JPH05215900A - Multi-pole electromagnet for electron accelerator - Google Patents

Abstract

(57) [Abstract] [Purpose] To eliminate the spatial interference with the synchrotron radiation extraction pipe of the deflection electromagnet without disturbing the multipole magnetic field in the bore. [Structure] A quadrupole electromagnet 40 as a multipole electromagnet includes a yoke 41 having a substantially ring-shaped radial cross section, and the yoke 41.
4 magnetic cores 42 that are integrally projected from the inside to the inside at an equal angle,
42, 42L, 42L and this magnetic core 42, 42, 42
Excitation coils 43 ... 43 individually wound around L and 42L. Thereby, the magnetic poles P _{1 to} P ₄ are formed. The portion between the magnetic poles P ₃ and P _{4 of the} yoke 41 (the portion along the radial direction of the orbit of the electron beam) is cut off. Magnetic pole P ₃ ,
The width of the magnetic cores 42L, 42L of P ₄ is made wider than the magnetic cores 42, 42 of the other magnetic poles P ₁ , P ₂ in the cross section in the yoke radial direction. The shapes of the tip surfaces of all the magnetic cores 42, 42, 42L, 42L maintain a hyperbolic curved surface based on the bore radius R ₀ .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-pole electromagnet of an electron accelerator used for VLSI microfabrication, and more particularly,
The present invention relates to a structure improvement of a multi-pole (four-pole, six-pole, eight-pole, etc.) electromagnet capable of eliminating spatial interference with a pipe for extracting radiated light from a bending electromagnet installed in an electron accelerator.

[0002]

2. Description of the Related Art First, an example of the entire structure of a conventional electron accelerator will be described with reference to FIG. The electron accelerator shown in FIG. 7 has a linear accelerator 1 that generates and accelerates electrons, a transport tube 2 that guides the electron beam output from the linear accelerator 1, and an electron beam that has been transported by the transport tube 2. The injector 3 that leads to the orbit OB and the ring-shaped vacuum duct 4 that forms the circular orbit OB with the injector 3 partially inserted are provided. The vacuum duct 4 is maintained in an ultra-high vacuum state, which prevents the electron beam from colliding with the residual gas and causing energy loss.

A high-frequency resonance cavity 5 for accelerating the beam incident from the linear accelerator 1 is inserted in the vacuum duct 4, and a plurality of deflection electromagnets 6 ... 6 for deflecting the electron beam and an electron beam. A plurality of quadrupole electromagnets 7 ... 7, which play a role of converging and diverging, and a plurality of sextupole electromagnets 8 ... 8 and one 8 which prevent the beam from becoming unstable, for example, due to energy shift between electrons during the beam circulation. A polar electromagnet 9 is inserted as shown. These multi-pole (four-pole, six-pole, eight-pole) electromagnets 7 ... 9 are arranged at positions close to the deflection electromagnets 6 ... 6, respectively.

The emitted light is emitted in the tangential direction of the deflection orbit when electrons are deflected by the deflection electromagnets 6 ..., and is used for various purposes such as VLSI microfabrication and physical property research. Therefore, the deflection electromagnets 6 ... 6 are provided with pipes (not shown) for taking out the radiated lights RA ... RA (see arrows in FIG. 7) in the tangential direction of the deflection orbit of the circular orbit OB which is curved at the radius of curvature ρ. It is connected. It should be noted that, of the deflecting electromagnets 6 ... 6 in FIG. 7, the radiated light RA is not shown to the deflecting electromagnet 6 closer to the linear accelerator 1, but the upper side or the lower side of the linear accelerator 1 in the direction orthogonal to the plane of the drawing is not shown. Similarly, a pipe for extracting synchrotron radiation can be installed by moving the pipe to.

Next, a concrete structure of the multi-pole electromagnets 7, 8 and 9 will be described with reference to FIGS.

