JP2006049020A - Device and method for generating mirror field for confining plasma used in ecr ion source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mirror field generation technique for confining plasma used for an ECR ion source, capable of changing mirror field intensity in adjusting an ion source and suitable for generating multicharged ions. <P>SOLUTION: The mirror field generator of this invention generating the mirror field for confining the plasma used for the ECR ion source comprises a pair of circular permanent magnets 4, 5 separately arranged in a direction of an ion source central-axis (X), and is provided with a mirror field generation part (2) generating the mirror field, a mirror field amplifying part (3) disposed between the pair of circular permanent magnets 4, 5 of the mirror field generation part (2), constituted of a plurality of fan-like permanent magnets arranged in a circle, and amplifying the mirror field generated by the mirror field generation part (2), and fan-like permanent magnet moving means 14, 18 moving each fan-like permanent magnet constituting the mirror field amplifying unit (3) in a radial direction of the ion source central-axis (X). The mirror field intensity can be changed by moving each fan-like permanent-like magnet in the radial direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The invention of this application relates to a mirror magnetic field generating apparatus and method for confining plasma used in an ECR (Electron Cyclotron Resonance) ion source, and more specifically, the mirror magnetic field strength not only when the ion source is stopped but also when the ion source is adjusted. The present invention relates to an apparatus and a method for generating a mirror magnetic field for confining plasma that can change the angle.

  In order to generate a high quality charged particle beam in an accelerator such as an AVF (Azimuthally Varying Field) cyclotron, the stability of the ECR ion source is an important factor in addition to the voltage stability of the accelerator. The ECR ion source generates ions by the interaction between a mirror magnetic field for confining plasma and a microwave. In order to generate the mirror magnetic field for confining the plasma, an electromagnet has been used at first. However, an electromagnet requires a large current input, requires a large facility for applying a high voltage, and further generates a charged particle beam extracted from an ion source due to the heat generated by a solenoid coil for generating a mirror magnetic field. There were problems such as fluctuations in intensity over time.

  Therefore, it is desirable to use a small permanent magnet that does not generate heat due to energization, rather than using an electromagnet, for generating a plasma confinement magnetic field of the ECR ion source.

  On the other hand, there are many cases where it is necessary to increase a specific valence, in particular, the amount of polyvalent ions produced, depending on the purpose and application. In such a case, in the conventional permanent magnet type ECR ion source, the ion source is stopped and the microwave power amount, phase, and other gas supply amount are changed, and the mirror magnetic field strength is changed each time. The reason is that since the ECR ion source is applied with a high voltage (several kV), the ion source cannot be touched during use, that is, while adjusting the ion source.

  A structural example of a conventional ECR ion source using a permanent magnet (Patent Document 1) will be described with reference to FIG. FIG. 9 is a cross-sectional view along the axial direction of a conventional ECR ion source. This ion source includes a waveguide (31), and a vacuum vessel (32) is disposed therein. The cross section of the vacuum vessel (32) is circular, has an input end (33) and an output end (34), and is axisymmetric about the ion source central axis (35). In the figure, (36) is a gas inlet, (37) is a connecting portion connected to a vacuum pump (not shown), and (38) is a holding member for holding the ion extraction electrode and the vacuum vessel (32).

  Annular permanent magnets (39), (40) are arranged on the input end (33) side of the vacuum vessel (32), and an annular permanent magnets (41), (42) are arranged on the output end (35) side. Is arranged. Further, annular permanent magnets (43), (44), (45) having an inner diameter larger than these permanent magnets are provided between the permanent magnets (39), (40) and the permanent magnets (41), (42). It has been. A hexapole magnet (46) is provided inside these permanent magnets (43), (44), (45). Further, (47) is a permanent magnet holding portion, which holds the permanent magnets (43) and (44) so as to be movable in the axial direction. (48) is an ion output port.

  In such a configuration, the permanent magnets (39) and (40) and the permanent magnets (41) and (42) play a role of generating a mirror magnetic field, and the permanent magnets (43) to (45) amplify (variable) the mirror magnetic field. The mirror magnetic field is generated in the vacuum vessel (32) by these permanent magnets.

