JPH05258896A - Wiggler magnet - Google Patents

Abstract

PURPOSE:To provide a convergence type wiggler magnet reducing the precision relaxation of the material, magnetization, and machining of a magnet group constituting the wiggler magnet and the reduction of the converging force due to the magnetic field intensity adjustment. CONSTITUTION:Magnets constituting a magnetic pole line are divided into multiple magnet pieces 7, 8, 9 in the magnet longitudinal direction perpendicular to the electron beam incidence direction and the facing direction of different magnetic poles, and the magnetic field intensity distribution between different magnetic poles of the divided magnets is changed in the magnet longitudinal direction. A magnetic field intensity distribution changing means in the magnet longitudinal direction changes the residual magnetic flux density of the magnets, or the magnetic pole width of the divided magnets in the electron beam incidence direction is changed, and the alignment order of the magnet pieces having different magnetic pole widths in the magnet longitudinal direction is made asymmetrical for each alternate magnetic pole, or the facing magnetic pole intervals of different magnetic poles of the divided magnets are adjusted symmetrically with the center axis in the facing alignment direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is provided in an industrial free electron laser device or SR device for use in lithography in the electronic industry, spectroscopic analysis in the industrial science and medical fields, photoexcitation reaction process, and the like. The present invention relates to a wiggler magnet that constitutes an oscillation part of a free electron laser.

[0002]

2. Description of the Related Art A free electron laser causes a high energy electron beam to enter a periodic alternating magnetic field (Wiggler magnetic field) to cause it to meander, and the synchrotron radiation generated at that time and the emitted electromagnetic wave are directed in the traveling direction of the electron. This is a laser generator that utilizes the fact that the effect of modulating the density distribution of γ is caused by a kind of resonance phenomenon and induced radiation action occurs. Free electron lasers have different oscillation mechanisms from those of gas lasers and solid-state lasers, and because of their high power, high efficiency, and the ability to easily obtain arbitrary wavelengths, there are growing expectations as a versatile industrial laser device. The oscillation wavelength in a free electron laser is proportional to the alternation period of the alternation magnetic field that causes the electron beam to meander (Wiggler period) and inversely proportional to the square of the electron beam energy, so it is necessary to select an appropriate electron beam accelerator and set operating conditions. Any wavelength can be obtained. In addition, the output at saturation is proportional to the current value of the electron beam, and since electromagnetic waves propagate in the vacuum space, the scaling law holds in principle and there is no limit to the output. This is why these characteristics are expected as next-generation industrial laser devices. As described above, the conventional example structure of the wiggler magnet that forms the periodic alternating magnetic field, which is the main part of the free electron laser, will be described below. FIG. 5 is a conceptual diagram showing the basic configuration of the oscillation part of the free electron laser device. When the electron beam 21 is incident in the central axis direction between the opposite poles of the wiggler magnet 20 composed of magnet rows with opposite poles arranged oppositely, The beam 21 meanders due to the alternating magnetic field to generate synchrotron radiation, and emitted light 24 is generated in the incident direction of the electron beam 21. The radiated light 24 generated is used for the total reflection mirror 2
The repeated reflection between the output mirror 23 and the output mirror 23 causes stimulated emission due to the interaction between the emitted light 24 and the electron beam 21, so that the light repeatedly reflected from the output mirror 23 having a transmittance of several percent. Can be taken out and used as a laser. FIG. 6 shows a Halbach-type wiggler magnet as a specific example of the wiggler magnet 20. As shown in the figure, magnets A and B in which magnets 25 having a rectangular parallelepiped shape are arranged so that their magnetic pole directions are periodically alternated are arranged so that different magnetic poles face each other. This magnet row A and B
When an electron beam is incident in the direction of the central axis (Z-axis direction) between the opposite direction of the magnetic field and the opposite direction (Y
Has a converging force in the axial direction, but does not act in the X-axis direction orthogonal to the incident direction of the electron beam,
If some focusing force is not applied, the electron beam will diverge in the X direction. Therefore, Z in FIG.
As a configuration of a converging-type Wiggler magnet capable of imparting a converging force in both X and Y axis directions to an electron beam incident in the axial direction, those shown in FIGS. 7 and 8 have been proposed.
The wiggler magnet shown in FIGS. 7 (a) and 7 (b) has a trapezoidal pole shape in which the magnetic pole shape is tapered in the X-axis direction.
By tapering, the edge focus effect is adjusted to weaken the diverging force of the electron beam in the X-axis direction and bring about the convergence effect. By setting the taper angle θ corresponding to the electron beam energy, it is possible to construct a converging-type Wiggler magnet having a converging force in both X and Y axis directions. In the wiggler magnet shown in FIGS. 8A and 8B, the magnetic pole shape is curved so that the magnetic field strength at both end portions between the opposite magnetic poles is larger than the central axis position, and the electron beam in the X-axis direction is It weakens the divergence and brings about the convergence effect.

