JP2000173487A - Multipole permanent magnet device for ecr - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multipole permanent magnet device capable of making the thickness in the radial direction thin and the size small with mechanical strength kept. SOLUTION: Multipole permanent magnets 23a, 23b are formed with a plurality of rod-like permanent magnets fixed to the outer circumference of a cylindrical base frame 26 so as to extend in the center axis direction of the base frame. A plurality of rod-like permanent magnets are divided into N sets with respect to circumferential direction of the base frame according to the number of magnetic poles N, the rod-like permanent magnet in each set is arranged so as to have the same magnetic pole in the center axis direction, but permanent magnets in adjacent sets with respect to circumferential direction of the base frame are arranged so as to have an opposite magnetic pole each other, and a plurality of rod-like permanent magnets are covered with a cylindrical yoke 24 having almost the same length as them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-pole permanent magnet device, and more particularly to a multi-pole permanent magnet device suitable for an ECR (electron cyclotron resonance) ion source device.

[0002]

2. Description of the Related Art A multi-pole permanent magnet device of this type is generally provided by assembling permanent magnets on a cylindrical frame at intervals in a circumferential direction and further combining a yoke.
In this type of multi-pole permanent magnet device, the arrangement of the permanent magnet block and yoke is not the same in every cross section of the multi-pole permanent magnet, and sometimes it is desired to change according to the location. Not always constant. In the traditional way,
When the outer diameter changes, while maintaining the mechanical strength,
At the same time, it was difficult to produce a small multipole permanent magnet.

[0003]

In a conventional multi-pole permanent magnet, a permanent magnet block is supported inside the outer frame which is cut out integrally, and the blocks are supported by each other like an arch structure of a stone bridge. And fixed with an adhesive. A problem with such a multi-pole permanent magnet is that the mechanical strength is reduced when the outer frame is divided and configured. If the outer frame is formed by division, when the adhesive force is deteriorated due to the passage of time or use conditions, the stronger the magnetic force of the permanent magnet, the more likely it is to break and the fragments may be scattered.

[0004] If the conventional method cannot form a single piece, the mechanical strength becomes insufficient. Alternatively, in order to maintain mechanical strength, there is a method of attaching a flange or the like for firm connection, but the size is increased.

An object of the present invention is to provide a multi-pole permanent magnet device which can be reduced in thickness in the radial direction and reduced in size while maintaining mechanical strength.

[0006]

According to the present invention, a first multi-pole permanent magnet composed of a plurality of rod-shaped permanent magnets is arranged on the outer peripheral surface of a cylindrical base frame in the direction of the central axis of the base frame. An assembly is provided, end frames are provided at both ends of the base frame, and a second multipolar permanent magnet assembly including a plurality of rod-shaped permanent magnets is provided outside at least one of the end frames, A main magnetic closed circuit is formed in a cross section orthogonal to the central axis of the base frame by the rod-shaped permanent magnets constituting the first multipole permanent magnet assembly, thereby forming the second multipole permanent magnet assembly. The ECR is formed by forming a magnetic closed end circuit having the same polarity as the first multi-pole permanent magnet assembly in a cross section orthogonal to the central axis of the end frame by using a rod-shaped permanent magnet. A multi-pole permanent magnet device is provided.

The first multi-pole permanent magnet assembly is composed of a plurality of rod-shaped permanent magnets fixed on the outer peripheral surface of the base frame so as to be aligned in a direction parallel to the central axis of the base frame. 1
The plurality of rod-shaped permanent magnets in the multi-pole permanent magnet assembly of (1) is divided into N sets of magnet assemblies in the circumferential direction of the base frame in accordance with the number N of magnetic poles (N is an even number). The rod-shaped permanent magnets belong to the same orientation of the magnetic poles in a plane orthogonal to the central axis of the base frame in each set, and the adjacent sets in the circumferential direction of the base frame have opposite magnetic poles. In addition, the outside of the plurality of rod-shaped permanent magnets in the first multi-pole permanent magnet assembly is covered with a yoke serving as a cylindrical outer frame having substantially the same length.

