JPH01310179A - Ecr type ion thruster - Google Patents

Abstract

PURPOSE:To minimize the leakage magnetic field in the surrounding part of the surface of an accelerating electrode by equalizing electron cyclotron resonance fields formed around the front of N pole and S pole. CONSTITUTION:Annular magnet columns 5 with about same magnetic field intensity and magnet width are placed on the wall face of a discharge container 3, N and S alternately, and annular magnet columns 9 about half in their magnet width are disposed on the side of an accelerating electrode 6. Annular magnet columns 10 with the magnet width such that the line of magnetic force in the discharge container 3 does not come out to the exterior are placed on the ceiling side. The width of the electron cyclotron resonance layer 11 formed around the front of the magnet columns 9, 10 at both ends is about half of that of the electron cyclotron resonance layer 11 formed around the front of the remaining magnet columns 5. Accordingly, the entire electron cyclotron resonance layer 11 is subjected to the mirror field confinement.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is directed to an ECR (Ejelectron Cyclofiot
ron Re5onance) type ion thruster.

(Prior technology) ECR used for orbit control of artificial satellites, etc.
A type ion thruster is usually constructed as shown in FIG. Plasma electrons generated from naturally ionized electrons due to cosmic rays, etc. are located several meters from the surface of the magnet 5 placed on the wall of the discharge vessel 3 (magnetic flux density 0.0875T).
), microwave (2,450 GHz) introduction system 2
X is accelerated by resonance absorption (electron cyclotron resonance) of microwaves supplied from the X, and the accelerated electrons are co-supplied from the gas introduction system 1. Electrode plasma was generated in the discharge chamber by colliding with the gas, and the xe+ ions in the ionized plasma were given kinetic energy by the accelerating electrodes (3 pieces) 6 and were neutralized by electrons emitted from the neutralizer 8. It is then ejected and becomes the thrust of the ion thruster.

At this time, most of the ionized plasma is within the cusp magnetic field formed near the wall of the discharge vessel 3 (forming multiple mirror magnetic fields).
The flute instability (/12ute 1nstabiQity) is generated between magnets 5 and 5 with a weak magnetic field.
It is emitted into the non-magnetic field area (the central part of the discharge chamber). The emitted plasma electrons are still being processed. Since it has enough energy to ionize the gas, it is used again. It collides with the gas to create residual ionized plasma. Since the ionized plasma in the non-magnetic field region is confined by the cusp magnetic field, the accelerating electrode 6
The majority of the water flows out in the direction shown in Figure 4. A diffusion plate for diffusing gas is shown, and 7 is a thruster case.

However, the cusp magnetic field shape of such an ECR type ion thruster is constructed by aligning S, -C, and magnet arrays of equal width in a straight line alternately for the same length, so that the acceleration The leakage magnetic field near the surface of the electrode 6 is large, and as shown by the solid line 12 in FIG.
The drawback is that the area is narrow and the diameter of the accelerating electrode 6 is narrow.

(Problems to be Solved by the Invention) The present invention is advantageous in that the leakage magnetic field in the vicinity of the surface of the accelerating electrode 6 is small, and as shown by the broken line 13 in FIG. The purpose of this invention is to provide a highly efficient ECR type ion thruster that can have a wide diameter.

[Structure of the invention]

(Means for Solving the Problems) The present invention has a cusp magnetic field shape in which annular magnet arrays are alternately arranged in NS parallel to the accelerating electrode surface, so that the electron cyclotron resonance regions formed near the N-pole front and the S-pole front are the same. It is characterized by adjusting the magnet width of the annular magnet rows at both ends so that

(Function) When a cusp magnetic field is constructed by arranging magnets with the same magnetic field strength and magnet width in a ring shape with the same length alternately, the plasma density near the surface of the accelerating electrode will be uniform as shown by the broken line 13 in Figure 5. (Because there is no circumferential magnetic field, the magnetic field near the surface of the accelerating electrode can be exponentially reduced by separating the accelerating electrode from the magnet ring.) However, as shown in FIG. 2, the magnetic fields of the magnet arrays at both ends do not constitute a mirror magnetic field configuration, and some of the electrons accelerated by <ECR collide with the wall and are lost. By removing the electron cyclotron resonance region that does not constitute the mirror magnetic field configuration, we have achieved a highly efficient cusp magnetic field configuration with a wide accelerating electrode diameter.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of an ECR type ion thruster using an annular cusp magnetic field according to an embodiment of the present invention. Annular magnet arrays 5 with the same magnetic field strength and magnet width are arranged alternately on the wall surface of the discharge vessel 3, and the end of the annular magnet array 5 on the accelerating electrode side is placed with an adjacent magnet array with the same magnetic field strength and polar orientation. An annular magnet array 9 with the opposite magnet width and about half the magnet width is arranged, and an annular magnet array 5 on the ceiling side is arranged.
An annular magnet array 10 having the same magnetic field strength, opposite pole direction to the adjacent magnet array, and magnet width set to such an extent that the magnetic force inside the discharge vessel is not released to the outside is disposed at the end of the annular magnet array 10. When the annular magnet array lO is on the central axis of the discharge vessel 3, it may not be annular but may be, for example, cylindrical. When the magnets are arranged in this way, the discharge vessel 3
Figure 3 shows the magnetic field lines of C. In addition, for WM single use, the wall surface of the discharge vessel 3 is flattened, and the magnet width of the magnet arrays 9 and 10 at both ends of 6 is shown to prevent lines of magnetic force from appearing outside the discharge vessel 3. Magnet row9. The width of the electron cyclotron resonance layer 11 formed near the front surface of IO is only about half that of the electron cyclotron resonance layer 11 formed near the front surface of the remaining magnet array 5.Therefore, the electron cyclotron resonance layer 11 is entirely covered by the mirror magnetic field. This means that they are being confined (shaded area in Figure 3).