[0003]

The X and Y directions orthogonal to the incident direction with respect to the electron beam incident into the wiggler magnet.
The configurations shown in FIGS. 7 and 8 as the configuration of the converging-type Wiggler magnet for giving a converging force in both axial directions have the following problems. (1) Since the length d in the X-axis direction (longitudinal width) of the permanent magnet that constitutes the wiggler magnet is about 10 cm as a specific example, the uniformity of the material that constitutes the permanent magnet and the uniformity of magnetization Considering the above, it is difficult to obtain uniform magnetic characteristics over the entire surface in the X-axis direction. (2) With the Wiggler magnet (Fig. 7) that has a trapezoidal magnetic pole shape with a taper angle, the appropriate taper angle is less than 1 degree for a high-energy electron beam, and the allowable angle range is very narrow. Therefore, high processing accuracy is required. For example, an appropriate taper angle θ for an electron beam having an energy of 40 MeV is 0.5
It is in the range of up to 0.8 degrees. (3) Wiggler magnet with curved magnetic pole shape (Fig. 8)
Then, it is difficult to process curves accurately. In particular, when the magnetic poles are composed of only permanent magnets, it becomes more difficult to curve the permanent magnets, which are often sintered bodies. (4) If the facing magnetic pole spacing is changed to change the magnetic field strength due to the facing of different magnetic poles, the focusing force also changes with the magnetic pole spacing in any of the converging-type Wiggler magnets shown in FIGS. The ability to converge is impaired. The present invention has been made in view of the above problems, and provides a converging-type Wiggler magnet in which the material of the magnet group constituting the wiggler magnet, the magnetization, the accuracy of machining, and the reduction of the focusing force due to the adjustment of the magnetic field strength are reduced. The purpose is that.

[0004]

In order to achieve the above object, the means adopted by the present invention is to generate a periodic alternating magnetic field by a magnetic pole array in which different magnetic poles are arranged to face each other, and to generate the periodic alternating magnetic field by the periodic alternating magnetic field. In a wiggler magnet for inducing radiated light from an electron beam incident on the central axis of the opposing arrangement direction, the magnets forming the magnetic pole row are opposed to each other in the electron beam incident direction and different magnetic poles. A wiggler magnet characterized in that it is divided into a plurality of magnet pieces in the magnet longitudinal direction orthogonal to the direction, and the magnetic field strength distribution between the opposed magnetic poles of each of the divided magnets is made different in the magnet longitudinal direction. Composed. The means for varying the magnetic field strength distribution in the magnet longitudinal direction varies the residual magnetic flux density of each of the divided magnets, or varies the magnetic pole width of each of the divided magnets in the electron beam incident direction to determine the magnetic pole width. The arrangement order of the different magnet pieces in the longitudinal direction of the magnets is made anti-symmetric for each alternating magnetic pole, or the magnetic pole interval where the different magnetic poles of the divided magnets face each other is changed symmetrically with respect to the central axis in the electron beam incident direction. It is carried out by