A space is provided between adjacent sets of the plurality of bar-shaped permanent magnets in the first multi-pole permanent magnet assembly in the circumferential direction of the base frame, and the space corresponding to the space is provided. A space is also formed in the base frame and the yoke.

The first multipole permanent magnet assembly has a magnetic pole number N
The rod-shaped permanent magnet, which is divided into N sets in the circumferential direction of the base frame according to the above, is constituted by a plurality of magnet groups in each set, and the magnetic poles are arranged in the same direction in each set.

The outer peripheral surfaces of the base frame and the end frame are formed on a polygonal flat surface for fixing a plurality of rod-shaped permanent magnets in the first and second multipole permanent magnet assemblies, respectively. The inner peripheral surfaces of the base frame and the end frames are cylindrical.

The rod-shaped permanent magnets in the first and second multipole permanent magnet assemblies have a substantially rectangular cross-sectional shape, and the rod-shaped permanent magnets belonging to the same group are adjacent to each other so that the base frame and the end portions are adjacent to each other. Adhere to the flat surface of the frame.

The plurality of rod-shaped permanent magnets in the second multi-pole permanent magnet assembly are divided into N sets in the circumferential direction of the end frame in accordance with the number N of magnetic poles (N is an even number). The rod-shaped permanent magnets at the center of the magnetic poles belonging to the set have the same combination of magnetic poles as the N sets of rod-shaped permanent magnets,
The directions of the magnetic poles in a plane perpendicular to the central axis of the base frame are set to be the same, and the rod-shaped permanent magnets at the ends of the magnetic poles adjacent to each other in the circumferential direction of the end frame are configured to have opposite magnetic poles.

The second multipole permanent magnet assembly has a magnetic pole number N
The rod-shaped permanent magnets, which are divided into N sets in the circumferential direction of the base frame in accordance with the above, are configured from a plurality of magnet groups in each set, and each set includes at least the first multi-pole permanent magnet assembly. The magnetic poles of the plurality of bar-shaped permanent magnets at adjacent portions are arranged in the same direction.

It is preferable that the end frames provided at both ends of the base frame are formed as extensions of the base frame, and the base frame and the extension are integrally formed.

The rod-shaped permanent magnet constituting the second multipole permanent magnet assembly has a substantially rectangular cross-sectional shape, and the outer peripheral surface of the end frame has a flat surface to which the rod-shaped permanent magnet is fixed. The outside of the second multi-pole permanent magnet assembly is covered with a cylindrical frame having substantially the same length.

It is preferable that the frame is aligned with a center axis of the base frame by a flange member provided outside the base frame.

[0017] The frame may be divided into a plurality of short, substantially cylindrical shapes.

The outer diameter of the yoke is preferably larger than the outer diameter of the frame.

A second multipole permanent magnet assembly composed of a plurality of bar-shaped permanent magnets is disposed on both outer sides of the end frame, and a mirror magnet is provided on each outer portion of the second multipole permanent magnet assembly. Place in close proximity.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2, an embodiment in which a multipole permanent magnet device according to the present invention is applied to an ECR ion source device will be described. The ion source device includes a pair of mirror electromagnets 11 and 12 spaced apart from each other to create a mirror magnetic field outside a cylindrical plasma chamber 10, and a mirror electromagnet 11 outside the plasma chamber 10. 12 and a multi-pole permanent magnet device 20 according to the invention. Each of the mirror electromagnets 11 and 12 is realized by a solenoid coil. Note that each of the mirror electromagnets 11 and 12 may be configured by a plurality of rod-shaped permanent magnets.

A connecting portion 21a having a waveguide portion is provided on a side surface of the plasma chamber 10, and a waveguide 13 is connected to introduce a microwave into the plasma chamber 10 from its radial direction. An RF window 22a is inserted into a portion where the waveguide and the plasma chamber are connected. The RF window 22a transmits microwaves from the atmosphere to the plasma chamber 10
While the vacuum of the plasma chamber 10 is maintained. The position of the RF window 22a on the side surface of the plasma chamber 10 is hardly irradiated with plasma due to the magnetic field structure, and compared to the case where the RF window 22a is introduced from the axial direction of the plasma chamber like a conventional ECR ion source for an ion implanter. There is an advantage that it is not easily stained. When the RF window 22a becomes dirty, it becomes conductive, so that the microwave is cut off and the operation cannot be continued.

