JP2007071055A - Hall thruster having magnetic circuit having magnetic field concentrating structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain intensity of a magnetic field in the vicinity of a positive electrode by concentrating the magnetic field in a downstream end area of an acceleration channel with a simple constitution. <P>SOLUTION: This Hall thruster has the acceleration channel 1 composed of an annular ring-shaped space formed of a channel outer peripheral wall 2a and an inner peripheral wall 2b and opening on its downstream end, a negative electrode arranged in the vicinity of the downstream end of the acceleration channel, the positive electrode 4 arranged in an upstream area of the acceleration channel, a propellant supply port 4a supplying propellant gas to the acceleration channel, a magnetic circuit formed of an outer peripheral magnetic core 5 arranged outside the channel outer peripheral wall, a central magnetic core 8 arranged inside the channel inner peripheral wall and a yoke 9 forming a magnetic path between the outer peripheral magnetic core and the central magnetic core on the upstream end side of the acceleration channel, and outside-inside magnetic coils 10 and 11 respectively attached to the outer peripheral magnetic core and the central magnetic core. An interval between the outer peripheral magnetic core and the central magnetic core is formed narrower than the upstream end in the downstream end. An inside magnetic coil is dislocated and arranged to one side on the downstream end to the central magnetic core. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, a hole thruster used for space propulsion, that is, an annular acceleration channel is made to act on a radial magnetic field and an axial electric field to electrostatically extract only ions from plasma generated in the acceleration channel. The present invention relates to a hall thruster that obtains a driving force by accelerating and ejecting. In particular, the present invention relates to a Hall thruster provided with a magnetic circuit having an improved magnetic field concentration structure.

  FIG. 10 shows the basic structure of the Hall thruster. The Hall thruster has an annular acceleration channel 31. The acceleration channel 31 is formed by a channel outer peripheral wall 32a and a channel inner peripheral wall 32b, and the downstream end thereof is open. A cathode 33 is disposed in the vicinity of the downstream end of the acceleration channel 31. An anode 34 is disposed upstream of the acceleration channel 31. The anode 34 is provided with a propellant supply port 34 a for supplying a propellant to the acceleration channel 31. For example, xenon is used as the propellant. An outer peripheral magnetic core 35 is arranged outside the channel outer peripheral wall 32a, and a central magnetic core 36 is arranged inside the channel inner peripheral wall 32b.

  A radial magnetic field and an axial electric field are applied to the acceleration channel 31. That is, although not shown, a magnetic coil is attached to a magnetic circuit formed by the outer peripheral magnetic core 35 and the central magnetic core 35, and a magnetic field in the radial direction is applied to the acceleration channel 31 by leakage of generated magnetic flux. A voltage is applied between the anode 34 and the cathode 33 to form an electric field in the axial direction.

  The electrons emitted from the cathode 33 and flowing into the acceleration channel 31 circulate in the acceleration channel 31 in the circumferential direction by the interaction between the electric field and the magnetic field, and form a current in the circumferential direction called a hole current. Be trapped. The propellant supplied from the propellant supply port 34a ionizes and collides with electrons confined as a hole current, and plasma is generated. Only ions from this plasma are accelerated and ejected by an axial electric field, and thrust is obtained by the reaction. The ejected ions are combined with electrons emitted from the cathode 33 to become neutral particles.

  As described above, the Hall thruster is a kind of electric propulsion machine, has a high energy conversion efficiency (propulsion efficiency) of 50% or more, and high specific thrust, that is, a large amount of energy that can be used for acceleration per unit amount of propellant. There are features. For this reason, the amount of required propellant is small, it is small and lightweight, and it is expected as a space propulsion device suitable for spacecraft attitude control and orbit control. Therefore, improvements for improving the performance are being rapidly advanced.

  One of the challenges to improve the performance of the Hall thruster is to increase the efficiency of ionization and ion acceleration. For this purpose, the magnetic field is concentrated in the downstream end region of the acceleration channel, and ionization is performed only in the narrow region. It is desirable that the leakage magnetic field near the anode be as small as possible.

