JP2769914B2 - Polarization generator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a polarization generator called a wiggler or an undulator used for an insertion type light source or a free electron laser, and a magnetization direction in ± Y direction of each magnet row. The present invention relates to a polarization generator in which the magnetic field distribution in the X direction of the magnet having the X is alternately arranged in the Z direction so as to be higher in one of the ± X directions, thereby converging the passing electron beam to reduce the energy loss.

2. Description of the Related Art When an electron beam close to the speed of light passes through a magnetic field, an electromagnetic wave,
In other words, synchrotron radiation is generated, but when the different magnetic pole magnets are alternately arranged and this electron beam is passed through a magnetic field in which the direction of the magnetic field changes alternately, light with higher brightness is obtained by interfering with each other. . Such a coherent radiation light generating device is called an insertion type light source,
For example, used in electron storage ring, the difference in polarization characteristics, 2N multiples of the type light is obtained wiggler magnetic field of frequency (N), which from the magnetic field is weak amplitude of orbital is very small but the N ² Strength The type that can obtain this light is called an undulator.

The configuration of the polarization generator is composed of a pair of magnet rows in which a large number of magnets of required dimensions with different magnetization directions are arranged in a required pattern so that the magnetic field direction changes alternately, and various mechanical support mechanisms are mounted on the vertical support. It is necessary to change the magnetic field strength to obtain the required high-brightness synchrotron radiation, and it is configured so that the gap between the magnet rows can be adjusted and positioned to the required gap (Lg) dimension. .

Problems to be Solved by the Invention For example, the configuration of a wiggler magnetic circuit used in a free electron laser capable of continuously changing an oscillation wavelength by changing the intensity and period of a magnetic field includes a fifth type.
As shown in the figure, a large number of magnets (2a, b) (3a, b) (11a, b) (12a, b) of required dimensions with different magnetization directions are , The horizontal direction perpendicular to the Z direction is ± X direction, and the vertical direction perpendicular to the Z direction is ±
In the case of the Y direction, a pair of magnet rows (1) (1) arranged in the Z direction in a required pattern so that the magnetic field direction changes alternately.
0) is opposed to each other using a mechanical support mechanism so that the gap can be adjusted.

In such a configuration of the magnet array, there is a problem that the beam is diffused and the beam energy is reduced, so that a desired free electron laser cannot be obtained.

Therefore, in order to increase the convergence of the beam and prevent beam energy loss, as shown in FIG.
A magnetic circuit in which a quadrupole magnet (20) having a magnetization direction in the direction of the center of the gap was arranged around (10), but there was a problem that the circuit became complicated and large, and the manufacturing cost was high.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a polarization generator having a configuration in which an electron beam is converged and a decrease in beam energy is small.

Means for Solving the Problems The present invention is directed to a pair of magnet rows in which a plurality of magnets having different magnetization directions are horizontally arranged in a required pattern, facing each other, forming a required gap between the magnet rows, and passing through the gap. The horizontal direction of the center of the gap through which electrons pass is defined as the Z direction, the horizontal direction perpendicular to the Z direction is defined as ± X direction, and the vertical direction perpendicular to the Z direction is defined as ± Y direction. In the case, the magnets having a magnetization direction in the ± Y direction of each magnet row have a characteristic that the magnetic field distribution in the X direction is highly inclined to one end in the X direction, and when arranging the magnets having the characteristics in the Z direction, A polarization generator in which the peak of the magnetic field distribution in the X direction is arranged so as to alternately appear in the Z direction in the + direction and the-direction in the X direction.

Effects of the Invention The present invention has been studied variously with respect to the magnet array in order to improve the degree of convergence of the electron beam in the polarization generator. As a result, in the configuration of the magnet array shown in FIG.
When the magnetic field distribution in the direction is measured, as shown in FIG. 6, B (magnetic field intensity) is maximized at the center (X = 0) in the gap width direction, and the magnetic field intensity decreases as the distance from the center decreases. When the electron beam flows in the Z-axis direction, the electron beam travels meandering, but since the magnetic field intensity is low except at the center, the beam is diffused and the energy loss increases, and each magnet row has a magnetization direction in the ± Y direction. By finding that the magnetic field distribution in the X direction of the magnet is alternately arranged in the Z direction such that the magnetic field distribution in the X direction becomes higher in one of the ± X directions, the passing electron beam can be converged and the energy loss can be reduced. It was done.