In such an ECR ion source device, a high magnetic field is formed in the plasma chamber 10 by the mirror electromagnets 11 and 12 and the multi-pole permanent magnet device 20, and an appropriate amount of ion generating gas is applied to the magnetic field. 2.45
(GHz) by introducing microwaves
The heating heats the electrons, generates plasma, and generates an ion beam in the axial direction of the plasma chamber 10. 87 for microwaves of 2.45 (GHz)
The presence of a magnetic field of 5 Gauss causes ECR heating of the electrons.

At the end of the mirror electromagnet 12, a casing 40-1 for extracting ions is provided.
-1, an extraction electrode 40-2 and an anode electrode 40-3 are provided.

Another function of the magnetic field described above is to effectively confine the plasma, thereby increasing ionization efficiency and reducing contamination of the RF window 22a. Plasma that tends to spread in the direction of the mirror electromagnet 11 and the multipole permanent magnet device 20 is lost, is not extracted as a beam, and is uneconomical, so it is strongly confined. Specifically, the mirror electromagnet 11 and the multi-pole permanent magnet device 2
The maximum value of the generated magnetic field of 0 must be at least 875 Gauss or more in the plasma chamber 10, and is ideal if it is 2 kGauss or more. The value of 2 kilogauss is about twice as large as that of a conventional ECR ion source device for an ion implantation device. When RF is introduced from the axial direction, the diameter of the plasma chamber becomes large due to microwave propagation. Therefore, it was practically difficult to generate a strong magnetic field of 2 kilogauss. On the other hand, the magnetic field of the mirror electromagnet 12 is made weaker than that of the mirror electromagnet 11 and the multi-pole permanent magnet device 20, and an escape path for plasma is created in that direction. As a result, ions in the plasma are extracted out of the plasma chamber 10 from the direction of the mirror electromagnet 12. The multipole permanent magnet device 20 according to the present invention will be described with reference to FIGS. The multi-pole permanent magnet device 20 includes four-pole permanent magnets 23a to 23d (first multi-pole permanent magnet assembly) and a cylindrical yoke 24 provided outside thereof. In particular, in this example, the four-pole permanent magnet 23a
To 23d are formed by combining two bar-shaped magnets having a trapezoidal cross-sectional shape with the wide bottom surface facing outward, and furthermore, the four-pole permanent magnets 23a to 23d are
6 is combined in a ring shape. The base frame 26 is made of a non-magnetic material, for example, aluminum. The directions of the magnetic poles of the four-pole permanent magnets 23a to 23d are
The magnetic poles facing each other in the central axis direction are the same, and the magnetic poles adjacent in the circumferential direction are arranged to be opposite poles.

The multi-pole permanent magnet device 20 combines a plurality of rod-shaped magnets extending in the central axis direction of the plasma chamber 10 from both ends of the base frame 26 in addition to the four-pole permanent magnets 23a to 23d in a ring shape. And two sets of multi-pole permanent magnets 25-1 to 25-2 (second multi-pole permanent magnet assemblies). As for the multipole permanent magnet 25-1,
Here, eight magnetic poles 25-1a to 25-1h are configured by combining 16 bar-shaped magnets into one set. Of the eight magnetic poles 25-1a to 25-1h, magnetic poles 25-1a to 25-25 corresponding to the four-pole permanent magnets 23a to 23d.
-1d indicates that the direction of the magnetic pole is a four-pole permanent magnet 23a-
It is arranged so as to be the same as the direction of the magnetic pole of 23d. Further, the magnetic poles 25-1f to 25-1h arranged between the magnetic poles 25-1a to 25-1d are arranged such that the magnetic poles are circumferential and opposite. Similarly, also in the multi-pole permanent magnet 25-2, eight magnetic poles are configured. Outside the multipole permanent magnets 25-1 to 25-2, a cylindrical frame 27-
1, 27-2 are provided.

