JPH05248346A - Electron impact type ion engine - Google Patents

Abstract

PURPOSE:To embody high thrust and high efficiency by using a field formation means to form inside a discharge container an electric field for restricting the area into which electrons advance along the lines of magnetic force of a cusp field generated by a plurality of magnets provided within the discharge container. CONSTITUTION:Annular magnets 12a-12e are provided on the inner wall surface of a discharge container 1 with alternating N and S poles, and magnet covers 13a, 13b made of nonmagnetic metal are provided around the magnets 12b, 12d. The electric potential of the magnent covers 13a, 13b is kept at the same electric potential as a hollow cathode for use as a main cathode by a power supply 14, i.e., to the cathode potential. When electrons (e) released from the hollow cathode and entering the discharge container 1 flow into a cusp area as they cling to the lines M of magnetic force of the cusp field after being bombarded with an operating gas, they are decelerated by an electrostatic field generated by the magnet cover 13a and are reflected near the field and allowed to advance into adjacent cusp field; i.e., the area into which the electrons advance is restricted so as to narrow a plasma passage, thus decreasing the loss of plasma.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron impact type ion engine used for maintaining north and south positions of space structures such as artificial satellites and for main propulsion.

[0002]

2. Description of the Related Art Conventionally, an electron impact type ion engine has been used for holding the north and south positions of orbital control and main propulsion of space structures such as artificial satellites.

The main part of such an electron-impact type ion engine is usually constructed as shown in FIG. That is, it is provided with a discharge vessel 1 formed of a ferrous material or the like in a cylindrical shape with a bottom, and the opening of this discharge vessel 1 is formed by three electrode plates including a screen grid 2, an acceleration grid 3 and a deceleration grid 4. It is covered by the acceleration electrode 5. Thousands of ion beam passage holes 6 are coaxially formed in the screen grid 2, the acceleration grid 3, and the deceleration grid 4, respectively. A small-diameter opening 7 is formed in the center of the bottom wall of the discharge vessel 1, and this opening 7 communicates with a gas introduction system 9 via a tubular body 8. And the cylindrical body 8
A hollow cathode 10 serving as a main cathode is arranged inside. In addition, as shown in FIG.
An annular magnet 12a so that the poles and the S poles are alternately on the inside,
12b, 12c, 12d and 12e are fixed.

In this electron bombardment type ion engine, the discharge container 1 and the magnets 12a ...
12e is kept at the anode potential. In this state, a propellant such as Xe gas (xenon gas) is introduced into the discharge vessel 1 from the gas introduction system 9 through the hollow cathode 10. A discharge is generated between the hollow cathode 10 and the discharge vessel 1, and the electrons emitted from the hollow cathode 10 are accelerated. The electrons collide with the Xe gas in the discharge vessel 1, and ionized plasma is generated in the discharge vessel 1. This ionized plasma is so-called confined in a region away from the inner peripheral surface of the discharge vessel 1 by the cusp magnetic field created by the magnets 12a to 12e. Acceleration electrode 5 is Xe ⁺ from ionized plasma Ions are extracted and given a kinetic energy of about 1 keV and emitted from the ion beam passage hole 6 to outer space to generate thrust. Neutralizer 11 is released Xe ⁺ It emits the same amount of electrons as the ion beam to outer space and neutralizes it, preventing space structures such as satellites from being charged.

By the way, recently, the use of the electron impact type ion engine constructed as described above as a main propulsion unit of an inter-orbit transport machine has been studied. The main propulsion unit requires a large thrust. Therefore, in order to realize the main propulsion machine, a large electron impact type ion engine can be installed at a few
It is necessary to arrange from 0 to several hundreds, that is, to form a cluster.

However, in the conventional electron-impact type ion engine, it was difficult to cluster several tens or more units for the following reason. That is, heat is usually generated in the electron impact type ion engine. Since almost all of the electric energy used in the acceleration electrode 5 is used for thrust, most of this heat generates ionized plasma in the discharge vessel 1,
This is due to the discharge power for maintaining. The generation of heat not only increases the capacity of the power supply, but also adversely affects adjacent engines.