FIG. 8 shows VII-VI of the quadrupole electromagnet 7 in FIG.
A cross-sectional view taken along line I is shown. This quadrupole electromagnet 7 has a vacuum duct 4
Therefore, it also has a cross section orthogonal to the circular orbit OB, and has a structure in which the vacuum duct 4 penetrates through the central portion in the axial direction. That is, a yoke 11 having a substantially octagonal radial cross section, four magnetic cores 12 ... 12 integrally projecting radially inward of the yoke 11 at equal angles, and the magnetic cores 12 ... Exciting coils 13 ... 13 individually wound. The center of the tip of each magnetic core 12 is rounded in contact with an imaginary circle having a bore radius R _{0 in} the radial cross section of the yoke, and the shape of this roundness is given by a hyperbola of 2XY = R ₀ ^2. ing. Here, X and Y are the abscissa and ordinate of the two-dimensional coordinate specified with the position (center point) where the electron beam passes in the direction perpendicular to the paper surface as the origin O, and the direction of the abscissa X is the electron. It corresponds to the radial direction of the circular orbit of the beam. Angle of the center axis in the yoke radial section of the magnetic core 12 ... 12 (i.e. axial contact points forms the origin O of the virtual circle of the bore radius R ₀ in its cross-section), respectively, 45 °, 13
They are equiangular at 5 degrees, 225 degrees, and 315 degrees. Further, the widths of the yoke core radial direction cross sections of the magnetic cores 12 ... 12 are all equal and set to a predetermined value in consideration of a space around which the exciting coil 13 is wound. As a result, when a current is supplied to each exciting coil 13 in a predetermined direction, magnetic field lines M ... M pass as schematically shown by dotted arrows in the drawing, and a magnetic field symmetrical vertically and horizontally in the radial section of the yoke. It is formed.

The distribution of the magnetic field By thus formed in the Y-axis direction in the Y = 0 plane of the magnetic field thus formed is shown in FIG. The gradient of the Y-axis direction magnetic field By, that is, dBy / dX, represents the quadrupole magnetic field component. The larger the area of the magnetic pole surface (that is, the front end surface of the magnetic core 12) according to the above equation, the more the ideal quadrupole magnetic field as shown in FIG.

Similarly, the sextupole electromagnet 8 will be described.
FIG. 10 is a sectional view taken along line IX-IX of the sextupole electromagnet 8 in FIG. The sextupole electromagnet 8 has a yoke 21 having a substantially dodecagonal radial cross section, and six magnetic cores 22 ... 22 integrally projecting at an equal angle toward the inside in the radial direction of the yoke 21. Excitation coils 23 ... 2 individually wound around the magnetic cores 22 ... 22
3 and 3. The rounded shape of the tip of each magnetic core 22 is
It contacts an imaginary circle of radius R ₀ and “3X ² Y−Y ³ = R ₀
^It has the shape given by the formula of " ³ ". Each magnetic core 22 ...
The mounting angles of 22 (angles of the axis formed by the origin O at the point of contact with the virtual circle having the bore radius R ₀ ) are 30 ° and 90 °, respectively.
The angles are equal to 150 degrees, 210 degrees, 270 degrees and 330 degrees. Other configurations are similar to those of the quadrupole electromagnet 7. Thereby, when each exciting coil 23 is excited in a predetermined direction, a magnetic field of magnetic force lines M ... M schematically shown by a dotted arrow in the drawing is formed.

The distribution of the magnetic field By thus formed in the Y-axis direction in the Y = 0 plane of the magnetic field is shown in FIG. Second-order differential of magnetic field By in the Y-axis direction, that is, d ² By /
dX ² represents the sextupole magnetic field component.

Further, similarly, the octupole electromagnet 9 will be described. FIG. 12 is a sectional view taken along line XI-XI of the octapole electromagnet 9 in FIG. The octapole electromagnet 9 has a radial cross section of approximately 16
A rectangular yoke 31 and eight magnetic cores 32 ... 32 that are integrally projected at an equal angle toward the inside of the yoke 31 in the radial direction.
32, and exciting coils 33 ... 33 individually wound around the magnetic cores 32. The rounded shape of the tip of each magnetic core 32 is in contact with an imaginary circle having a radius R ₀ and is “4X ³ Y-4”.
The shape is determined by the formula of "XY ³ = R ₀ ⁴ ". The mounting angles of the magnetic cores 32 ... 32 (the angle of the axis formed by the origin O at the point of contact with the virtual circle having the bore radius R ₀ ) are 22.5, respectively.
Degrees, 67.5 degrees, 112.5 degrees, 157.5 degrees, 20
2.5 degrees, 247.5 degrees, 292.5 degrees and 337.5 degrees
They are equiangular in degrees. Other configurations are similar to those of the quadrupole electromagnet 7 and the hexapole electromagnet 8. This allows
When each exciting coil 33 is excited in a predetermined direction,
A magnetic field of magnetic force lines M ... M schematically shown by a dotted arrow is formed.

The distribution of the magnetic field By thus formed in the Y-axis direction on the Y = 0 plane of the magnetic field thus formed is shown in FIG. Third-order differentiation of the magnetic field By in the Y-axis direction, that is, d ³ By /
dX ³ represents the octupole magnetic field component.