  As an example for concentrating a magnetic field in the downstream end region of the acceleration channel, Patent Document 1 describes a configuration in which combinations of magnetic fields formed by three coils are appropriately adjusted.

  Further, as another example for concentrating the magnetic field in the downstream end region of the acceleration channel, the configuration shown in FIG. 11 is known. The acceleration channel 41 includes an annular space formed by the channel outer peripheral wall 42a and the channel inner peripheral wall 42b. A cathode 43 is disposed near the downstream end of the acceleration channel 41. An anode 44 is disposed in the upstream region of the acceleration channel 41. A propellant supply port 45 is provided at the upstream end of the acceleration channel 41.

  An outer peripheral magnetic core 46 is arranged outside the channel outer peripheral wall 42a, and a central magnetic core 47 is arranged inside the channel inner peripheral wall 42b. The rear end plate 48 disposed on the upstream end side of the acceleration channel 41 functions as a yoke that forms a magnetic path between the outer peripheral magnetic core 46 and the central magnetic core 47. An outer magnetic coil 49 and an inner magnetic coil 50 are attached to the outer magnetic core 46 and the central magnetic core 47, respectively. Magnetic shields 51 and 52 are disposed between the outer magnetic coil 49 and the acceleration channel 41 and between the inner magnetic coil 50 and the acceleration channel 41.

In this Hall thruster, magnetic shields 51 and 52 are provided to block the leakage magnetic flux, and the leakage magnetic flux is allowed to pass only in the downstream end region of the acceleration channel 41, whereby a magnetic field distribution concentrated at a desired position is formed.
Japanese National Patent Publication No. 8-500699

  In the configuration of the conventional example, a desired magnetic field concentration is performed by increasing the number of coils that generate magnetic flux or by providing a magnetic shield. Accordingly, an additional member for concentrating the magnetic field is necessary, which is complicated in structure and hinders downsizing of the apparatus.

  An object of the present invention is to provide a Hall thruster in which the magnetic field is effectively concentrated in the downstream end region of the acceleration channel with a simple configuration, and the strength of the magnetic field in the vicinity of the anode is sufficiently suppressed.

  The basic structure of the Hall thruster of the present invention is as follows: an acceleration channel comprising an annular space formed by a channel outer peripheral wall and a channel inner peripheral wall, the downstream end of which is open, and an external portion adjacent to the downstream end of the acceleration channel. , An anode disposed upstream of the acceleration channel, a propellant supply port for supplying a propellant gas to the acceleration channel, and an outer peripheral magnet disposed outside the outer peripheral wall of the channel A magnetic circuit formed by a core, a central magnetic core disposed inside the inner peripheral wall of the channel, and a yoke that forms a magnetic path between the outer magnetic core and the central magnetic core on the upstream end side of the acceleration channel And magnetic coils respectively attached to the outer peripheral magnetic core and the central magnetic core. By the action of the magnetic field applied in the radial direction of the acceleration channel by the magnetic flux generated by the magnetic coil leaking from the magnetic circuit, and the electric field applied in the axial direction of the acceleration channel by the cathode and the anode, The propellant supplied from the propellant supply port is ionized, and the generated ions are accelerated to generate thrust.

  In order to solve the above problems, the Hall thruster according to the first configuration of the present invention is such that the distance between the outer peripheral magnetic core and the central magnetic core is narrower at the downstream end than the upstream end, The attached inner magnetic coil is arranged to be unevenly distributed on the downstream end side with respect to the central magnetic core.

  The hall thruster of the second configuration of the present invention is characterized in that the diameter of the central magnetic core is larger at the downstream end than at the upstream end.

  The Hall thruster of the third configuration of the present invention is characterized in that an inner magnetic coil attached to the central magnetic core is arranged to be unevenly distributed on the downstream end side with respect to the central magnetic core.