In such a structure, when changing the magnetic field strength, the ECR ion source is stopped, and the permanent magnet holder (47) is used to adjust the position by moving the positions of the permanent magnets (43) and (45). Yes.
JP 2001-338589 A

  However, in the conventional ECR ion source mirror magnetic field strength change method as described above, the permanent magnet can be moved in the axial direction only when the ion source is stopped, and cannot be moved when the ion source is adjusted. For this reason, the mirror magnetic field intensity could not be changed immediately in response to changes in the microwave power amount, phase, and other gas supply amounts during ion source adjustment.

  In addition, the higher the magnetic field of the ECR ion source, the more multivalent ions can be generated. However, considering the performance of the existing permanent magnet, the gap between the mirror magnetic field generating permanent magnet and the mirror magnetic field amplifying permanent magnet is increased. If it is not dense, the magnetic field strength cannot be increased. However, in the mirror magnetic field intensity changing method as shown in FIG. 9, since it cannot move in the axial direction unless a certain gap is provided between the mirror magnetic field generating permanent magnet and the mirror magnetic field amplifying permanent magnet, as a result, The maximum magnetic field strength that can be obtained is reduced, making it difficult to generate multivalent ions.

  The invention of this application solves the problems of the prior art, can change the mirror magnetic field intensity even when adjusting the ion source, and is a plasma confinement used in an ECR ion source suitable for the generation of multiply charged ions. An object of the present invention is to provide a mirror magnetic field generation apparatus and method.

  In order to solve the above problems, the invention of this application is firstly a device for generating a mirror magnetic field for plasma confinement used in an ECR ion source, which is a pair of devices spaced apart in the direction of the central axis of the ion source. Mirror magnetic field generator, which consists of an annular permanent magnet, is provided between a mirror magnetic field generator for generating a mirror magnetic field and a pair of annular permanent magnets in the mirror magnetic field generator, and is configured by arranging a plurality of fan-shaped permanent magnets in an annular shape. A mirror magnetic field amplifying unit for amplifying the mirror magnetic field generated by the unit, and fan-shaped permanent magnet moving means for moving each fan-shaped permanent magnet constituting the mirror magnetic field amplifying unit in the radial direction with respect to the central axis of the ion source, Provided is a mirror magnetic field generator characterized in that the mirror magnetic field intensity can be changed by the radial movement of a fan-shaped permanent magnet.

  According to a second aspect of the present invention, there is provided the mirror magnetic field generating device according to the first aspect, wherein the mirror magnetic field amplifying unit includes a front mirror magnetic field amplifying unit and a rear mirror amplifying unit.

  Thirdly, in the second invention, the fan-shaped permanent magnet of the mirror magnetic field amplifying unit is formed by dividing the annular structure into three, and each fan-shaped permanent magnet of the front mirror magnetic field amplifying unit is Provided is a mirror magnetic field generator characterized in that each mirror-shaped permanent magnet of a rear mirror amplifying unit is arranged by being shifted by 60 degrees in the circumferential direction.

  According to a fourth aspect of the present invention, the fan-shaped permanent magnets of the mirror magnetic field amplifying unit are provided on the fan-shaped magnet main body and on both sides in the circumferential direction, and the size is the fan-shaped magnet main body. The mirror magnetic field generator according to any one of claims 1 to 3, characterized by comprising a fan-shaped nonmagnetic portion that is half of the above.

  According to a fifth aspect of the present invention, the mirror magnetic field generator according to any one of the first to fourth aspects of the present invention and an annular multipolar permanent magnet disposed radially inward of the mirror magnetic field amplification unit are provided. An ECR ion source is provided.

  According to a sixth aspect of the present invention, there is provided the ECR ion source according to the fifth aspect, wherein the multipole permanent magnet is a hexapole permanent magnet.

  The seventh is a method for generating a mirror magnetic field for plasma confinement used for an ECR ion source, for generating a pair of mirror magnetic fields spaced apart in the direction of the central axis of the ion source in order to generate a mirror magnetic field. A mirror magnetic field amplifying permanent magnet for amplifying the generated mirror magnetic field is provided between the annular permanent magnets, and a plurality of fan shapes that are movable in the radial direction with respect to the central axis of the ion source as the mirror magnetic field amplifying permanent magnet Mirror magnetic field generation characterized in that the mirror magnetic field strength can be changed by moving each fan-shaped permanent magnet in the radial direction with respect to the central axis of the ion source, using a structure in which permanent magnets are arranged in an annular shape Provide a method.