Therefore, to realize clustering,
There is a need for an efficient electron bombardment type ion engine that minimizes electrical energy that does not contribute to thrust, that is, discharge power. In order to minimize the discharge power, it is necessary to reduce the loss of ionized plasma to the discharge vessel.

For this reason, conventionally, as shown in FIGS. 6 and 7, the ring cusp magnetic field generated by the annular magnets 12a to 12e is used to confine the ionized plasma. When the magnets 12a to 12e are arranged in this way, the lines of magnetic force are as shown by M in FIG.
, And does not exist near the wall surface of the discharge vessel 1. Therefore, the ionized plasma can be confined in a region away from the inner surface of the discharge vessel 1. Also, the magnet 12
By appropriately setting the intervals a to 12e, it is possible to widen the region where the ion saturation current density is uniform in the vicinity of the screen grid 2 and to extract a large-diameter ion beam.

However, with the above structure, the electrons e emitted from the hollow cathode 10 which is the main cathode move while colliding with the Xe gas in the central portion of the discharge vessel 1 and the magnets 12a-12.
When flowing to the magnetic field line cusp while being wrapped around the magnetic field line M in the vicinity of e, Xe ⁺ A part of the ions is pulled by the electric field created by the electron e, flows into the magnetic field cusp portion like the electron e, and recombines with the electron e on the surfaces of the magnets 12a to 12e. That is, this Xe ⁺ A large loss occurs due to the recombination of ions and electrons e. This recombination region is an ionization plasma loss part, and the smaller the area of this part, the better the confinement and the smaller the loss. However, since this region also serves as the flow path of the discharge current, if it is too small, the discharge voltage rises, which causes a new problem. The limit was about ten or so at most.

Although it is conceivable to further confine the ionized plasma by reducing the number of 5-ring magnets to 3 as shown in FIG. 8, in this case, the ion saturation current density in the vicinity of the screen grid 2 is increased. Is lost, it is difficult to extract a large-diameter ion beam.

[0011]

As described above, in the conventional electron impact type ion engine, it is difficult to sufficiently suppress the loss while maintaining the uniformity of the ion saturation current density in the vicinity of the screen grid. It has been difficult to cluster several tens or more.

Therefore, the object of the present invention is to provide a high thrust and high efficiency electron impact type ion engine capable of strengthening the confinement of ionized plasma while maintaining the uniformity of the ion saturation current density in the vicinity of the screen grid. There is.

[0013]

In order to achieve the above object, the present invention provides a discharge vessel, a gas introduction system connected to the discharge vessel for introducing a working gas into the discharge vessel, and the discharge vessel. A main cathode provided in a space leading to the, a means for causing electrons emitted from the main cathode to collide with the working gas to generate plasma in the discharge vessel, and the discharge vessel provided in the discharge vessel Electron bombardment type ion equipped with a plurality of magnets that form a cusp magnetic field for positioning the plasma in a region distant from the inner wall, and an accelerating electrode that takes out ions in the plasma and accelerates them out of the discharge vessel. The engine is provided with an electric field forming means for forming an electric field in the discharge container, which restricts an advancing region of electrons traveling along magnetic lines of force of the cusp magnetic field.

[0014]

The electron e emitted from the main cathode and propelled into the discharge vessel collides with the working gas and then tries to flow into the cusp region while being wrapped around the magnetic field lines of the cusp magnetic field. But,
Since an electric field that limits the traveling area of electrons is provided nearby, the electrons e are affected by this electric field and flow only to a specific restricted area. Losing Xe ⁺ The ions are attracted by the electric field created by the electron e, move to the cusp region, and recombine. Therefore, the loss of ionized plasma is reduced by the amount that the electron traveling region is limited. As a result, the discharge power for generating and maintaining the ionized plasma can be reduced, and the heat generation can be reduced. Therefore, clustering of several tens to several hundreds becomes possible.

The flow of the electrons e is not affected except in the vicinity of the place where the electric field is forcibly given. Moreover, since the ionized plasma cancels the electric field, the influence of the forcibly applied electric field is extremely narrow. Therefore, a magnetic field arrangement that can maintain the uniformity of the ion saturation current density in the vicinity of the screen grid can be adopted, and an ion beam having a large diameter can be extracted.