  According to the above configuration, the downstream of the acceleration channel can be achieved by a very simple configuration that does not require an additional member such as the distance between the outer magnetic core and the central magnetic core, the cross-sectional area of the central magnetic core, or the adjustment of the arrangement of the inner magnetic coil A Hall thruster in which the magnetic field is effectively concentrated in the end region and the strength of the magnetic field in the vicinity of the anode is sufficiently suppressed can be obtained.

  In the hall thruster of the first configuration of the present invention, the outer peripheral magnetic core may have a shape inclined with respect to the central magnetic core in the axial direction of the acceleration channel.

Moreover, it is preferable that the diameter D ₀ of the upstream end of the outer peripheral magnetic core and the diameter D ₁ of the downstream end of the outer peripheral magnetic core satisfy the relationship of the following formula (1). Thereby, it becomes easy to appropriately set the ratio of the magnetic flux density in the downstream end region of the acceleration channel and the vicinity of the anode.

1.2 × D ₁ <D ₀ <1.5 × D ₁ (1)
In the Hall thruster according to the second configuration of the present invention, the central magnetic core may have a two-stage structure formed by the large diameter portion on the downstream end side and the small diameter portion on the upstream end side.

  In this configuration, the length Lc of the small-diameter portion is preferably in a range satisfying the relationship of Lc ≧ 0.5L with respect to the length L of the central magnetic core.

The diameter W ₁ of the small diameter portion of the central magnetic core, the diameter W ₂ of the large-diameter portion, it is preferable to satisfy the relation of the following equation (2). Thereby, it becomes easy to appropriately set the ratio of the magnetic flux density in the downstream end region of the acceleration channel and the vicinity of the anode.

_{W 2/2 <W 1 <} 3W 2/4 (2)
In the above configuration, the inner magnetic coil attached to the central magnetic core may be arranged to be unevenly distributed on the downstream end side with respect to the central magnetic core.

  When the inner magnetic coil is configured to be unevenly distributed on the downstream end side with respect to the central magnetic core, the distance Lb from the upstream end of the central magnetic core to the upstream end of the inner magnetic coil is A range satisfying the relationship of Lb ≧ 0.5L with respect to the length L of the central magnetic core is preferable.

   Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
The structure of the hole thruster in the first embodiment will be described with reference to the cross-sectional view of FIG. The acceleration channel 1 is formed of an annular space formed by a channel outer peripheral wall 2a and a channel inner peripheral wall 2b, and the downstream end thereof is open. The channel outer peripheral wall 2a and the channel inner peripheral wall 2b are formed using a ceramic such as boron nitride (BN), for example. A hollow cathode is arranged on the outside adjacent to the downstream end of the acceleration channel 1 as in the conventional example, but the illustration is omitted. The upstream end of the acceleration channel 1 is sealed by a sealing member 3. An anode 4 is fixed to the sealing member 3 and is located in the upstream region of the acceleration channel 1. The anode 4 is provided with a propellant supply port 4 a for supplying a propellant to the acceleration channel 1.

  The outer peripheral magnetic core 5 is disposed outside the channel outer peripheral wall 2 a and is connected to the connecting member 7 via the front end plate 6. The connecting member 7 is coupled to the sealing member 3. Therefore, the position of the outer peripheral magnetic core 5 with respect to the acceleration channel 1 is fixed via the front end plate 6, the connecting member 7 and the sealing member 3. A central magnetic core 8 is disposed inside the channel inner peripheral wall 2b. The rear end plate 9 disposed on the upstream end side of the acceleration channel 1 couples the outer peripheral magnetic core 5 and the central magnetic core 8 to support the central magnetic core 8, and the outer peripheral magnetic core 5 and the central magnetic core 8. It functions as a yoke that forms a magnetic path therebetween. Accordingly, a magnetic circuit is formed by the outer peripheral magnetic core 5, the central magnetic core 8 and the rear end plate 9. An outer magnetic coil 10 and an inner magnetic coil 11 are attached to the outer magnetic core 5 and the central magnetic core 8, respectively.