[0005]

According to the present invention, each magnet constituting the magnetic pole array is divided into a plurality of magnet pieces in the magnet longitudinal direction orthogonal to the electron beam incident direction and the facing direction of the different magnetic poles, so that the magnet pieces are predetermined. Since the Wiggler magnet is configured as a group of magnets assembled in an array and the volume of the magnet pieces is reduced, it is easy to obtain magnets having uniform magnetic characteristics. By making the magnetic field strength distribution of the magnetic field formed by opposing the different magnetic poles of each pole piece different in the longitudinal direction of the magnet, a converging force in the longitudinal direction of the magnet is given to the electron beam incident between the opposing magnetic poles. You can In order to make the magnetic field strength distribution in the magnet longitudinal direction different, in order to make the residual magnetic flux density of the magnet pieces arranged in the magnet longitudinal direction different, the magnetic field strength distribution in the direction orthogonal to the electron beam incident direction is If the magnetic field gradient is such that the magnetic field strength increases as the distance from the electron beam entrance central axis increases, the focusing force for the electron beam can be increased by the same action as when the magnet is curved in the longitudinal direction. Also, by making the magnetic pole widths of the respective magnet pieces different in the electron beam incident direction and making the arrangement order of the magnet pieces of different magnetic pole widths in the magnet longitudinal direction antisymmetric for each alternate magnetic pole, the taper angle in the magnet longitudinal direction can be made. The focusing force for the electron beam can be increased by the same action as the arrangement of the provided magnets. In addition, the magnetic field intensity distribution in the direction orthogonal to the electron beam incident direction is changed by changing the magnetic pole interval where the different magnetic poles of each magnet piece face each other symmetrically with respect to the central axis of the electron beam incident direction. If the magnetic field gradient is such that the magnetic field strength increases as the distance from the target increases, the focusing force for the electron beam can be increased by the same action as bending in the longitudinal direction of the magnet, and the optimum focusing force can be obtained by adjusting the magnetic pole spacing. You can also

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings for the understanding of the present invention. The following embodiments are examples of embodying the present invention and do not limit the technical scope of the present invention. 1 is a perspective view showing the structure of a wiggler magnet according to a first embodiment of the present invention, FIG. 2 is a partial plan view showing a magnetic pole arrangement of a wiggler magnet according to a second embodiment of the present invention, and FIG. FIG. 4 is a perspective view showing a constitution of a wiggler magnet according to a third embodiment of the present invention, and FIG. 4 is a perspective view showing a constitution of a wiggler magnet according to a fourth embodiment of the present invention. In the wiggler magnet 1 according to the first embodiment of the present invention shown in FIG. 1, permanent magnets 6 divided into magnet pieces 7, 8 and 9 are arranged so that the magnetic pole directions are periodically alternated in the Z-axis direction. The magnet array A and the magnet array B are arranged such that the different magnetic poles alternately alternate and face each other in the Y-axis direction with the axis of the electron beam incident direction (Z-axis direction) as the central axis. Regarding the residual magnetic flux densities of the magnet pieces 7, 8 and 9, the magnet pieces 7 and 9 located at both ends in the X-axis direction are large, and the magnet piece located in the center is arranged small. By thus increasing the magnetic field strength distribution in the X-axis direction on both sides with respect to the electron beam incident direction, it is possible to give a converging action to the passing electron beam. By dividing each magnet 6 into the magnet pieces 7, 8 and 9 as described above, it is possible to change the magnetic field strength distribution in the X-axis direction and variously exert the effect of converging the electron beam. The above is the magnet piece 7,
As for the change of the residual magnetic flux density of Nos. 8 and 9, the magnet pieces 7, 8,
The magnetic field strength distribution can be changed in the X-axis direction also by changing the magnetic pole width for each 9 and changing the distance between different magnetic poles. The wiggler magnet 2 shown as a second embodiment in FIG.
FIG. 2 is a plan view showing a portion of the magnet array A or B, which is indicated by X- in FIG.
It corresponds to the aob plane in the Y plane. The different magnetic poles change the widths of the magnet pieces 7, 8 and 9 facing each other in the magnet rows A and B in the Z-axis direction, and further, the arrangements of the magnetic pole width changes are alternately reversed. By changing the magnetic pole width in this way, the magnetic field strength distribution changes in the X-axis direction, and the electron beam incident in the Z-axis direction can be converged by the edge focus action. The magnetic pole structure having the taper angle shown in FIG. 7 of the conventional example brings about a focusing action for an electron beam, but since the magnet is divided into magnet pieces 7, 8 and 9, There is an advantage that it is easy to process the rectangular magnet pieces 7, 8 and 9 and to make the magnetic characteristics uniform.