  Eighthly, in the seventh invention, there is provided a mirror magnetic field generating method characterized in that the mirror magnetic field amplifying permanent magnet is divided into a front part and a rear part.

  Ninth, in the eighth invention, as the fan-shaped permanent magnet constituting the mirror magnetic field amplifying permanent magnet, the annular structure is divided into three, and each fan-shaped permanent magnet in the front part. A mirror magnetic field generating method is provided, in which a magnet is disposed by being shifted by 60 degrees in the circumferential direction with respect to the rear fan-shaped permanent magnet.

  Furthermore, tenthly, in any one of the seventh to tenth inventions, the fan-shaped permanent magnets of the mirror magnetic field amplifying unit are provided on the fan-shaped magnet body and on both sides in the circumferential direction, and the size is fan-shaped. Provided is a method for generating a mirror magnetic field characterized by using a fan-shaped nonmagnetic portion that is half of a magnet body.

  According to the first to fourth inventions and the seventh to tenth inventions of this application, the mirror magnetic field strength can be changed even when the ECR ion source using the permanent magnet is stopped and adjusted. It becomes possible to increase the valence, particularly the amount of multivalent ions produced.

  Therefore, not only the stability of the ECR ion source but also the amount of ion generation can be controlled, so that ions can be incident on the AVF cyclotron more stably, which can contribute to the stability of the charged particle beam accelerated by the accelerator.

  According to the fifth and sixth inventions of this application, since any one of the first to fourth inventions is used, an ECR ion source having excellent stability is provided, and the ion generation amount is efficiently controlled. Since ions can be incident on the AVF cyclotron more stably, it is possible to contribute to the stability of the charged particle beam accelerated by the accelerator.

  The invention of this application has the features as described above, and an embodiment thereof will be described below.

  FIG. 1 is a cross-sectional view of an essential part of an ECR ion source including a mirror magnetic field generator, which is an embodiment of the invention of this application, along the ion source central axis direction. 2A and 2B are a front view and a side view, respectively, of a mirror magnetic field generator (a drive unit is not shown). 3A, 3B, 3C, and 3D are respectively a cross-sectional view along line AA ′, a cross-sectional view along line BB ′, and a cross-sectional view along line CC ′ in FIG. FIG. FIG. 4 is a cross-sectional view taken along line E-E ′ of FIG.

  The mirror magnetic field generator (1) includes a mirror magnetic field generator (2) that generates a mirror magnetic field, and a mirror magnetic field amplifier (3) that amplifies the mirror magnetic field generated by the mirror magnetic field generator (2). The mirror magnetic field generator (2) is composed of a pair of annular permanent magnets, ie, a front annular permanent magnet (4) and a rear annular permanent magnet (5), which are spaced apart in the ion source central axis (X) direction. In the specification of this application, “front part” means the input end side (ion generation gas introduction side), and “rear part” means the opposite side. Between the front annular permanent magnet (4) and the rear annular permanent magnet (5), a mirror magnetic field amplifying part (3) comprising a front mirror magnetic field amplifying part (6) and a rear mirror magnetic field amplifying part (7) is arranged. Has been. As shown in FIG. 3B, the front mirror magnetic field amplification unit (6) is composed of three fan-shaped permanent magnets (8) [(8A), (8B), (8C)] and does not move in the radial direction. In the closed state, it is annular as a whole. The rear mirror magnetic field amplifying unit (7) is also composed of three fan-shaped permanent magnets (9) [(9A), (9B), (9C)] as shown in FIG. 3 (c), and is closed without moving in the radial direction. As a whole, it is annular. The inner diameter of the mirror magnetic field amplifying section (3) is set larger than the inner diameter of the mirror magnetic field generating section (2), and the hexapole permanent magnet (10) is arranged inside thereof.

  An iron yoke (11) is provided around the mirror magnetic field generator (2) and the mirror magnetic field amplifier (3). In the figure, (12) is an aluminum casing.