  A magnetic field is applied in the radial direction of the acceleration channel 1 by the magnetic flux generated by the outer magnetic coil 10 and the inner magnetic coil 11 leaking from the magnetic circuit. An electric field is applied in the axial direction of the acceleration channel 1 by the cathode and the anode 4. Due to the action of the magnetic field and the electric field, the propellant supplied from the propellant supply port 4a is ionized, and the generated ions are accelerated to generate thrust.

In the present embodiment, the distance between the outer magnetic core 5 and the central magnetic core 8 is set to be narrower at the downstream end than at the upstream end. In the illustrated configuration, the outer peripheral magnetic core 5 has a shape inclined with respect to the central magnetic core 8 in the axial direction of the acceleration channel 1. That is, the diameter D ₀ at the upstream end of the outer peripheral magnetic core 5 is larger than the diameter D ₁ at the downstream end. Thereby, the magnetic field applied to the acceleration channel 1 is concentrated at the downstream end.

  Furthermore, the inner magnetic coil 4 attached to the central magnetic core 8 is unevenly distributed on the downstream end side. That is, the distance Lb from the upstream end of the central magnetic core 8 shown in FIG. 1 to the upstream end of the inner magnetic coil 4 is set to 0.5L. Thereby, the position where the magnetic flux is generated is biased toward the downstream end side, and the concentration of the magnetic field on the downstream end region of the acceleration channel 1 is improved.

  With the above configuration, the magnetic field applied to the acceleration channel 1 is concentrated at the downstream end, and the strength of the magnetic field is sufficiently suppressed in the vicinity of the anode 4. As a result, ionization and acceleration are concentrated in a narrow area where the magnetic field is concentrated. The efficiency of ionization and ion acceleration can be increased.

The effects based on the configuration of the magnetic circuit according to the present embodiment are shown in FIGS. FIG. 2 shows the magnetic field formed in the Hall thruster of FIG. However, only the upper half section of the Hall thruster in FIG. 1 is shown. Reference numeral 12 denotes magnetic lines of force. FIG. 3 shows the relationship between the position of the acceleration channel 1 in FIG. 2 in the axial direction and the strength of the applied magnetic field (magnetic flux density). P ₁ is a position corresponding to the downstream end of the acceleration channel 1. La is ½ of the length L of the central magnetic core 8, and thus P ₀ corresponds to a position in the vicinity of the anode 4. The magnetic flux density is expressed in percentage of the maximum value B _max.

As can be seen from FIG. 3, the magnetic field is sufficiently concentrated in the downstream end region of the acceleration channel 1, and the magnetic flux density B ₀ in the vicinity of the anode is sufficiently suppressed. The concentration of such a magnetic field is practically sufficient as long as the condition of B ₀ <0.2B _max is satisfied. For this purpose, it is desirable that the diameter D ₀ at the upstream end of the outer magnetic core 5 and the diameter D ₁ at the downstream end of the outer magnetic core 5 satisfy the relationship of the following formula (1).

1.2 × D ₁ <D ₀ <1.5 × D ₁ (1)
State of the applied magnetic field is also affected by the length L of the central magnetic core 8, in the length L and a practical range of diameter D _1, by satisfying the relationship of formula (1), the above-mentioned It is possible to obtain the relationship of magnetic flux density. As an example of dimensions, if L = 80 cm and D ₁ = 180 cm, the above magnetic flux density condition can be easily satisfied.

  In addition, if the distance Lb from the upstream end of the central magnetic core 8 to the upstream end of the inner magnetic coil 4 is in the range of Lb ≧ 0.5L, the above effect can be sufficiently obtained.

(Embodiment 2)
The structure of the hole thruster in the second embodiment will be described with reference to the cross-sectional view of FIG. The basic structure is the same as that of the first embodiment shown in FIG. 1, and the same reference numerals are assigned to the same elements, and the description is not repeated.