[0012]

However, since the arrangement positions of the above-mentioned multi-pole electromagnets 7 to 9 are very close to the deflection electromagnets 6 ... 6, a pipe for taking out radiation light of the deflection electromagnet 6 is used. Yokes 11, 2 of those multi-pole electromagnets 7-9
1 and 31 spatially interfere with each other, and the pipe mounting angle is restricted. For example, in the example of FIG. 7 described above, the emitted light is naturally emitted over all deflection angles (in the figure, 90 degrees with the incident side being 0 degree), one of the deflection electromagnets 6 in the figure is used. Since the angle at which the radiated light can be taken out is at most 60 degrees, the pipe cannot be attached to the remaining range of about 30 degrees. In other words, since there is such an unusable angle range, there is a problem in that the utilization rate of emitted light is significantly reduced.

Further, due to the unusable angular range, miniaturization of the electron accelerator has been hindered. In other words, the more we try to miniaturize the entire electron accelerator,
Inevitably, the space between the electromagnets becomes narrower, and the range of angles in which the emitted light can be taken out becomes narrower, and the poor utilization becomes noticeable.

The present invention has been made in view of the inconveniences of the prior art described above, and has a structure that does not restrict the angle range of radiation of emitted light from the deflecting electromagnet, and it is possible to increase the utilization rate of the emitted light in many electron accelerators. It is an object to provide a polar electromagnet.

[0015]

In order to achieve the above object, a multi-pole electromagnet of an electron accelerator according to the present invention allows an electron orbit to pass through a central portion of an axial bore and has a radial cross section. A yoke arranged so as to be orthogonal to the orbit, and an even number of four or more magnetic cores protruding from this yoke toward the orbiting orbit at the center at equal angles, and the even number of magnetic cores individually. A winding exciting coil is provided, and the tip surfaces of the even number of magnetic cores facing the orbits are formed into curved surfaces based on a predetermined bore radius. Furthermore, of the above yokes,
The connecting portion between the magnetic cores located in the radial direction of the orbit is cut off, and the width in the cross section of the magnetic core adjacent to the cut yoke portion is increased while maintaining the curved state of the magnetic core tip based on the bore radius. I am letting you.

The number of magnetic poles composed of the magnetic core and the exciting coil is any one of 4, 6, and 8, for example.
When the number of magnetic poles is 4N (N = 1, 2, 3 ...), the cut-out portion of the yoke is at two locations where the radial axis of the orbit of the electron intersects with the yoke. At least one of the yoke parts of. The number of magnetic poles is 4N + 2
In the case of (N = 1, 2, 3 ...), the cut-off portion of the yoke is
It is either one of two yoke portions where the radial axis of the orbit of the electron intersects with the yoke.

[0017]

In the multipolar electromagnet of the electron accelerator according to the present invention, the magnetic lines of the two magnetic poles adjacent to the cut-off portion of the yoke are not divided because the shortest magnetic path is divided. Is used as the magnetic path (at this time, if the yoke part on the opposite side located via the bore in the center part is also cut off, the magnetic flux is integrated with both magnetic poles adjacent to the cut part on the opposite side. Configure the road). Therefore, the magnetic path of the magnetic pole adjacent to the cut portion becomes long, and the magnetic resistance increases by that amount, but the magnetic resistance decreases by that amount because the width of the magnetic core is wide. As a result, the total magnetic resistance of the magnetic poles adjacent to the cut portion is almost the same as that in the case where the magnetic pole is not cut, and therefore the magnetic field in the bore is not disturbed. Further, the shape of the tip end surface on the bore side of the magnetic core adjacent to the excised portion complies with the equation for forming a multipolar magnetic field derived from the bore radius. Therefore, a good multipole magnetic field is formed in the bore. In addition, since it is possible to position the pipe for extracting the radiated light from the bending electromagnet in the empty space where the yoke is removed,
As in the prior art, the pipe and the multi-pole electromagnet hardly interfere spatially, and the mountable angle range of the pipe remarkably expands. As a result, a sufficient radiant light extraction angle range can be secured without magnetically adversely affecting the beam, and the utilization rate of the radiated light can be significantly increased.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. It should be noted that the same components as those of the related art are denoted by the same reference numerals, and the description thereof will be omitted.