  At a required position of the casing (12), a pedestal (13) that can withstand the strong attractive force of the permanent magnet is provided with each fan-shaped permanent magnet (8A), (8B), (8C), (9A), (9B), The fan-shaped permanent magnets (8A), (8B), (8C), (9A), (9B), and (9C) are attached to the gantry (13) in the radial direction. The drive part (14) to move is installed. This drive part (14) can be comprised from the stepping motor (15) and the bevel gearwheel (17) attached to the drive shaft (16), for example. The yoke (11) and the casing (12) provided on the outside of each fan-shaped permanent magnet (8A), (8B), (8C), (9A), (9B), (9C) ) And the other part of the casing (12), and on the outer side, each fan-shaped permanent magnet (8A), (8B), (8C), (9A), (9B), (9C) A ball screw (18) having a portion that meshes with the bevel gear (17) is attached as a support when moving in the radial direction. The maximum moving distance when each fan-shaped permanent magnet (8A), (8B), (8C), (9A), (9B), (9C) is moved in the radial direction by the drive unit (14) is Although it depends on the size, an appropriate amount is usually about 50 mm. The radial movement of each of the fan-shaped permanent magnets (8A), (8B), (8C), (9A), (9B), and (9C) may be performed synchronously or independently. .

  The front annular permanent magnet (4) and the rear annular permanent magnet (5) constituting the mirror magnetic field generation unit (2) are, for example, 12 pieces having magnetization directions as shown in FIGS. 3 (a) and 3 (d). A combination of sector permanent magnets can be used. The magnetization directions of the front annular permanent magnet (4) and the rear annular permanent magnet (5) are opposite to each other.

The front mirror magnetic field amplifying unit (6) of the mirror magnetic field amplifying unit (3) includes three fan-shaped permanent magnets (8A) and (8B) having a circumferential angle of 120 degrees as shown in FIG. , (8C). The fan-shaped permanent magnet (8A) includes fan-shaped permanent magnet bodies (8a ₁ ) and (8a ₂ ) on the circumferential center side, and fan-shaped nonmagnetic portions (8a ₃ ) provided on both sides in the circumferential direction. ), (8a ₄ ). Similarly, the fan-shaped permanent magnet (8B) includes fan-shaped permanent magnet bodies (8b ₁ ) and (8b ₂ ) on the circumferential center side and fan-shaped nonmagnetic portions provided on both sides in the circumferential direction. (8b ₃ ) and (8b ₄ ), and the fan-shaped permanent magnet (8C) includes fan-shaped permanent magnet bodies (8c ₁ ) and (8c ₂ ) on the center side in the circumferential direction and both sides in the circumferential direction. The fan-shaped nonmagnetic portions (8c ₃ ) and (8c ₄ ) provided in The magnetization direction of the fan-shaped permanent magnet bodies (8a ₁ ), (8a ₂ ); (8b ₁ ), (8b ₂ ); (8c ₁ ), (8c ₂ ) is outward as shown in the figure. . The fan-shaped nonmagnetic portions (8a ₃ ), (8a ₄ ); (8b ₃ ), (8b ₄ ); (8c ₃ ), (8c ₄ ) are provided as ring spacers, for example, nonmagnetic stainless steel (SUS316). ) Etc. are used.

Similarly, the rear mirror magnetic field amplifying unit (7) of the mirror magnetic field amplifying unit 3 includes three fan-shaped permanent magnets (9A) and (9B) having a circumferential angle of 120 degrees as shown in FIG. 3 (c). , (9C). The fan-shaped permanent magnet (9A) includes fan-shaped permanent magnet bodies (9a ₁ ) and (9a ₂ ) on the center side in the circumferential direction and fan-shaped nonmagnetic portions (9a ₃ ) provided on both sides in the circumferential direction. ) And (9a ₄ ), and the fan-shaped permanent magnet (8B) is provided on the both sides in the circumferential direction of the fan-shaped permanent magnet bodies (9b ₁ ) and (9b ₂ ) on the center side in the circumferential direction. Fan-shaped non-magnetic portions (9b ₃ ) and (9b ₄ ). The fan-shaped permanent magnet (9C) is a fan-shaped permanent magnet body (9c ₁ ), (9c ₂ ) on the center side in the circumferential direction. And fan-shaped non-magnetic portions (9c ₃ ) and (9c ₄ ) provided on both sides in the circumferential direction. The magnetization directions of the fan-shaped permanent magnet bodies (9a ₁ ), (9a ₂ ); (9b ₁ ), (9b ₂ ); (9c ₁ ), (9c ₂ ) are inward as shown in the figure. . The fan-shaped non-magnetic portions (9a ₃ ), (9a ₄ ); (9b ₃ ), (9b ₄ ); (9c ₃ ), (9c ₄ ) are provided as ring spacers, such as non-magnetic stainless steel (SUS316). ) Etc. are used.