The electrons in the mirror magnetic field are reflected at a position slightly outside the electron cyclotron resonance layers 11 at both ends, and undergo reciprocating motion. The reciprocating electrons pass through the electron cyclotron resonance layer 11 four times in one reciprocation, where they resonate and absorb microwaves to increase their rotational energy. The increased energy is used. When the ionization energy of It will collide with the gas and generate ionized plasma. The ionized plasma generated within the mirror magnetic field (shaded area in Figure 3) is emitted from the center where the lines of magnetic force are convex due to flute instability.

Of the emitted plasma electrons, engineering. Electrons with energy greater than the ionization energy of are trapped within the cusp magnetic field. Collisions with gas generates ionized plasma in the center of the discharge vessel.

Plasma uniformity is strongly influenced by the plasma generated in the center of the discharge vessel, so an annular cusp magnetic field configuration with a wide non-magnetic field region near the accelerating electrode surface is more uniform than a linear cusp magnetic field configuration. The plasma region becomes wider (dashed line 13 in Fig. 5). −Engineered from various plasma regions. Since + ions can be extracted, the diameter of the accelerating electrode can be made larger in the case of the annular cusp magnetic field arrangement of this patent example than in the case of the conventional linear cusp magnetic field arrangement. Furthermore, the problem of high-speed energy electrons colliding with the discharge vessel 3 due to the annular cusp magnetic field configuration is eliminated.

In this patent example, as a method of removing the region that does not constitute mirror magnetic field confinement in the electron cyclotron resonance MiJ11, it is carried out with the width of the annular magnet arrays 9 and 10 at both ends, but the point is that the electron cyclotron resonance layer 11 is completely removed. Anything is fine as long as it constitutes mirror magnetic field confinement.

Used as introduced gas. I used . It is not limited to. Further, although three accelerating electrodes 6 are used, the number is not limited to three. Although the microwave frequency is 2.450 GHz and the electron cyclotron resonance magnetic flux density is 0.0875 T, the present invention is not limited to these values.

〔Effect of the invention〕

As described above, according to the present invention, a small ECR type ion thruster having high efficiency and a large diameter accelerating electrode can be formed.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway perspective view showing the essentials of an ECR-type ion thruster according to an embodiment of the present invention, and Fig. 2 is an overview of the annular cusp magnetic field configuration in the discharge vessel when the magnetic field lines are not terminated. Figure 3 is a schematic diagram of the annular cusp magnetic field configuration with terminal processing of magnetic lines of force according to this patent, Figure 4 is a partially cutaway perspective view showing the main part of a conventional ECR type burr ion thruster, and Figure 5 is a diagram of this patent. 6 is a comparison diagram of the uniformity of plasma density between the conventional example and the conventional example.
1... Gas introduction system 2... Microwave introduction system 3... Discharge vessel 4... Gas diffusion plate 5.9
．． to...Magnet 6...Acceleration electrode (3 pieces) 7.
... Thruster case 8 ... Neutralizer 11 ... Electron cyclotron resonance layer 12 ... Conventional plasma uniformity 13 ... Plasma modality of this patent Agent Patent attorney Noriyuki Chika Figure 1, Figure 2, by Hikaru Matsuyama

Claims (2)

[Claims] (1) In an ion thruster consisting of a gas introduction system, a microwave introduction system, a discharge vessel whose walls are covered with a cusp magnetic field, an accelerating electrode, a neutralizer, a power supply, etc., electrons are formed near the front surface of the N pole. An ECR characterized in that the surface area of the magnet is adjusted so that the areas of the cyclotron resonance layer and the electron cyclotron resonance layer formed near the S-pole front surface are approximately the same.
type ion thruster. (2) Claim characterized in that the cusp magnetic field is constituted by a ring-shaped array of magnets, and the width of the surface of the magnet arrays at both ends is adjusted to prevent lines of magnetic force inside the discharge vessel from coming out. 1. The ECR type ion thruster described in 1.