(First Embodiment) A first embodiment will be described with reference to FIG. A quadrupole electromagnet 40 is shown in FIG. The quadrupole electromagnet 40 is attached to the electron accelerator shown in FIG. 7, and its attachment position is also the same as that of the quadrupole electromagnet 7. Therefore, FIG. 1 shows a cross section equivalent to the line VII-VII in FIG.

The quadrupole electromagnet 40 shown in FIG. 1 has a cross section orthogonal to the vacuum duct 4, that is, the orbit OB of the electron beam, and has a structure in which the vacuum duct 4 penetrates through the center thereof. That is, a ring-shaped yoke 41 having a substantially octagonal radial cross-section and partly removed, and four magnetic cores 42 integrally projecting from the yoke 41 toward the inner side in the radial direction at an equal angle, 42, 42L, 42L and this magnetic core 42,
42, 42L, Excitation coil 4 individually wound around 42L
3 ... 43. Therefore, the exciting coil 43 ...
When a current in a predetermined direction is supplied to 43, four magnetic poles P _{1 to} P ₄ are formed as shown in FIG.

Here, the symbols X and Y in the figure are the positions O of the electron beam passing in the direction perpendicular to the paper surface, as in the conventional case.
The horizontal axis of the two-dimensional coordinates specified with the (center point) as the origin,
It is the vertical axis and the direction of the horizontal axis X corresponds to the radial direction of the orbit of the electron beam.

The magnetic pole P _{3 of} the yoke 41 intersecting the horizontal axis X,
The connecting portion between P ₄ is partially cut off as shown in FIG. 1. To compensate the disturbance of the magnetic field in the bore with this resection of the pole _P 1 to P _4, the magnetic core of the magnetic poles _P 3, _{P 4} 42L
The width (hereinafter, referred to as lateral width) Wb of the yoke 41 in the radial direction is formed wider than the lateral width Wa of the magnetic poles P ₁ and P _{2 by} a predetermined value (Wb> Wa). The magnetic core portions in which the lateral widths of the magnetic poles P ₃ and P ₄ are widened are formed in such a state that the magnetic core portions are projected to the cutting side. However, the magnetic pole P
_Even if the exciting coils 43, 43 are wound between ₃ and P ₄ , a predetermined empty space is still formed.

The lateral widths Wa and Wb of the magnetic cores 42, 42, 42L and 42L are the same from the root to the tip. Then, the tip surfaces of the magnetic cores 42, 42, 42L, 42L are
In the radial cross section of the yoke 41, the yoke 41 has a rounded shape that is in contact with an imaginary circle having a bore radius R ₀ .

## EQU1 ## 2XY = R ₀ ² is given by the hyperbola of Expression 1. Magnetic cores 42, 42, 42L,
The angles of the axes formed by the origin O and the point where 42L contacts the virtual circle having the bore radius R ₀ are 45 degrees and 13 degrees, respectively, as in the conventional case.
They are equiangular at 5 degrees, 225 degrees, and 315 degrees.

Next, the function and effect of the first embodiment will be described.

When a direct current is supplied to the above-mentioned exciting coils 43 ... 43 in a predetermined direction, as shown in FIG.
A pole is generated and magnetic poles P _{1 to} P ₄ are formed. This magnetic pole P
_{Due to 1 to} P ₄ , magnetic force lines pass as schematically shown by dotted lines Ma to Md in the figure. Among these, the magnetic force lines Ma generated by the magnetic poles P ₄ and P ₁ and the magnetic force lines M generated by the magnetic poles P ₁ and P ₂
The magnetic field line Mc generated by b and the magnetic poles P ₂ and P ₃ flows through the yoke portion connecting the adjacent magnetic poles as in the conventional case. However, the magnetic force line Md generated by the magnetic poles P ₃ and P ₄
, The yoke portion connecting them at the shortest distance is divided, so that it passes through the yoke portion on the side of the magnetic poles P ₁ and P ₂ on the opposite path to form a closed magnetic circuit.

That is, the magnetic path length of the magnetic force line Md is longer than that of the other three magnetic force lines Ma to Mc. Therefore, if the magnetic poles P ₃ and P ₄ are set to have the same width as the other magnetic poles P ₁ and P ₂ without being widened, the magnetic path becomes longer and the magnetic resistance becomes larger. The magnetic field in the bore generated in the minus region of X is disturbed.