The two sets of multipole permanent magnets 25-1 and 25
-2 indicates mirror electromagnets 11 and 12 and plasma chamber 1
0, and if a yoke is present, the magnetic field generated in the plasma chamber 10 by the mirror electromagnets 11 and 12 becomes small.
No yoke 24 to be combined with 3d is provided. In any case, the permanent magnet used in the multi-pole permanent magnet device 20 has a magnetization direction perpendicular to the magnetic pole surface and has the same residual magnetic flux density in all cases.

The multi-pole permanent magnet 25-1 is not indispensable and may be omitted. In this case, the multi-pole permanent magnet 25
The end (end frame) of the base frame 26 extended to form -1 may not be provided. Further, the portions corresponding to the both ends may be formed separately from the base frame 26. Further, the inside of the base frame 26 has a cylindrical shape, but on the outer surface, a bonding surface is flat to facilitate adhesion of the four-pole permanent magnets 23a to 23d and the multi-pole permanent magnets 25-1 and 25-2. I have to. For this reason, the outside of the base frame 26 has a polygonal shape.

Incidentally, four long holes 24a to 24d are provided on the side surface of the yoke 24 at intervals in the circumferential direction. This is to enable the connection of the waveguides described in FIG. 2 to be performed at four arbitrary positions. The base frame 26 is provided with the long hole 26a only at the position corresponding to the long hole 24a, but depending on the connection position of the waveguide, the long holes 24b to 2b are provided.
An elongated hole similar to the elongated hole 26a is provided at a location corresponding to 4d. Therefore, not only a location corresponding to the elongated hole 24a in the base frame 26 but also a location corresponding to the elongated holes 24b to 24d is a space. It has been removed from the installation area of the four-pole permanent magnets 23a to 23d. The location where the long hole is provided in the base frame 26 corresponds to the corner of the polygonal shape. However, when the long hole is provided, the corner is ground.

Of course, the yoke 24 of the base frame 26
A slot may be provided in advance at a position corresponding to the three slots 24a to 24d. In this case, the plasma chamber 10 is also provided with a long hole at a position corresponding to the long hole of the base frame 26. However, in order to maintain the degree of vacuum in the plasma chamber 10, a long hole to which the waveguide 13 is not connected is provided. Must be closed with something like a lid plate.

Returning to FIG. 1, a gas introduction pipe 29 for generating ions is connected to the left end of the plasma chamber 10. The right end of the plasma chamber 10 is opened to serve as an ion beam outlet, and a guide tube (not shown) for guiding the ion beam to the irradiation unit is connected to the opening of the plasma chamber 10.

In such an ion source device for ECR, a high magnetic field having a minimum B structure is formed in the plasma chamber 10 by the pair of mirror electromagnets 11 and 12 and the multi-pole permanent magnet device 20, and the magnetic field is used to generate ions. By introducing a microwave for use and a microwave of 2.45 (GHz), an ion beam can be generated in the axial direction of the plasma chamber 10.

The multi-pole permanent magnet device 20 is manufactured as follows. First, a cylindrical base frame 26 made of a non-magnetic material is prepared, and four-pole permanent magnets 23a to 23d are adhered to the outside of the base frame 26, and a multi-pole permanent magnet 25-1, 25-2 is adhered. Next, the yokes 24 are combined on the outside thereof, and the multipole permanent magnets 25
Frame bodies 27-1 and 27-2 are provided outside -1, 25-2.

Here, positions close to both ends of the base frame 26,
That is, the flange portions 26-1 and 26 extending in the radial direction are respectively provided at the boundaries between the installation regions of the four-pole permanent magnets 23a to 23d and the installation regions of the multipolar permanent magnets 25-1 and 25-2.
-2 is formed. In particular, the protrusion length of the flange portion 26-1 is slightly larger than that of the flange portion 26-2,
A notch 24-1 is provided in the circumferential direction on the inner circumference of the end of the yoke 24 corresponding to the flange 26-1. Thus, the tip of the flange 26-1 has a positioning function when the yoke 24 is assembled. In addition, the flange 26
-1, 26-2, the frame 27-1, 27-
Steps 26-1a and 26-2a are provided for positioning the second step 2. The step 26- during processing of the four-pole permanent magnets 23a to 23d is provided on the inner surface of the flange sections 26-1 and 26-2.
1b and 26-2b are provided.