In the present invention, as will be described later, the means for making the magnetic field distribution in the X direction of a magnet having a magnetization direction in the ± Y direction of each magnet row highly inclined to one end in the X direction includes a size in the X direction. By changing or changing the magnitude in the Y direction to give the magnetic field distribution characteristics in the X direction inclined to one end in the X direction, or changing the orientation direction to the normal orientation at one end in the X direction and the other direction The edge has a means to deliberately disturb and change the orientation.

Disclosure Based on the Drawings FIGS. 1a, 1b and 1c are perspective explanatory views showing the configuration of a magnet array of a polarization generator according to the present invention.

 2a and 2b are explanatory diagrams showing a magnetic field distribution in the X direction.

Configuration 1 The configuration of the magnet row according to the present invention shown in FIG. 1a is such that magnets are arranged on a pair of magnet holding plates (not shown) which are horizontally supported so as to be able to move up and down and whose facing distance (gap) can be adjusted. However, as is apparent from the lower magnet row (10), magnets (13a, b) (14a, b) of various dimensions and magnetization directions are arranged in the Z direction in a required pattern so that the magnetic field direction changes alternately. I have.

More specifically, the two types of magnets (14a) (14b) whose magnetization direction is Y in the magnet array (10) are different from the other magnets (13a) (1).
As in 3b), the thickness (Y direction) and the length (X direction) are constant, but the width (Z direction) changes to the length (X direction), and when viewed from the top (Y direction), it is trapezoidal. The magnets (14a) and (14b) have a parallelogram between the magnets (14a) and (14b) when viewed from above (Y direction). Magnets (13a) and (13b) whose magnetization directions are ± Z directions are arranged to form a required pattern in which the magnetic field direction changes alternately.

That is, the magnet (14a) whose magnetization direction is the −Y direction is + X
Magnetic field distribution in the X direction is
As shown in FIG. 2A, the magnetic field distribution in the X direction is shown in FIG. 2B because the magnet (14b) having the magnetization direction in the + Y direction is large in the -X direction. As shown in the figure, the characteristics are highly inclined toward the end in the −X direction.

When the electron beam passes between the pair of upper and lower magnet rows having such a configuration, the direction of inclination of the magnetic field distribution that is highly inclined toward one end in the X direction appears alternately in the Z direction when viewed in the Z direction. Is prevented, the electron beam converges, and the loss of beam energy can be reduced.

The degree of inclination of the magnetic field distribution inclined to one end in the X direction shown in FIG. 2 is appropriately selected according to the required degree of convergence of the electron beam, and the shape and dimensions of the magnet are appropriately determined according to the magnet characteristics and the requirements. Selected.

Configuration 2 The configuration of the magnet array according to the present invention shown in FIG. 1B comprises the same technical means as the configuration shown in FIG. 1A, and has a magnet array (10) having a similar pattern in which the direction of the magnetic field changes alternately. ), Two types of magnets (15
a) (15b) has the same length (X direction) and width (Z direction) as the other magnets (11a) and (11b) arranged between the magnets (15a) and (15b), but has a thickness (Y direction) is the length (X
Direction), and have the same shape and dimensions as a trapezoid when viewed from the Z direction.
The directions are alternately reversed. When viewed in the Z direction, the directions of inclination of the magnetic field distribution that are highly inclined to one end in the X direction appear alternately in the opposite direction, and are the same as those shown in FIG. It has a function and effect.

Configuration 3 The configuration of the magnet row according to the present invention shown in FIG. 1c is exactly the same as the above-described magnet row shown in FIG. 5, except that the magnets (16a) and (16b) whose magnetization directions are in the Y direction are provided inside the magnets. The particle orientation of the X direction is configured so that one end is normal orientation and the other end is intentionally disturbed in orientation to have the same magnetic field distribution as in FIGS. 2a and 2b. The direction of inclination of the magnetic field distribution that is highly inclined to one end in the X direction appears alternately in the opposite direction, and has the same effect as the configuration shown in FIG. 1A.

In any of the above-described configurations, the mechanical mechanism for horizontally supporting the pair of magnet holding plates each having the above-described magnet row so as to be able to move up and down and adjusting the facing distance (gap) includes a support beam on which the magnet row is mounted. It is possible to adopt a configuration in which a vertical support is brought into contact with a vertical support through a linear motion bearing, a configuration in which a vertical support having a required shape is inserted, or a known configuration using a ball screw.

Alternatively, a pair of horizontal beams is supported on an upright column via a lifting bracket so as to be able to move up and down, a magnet row is supported by the horizontal beam, and the lifting bracket is united by a coupling having a phase adjustment mechanism. A polarized light generator (Japanese Patent Application No. Hei 1 (1994)) capable of adjusting and positioning the gap between a pair of magnet rows facing each other with extremely high precision and high parallelism by screwing into a pair of screw shafts each having a reverse screw threaded. 257337
The vertical sliding surface of the lifting bracket is a tapered surface, and a low friction coefficient slider member having an inverse taper surface is used for the lifting support mechanism. Such as eliminating gaps between
A high-precision mechanical mechanism that handles displacements in units of μm can be employed.