However, in this embodiment, the magnetic poles P ₃ , P ₄
On the other hand, since the rounded shape of the tip end face is regulated by the formula 1 and the lateral width is made thicker in the entire longitudinal direction of the magnetic core, the magnetic resistance with respect to the magnetic force line Md is almost the same as when the conventional yoke is not removed. The magnetic field is not disturbed in the minus region of the horizontal axis X in the bore. In addition, each magnetic pole P ₁ ~
The contact position with the bore radius of P ₄ maintains the same angle as in the conventional case, and the increased curvature of the tip surface is also set according to the above equation 1, so that the ideal position is almost the same as that shown in FIG. Quadrupole magnetic field is formed in the vacuum duct 4 orthogonal to the electron beam. Therefore, it is possible to exert a predetermined electromagnetic force and achieve the intended purpose of the beam movement without magnetically adversely affecting the electron beam.

As described above, even when a part of the yoke 41 is cut off, a good quadrupole magnetic field can be formed in the bore at the center thereof as in the conventional case, and the cut yoke part becomes an empty space. Therefore, there is no problem even if the radiation light extraction pipe PP attached to the deflection electromagnet 6 shown in FIG. 7 is arranged in the empty space portion (see FIG. 1).
The restrictions on the mounting angle of the pipe and the mounting position of the pipe are greatly relaxed, and the problem of interference as in the past is almost eliminated. As a result, the vacant space and the space outside the space can be effectively used, and the utilization rate of radiated light can be significantly improved.

On the other hand, when downsizing the entire electron accelerator,
Although the distance between the electromagnets becomes smaller and smaller, even in that case, the installation angle range of the synchrotron radiation extraction pipe can be widened at the part where the yoke is removed while maintaining the same operating condition as before, maintaining high performance. It is possible to reduce the size.

(Second Embodiment) A second embodiment will be described with reference to FIG. The quadrupole electromagnet 45 shown in FIG. 2 is also attached to the electron accelerator in the same manner as the quadrupole electromagnet 40 of the first embodiment. The same components as those in the first embodiment are designated by the same reference numerals.

The quadrupole electromagnet 45 according to the second embodiment is
The yoke 41 applied to the first embodiment is excised on both left and right sides in the drawing in the X-axis direction. That is, the magnetic poles P ₁ , P in the plus direction of the X axis of the yoke 41 in the first embodiment.
By cutting between the _two , the yoke has a divided structure of an upper yoke 41a and a lower yoke 41b as shown in FIG. Therefore, not only the magnetic poles P ₃ and P ₄ but also the magnetic cores 42L and 42L of the magnetic poles P ₁ and P ₂ facing the newly cut right side portion are the first
The width is wide as in the embodiment. The other configurations are the same as those in the first embodiment.

Therefore, the magnetic force line Ma between the magnetic poles P ₄ and P _{1 is}
And the magnetic field lines Mc between the poles _P 2, _{P 3} the first embodiment, i.e., generated in a conventional manner pole _P 1, _{P 2} and between the magnetic poles P
The magnetic lines of force between ₃ and P ₄ are both generated in the counterclockwise direction in FIG. 2, so that the same magnetic path is formed in cooperation with each other, and the upper yoke 41a and the lower yoke 41a are formed as indicated by the dotted line Me in the drawing. It becomes a long magnetic circuit that goes around the outer circumference of 41b. Even in this case, each magnetic pole P
_Due to the fact that the lateral width of _{1 to} P ₄ is widened to reduce the magnetic resistance and the shape of the tip surface is a prescribed curved surface, a good quadrupole magnetic field can be obtained over both positive and negative regions of the X axis in the bore. Is formed. At the same time, since both sides of the quadrupole electromagnet 45 facing each other in the radial direction of the electron beam are cut off, it is possible to increase the utilization rate of the radiated light by utilizing the vacant spaces of both of them and to prevent interference with other devices. Can also be eliminated.

(Third Embodiment) A third embodiment will be described with reference to FIG. FIG. 3 shows a sextupole electromagnet 50. The sextupole electromagnet 50 is attached to the electron accelerator shown in FIG. 7, and its mounting position is also the same as that of the sextupole electromagnet 8. Therefore, FIG. 3 shows a cross section equivalent to the line IX-IX in FIG. 7.

The sextupole electromagnet 50 shown in FIG. 3 has a ring-shaped yoke 51 with a substantially dodecagonal radial cross section and a part cut off, and an equal angle from the yoke 51 toward the inside in the radial direction. Six magnetic cores 52 ... 52, 52L, which are provided integrally with each other,
52L and excitation coils 53 ... 53 individually wound around the magnetic cores 52 ... 52, 52L, 52L. Therefore, the six magnetic poles P _{1 to} P ₆ are formed as illustrated.

