cathode closer to the thruster will exacerbate the ion erosion effect on the cathode, reducing the thruster's lifespan. Therefore, it is necessary to increase the size of the magnetic cage to reduce coupling voltage, improve voltage utilization, and enhance thruster discharge efficiency while ensuring the lifespan of both the cathode and the thruster.

[0029] Therefore, this embodiment provides a Hall thruster with an enlarged magnetic cage and a guide column, such as... Figures 1-3 As shown, the system includes an inner magnetic pole 1, an inner iron core 2, an inner excitation coil 3, an inner magnetic screen 4, an anode 5, a base plate 6, an outer magnetic screen 7, a permanent magnet structure 8, an outer magnetic pole 9, a discharge channel 10, an outer excitation coil 11, and an outer magnetic guide column 12. Both the inner magnetic screen 4 and the outer magnetic screen 7 are annular structures. The inner iron core 2, inner magnetic screen 4, discharge channel 10, and outer magnetic screen 7 are also annular structures, sequentially moving away from the axis and fixed to the base plate 6. An anode 5 is disposed within the discharge channel 10. The inner magnetic pole 1 is fixed to the inner iron core 2. The outer magnetic guide columns 12 are evenly distributed on the base plate 6. The outer magnetic pole 9 is fixed to the outer magnetic guide column 12. The outer magnetic pole 9 is a plate-shaped structure with four straight edges. A permanent magnet structure 8, with the opposite direction to the magnetic pole of the outer excitation coil 11, is fixed on each straight edge. This allows for adjustment of the initial position, initial angle, and angle between the magnetic cage at the edge of the outer magnetic pole 9 and the outlet plane of the Hall thruster after the magnetic cage's extension trend has stabilized, thereby expanding the magnetic cage.

[0030] In this embodiment, the magnetic cage structure is enlarged by setting a permanent magnet structure 8 on the outer edge of the outer magnetic pole 9. The enlargement effect of the magnetic cage is adjusted by adjusting the shape and installation position of the permanent magnet structure, thereby achieving the adjustment of the magnetic cage.

[0031] Example 2, based on Example 1, is further defined as follows: the inner magnetic pole 1 is a flat cylindrical structure, located on the circular upper end face of the inner iron core 2, and coaxial with the inner iron core 2; the inner excitation coil 3 is tightly wound on the side of the inner iron core 2; the ceramic discharge channel is a double-layered ring chamber structure with one end open, located between the inner magnetic screen 4 and the outer magnetic screen 7; the outer magnetic column 12 is located outside the outer magnetic screen 7, with its bottom end fixed on the base plate 6, and is arranged on the diagonal axis of symmetry of the base plate 6 and evenly distributed circumferentially; the outer magnetic pole 9 is located on the upper end face of the outer magnetic column 12, aligned with the base plate 6; the outer excitation coil 11 is tightly wound on the side of the outer magnetic column 12. The magnetic pole directions of the inner and outer excitation coils are opposite. The anode 5 is located inside the ceramic discharge channel, fixed on the closed end face of the discharge channel chamber, and the bottom part of the anode 5 passes through the ceramic discharge channel and the base plate 6, and is connected to the external gas path and circuit.

[0032] Example 3: Based on any of the above examples, this example further specifies that the material of the permanent magnet structure 8 is the soft magnetic material SmCo24. This material has high magnetic properties, good temperature performance, and will not undergo severe demagnetization at high temperatures.

[0033] Example 4: This example further defines the arrangement and shape of the permanent magnet structure 8. Specifically, the edge of each straight side is a stepped structure, the permanent magnet structure is fixed on the step, the permanent magnet structure covers the outer side of the stepped structure, and the permanent magnet structure has an extension section extending upstream or downstream of the Hall thruster channel. The above-described limitations achieve axial positioning and assembly of the permanent magnet structure.

[0034] Combination Figure 2 , Figures 4-7 Note that existing magnetic column Hall thrusters, such as Figure 4 As shown; a permanent magnet structure 8 is set at the straight edge of the outer magnetic pole 9, as... Figure 5 As shown, the axial length of the permanent magnet structure 8 is 3mm, and its upper and lower surfaces are flush with the upper and lower surfaces of the outer magnetic pole 9, respectively; the axial dimension of the permanent magnet structure is extended 2mm upstream of the thruster channel, as shown. Figure 6 and Figure 8 As shown; will Figure 5 The axial dimension of the permanent magnet structure extends 2mm downstream of the thruster, such as... Figure 7 and Figure 9 As shown. Figure 6 or Figure 8 and Figure 7 or Figure 9 The permanent magnet structure 8 can all be in Figure 5 The magnetic cage was further enlarged based on this.