  As shown in FIGS. 3B and 3C, the fan-shaped permanent magnets (8A), (8B), and (8C) of the front mirror magnetic field amplification unit (6) are connected to the rear mirror magnetic field amplification unit (7). The positional relationship is shifted by 60 degrees in the circumferential direction with respect to the fan-shaped permanent magnets (9A), (9B), and (9C).

  The reason why the mirror magnetic field amplifying part (3) is divided into the front part and the rear part as described above is that the magnetization directions need to be different. With such a relationship in the magnetization direction, it is possible to obtain a large magnetic field strength by concentrating the magnetic lines of force. An annular fluororesin (Teflon (registered trademark)) plate having a thickness of about 3 mm is attached between the front mirror magnetic field amplification unit (4) and the rear mirror magnetic field amplification unit (5). By doing so, it is possible to prevent the magnets of the front and rear mirror magnetic field amplifying units (4) and (5) from rubbing with each other, thereby enabling smooth driving. Of course, driving is possible even without a fluororesin plate.

In addition, the hexapole permanent magnet (10) provided in the ECR ion source including the mirror magnetic field generator (1), which is an embodiment of the invention of this application, has, for example, 12 pieces having a magnetization direction as shown in FIG. These fan-shaped permanent magnets can be combined and integrated. The detailed relationship between the magnetization directions is shown in FIG. As shown in FIG. 5, the magnetization direction of the hexapole permanent magnet (10) as a whole is three inward (inner 1, inner 2, inner 3) and three outward (outer 1, outer 2, There is outside 3). For this reason, in the front and rear mirror magnetic field amplifying units (6) and (7), as shown in FIGS. 3 (b) and 3 (c), the direction is the same as the magnetization direction of the hexapole permanent magnet (10). fan-shaped permanent magnet body only partially _{(8a 1), (8a 2} ); (8b 1), (8b 2); (8c 1), (8c 2) and _{(9a 1), (9a 2} ); ( 9b ₁ ), (9b ₂ ); (9c ₁ ), (9c ₂ ), and the other portions are fan-shaped nonmagnetic parts (8a ₃ ), (8a ₄ ); (8b ₃ ), ( _{8b 4); (8c 3)} , (8c 4) and _{(9a 3), (9a 4} ); (9b 3), (9b 4); (9c 3), installed as a ring spacers (9c ₄₎ Yes. If a permanent magnet having a magnetization direction opposite to the magnetization direction of the hexapole permanent magnet (10) is installed, the demagnetization temperature of the hexapole permanent magnet (10) is lowered due to the characteristics of the permanent magnet. In the ECR ion source, it can be predicted that the temperature of the hexapole permanent magnet (10) closest to the plasma is most likely to rise. Therefore, the hexapole permanent magnet (10) having a high demagnetization temperature is desired in use. However, if the hexapole permanent magnet (10) is demagnetized, it must be remanufactured and replaced. In this case, a cost of several million yen is required at the present time. The demagnetization temperature is determined by the relationship with the coercive force, but the coercivity and magnetic field strength of the permanent magnet are approximately inversely proportional, and the magnet with strong coercive force (high demagnetization temperature) has low residual magnetic flux density. Therefore, a hexapole magnet cannot be selected simply by coercive force alone. Therefore, in order to increase the intensity of the mirror magnetic field by the fan-shaped permanent magnets (8) and (9) for amplifying the mirror magnetic field and to prevent the demagnetization temperature of the hexapole permanent magnet (10) from being lowered, The relationship between the magnetization directions of the fan-shaped permanent magnets (8) and (9) and the hexapole permanent magnet (10) is as shown in FIGS. 3 (b), 3 (c), and 5 (21) are layers for fixing the hexapole permanent magnet (10) so that it does not fall apart. For example, it is formed of stainless steel (SUS316 or the like). Can do. Further, (22) in FIG. 1 is a yoke for connecting the layer of the hexapole permanent magnet (10) (21 in FIG. 5) and the casing (12) collecting the mirror magnetic field generating part (2), for example, aluminum. Etc. can be formed.