The magnetic pole P _{5 of} the yoke 51 intersecting the horizontal axis X,
The connecting portion between P ₆ is partially cut off as shown in the figure. To compensate for the disturbance of the magnetic field of the bore due to this ablation,
Pole _P 5, core 52L of the horizontal width of the _{P 6} is other pole _P 1 ~
It is formed wider than that of P _{4 by} a predetermined value. Further, each tip end surface of the magnetic cores 52 ... 52, 52L, 52L is rounded in contact with an imaginary circle having a bore radius R _{0 in} the radial cross section of the yoke 51, and this rounded shape is different from the conventional shape. Similarly,

## EQU2 ## 3X ² Y-Y ³ = R ₀ ³ ... The angles of the axes formed by the origin O and the point where the magnetic cores 52 ... 52, 52L, 52L contact the virtual circle of the bore radius R ₀ are 30 °, 90 °, 1 respectively, as in the conventional case.
The angles are equal to 50 degrees, 210 degrees, 270 degrees and 330 degrees.

Therefore, the magnetic force lines Ma of the magnetic poles P _{1 to} P ₆ are
~ Mf is as shown by the dotted line, and the magnetic pole P facing the excised portion
Only the magnetic path length of the magnetic field lines Mf of ₅ and P ₆ becomes long. However, because of the wide core 52L of the horizontal width of the pole P _5, P _6, overall almost unchanged reluctance and conventionally, moreover, the magnetic pole surface of each pole P ₁ to P _6, i.e. cores 52 ... 52,
Since the shapes of the tip surfaces of 52L and 52L are set by the equation 2, the magnetic field in the X-axis minus region in the bore is not disturbed, and a substantially ideal hexapole magnetic field is formed as in FIG. .. At the same time, arbitrarily set the radiation port of the deflection electromagnet, can withdraw pipe empty space between the pole P _5, P _6, can be effectively utilized the free space.

(Fourth Embodiment) A fourth embodiment will be described with reference to FIG. An octupole electromagnet 60 is shown in FIG. The octupole electromagnet 60 is attached to the electron accelerator shown in FIG. 7, and its attachment position is also the same as that of the octupole electromagnet 9. Therefore, FIG. 4 shows a cross section equivalent to the line XI-XI in FIG. 7.

The octupole electromagnet 60 shown in FIG. 4 has a ring-shaped yoke 61 which is formed by passing the vacuum duct 4 through the central portion thereof and has a radial cross section of a substantially hexagonal shape and part of which is cut off.
62, 62L, 62L and eight magnetic cores 62 ... 62, 62L, 62L integrally projecting from 1 toward the inner side in the radial direction, and the exciting coils 63 individually wound around the magnetic cores 62, 62, 62L, 62L. And 63. Therefore, eight magnetic poles P _{1 to} P ₈ are formed as shown in the figure.

The magnetic pole P _{7 of} the yoke 61 intersecting the horizontal axis X,
The connecting portion between P ₈ is partially cut off as shown in the figure. To compensate for the disturbance of the magnetic field of the bore due to this ablation,
The lateral width of the magnetic core 62L of the magnetic poles P ₇ and P ₈ is equal to that of the other magnetic poles P ₁ to
It is formed wider than that of P _{6 by} a predetermined value. Further, each of the tip end surfaces of the magnetic cores 62 ... 62, 62L, 62L has a rounded shape in contact with a virtual circle having a bore radius R _{0 in} the radial cross section of the yoke 61, and this rounded shape is different from the conventional shape. Similarly,

## EQU3 ## 4X ³ Y-4XY ³ = R ₀ ⁴ Equation 3 is given. The angles of the axes formed by the origin O and the point where the magnetic cores 62 ... 62, 62L, 62L contact the virtual circle of the bore radius R ₀ are 22.5 degrees and 67.5, respectively, as in the conventional case.
Degrees, 112.5 degrees, 157.5 degrees, 202.5 degrees, 24
It is equiangular at 7.5 degrees, 292.5 degrees and 337.5 degrees.

Therefore, the magnetic force lines Ma of the magnetic poles P _{1 to} P ₈ are
Mh is as shown by the dotted line, and only the magnetic path length of the magnetic force line Mh of the magnetic poles P ₇ and P ₈ facing the cut portion is increased. However, because of the wide width of the core 62L of the pole P _7, P _8, overall almost unchanged reluctance and conventionally, moreover, the magnetic pole surface of each pole P ₁ to P _8, i.e. the magnetic core 62 ... 6
Since the shapes of the tip surfaces of 2, 62L and 62L are set by the equation 3, the magnetic field in the X-axis negative region in the bore is not disturbed, and an almost ideal octupole magnetic field is formed as in FIG. To be done. At the same time, the vacant space between the magnetic poles P ₇ and P ₈ can be used to increase the utilization rate of the emitted light.