[0016]

Embodiments will be described below with reference to the drawings.

FIG. 1 shows a partially cutaway perspective view of an electron impact type ion engine according to a first embodiment of the present invention. Further, FIG. 2 shows a cross-sectional view of the discharge vessel in this embodiment. In these figures, the same parts as those in FIGS. 6 and 7 are designated by the same reference numerals. Therefore, the description of the overlapping parts will be omitted.

Also in the electron impact type ion engine according to this embodiment, the annular magnet 12 is provided on the inner wall surface of the discharge vessel 1.
a, 12b, 12c, 12d and 12e are provided with the N pole and the S pole alternately inside. And the magnet 12
A magnet cover 13 made of non-magnetic metal is provided around b and 12d.
a and 13b are provided in a state of being insulated from the discharge vessel 1 and the magnets 12b and 12d. The electric potentials of the magnet covers 13a and 13b are kept at the same electric potential as the hollow cathode 10 for the main cathode, that is, the cathode electric potential, by the power source 14, as shown in FIG.

With such a structure, the electrons e emitted from the hollow cathode 10 for the main cathode and entering the discharge vessel 1 collide with the working gas, and then wrap around the magnetic force lines M of the cusp magnetic field in the cusp region. I try to pour. At this time, for example, as shown in FIG. 2, taking a portion through which a magnetic force line M extending from the N pole of the magnet 12a to the S pole of the magnet 12b passes as an example, the electrons that try to travel toward the S pole while being wrapped around the magnetic force line M are taken. e is a magnet cover 1 kept at the cathode potential
It is decelerated by the electrostatic field due to 3a, is reflected in the vicinity of this magnet cover 13a, and advances to the adjacent cusp region.
Xe ⁺ Ions are attracted by the electric field created by the electron e, so the attracted Xe ⁺ Ion is the magnet cover 13
Before reaching a, the direction is changed to proceed to the adjacent cusp region. Therefore, the plasma flow path is narrowed by the extent that the traveling region of the electrons e is limited, and the plasma loss is reduced. Therefore, discharge power can be reduced and heat generation can be suppressed.

FIG. 3 is a schematic vertical sectional view of a main part of an electron impact type ion engine according to a second embodiment of the present invention. In this figure, the same parts as those in FIG. 2 are designated by the same reference numerals. Therefore, the description of the overlapping parts will be omitted.

In this embodiment, the magnets 12a, 12c, 12
Magnet covers 13a, 13b, 13c made of a non-magnetic metal material are provided so as to cover the inner peripheral surface of e in an insulating state from these magnets. The power supply 14 keeps the discharge vessel 1 and the magnets 12a, 12b, 12c, 12d, 12e at the same potential as the hollow cathode as the main cathode, and keeps the magnet covers 13a, 13b, 13c at the anode potential.

With this structure, the confinement of ionized plasma is slightly worse than in the case of the first embodiment, but the loss of ionized plasma can be suppressed. In addition, since each magnet is not used as a discharge electrode in this embodiment, the magnet is not directly heated by the discharge current, and therefore the magnet is less likely to be demagnetized.

FIG. 4 is a schematic vertical sectional view of the main part of the electron impact type ion engine according to the third embodiment of the present invention. Also in this figure, the same parts as those in FIG. 2 are denoted by the same reference numerals. Therefore, the description of the overlapping parts will be omitted.

In this embodiment, the magnets 12b and 12d are attached to the inner wall surface of the discharge vessel 1 via the insulator 15. The magnets 12b and 12d are supplied with the same potential as the hollow cathode, which is the main cathode, by the power supply 14, and the discharge container 1
An anode potential is applied to the remaining magnets 12a, 12c and 12e.

With such a structure, the same effects as those of the embodiment shown in FIG. 2 can be obtained, and the magnet cover is not required, so that the structure is simple and the assembling is facilitated. be able to.

FIG. 5 is a schematic vertical sectional view of a main part of an electron impact type ion engine according to a fourth embodiment of the present invention. Also in this figure, the same parts as those in FIG. 2 are denoted by the same reference numerals. Therefore, the description of the overlapping parts will be omitted.