A wiggler magnet 3 shown as a third embodiment in FIG. 3 is capable of adjusting the magnetic pole spacing of the magnet pieces 7, 8 and 9 in the different magnetic pole facing direction (Y-axis direction). Adjustment is performed by changing symmetrically in the X-axis direction and the Y-axis direction with the incident direction (Z-axis direction) as the central axis. By reducing the distance between the different magnetic poles of the magnet pieces 7 and 9 located on both sides in the Z-axis direction and increasing the distance between the different magnetic poles of the central magnet piece 8, the magnetic field strength distribution is increased on both sides in the electron beam incident direction. Becomes larger, the change in the residual magnetic flux density for each of the magnet pieces 7, 8, 9 shown in the first embodiment (FIG. 1), or the focusing action on the electron beam equivalent to the curved magnetic pole (FIG. 8) shown in the conventional example. Is demonstrated. Moreover, since the opposing magnetic pole spacing can be adjusted, the focusing action can be adjusted to select the optimum magnetic pole spacing. A wiggler magnet 4 shown as a fourth embodiment in FIG. 4 is a praseodymium magnet as a permanent magnet.
An iron-boron magnet is used, and the magnet pieces 7, 8 and 9 shown in the first to third embodiments are integrally manufactured for each X-direction magnet array. The praseodymium-iron-boron magnet is oriented in the direction of magnetization in the rolling process, and has the characteristic of being easier to machine than the conventional rare earth magnet that is a sintered body. As shown in the figure, the width is several cm and the thickness is several before magnetization.
The partial magnets 10, 11 and 12 having a cm length of 2 to 3 m are manufactured and processed into rectangular magnetic poles as illustrated.
The arrangement of the magnetic pole shapes is such that the magnetic pole widths of the partial magnets 10, 11 and 12 in the Z-axis direction are changed and the change widths are alternately arranged, as in the embodiment in which the magnetic pole width is changed as shown in FIG. To be done. The partial magnets 10, 11 and 12 are manufactured, magnetized and arranged as shown in the figure to complete the wiggler magnet 4. Each of the wiggler magnets 1 to 4 shown as examples above
In each case, the magnet piece is formed by dividing the magnet into three pieces in the longitudinal direction of the magnet, but the number of divisions is such that an optimum electron beam converging action can be obtained, and an appropriate number of divisions is selected in consideration of the difficulty of processing and adjustment. be able to.

[0008]