  According to the above embodiment, when changing the intensity of the mirror magnetic field at the time of adjusting the ion source of the mirror magnetic field, the stepping motor (15) of the drive unit (14) is driven by the operation in the operation unit (not shown), and the ball screw (18). The fan-shaped permanent magnets (8A), (8B), (8C) and (9A), (9B), (9C) are moved by the required distance in the radial direction as shown in FIG. Can do. This makes it possible to vary the mirror magnetic field strength during ion source adjustment. Of course, it goes without saying that the same operation can be performed when the ion source is stopped.

  Next, examples of the invention of this application will be described, but this does not limit the invention of this application.

  A mirror magnetic field generator having a total length of 260 mm and an outer diameter of 262 mm as shown in FIG. 1 was produced. Each dimension is as follows. In addition, as a permanent magnet for generating a mirror magnetic field and a permanent magnet for amplifying a mirror magnetic field, N48H manufactured by Shin-Etsu Chemical Co., Ltd., which is a neodymium-based permanent magnet (NdFeB), is used. NdMH (NdFeB) manufactured by Shin-Etsu Chemical Co., Ltd. was used. In addition, stainless steel (SUS316) is used for the nonmagnetic part of the fan-shaped permanent magnet, SS400 is used for the iron yoke, and A5054 is used for the aluminum casing, and the mirror magnetic field generating permanent magnet and the hexapole permanent magnet are connected. Aluminum (A2017) was used for the yoke to be made.

Plasma chamber inner diameter 32mm, outer diameter 39mm, length 260mm
Hexapole permanent magnet inner diameter 41mm, outer diameter 102mm, length 120mm
For mirror magnetic field generation
Permanent magnet (front and rear) inner diameter 41mm, outer diameter 182mm, length 60mm
For mirror magnetic field amplification
Permanent magnet (front and rear) Inner diameter 116mm, outer diameter 182mm, length 55mm
Iron yoke inner diameter 182mm, outer diameter 222mm
Aluminum yoke inner diameter 222mm, outer diameter 262mm
With the configuration as described above, the six mirror magnetic field amplifying permanent magnets (fan-shaped) could be moved 50 mm at equal distances in the radial direction from the central axis of the ion source, as shown in FIG. FIG. 8 shows data of the mirror magnetic field strength ratio that accompanies the movement when moved by 50 mm in the radial direction.

  As mentioned above, although embodiment and the Example of invention of this application were described, it cannot be overemphasized that the invention of this application is not limited to these, and various aspects are possible about a detail.

  For example, as for the number of divisions of the mirror magnetic field amplifying permanent magnet and the means for driving in the radial direction, an appropriate number other than those described above and a driving mechanism can be adopted.

It is sectional drawing along the ion source central axis of the principal part of the ECR ion source containing the mirror magnetic field generator which is embodiment of invention of this application. (A) And (b) is the front view and side view of a mirror magnetic field generator, respectively. (A), (b), (c), (d) are AA 'sectional drawing, BB' sectional view, CC 'sectional view, DD' of FIG. 2 (a), respectively. It is line sectional drawing. FIG. 3 is a cross-sectional view taken along line E-E ′ of FIG. It is sectional drawing which shows the magnetization direction of a hexapole permanent magnet. It is sectional drawing which shows the magnetization direction of a hexapole permanent magnet in detail. It is sectional drawing perpendicular | vertical to an axial direction which shows the mode before and behind the drive of each fan-shaped permanent magnet of a front part and a rear mirror magnetic field amplification part. In an Example, it is a figure which shows the data of the mirror magnetic field strength ratio accompanying the movement at the time of moving each fan-shaped permanent magnet of a front part and a rear mirror magnetic field amplification part 50 mm in radial direction. It is sectional drawing along the axial direction which shows the structure of the conventional ECR ion source.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mirror magnetic field generator 2 Mirror magnetic field production | generation part 3 Mirror magnetic field amplification part 4 Front annular permanent magnet 5 Rear annular permanent magnet 6 Front mirror magnetic field amplification part 7 Rear mirror magnetic field amplification part 8 (8A, 8B, 8C) Fan-shaped permanent Magnet 9 (9A, 9B, 9C) Fan-shaped permanent magnet 10 Hexapole permanent magnet 11 Yoke 12 Casing 13 Mounting base 14 Drive unit 15 Stepping motor 17 Bevel gear 18 Ball screw