In this embodiment, the magnets 12a, 12c and 12e are used.
Are attached to the inner wall surface of the discharge vessel 1 via an insulator 15. A power source 1 is used for the magnets 12a, 12c, 12e.
Anode potential is given by 4 and the remaining magnets 12b, 12
The same potential as the hollow cathode, which is the main cathode, is applied to d and the discharge container 1. With this configuration, the same effect as that of the embodiment shown in FIG. 4 can be obtained.

The present invention is not limited to the above embodiments. That is, although the case where the number of magnets is 5 has been described in the above-described embodiment, the number of magnets is not limited to 5. Further, although Xe gas was used as the propellant, it is not limited to Xe gas. Although three accelerating electrodes are used, the number of accelerating electrodes is not limited to three. Further, in the above-described embodiment, a plurality of annular magnets are used to form the cusp magnetic field, but linear magnets may be combined.

[0029]

As described in detail above, according to the present invention,
A high-impact, high-efficiency electron-impact type ion engine is obtained,
It can contribute to the clustering of several tens to several hundreds.

[Brief description of drawings]

FIG. 1 is a perspective view showing a partially cutaway electron impact ion engine according to a first embodiment of the present invention.

FIG. 2 is a schematic vertical cross-sectional view for explaining the internal structure of a discharge container in the electron impact type ion engine.

FIG. 3 is a schematic vertical sectional view of a main part of an electron impact type ion engine according to a second embodiment of the present invention.

FIG. 4 is a schematic vertical sectional view of a main part of an electron impact type ion engine according to a third embodiment of the present invention.

FIG. 5 is a schematic vertical sectional view of a main part of an electron impact ion engine according to a fourth embodiment of the present invention.

FIG. 6 is a perspective view showing a conventional electron impact type ion engine with a part thereof cut away.

FIG. 7 is a schematic vertical cross-sectional view for explaining the internal structure of a discharge container in the electron impact type ion engine.

FIG. 8 is a schematic vertical cross-sectional view for explaining a cusp magnetic field in the discharge container when the number of magnets is changed in the conventional electron impact ion engine.

[Explanation of symbols]

1 ... Discharge container, 5 ... Accelerating electrode, 9
... Gas introduction system, 10 ... Hollow cathode for main cathode, 12a to 12e ... Magnet, 1
3a to 13c ... Magnet cover, 14 ... Power supply.

Claims (5)

[Claims] 1. A discharge vessel, a gas introduction system connected to the discharge vessel to introduce a working gas into the discharge vessel, a main cathode provided in a space communicating with the discharge vessel, and discharge from the main cathode. Means for colliding the generated electrons with the working gas to generate plasma in the discharge vessel, and a cusp magnetic field for positioning the plasma in a region provided in the discharge vessel and apart from the inner wall of the discharge vessel. In an electron impact ion engine including a plurality of magnets to be formed and an accelerating electrode for extracting ions in the plasma and accelerating them to send them to the outside of the discharge vessel, the progress of electrons advancing along the magnetic field lines of the cusp magnetic field. An electron impact type ion engine comprising an electric field forming means for forming an electric field for limiting a region in the discharge vessel. 2. The electric field forming means includes a magnet cover for covering a part of the plurality of magnets held at an anode potential in an insulating state from the magnets, and the magnet cover having the same potential as the main cathode. The electron-impact-type ion engine according to claim 1, further comprising a holding means. 3. The electric field forming means includes a magnet cover for covering a part of the plurality of magnets in an insulating state from the magnets, a magnet cover for holding the magnet cover at an anode potential, and the discharge container and the magnet. The electron impact ion engine according to claim 1, further comprising: a unit that holds a plurality of magnets at the same potential as the main cathode. 4. The electric field forming means comprises means for holding a part of magnets of the discharge vessel and the plurality of magnets at an anode potential and holding the remaining magnets at the same potential as the main cathode. The electron impact ion engine according to claim 1, wherein 5. The electric field forming means comprises means for holding a part of magnets of the discharge vessel and the plurality of magnets at the same potential as the main cathode and holding the remaining magnets at an anode potential. The electron impact ion engine according to claim 1, wherein