As described above, according to the present invention, each magnet constituting the magnetic pole array is divided into a plurality of magnet pieces in the magnet longitudinal direction orthogonal to the electron beam incident direction and the opposite direction of the different magnetic poles. As a result, the Wiggler magnet is configured as a magnet group in which the magnet pieces are assembled in a predetermined arrangement, and the volume of the magnet pieces is reduced, so that it is easy to obtain a magnet having uniform magnetic characteristics. By making the magnetic field strength distribution of the magnetic field formed by opposing the different magnetic poles of each pole piece different in the longitudinal direction of the magnet, a converging force in the longitudinal direction of the magnet is given to the electron beam incident between the opposing magnetic poles. You can In order to make the magnetic field strength distribution in the magnet longitudinal direction different, in order to make the residual magnetic flux density of the magnet pieces arranged in the magnet longitudinal direction different, the magnetic field strength distribution in the direction orthogonal to the electron beam incident direction is If the magnetic field gradient is such that the magnetic field strength increases as the distance from the electron beam entrance central axis increases, the focusing force for the electron beam can be increased by the same action as when the magnet is curved in the longitudinal direction. Also, the magnetic pole width of each magnet piece in the electron beam incident direction is different,
Further, by making the arrangement order of the magnet pieces having different magnetic pole widths in the magnet longitudinal direction antisymmetric for each alternate magnetic pole, the focusing force for the electron beam is enhanced by the same action as the arrangement of the magnets having the taper angle in the magnet longitudinal direction. be able to. In addition, by adjusting the magnetic pole spacing where the different magnetic poles of each magnet piece face each other symmetrically with respect to the central axis in the facing arrangement direction, the magnetic field strength distribution in the direction orthogonal to the electron beam incident direction can be adjusted from the electron beam incident central axis. When the magnetic field gradient is such that the magnetic field strength increases as it moves away from the outside, the focusing force for the electron beam can be increased by the same action as bending the magnet in the longitudinal direction of the magnet, and the optimal focusing force can be obtained by adjusting the magnetic pole spacing. it can.

[Brief description of drawings]

FIG. 1 is a perspective view of a wiggler magnet according to a first embodiment of the present invention.

FIG. 2 is a plan view of a main portion of a wiggler magnet according to a second embodiment of the present invention.

FIG. 3 is a perspective view of a main part of a wiggler magnet according to a third embodiment of the present invention.

FIG. 4 is a perspective view of a main portion of a wiggler magnet according to a fourth embodiment of the present invention.

FIG. 5 is a conceptual diagram showing a basic configuration of laser oscillation by a wiggler magnet.

FIG. 6 is a perspective view showing a configuration of a conventional Halbach-type wiggler magnet.

FIG. 7 is a perspective view showing a configuration of a converging-type Wiggler magnet using a tapered magnetic pole of a conventional example.

FIG. 8 is a perspective view showing a configuration of a converging-type Wiggler magnet using a curved magnetic pole of a conventional example.

[Explanation of symbols]

 1,2,3,4 --- Wiggler magnet 7,8,9--Magnet piece X--Magnet longitudinal direction Y--Different magnetic pole facing direction Z--Electron beam incident direction (Magnetic pole array direction)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location H01S 3/30 A 8934-4M H05H 13/04 F 9014-2G

Claims (4)

[Claims] 1. A periodic alternating magnetic field is generated by a magnetic pole array in which different magnetic poles are opposed to each other, and the electron beam incident on the central axis of the magnetic pole array in the opposing arrangement direction is meandered by the periodic alternating magnetic field. In a Wiggler magnet for inducing radiated light from an electron beam, each magnet constituting the magnetic pole array is divided into a plurality of magnet pieces in the magnet longitudinal direction orthogonal to the electron beam incident direction and the opposite direction of different magnetic poles, and the division A magnetic field strength distribution between different magnets facing each other is different in the longitudinal direction of the magnet. 2. The wiggler magnet according to claim 1, wherein the magnetic field strength distribution in the longitudinal direction of the magnet is varied by varying the residual magnetic flux density of each of the divided magnets. 3. The magnetic pole widths of the divided magnets in the electron beam incident direction are made different, and the arrangement order of the magnet pieces having different magnetic pole widths in the magnet longitudinal direction is made antisymmetric for each alternating magnetic pole. The wiggler magnet according to claim 1, wherein the magnetic field strength distribution in the longitudinal direction of the magnet is different. 4. The magnetic field strength distribution in the longitudinal direction of the magnets is varied by changing the magnetic pole interval in which the different magnetic poles of the divided magnets face each other symmetrically with respect to the central axis in the electron beam incident direction. 1. The wiggler magnet according to 1.