Claims (10)

An apparatus for generating a mirror magnetic field for plasma confinement used in an ECR ion source,
A mirror magnetic field generation unit configured to generate a mirror magnetic field, comprising a pair of annular permanent magnets spaced apart in the ion source central axis direction;
A mirror magnetic field amplification unit that is provided between a pair of annular permanent magnets of the mirror magnetic field generation unit and is configured by annularly arranging a plurality of fan-shaped permanent magnets, and amplifies the mirror magnetic field generated by the mirror magnetic field generation unit;
A fan-shaped permanent magnet moving means for moving each fan-shaped permanent magnet constituting the mirror magnetic field amplification unit in the radial direction with respect to the central axis of the ion source,
A mirror magnetic field generator characterized in that the mirror magnetic field intensity can be changed by the radial movement of each fan-shaped permanent magnet.   2. The mirror magnetic field generator according to claim 1, wherein the mirror magnetic field amplifying unit includes a front mirror magnetic field amplifying unit and a rear mirror magnetic field amplifying unit.   The fan-shaped permanent magnet of the mirror magnetic field amplifying unit is formed by dividing the annular structure into three, and each fan-shaped permanent magnet of the front mirror magnetic field amplifying unit is respectively corresponding to each fan-shaped permanent magnet of the rear mirror amplifying unit. 3. The mirror magnetic field generator according to claim 2, wherein the mirror magnetic field generator is arranged so as to be shifted 60 degrees in the circumferential direction.   Each fan-shaped permanent magnet of the mirror magnetic field amplifying unit is composed of a fan-shaped magnet main body and fan-shaped nonmagnetic portions that are provided on both sides in the circumferential direction and are half the size of the fan-shaped magnet main body. The mirror magnetic field generator in any one of Claim 1 to 3. The mirror magnetic field generator according to any one of claims 1 to 4,
An ECR ion source comprising an annular multipole permanent magnet disposed radially inward of a mirror magnetic field amplification unit.   6. The ECR ion source according to claim 5, wherein the multipole permanent magnet is a hexapole permanent magnet. A method of generating a mirror magnetic field for plasma confinement used in an ECR ion source,
In order to generate a mirror magnetic field, a mirror magnetic field amplifying permanent magnet for amplifying the generated mirror magnetic field is provided between a pair of mirror magnetic field generating annular permanent magnets spaced apart in the ion source central axis direction,
As a permanent magnet for amplifying a mirror magnetic field, use a structure in which a plurality of fan-shaped permanent magnets that can move in the radial direction with respect to the central axis of the ion source are arranged in an annular shape,
A method of generating a mirror magnetic field, characterized in that the mirror magnetic field strength can be changed by moving each fan-shaped permanent magnet in the radial direction with respect to the central axis of the ion source.   8. The method of generating a mirror magnetic field according to claim 7, wherein the mirror magnetic field amplifying permanent magnet is divided into a front part and a rear part.   As the fan-shaped permanent magnet constituting the mirror magnetic field amplifying permanent magnet, the annular structure is divided into three parts, and the front fan-shaped permanent magnets are arranged in the circumferential direction with respect to the rear fan-shaped permanent magnet. 9. The method for generating a mirror magnetic field according to claim 8, wherein the mirror magnetic fields are arranged so as to be shifted by 60 degrees.   Each fan-shaped permanent magnet of the mirror magnetic field amplifying unit is composed of a fan-shaped magnet body and fan-shaped nonmagnetic portions that are provided on both sides in the circumferential direction and are half the size of the fan-shaped magnet body. The method of generating a mirror magnetic field according to claim 7.

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