(Fifth Embodiment) A fifth embodiment will be described with reference to FIG. The octupole electromagnet 65 shown in FIG. 5 is also attached to the electron accelerator in the same manner as the octupole electromagnet 60 of the fourth embodiment. The same components as those in the fourth embodiment are designated by the same reference numerals.

The octupole electromagnet 65 of the fifth embodiment has a fourth
The yoke 61 applied to the embodiment is cut off on both the minus and plus sides in the figure in the X-axis direction. That is, in addition to the cutting of the fourth embodiment, the yoke 61 is cut by cutting the yoke connecting portion between the magnetic poles P ₃ and P _{4 in the} positive direction of the X-axis, so that the yoke 61, as shown in FIG. Lower yoke 6
It has a division structure of 1b. Therefore, not only the magnetic poles P ₇ and P ₈ but also the magnetic poles P ₃ and P ₄ facing the newly cut right side portion
The magnetic cores 62L and 62L have a wide width similarly to the fourth embodiment. The other structure is the same as that of the fourth embodiment.

Therefore, with respect to the magnetic poles P ₃ , P ₄ , P ₇ , and P ₈ , unlike the other magnetic poles, the path of the magnetic line of force Mi having a long magnetic path is integrally formed in the clockwise direction. Even in this case, since the lateral width of the magnetic core 62L is widened and the magnetic resistance is reduced, and the shape of the tip surface is a prescribed curved surface, it is possible to achieve good performance in both plus and minus regions of the X axis in the bore. An octupole magnetic field is formed. at the same time,
Since the right and left X-axis directions of the octupole electromagnet 65 are cut off,
By utilizing both of these empty spaces, it is possible to improve the utilization efficiency of the radiated light and eliminate interference with other devices.

In the above-mentioned embodiments, three types of multipole electromagnets, four poles, six poles and eight poles are described, but other multipole electromagnets having four or more poles are also applicable.
In that case, in a multipole electromagnet having 4N (N = 1, 2, 3 ...) Pole, as shown in FIGS. 1 and 4, only one side in the X-axis direction (that is, the radial direction of the orbit of the electron beam). A structure in which the yoke is removed and the lateral width of each magnetic pole facing the removed portion is widened, and as shown in FIGS. 2 and 5, the yokes on both the left and right sides in the X-axis direction are removed and both of them are removed. Both modes, that is, a structure in which the lateral width of each magnetic pole facing the cut portion is widened, can be adopted as necessary. Furthermore, 4N + 2 (N =
1, 2, 3 ...) multi-pole electromagnets, as shown in FIG. 3, a structure in which a yoke on only one side in the X-axis direction is cut off and the lateral width of each magnetic pole facing the cut-out portion is widened is adopted. Can be taken. The reason why the 4N + 2 multi-pole electromagnet is limited to the excision on only one side is that the directions of the magnetic force lines of the two magnetic poles facing each other in both directions of the X axis are different from each other.

Further, in the above-mentioned embodiment, the width of the magnetic core of the magnetic pole on the XY plane is constant in the radial direction of the yoke. For example, the magnetic core 72L shown in FIG. 7
(1 is a part of the yoke, 73 is an exciting coil), the middle part of the body has a narrow width similar to the conventional one, and the tip side and the root side are set to a wide width that can reduce the magnetic resistance to a predetermined value. You may.

[0046]

As described above, the multi-pole electromagnet of the electron accelerator according to the present invention cuts off the yoke connecting portion between the magnetic cores along the radial axis of the orbit of the electron beam to reduce the bore radius. Since the width of the magnetic core adjacent to the excised yoke portion was increased while maintaining the curved state of the magnetic core tip determined based on the above, the magnetic path of the magnetic force line from the magnetic pole adjacent to the excised portion became a detour and the magnetic resistance The increase in the magnetic field can be offset by the decrease in the magnetic resistance due to the width of the magnetic core, and the total magnetic resistance can be kept almost constant, so that the magnetic field in the bore is not disturbed and the tip of the magnetic core on the bore side does not occur. Since the shape keeps a predetermined curved surface, an almost ideal multi-pole magnetic field can be formed, so that the moving state of the circulating electron beam can be kept good. On the other hand, by cutting a part of the yoke, it becomes possible to position the radiated light extraction pipe extending from the deflection electromagnet in the empty space of the cut part, and the space interference between the pipe and the yoke which has been seen in the past can be prevented. The emitted light can be removed from any position of the deflection angle of the deflection electromagnet, and the utilization rate of the emitted light can be significantly increased. In this way, since the electron accelerator has the same performance as that of the conventional electron accelerator and the utilization rate of the synchrotron radiation is increased, it is possible to provide the electron accelerator having high investment efficiency. Further, even when the electron accelerator is miniaturized, by utilizing the multi-pole electromagnet of the present invention, it is possible to minimize the deterioration of the utilization rate of synchrotron radiation, so that it is possible to reduce the cost by miniaturizing while maintaining high performance. Can be realized.