[0035] The specific principle is as follows: Figure 2 As shown: The thruster's magnetic field forms two pathways between the inner and outer magnetic poles and between the outer magnetic pole base plate, forming two magnetic poles, one inner and one outer. These two poles press against each other to form a magnetic cage structure. The magnetic cage structure extends to infinity, originating from the surface of the outer magnetic pole 9 (usually the upper and side surfaces, such as...). Figure 2 The original magnetic cage boundary is shown; by adding a magnetic field to the permanent magnet structure 8, the magnetic field near the magnetic cage is distorted, moving the starting point of the magnetic cage from the upper surface of the outer magnetic pole 9 to the lower surface, and increasing the initial angle between the magnetic cage and the Hall thruster from an acute angle to an obtuse angle (as shown). Figure 2 The new structure of the magnetic cage (shown with the addition of a permanent magnet structure) is designed to push the magnetic cage outward radially, while increasing the angle between the magnetic cage and the thruster axis after the extension trend stabilizes.

[0036] Example 5: Based on Example 4, this example further illustrates the relationship between the axial position of the permanent magnet structure 8 and the magnetic field strength of the external excitation coil 11 and the internal excitation coil 3.

[0037] Figure 4 In a traditional Hall thruster with a magnetic column, the external excitation coil 11 has an excitation ampere-turns of 320A, and the internal excitation coil 3 has an excitation ampere-turns of 522A. Correspondingly... Figure 12 The solid line represents its magnetic cage (as in curve a);

[0038] Figure 5 The Hall thruster with a permanent magnet structure 8 is equipped with a magnetic column. The external excitation coil 11 has an excitation ampere-turns of 330A, and the internal excitation coil 3 has an excitation ampere-turns of 515A. Figure 12 A uniform dashed magnetic cage (such as curve b);

[0039] Figure 6 The permanent magnet structure 8 extends upstream of the thruster channel in an axial direction. The external excitation coil 11 has an excitation ampere-turns of 320A, and the internal excitation coil 3 has an excitation ampere-turns of 530A. Figure 12 The midpoint line represents the magnetic cage (as in curve c);

[0040] Figure 7 The permanent magnet structure 8 extends upstream of the thruster channel in an axial direction. The external excitation coil 11 has an excitation ampere-turns of 339A, and the internal excitation coil 3 has an excitation ampere-turns of 523A. Figure 12 Medium-short dashed line magnetic cage (e.g., curve d). In this embodiment, the permanent magnet structure can be an independent permanent magnet.

[0041] exist Figure 12By comparing the magnetic cages in curves a and b, it can be seen that the radial displacement effect of the permanent magnet structure 8 on the magnetic cage is more significant. By comparing the magnetic cages in curves b, c, and d, it can be seen that extending the axial dimension of the permanent magnet structure 8 upstream and downstream of the channel can enhance the increase in the size of the magnetic cage. Among them, extending the axial dimension of the permanent magnet downstream of the channel has a more significant effect.

[0042] Example 6: Based on any one of Examples 1-3 above, this example further defines other cross-sectional shapes and arrangements of the permanent magnet structure 8, such as rectangular or triangular.

[0043] For example: Figure 10 As shown, the edge of each straight edge is a stepped structure, the permanent magnet structure is a cuboid, and the permanent magnet structure is fixed on the steps. As an executable solution, the permanent magnet structure 8 is a permanent magnet without any constraints, the outer surface of the permanent magnet is flush with the outer surface of the stepped structure, and the upper and lower surfaces of the outer magnetic pole 9 are flush with the upper and lower surfaces of the permanent magnet.

[0044] For example: Figure 11 As shown, each straight edge has an inclined surface, and the permanent magnet structure is a triangular prism, which is fixed on the inclined surface. As an feasible solution, the permanent magnet structure 8 is a permanent magnet without any constraints. After assembly, the upper surface of the outer magnetic pole 9 is flush with the upper surface of the permanent magnet, and the outer surface of the outer magnetic pole 9 is flush with the outer surface of the permanent magnet.

[0045] Alternatively, the structure of placing permanent magnets on the outer magnetic poles can be expanded by setting support components on the outer magnetic poles. Specifically, the permanent magnet structure 8 includes permanent magnets and support components. The support components are fixed on the outer magnetic poles 9, and the permanent magnets are mounted on the support components.

[0046] As can be seen above, the effect of magnetic cage enlargement can be adjusted by modifying the design dimensions, shape, and assembly method of the permanent magnet structure. Extending the axial dimension of the permanent magnet upstream and downstream of the channel can both lead to magnetic cage enlargement. Moreover, for the same increase in axial dimension, the magnetic cage enlargement effect is more pronounced when the axial dimension of the permanent magnet is extended downstream of the channel. Changing the cross-section of the permanent magnet structure to other geometric shapes such as rectangles or triangles, or assembling the permanent magnet structure or permanent magnet by setting support components (such as clamps) at the edge of the outer magnetic poles, or setting permanent magnet collars on the outer magnetic poles, all affect the shape of the magnetic cage. Any method involving assembling permanent magnets on the outer magnetic poles is within the scope of this invention.

[0047] Second implementation method,

[0048] Based on any one of the embodiments 1-6 above, a method for adjusting the magnetic cage structure is provided. The method is as follows: by adding a magnetic field to the permanent magnet structure 8, the magnetic field near the magnetic cage is distorted, the starting point of the magnetic cage is moved from the upper surface of the outer magnetic pole to the lower surface, the initial angle between the magnetic cage and the thruster is increased from an acute angle to an obtuse angle, the magnetic cage is pushed outward radially, and the angle between the magnetic cage and the thruster axis is increased after the extension trend stabilizes.