As described above, the base frame 26 is provided with the elongated hole 26a for installing the connecting portion 21a. The inside of the base frame 26 has a cylindrical shape, but the outside surface is flattened to facilitate adhesion of the four-pole permanent magnets 23a to 23d and the multi-pole permanent magnets 25-1 and 25-2. ing.

The mirror electromagnets 11 and 12 are supported by a support member (not shown), and a multi-pole permanent magnet device 20 is incorporated in a central circular space between the mirror electromagnets 11 and 12. Next, a cylindrical plasma chamber 10 sufficiently longer than this is provided inside the base frame 26.
Is incorporated.

The conditions required for the above assembly are listed below.

The base frame 26 is formed integrally by shaving.

The outer peripheral surface of the base frame 26 has a polygonal cross section and is flattened.

When the arrangement of the four-pole permanent magnets 23a to 23d and the multi-pole permanent magnets 25-1 and 25-2 changes, the dimensions of the polygon may be changed.

In order to position the yoke 25, flanges 26-1 and 26-2 are formed on the outer periphery of the base frame 26.
Sometimes it is not made. The method for forming the flanges 26-1 and 26-2 is as follows.

In the first method, a flange is formed at the same time when the base frame 26 is cut out.

In the second method, a ring-shaped member serving as a flange is fitted into the base frame 26 later.

In the third method, steps 26-1a, 26-a
It is configured by attaching three or more spacers having 1b later.

The yoke 24 is finished in a cylindrical shape.

The inner surface of the yoke 24 has a substantially columnar shape, but the notch 24-1 is partially provided so that the axial positioning of the yoke 24 with respect to the base frame 26 can be simplified. .

Each surface of the permanent magnet is flattened.

The center axis of the yoke 24 is fitted to the flange of the base frame 26 and is aligned with the axis of the base frame 26.

The base frame 26 is connected to the yoke 24 via the flange.
Of the permanent magnet blocks 23a to 23d, 25-
1a to 25-1h are not used for centering the yoke 24.

According to the above multi-pole permanent magnet device,
A high magnetic field having a minimum B structure is formed in the plasma chamber 10 by a combination with a pair of appropriate mirror electromagnets 11 and 12. As is well known, the magnetic field of the minimum B structure is an ECR (Elect) in the plasma chamber 10.
tron Cyclotron Resonance)
A region where resonance occurs and where the ECR resonance occurs is a confined magnetic field structure that is closed in the plasma chamber 10. In other words, the inner wall surface of the plasma chamber 10 and E
The CR zones do not intersect, and the magnetic field of this minimum B structure is ECR magnetic field B _ECR (2.4
For 5 MHz, which is the magnetic field that must traverse the B _ECR before striking the inner wall of the plasma chamber 10 can be said in any direction starting from a weak one point than 875 gauss). The ECR zone referred to here is a region in which ECR resonance points are continuously formed as a plane.

In such a confined magnetic field, compared to the conventional microwave ion source device, the electrons of the plasma generated in the plasma chamber 10 are suppressed from being dissipated in the radial direction of the plasma chamber 10, Since the electron confinement time is extended and the heating of the electrons is promoted by the ECR heating action, particularly when the degree of vacuum in the plasma chamber 10 is high, multi-charged ions are easily generated when colliding with gas atoms. Then, all ions including such multiply-charged ions are efficiently prevented from leaking in the radial direction of the plasma chamber 10, and the adhesion to the inner wall of the plasma chamber 10 and the RF window is suppressed. This means that it is possible to suppress a decrease in microwave transmission efficiency due to conductivity due to the attachment of ions to the RF window 22a.