In the present embodiment, the shapes of the central magnetic core 20 and the outer peripheral magnetic core 22 are different from those of the first embodiment. The outer peripheral magnetic core 22 is not inclined with respect to the central magnetic core 20 and is parallel. The central magnetic core 20 has a two-stage structure formed by a small diameter portion 20a on the upstream end side and a large diameter portion 20b on the downstream end side. That is, the diameter W ₂ of the large diameter portion 20b is larger than the diameter W ₁ of the small diameter portion 20a. The length Lc of the small diameter portion 20 a having the diameter W ₁ is ½ of the length L of the central magnetic core 20. Both the inner magnetic coil 21 and the outer magnetic coil 23 are arranged over the entire axial direction.

  According to this configuration, as in the first embodiment, the distance between the outer magnetic core 22 and the central magnetic core 20 is narrower at the downstream end than at the upstream end. Therefore, the magnetic field applied to the acceleration channel 1 is concentrated in the downstream end region, and the strength of the magnetic field is sufficiently suppressed in the vicinity of the anode 4. As a result, ionization and acceleration are concentrated in a narrow area where the magnetic field is concentrated. The efficiency of ionization and ion acceleration can be increased. In addition, if the length Lc of the small diameter part 20a is Lc> = 0.5L, the said effect can fully be acquired.

The effects based on the configuration of the magnetic circuit according to the present embodiment are shown in FIGS. FIG. 5 shows the magnetic field formed in the Hall thruster of FIG. However, only the upper half section of the Hall thruster in FIG. 4 is shown. FIG. 6 shows the relationship between the position of the acceleration channel 1 in FIG. 5 in the axial direction and the strength of the applied magnetic field. As in FIG. 3, P ₁ is a position corresponding to the downstream end of the acceleration channel 1. La is ½ of the length L of the central magnetic core 20, and thus P ₀ corresponds to a position in the vicinity of the anode 4. The magnetic flux density is expressed in percentage of the maximum value B _max.

As can be seen from FIG. 6, the magnetic field is sufficiently concentrated in the downstream end region of the acceleration channel 1, and the magnetic flux density B ₀ in the vicinity of the anode is sufficiently suppressed. In order to satisfy the condition of B ₀ <0.2B _max as in the first embodiment, it is desirable to configure so as to satisfy the relationship of the following formula (2).

_{W 2/2 <W 1 <} 3W 2/4 (2)
The state of the applied magnetic field is also affected by the length L of the central magnetic core 20, the outer diameter D of the outer magnetic core 22, the inner diameter D ₂ of the channel outer peripheral wall 2a, and the outer diameter D ₃ of the channel inner peripheral wall 2b. In the practical range of these dimensions, the above-described magnetic flux density relationship can be obtained by satisfying the relationship of the expression (2). As an example of dimensions, if L = 80 cm, D = 180 cm, D ₂ = 100 cm, and D ₃ = 56 cm, the above magnetic flux density condition can be easily satisfied.

(Embodiment 3)
The structure of the hole thruster in the third embodiment will be described with reference to the cross-sectional view of FIG. The basic structure is the same as that of the second embodiment shown in FIG. 4. The same reference numerals are assigned to the same elements, and the repeated description is omitted.

  In the present embodiment, in order to further enhance the magnetic field concentration effect in the downstream end region, the inner magnetic coil 24 attached to the central magnetic core 20 is arranged unevenly on the downstream end side. That is, the distance Lb from the upstream end of the central magnetic core 20 shown in FIG. 7 to the upstream end of the inner magnetic coil 24 is set to 0.5L. Thereby, the position where the magnetic flux is generated is biased toward the downstream end side, and the concentration of the magnetic field on the downstream end region of the acceleration channel 1 is improved. If the distance Lb is Lb ≧ 0.5L, the above effect can be sufficiently obtained.