EXAMPLE In the configuration of the magnet row according to the present invention shown in FIG. 1, an Nd-B-Fe-based permanent magnet was used as the magnet material, and the magnet direction in the Y direction was changed to a width of 4 mm (one end) and a width of 8 mm.
The upper surface of mm (other end), thickness = 15 mm, length = 80 mm is trapezoidal, and the magnet dimension in the Z direction is magnetized. The upper surface of width = 4 mm, thickness = 15 mm, length = 80 mm is a parallelogram. The total length of the magnet row was set to 1800 mm, and a wiggler as shown in FIG.

Also, for comparison, the same magnet size of 4 m
A wiggler provided with a quadrupole shown in FIG. 7 was prepared with the magnet row shown in FIG. 5 having a size of m (width) × 15 mm (thickness) × 80 mm (length).

When the magnetic field strength at the X = 0 position from the beam entrance to the exit of the obtained wiggler according to the present invention was measured,
The results shown in FIG. 3a were obtained.

When the magnetic field strength was measured at the position of X = 20 mm as shown in FIG. 4B, the result shown in FIG. 4A was obtained.

In the wiggler according to the present invention, as shown in FIG. 4a, the magnetic field strength at X = 20 is higher than the magnetic field strength at X = 0, the electron beam heading in the X direction is converged, and the diffusion of the electron beam and the beam energy Loss could be prevented, and it was equivalent even when compared to a wiggler with a quadrupole.

Effect of the Invention In the polarization generator according to the present invention, the magnetic field distribution in the X direction of the magnets having a magnetization direction in the ± Y direction of each magnet row is alternately arranged in the Z direction such that the magnetic field distribution in the X direction becomes higher in one of the ± X directions. Thereby, the passing electron beam is not converged without increasing the size and complexity of the apparatus, and the beam energy is not reduced.

[Brief description of the drawings]

FIGS. 1a, 1b and 1c are perspective explanatory views showing the configuration of a magnet array of a polarization generating device according to the present invention. FIGS. 2a and 2b are explanatory diagrams showing the magnetic field distribution in the X direction of the magnet array according to the present invention. FIGS. 3a, b and 4a, b are an explanatory view of the magnetic field intensity distribution from the entrance to the exit of the electron beam of the polarization generator according to the present invention and the lower magnet row viewed from above. FIG. 5 is an explanatory perspective view showing a configuration of a magnet array of a conventional polarization generator. FIG. 6 is an explanatory diagram showing a magnetic field distribution in the X direction of a conventional magnet array. FIG. 7 is an explanatory view showing a configuration of a magnet array of a conventional polarization generator. 1,10 ... magnet row, 2a, 2b, 3a, 3b, 11a, 11b, 12a, 12b ... magnet, 13a, 13b, 14a, 14b, 15a, 15b, 16a, 16b ... magnet.

Claims (4)

(57) [Claims] A pair of magnet rows in which a plurality of magnets having different magnetization directions are horizontally arranged in a required pattern are opposed to each other to form a required gap between the magnet rows, and a magnetic field is applied to electrons passing through the gap. When the horizontal direction of the center of the gap through which electrons pass is the Z direction, the horizontal direction perpendicular to the Z direction is ± X direction, and the vertical direction perpendicular to the Z direction is ± Y direction, A magnet having a magnetization direction in the ± Y direction has a characteristic that the magnetic field distribution in the X direction is highly inclined to one end in the X direction. When the magnets having the characteristics are arranged in the Z direction, the magnetic field distribution in the X direction is reduced. A polarized light generator characterized in that peaks are arranged so as to appear alternately in the + direction and the-direction in the X direction in the Z direction. 2. A magnet having a magnetizing direction in the ± Y direction of each magnet row having a magnetic field distribution in the X direction which is changed in size in the X direction and is inclined to one end in the X direction. The polarization generator according to claim 1, wherein 3. A magnet having a magnetizing direction in the ± Y direction of each magnet row having a magnetic field distribution in the X direction inclined to one end in the X direction by changing the size in the Y direction. The polarization generator according to claim 1, wherein 4. A magnet having a magnetizing direction in the ± Y direction of each magnet row having a magnetic field distribution in the X direction inclined to one end in the X direction by changing the particle orientation. Item 2. A polarization generator according to Item 1.