As described above, when the ion trapping efficiency is improved, the amount of gas introduced into the plasma chamber 10 can be reduced, and the degree of contamination in the plasma chamber 10 can be reduced. Further, even if the introduced gas is a corrosive gas, its ions are generated in the plasma chamber 10.
Can be prevented from adhering to the inner wall and being corroded.
This means that the life of the ion source device is prolonged.

In addition, the multi-pole permanent magnets in the region into which the microwave is introduced are four-pole permanent magnets 23a to 23d, so that the interaction between the pair of mirror electromagnets 11 and 12 and the magnetic field causes the plasma chamber 10 to operate. An elongated cross-sectional ion beam that intersects the central axis at right angles can be generated. It is known that the cross-sectional shape of the ion beam changes according to the number of poles of the multi-pole permanent magnet in a region where microwaves are introduced. By the way, in the case of 6 poles,
The cross-sectional shape is substantially triangular, and in the case of eight poles, it is substantially square. Note that the magnetic field intensity formed in the plasma chamber 10 is preferably a magnetic field of 2 kilogauss or more.

Next, the operation of the pair of mirror electromagnets 11 and 12 and the yoke 24 will be described with reference to FIG. It is known that when the frequency of the microwave introduced into the plasma chamber 10 is 2.45 (MHz), the ECR resonance occurs when the magnetic field intensity is 875 (Gauss). The absolute value | B | of the magnetic field generated by the mirror electromagnets 11 and 12 at the center axis r = 0 of the plasma chamber 10 is as shown in FIG. In order to cause ECR resonance, as shown in FIG.
It is necessary to form a convex valley on the lower side such that the curves intersect at 5 (Gauss).

If the distance between the mirror electromagnets 11 and 12 is too small compared to the inner diameter of the mirror electromagnets 11, 12, the absolute value of the magnetic field | B | No, the ECR resonance point disappears.
For this purpose, a cylindrical iron yoke 24 is interposed between the mirror electromagnets 11 and 12 so as to absorb the lines of magnetic force near r = 0 and lower the valley to the lower side.

Since the multi-pole permanent magnet combined with the mirror electromagnets 11 and 12 cannot generate a magnetic field in the plasma chamber 10 unless it is inside the yoke 24, the four-pole permanent magnets 23a to 23d are formed using rod-shaped magnets. By doing so, it is possible to use the thin space between the yoke 24 and the plasma chamber 10 to accommodate the space.

Next, the principle of the ion confinement effect by the magnetic field of the four-pole permanent magnet will be described with reference to FIG.
In FIG. 6, the lines of magnetic force between the four-pole permanent magnets are symbolically shown one by one. The dashed line indicates the isomagnetic field intensity range of the absolute value of the magnetic field | B |. The closer to the center, the closer to the circle the magnetic field intensity becomes isotropic, but it becomes distorted as it approaches the magnetic pole. Loses its target. The charged particles existing in such a magnetic field tend to move toward the magnetic pole while moving in a spiral around the magnetic field lines. In other words, the charged particle tries to move to the direction where the center of rotation becomes stronger in the magnetic field. Such charged particles are also subjected to a repulsive action such that they move in the opposite direction as the magnetic field strength increases as they approach the pole. The degree of this rebound is determined by the initial direction of motion, and the strength ratio of the magnetic field (FIG. 5)
To quote (b), the larger the ratio between the minimum value and the peak value between the valleys of the curve, the greater the tendency to rebound. According to such a principle, an ion confinement effect in which the residence time of the ions is prolonged occurs. On the other hand, the RF window 22a is located at a position parallel to the magnetic field lines, and the ions are unlikely to move in a direction perpendicular to the magnetic field lines. This also contributes to the difficulty of ion attachment to the RF windows 22a.

By the way, the frequency of the microwave is set to 2.45.
(GHz) because the generator of this frequency is used in household electric appliances, for example, a microwave oven, and is provided at the lowest cost. If it is not necessary to consider this point, Alternatively, another frequency may be used.

Although the present invention has been described with reference to the case of a four-pole permanent magnet, it goes without saying that the number of magnetic poles is not limited to four. Also, the case where the present invention is applied to an ECR ion source device has been described. However, the multipolar permanent magnet device for ECR according to the present invention is not limited to the above-described embodiment, and a high magnetic field is required. Needless to say, the present invention can be applied to the permanent magnet device as a whole.