The effects based on the configuration of the magnetic circuit according to the present embodiment are shown in FIGS. FIG. 8 shows the magnetic field formed in the Hall thruster of FIG. However, only the upper half section of the Hall thruster in FIG. 7 is shown. FIG. 9 shows the relationship between the position of the acceleration channel 1 in FIG. 8 in the axial direction and the strength of the applied magnetic field. As in FIG. 3, P ₁ is a position corresponding to the downstream end of the acceleration channel 1. La is ½ of the length L of the central magnetic core 20, and thus P ₀ corresponds to a position in the vicinity of the anode 4.

As can be seen from FIG. 9, the magnetic field is sufficiently concentrated in the downstream end region of the acceleration channel 1, and B ₀ is sufficiently suppressed in the magnetic flux density in the vicinity of the anode. In order to satisfy the condition of B ₀ <0.2B _max as in the first embodiment, it is desirable to configure so as to satisfy the relationship of the above formula (2).

  Although not shown, the magnetic field is sufficiently concentrated in the downstream end region of the acceleration channel 1 only by arranging the inner magnetic coil attached to the central magnetic core so as to be unevenly distributed on the downstream end side with respect to the central magnetic core. It is also possible to make it.

  The Hall thruster of the present invention concentrates the magnetic field in the downstream end region of the acceleration channel and improves the efficiency of ionization and ion acceleration. Therefore, it is used for attitude control or orbit control of spacecraft such as artificial satellites and planetary probes. It is useful as a propulsion device for spacecraft.

Sectional drawing of the Hall thruster in Embodiment 1 of this invention Sectional drawing which shows the magnetic field formed in the hall thruster Diagram showing the relationship between the strength of the magnetic field and the position in the acceleration channel axis direction Sectional drawing of the Hall thruster in Embodiment 2 of this invention Sectional drawing which shows the magnetic field formed in the hall thruster Diagram showing the relationship between the strength of the magnetic field and the position in the acceleration channel axis direction Sectional drawing of the Hall thruster in Embodiment 3 of this invention Sectional drawing which shows the magnetic field formed in the hall thruster Diagram showing the relationship between the strength of the magnetic field and the position in the acceleration channel axis direction Perspective view showing the basic structure of the Hall thruster Sectional view showing a conventional hall thruster

Explanation of symbols

1, 31, 41 Acceleration channel 2a, 32a, 42a Channel outer peripheral wall 2b, 32b, 42b Channel inner peripheral wall 3 Sealing member 4, 34, 44 Anode 4a, 34a, 45 Propellant supply port 5, 22, 35, 46 Core 6 Front end plate 7 Connecting members 8, 20, 36, 47 Central magnetic core 9, 48 Rear end plates 10, 23, 49 Outer magnetic coils 11, 21, 50 Inner magnetic coil 12 Magnetic field lines 20a Small diameter portion 20b Large diameter portion 33 , 43 Cathode 51, 52 Magnetic shield

Claims (10)