[0049] By setting a permanent magnet structure at the straight edge of the outer magnetic pole, adjusting the initial position and angle of the magnetic cage on the magnetic pole surface, and increasing the angle between the magnetic cage and the thruster after the outward extension trend of the magnetic cage stabilizes, a method can be formed to adjust the degree of magnetic cage enlargement by adjusting the design parameters of the permanent magnet (such as axial dimensions, shape, and assembly method). Through the above design and method, while reducing coupling voltage drop, improving voltage utilization, and increasing thruster discharge efficiency, the lifespan of the cathode and thruster is guaranteed.

[0050] exist Figure 13 In the middle, corresponding Figures 4-7 Four structures and Figure 12 The magnetic field strength along the centerline of the Hall thruster channel of the magnetic guide column shows that the magnetic field strength along the centerline of the four structural channels is basically the same. The increase in the size of the magnetic cage can be adjusted by extending the permanent magnet structure 8 downstream or upstream of the Hall thruster channel.

[0051] The present invention has been disclosed above with reference to preferred embodiments, but it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed structure and technical content to create equivalent embodiments without departing from the scope of the present invention, and all such modifications or alterations shall still fall within the scope of the present invention.

Claims

1. A Hall thruster with an enlarged magnetic cage and a guide column, characterized in that: It includes an inner magnetic pole (1), an inner iron core (2), an inner excitation coil (3), an inner magnetic screen (4), an anode (5), a base plate (6), an outer magnetic screen (7), a permanent magnet structure (8), an outer magnetic pole (9), a discharge channel (10), an outer excitation coil (11), and an outer magnetic column (12). The inner magnetic screen (4) and the outer magnetic screen (7) are both ring structures. The inner iron core (2), the inner magnetic screen (4), the discharge channel 10 and the outer magnetic screen (7) are all ring structures. They are arranged away from the axis and fixed on the base plate (6). An anode (5) is provided in the discharge channel (10). The inner magnetic pole (1) is fixed on the inner iron core (2). The outer magnetic column (12) is evenly distributed on the base plate (6). The outer magnetic pole (9) is fixed on the outer magnetic column (12). The outer magnetic pole (9) is a plate structure with four straight sides. A permanent magnet structure (8) opposite to the direction of the magnetic pole of the outer excitation coil (11) is fixed on each straight side to realize the adjustment of the angle between the magnetic cage at the starting position, starting angle and the extension trend of the magnetic cage and the outlet plane of the Hall thruster after the magnetic cage is stabilized, thereby expanding the magnetic cage. Each straight edge has a stepped structure, and the permanent magnet structure is fixed on the step. The permanent magnet structure covers the outer side of the stepped structure and has an extension section that extends upstream or downstream of the Hall thruster channel.

2. The Hall thruster with an enlarged magnetic cage according to claim 1, characterized in that: The permanent magnet structure (8) is made of soft magnetic material SmCo24.

3. The Hall thruster with an enlarged magnetic cage according to claim 1, characterized in that: Each straight edge has a stepped structure, and the permanent magnet structure is a cuboid, which is fixed to the step.

4. The Hall thruster with an enlarged magnetic cage according to claim 1, characterized in that: Each straight edge has an inclined surface, and the permanent magnet structure is a triangular prism, which is fixed on the inclined surface.

5. The Hall thruster with an enlarged magnetic cage according to claim 1, characterized in that: The permanent magnet structure (8) includes a permanent magnet and a support member. The support member is fixed on the outer magnetic pole (9), and the permanent magnet is mounted on the support member.

6. The Hall thruster with an enlarged magnetic cage according to claim 1, characterized in that: When the permanent magnet structure (8) extends upstream of the Hall thruster channel, the excitation ampere-turns of the external excitation coil (11) are 320A and the excitation ampere-turns of the internal excitation coil (3) are 530A.

7. The Hall thruster with an enlarged magnetic cage according to claim 1, characterized in that: When the permanent magnet structure (8) extends downstream of the Hall thruster channel, the excitation ampere-turns of the outer excitation coil (11) are 339A and the excitation ampere-turns of the inner excitation coil (3) are 523A.

8. A method for adjusting a magnetic cage using a Hall thruster with a magnetic guide column as described in claim 1, characterized in that: By adding a permanent magnet structure (8) to the magnetic field, the magnetic field near the magnetic cage is distorted, the starting point of the magnetic cage is moved from the upper surface of the outer magnetic pole to the lower surface, the initial angle between the magnetic cage and the thruster is increased from an acute angle to an obtuse angle, the magnetic cage is pushed outward along the radial direction, and the angle between the magnetic cage and the thruster axis is increased after the extension trend stabilizes.

9. The method for adjusting a magnetic cage using a Hall thruster with an enlarged magnetic column according to claim 8, characterized in that: The extent of magnetic cage enlargement is adjusted by extending the permanent magnet structure (8) downstream or upstream of the Hall thruster channel.

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