[0059]

According to the multipole permanent magnet device according to the present invention described above, the following effects can be obtained.

Even if the permanent magnet block does not have an arch structure like a stone bridge, it does not come off inside.

Since the permanent magnet blocks are not necessarily brought into close contact with each other, fine precision is not required for the surface angle and the like.

Since the outer periphery of the base frame is flat and the inner surface of the yoke is curved, the permanent magnet blocks, which are hard to be displaced in the circumferential direction, do not necessarily adhere to each other, so that the permanent magnet blocks can be arranged apart in the circumferential direction. .

If a long hole is formed in each of the base frame and the yoke in the gap between the permanent magnet blocks, an opening for introducing microwaves can be provided in the radial direction.

RF can be introduced from the radial direction of the plasma chamber through the opening, and even if the permanent magnet block is peeled off, it is unlikely to be shifted laterally.

The yoke serves as a cover, and does not fly out even if the permanent magnet is peeled off.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a structure of an ECR ion source device to which the present invention is applied.

FIG. 2 is a sectional view taken along line AA 'of FIG.

FIG. 3 is a view showing a preferred embodiment of a multi-pole permanent magnet device according to the present invention, wherein FIG. 3 (a) is a partial cross-sectional side view, and FIG. 3 (b) is along line BB ′ in FIG. 3 (a). Sectional view, figure (c)
FIG. 4 is a sectional view taken along line CC ′ of FIG.

FIG. 4 is a side view and a cross-sectional view of the yoke, the base frame, and the frame shown in FIG. 3;

5A and 5B are diagrams for explaining the operation of the mirror electromagnet and the yoke shown in FIG. 1; FIG.
FIG. 6B is a characteristic diagram showing the absolute value strength | B | of the magnetic field with respect to the distance Z in FIG.

FIG. 6 is a view for explaining the operation of the four-pole permanent magnet shown in FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Plasma chamber 11, 12 Mirror electromagnet 13 Waveguide 20 Multi-pole permanent magnet device 21a Connection part 22a RF window 23a-23d 4-pole permanent magnet 24 Yoke 25-1, 25-2 Multi-pole permanent magnet 26 Base frame 27-1 , 27-2 Frame 29 Gas introduction pipe

Claims (13)