[Brief description of drawings]

FIG. 1 is a cross section of the quadrupole electromagnet of the first embodiment (VII- in FIG. 7).
Sectional view showing a section corresponding to the line VII).

FIG. 2 is a cross section of the quadrupole electromagnet of the second embodiment (VII- in FIG. 7).
Sectional view showing a section corresponding to the line VII).

FIG. 3 is a cross section of the sextupole electromagnet of the third embodiment (IX-I in FIG. 7).
A cross-sectional view showing (corresponding to a cross section along the X-ray).

FIG. 4 is a cross section of the octapole electromagnet of the fourth embodiment (XI-X in FIG. 7).
A sectional view showing (corresponding to a section taken along line I).

FIG. 5 is a cross section of the octapole electromagnet of the fifth embodiment (XI-X in FIG. 7).
A sectional view showing (corresponding to a section taken along line I).

FIG. 6 is a partial cross-sectional view showing another example of magnetic poles.

FIG. 7 is a system configuration diagram showing the entire electron accelerator.

FIG. 8 is a sectional view taken along line VII-VII in FIG. 7, showing a conventional quadrupole electromagnet.

FIG. 9 is a graph showing a magnetic field distribution of a quadrupole electromagnet.

FIG. 10 is a sectional view taken along line IX-IX in FIG. 7, showing a conventional sextupole electromagnet.

FIG. 11 is a graph showing a magnetic field distribution of a sextupole electromagnet.

FIG. 12 is a sectional view taken along line XI-XI in FIG. 7, showing a conventional octupole electromagnet.

FIG. 13 is a graph showing a magnetic field distribution of an octupole electromagnet.

[Explanation of symbols]

 4 vacuum duct 40,45 quadrupole electromagnet 41 yoke 41a, 41b upper side, lower yoke 42,42L magnetic core 43 exciting coil 50 six-pole electromagnet 51 yoke 52,52L magnetic core 53 exciting coil 60,65 octapole electromagnet 61 continuous iron 61a, 61b Upper and lower yokes 62, 62L Magnetic core 63 Excitation coil 71 Yoke 72L Magnetic core 73 Excitation coil

Claims (4)

[Claims] 1. A yoke arranged so as to pass an orbit of electrons through a central portion of an axial bore and a radial cross section thereof is orthogonal to the orbit, and from the yoke to the orbit of the central portion. Equipped with four or more even numbered magnetic cores projecting at equal angles toward each other, and an exciting coil individually wound around the even numbered magnetic cores, and the tip surface of the even numbered magnetic cores facing the orbit. A curved surface based on a predetermined bore radius, in a multi-pole electromagnet of an electron accelerator, in the yoke, the connecting portion between the magnetic cores located in the radial direction of the orbit is cut off, based on the bore radius. A multipolar electromagnet for an electron accelerator, wherein the width of the magnetic core adjacent to the excised yoke portion is increased while maintaining the curved state of the magnetic core tip. 2. The multi-pole electromagnet for an electron accelerator according to claim 1, wherein the number of magnetic poles composed of the magnetic core and the exciting coil is any one of 4, 6, and 8. 3. When the number of magnetic poles consisting of the magnetic core and the exciting coil is 4N (N = 1, 2, 3 ...), the cut-out portion of the yoke is the radial axis of the orbit of the electron and the The multi-pole electromagnet for an electron accelerator according to claim 1, wherein at least one of the two yoke portions where the yoke intersects is provided. 4. When the number of magnetic poles composed of the magnetic core and the exciting coil is 4N + 2 (N = 1, 2, 3 ...), the cut-out portion of the yoke is the radial axis of the orbit of the electron and the The multi-pole electromagnet for an electron accelerator according to claim 1, wherein one of the two yoke portions intersecting with the yoke is one of them.