An acceleration channel comprising an annular space formed by a channel outer peripheral wall and a channel inner peripheral wall, the downstream end of which is open;
An externally disposed cathode adjacent to the downstream end of the acceleration channel;
An anode disposed upstream of the acceleration channel;
A propellant supply port for supplying propellant gas to the acceleration channel;
An outer peripheral magnetic core disposed outside the outer peripheral wall of the channel, a central magnetic core disposed inside the inner peripheral wall of the channel, and between the outer peripheral magnetic core and the central magnetic core on the upstream end side of the acceleration channel A magnetic circuit formed by a yoke forming a magnetic path;
Magnetic coils respectively attached to the outer peripheral magnetic core and the central magnetic core,
By the action of the magnetic field applied in the radial direction of the acceleration channel by the magnetic flux generated by the magnetic coil leaking from the magnetic circuit, and the electric field applied in the axial direction of the acceleration channel by the cathode and the anode, In the Hall thruster in which the propellant supplied from the propellant supply port is ionized and the generated ions are accelerated to generate thrust,
An interval between the outer peripheral magnetic core and the central magnetic core is narrower at the downstream end than at the upstream end,
The hall thruster, wherein an inner magnetic coil attached to the central magnetic core is arranged to be unevenly distributed on the downstream end side with respect to the central magnetic core.   The Hall thruster according to claim 1, wherein the outer peripheral magnetic core has a shape inclined with respect to the central magnetic core in an axial direction of the acceleration channel. 3. The Hall thruster according to claim 1, wherein a diameter D ₀ of an upstream end of the outer magnetic core and a diameter D ₁ of a downstream end of the outer magnetic core satisfy a relationship of the following formula (1).
1.2 × D ₁ <D ₀ <1.5 × D ₁ (1) An acceleration channel comprising an annular space formed by a channel outer peripheral wall and a channel inner peripheral wall, the downstream end of which is open;
An externally disposed cathode adjacent to the downstream end of the acceleration channel;
An anode disposed upstream of the acceleration channel;
A propellant supply port for supplying propellant gas to the acceleration channel;
An outer peripheral magnetic core disposed outside the outer peripheral wall of the channel, a central magnetic core disposed inside the inner peripheral wall of the channel, and between the outer peripheral magnetic core and the central magnetic core on the upstream end side of the acceleration channel A magnetic circuit formed by a yoke forming a magnetic path;
Magnetic coils respectively attached to the outer peripheral magnetic core and the central magnetic core,
By the action of the magnetic field applied in the radial direction of the acceleration channel by the magnetic flux generated by the magnetic coil leaking from the magnetic circuit, and the electric field applied in the axial direction of the acceleration channel by the cathode and the anode, In the Hall thruster in which the propellant supplied from the propellant supply port is ionized and the generated ions are accelerated to generate thrust,
The hall thruster characterized in that the diameter of the central magnetic core is larger at the downstream end than at the upstream end.   5. The hall thruster according to claim 4, wherein the central magnetic core has a two-stage structure formed by a large-diameter portion on the downstream end side and a small-diameter portion on the upstream end side.   6. The hole thruster according to claim 5, wherein the length Lc of the small diameter portion is in a range satisfying a relationship of Lc ≧ 0.5L with respect to the length L of the central magnetic core. The hall thruster according to claim 5 or 6, wherein a diameter W _{1 of the} small diameter portion and a diameter W _{2 of the} large diameter portion of the central magnetic core satisfy a relationship of the following formula (2).
_{W 2/2 <W 1 <} 3W 2/4 (2)   The hall thruster according to any one of claims 4 to 7, wherein an inner magnetic coil attached to the central magnetic core is arranged to be unevenly distributed on the downstream end side with respect to the central magnetic core. An acceleration channel comprising an annular space formed by a channel outer peripheral wall and a channel inner peripheral wall, the downstream end of which is open;
An externally disposed cathode adjacent to the downstream end of the acceleration channel;
An anode disposed upstream of the acceleration channel;
A propellant supply port for supplying propellant gas to the acceleration channel;
An outer peripheral magnetic core disposed outside the outer peripheral wall of the channel, a central magnetic core disposed inside the inner peripheral wall of the channel, and between the outer peripheral magnetic core and the central magnetic core on the upstream end side of the acceleration channel A magnetic circuit formed by a yoke forming a magnetic path;
Magnetic coils respectively attached to the outer peripheral magnetic core and the central magnetic core,
By the action of the magnetic field applied in the radial direction of the acceleration channel by the magnetic flux generated by the magnetic coil leaking from the magnetic circuit, and the electric field applied in the axial direction of the acceleration channel by the cathode and the anode, In the Hall thruster in which the propellant supplied from the propellant supply port is ionized and the generated ions are accelerated to generate thrust,
The hall thruster, wherein an inner magnetic coil attached to the central magnetic core is arranged to be unevenly distributed on the downstream end side with respect to the central magnetic core. The distance Lb from the upstream end of the central magnetic core to the upstream end of the inner magnetic coil is a range satisfying a relationship of Lb ≧ 0.5L with respect to the length L of the central magnetic core. , 8, and 9. The hall thruster according to claim 1.

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