[Claims] A first multi-pole permanent magnet assembly comprising a plurality of rod-shaped permanent magnets disposed on an outer peripheral surface of a cylindrical base frame so as to be arranged in a central axis direction of the base frame; And a second multi-pole permanent magnet assembly comprising a plurality of bar-shaped permanent magnets disposed outside at least one of the end frames. The first multi-pole permanent magnet assembly The main magnetic closed circuit is formed in a cross section orthogonal to the central axis of the base frame by the rod-shaped permanent magnets, and the end frame is formed by the rod-shaped permanent magnets forming the second multipole permanent magnet assembly A multipole permanent magnet device for ECR, wherein an end magnetic closed circuit having the same polarity as the first multipole permanent magnet assembly is formed in a cross section orthogonal to the central axis of the ECR. 2. The multi-pole permanent magnet device for ECR according to claim 1, wherein the first multi-pole permanent magnet assembly is arranged on an outer peripheral surface of the base frame in a direction parallel to a central axis of the base frame. The plurality of bar-shaped permanent magnets in the first multi-pole permanent magnet assembly are arranged in a circumferential direction of the base frame in accordance with the number N of magnetic poles (N is an even number). , The rod-shaped permanent magnets belonging to each group have the same direction of magnetic poles in a plane orthogonal to the central axis of the base frame in each set, and the poles of the base frame are The pairs adjacent to each other in the circumferential direction are configured to have magnetic poles opposite to each other, and
Characterized in that a plurality of rod-shaped permanent magnets in the multi-pole permanent magnet assembly according to (1) are covered with a yoke serving as a cylindrical outer frame having substantially the same length. apparatus. 3. The multi-pole permanent magnet device for ECR according to claim 2, wherein adjacent sets of the plurality of rod-shaped permanent magnets in the first multi-pole permanent magnet assembly with respect to a circumferential direction of the base frame. A multi-pole permanent magnet device for ECR, wherein a space is provided between the base frame and the yoke body corresponding to the space. 4. The multi-pole permanent magnet device for ECR according to claim 3, wherein the first multi-pole permanent magnet assembly is divided into N sets in the circumferential direction of the base frame in accordance with the number N of magnetic poles. The above-mentioned rod-shaped permanent magnet is constituted by a plurality of magnet groups in each set, and the magnetic poles are aligned in the same direction in each set. 5. The multi-pole permanent magnet device for ECR according to claim 1, wherein the outer peripheral surfaces of the base frame and the end frame are formed in a plurality of rod-like shapes in the first and second multi-pole permanent magnet assemblies, respectively. A multi-pole permanent magnet device for ECR, wherein a permanent magnet is formed on a polygonal flat surface and inner peripheral surfaces of the base frame and the end frame are cylindrical. 6. The multi-pole permanent magnet device for ECR according to claim 5, wherein the rod-shaped permanent magnets in the first and second multi-pole permanent magnet assemblies have a substantially square cross-sectional shape, and are formed in the same set. The multipole permanent magnet device for ECR, wherein the rod-shaped permanent magnets belonging to the base frame and the end frame are fixed to the flat surfaces of the base frame and the end frame adjacent to each other. 7. The multi-pole permanent magnet device for ECR according to claim 1, wherein the plurality of rod-shaped permanent magnets in the second multi-pole permanent magnet assembly are arranged in accordance with a magnetic pole number N (N is an even number). The end frame is divided into N sets in the circumferential direction, and the rod-shaped permanent magnets at the center of the magnetic poles belonging to each set are arranged at the center of the base frame so that the same magnetic pole combination as the N sets of rod-shaped permanent magnets is made. The direction of the magnetic poles in a plane perpendicular to the axis is the same, and the rod-shaped permanent magnets at the ends of the magnetic poles adjacent to each other in the circumferential direction of the end frame are made to have opposite magnetic poles. Multi-pole permanent magnet device. 8. The multi-pole permanent magnet device for ECR according to claim 7, wherein the second multi-pole permanent magnet assembly is divided into N sets in the circumferential direction of the base frame in accordance with the number N of magnetic poles. Said rod-shaped permanent magnet, comprising a plurality of magnet groups in each set,
A multipole permanent magnet device for ECR, wherein in each set, the magnetic poles of a plurality of rod-shaped permanent magnets at least in a portion adjacent to the first multipole permanent magnet assembly are aligned in the same direction. 9. The multi-pole permanent magnet device for ECR according to claim 8, wherein the end frames provided at both ends of the base frame are configured to be extensions of the base frame. A multi-pole permanent magnet device for ECR, characterized in that an extension body is integrally formed. 10. The multi-pole permanent magnet device for ECR according to claim 8, wherein the rod-shaped permanent magnets constituting the second multi-pole permanent magnet assembly have a substantially rectangular cross-sectional shape, and The outer peripheral surface has a flat surface to which the bar-shaped permanent magnet is fixed, and a cylindrical frame having substantially the same length as the outer surface of the second multi-pole permanent magnet assembly. E characterized by the following:
Multi-pole permanent magnet device for CR. 11. The multi-pole permanent magnet device for ECR according to claim 10, wherein the frame is aligned with a center axis of the base frame by a flange member provided outside the base frame. Multi-pole permanent magnet device for ECR. 12. The multi-pole permanent magnet device for ECR according to claim 8, wherein an outer diameter of the yoke body is larger than an outer diameter of the frame body. 13. The multi-pole permanent magnet device for ECR according to claim 8, wherein a second multi-pole permanent magnet assembly comprising a plurality of rod-shaped permanent magnets is disposed on both outer sides of the end frame, and a mirror magnet is provided. A multi-pole permanent magnet device for ECR, wherein the multi-pole permanent magnet device is disposed in close proximity to each outer portion of the second multi-pole permanent magnet assembly.