JP3480524B2 - Magnetic field generator for insertion light source emitting white light with narrow divergence angle and method of emitting white light - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field generator for use in an insertion light source which is inserted into a linear portion of an electron accelerator or an electron storage device to generate white radiated light, and a method for radiating white light.

[0002]

2. Description of the Related Art FIG. 7 is a schematic view of a conventional magnetic field generator used as an insertion light source for obtaining emitted light.
In the magnetic field generator, a pair of magnet rows 100 and 102 are arranged along the movement direction of the electrons e ⁻ , that is, the z-axis direction and at a predetermined interval in the y-axis direction. The magnetization direction of each permanent magnet 104 of the upper magnet array 100 (represented by the direction of the arrow in FIG. 7) is arranged so as to rotate clockwise by 90 ° along the direction in which the electrons go. On the other hand, each permanent magnet 1 of the lower magnet row 102
The magnetizing direction of 04 is turned 90 degrees counterclockwise along the direction of electrons, and is arranged such that permanent magnets having the same magnetizing direction are aligned in the y-axis direction of the upper and lower magnet rows. There is. With such a configuration, a periodic magnetic field is generated, and four consecutive magnets generate one period of the periodic magnetic field. This periodic magnetic field generally has a sinusoidal magnetic field distribution. It should be noted that a magnetic circuit composed of only permanent magnets as shown in FIG. 7 is called a hull back type.

As is well known, when high-energy electrons are moved in a periodic magnetic field generated by the magnetic field generator shown in FIG. 7, radiated light having a high directivity and a very appropriate degree can be obtained. A device for obtaining such emitted light is called an insertion light source.

In particular, an insertion light source device for obtaining white radiated light is called a wiggler. As shown in FIG. 8, the radiated light 110 from the wiggler has an angular divergence larger than necessary. Synchrotron radiation 11 near the center used as shown in FIG.
Outside of 2, there is unwanted radiation 114 that diverges at an angle away from the center. When the unnecessary light 114 impinges on a wall of a vacuum chamber called a beam line through which radiated light passes and an optical element (not shown), a large amount of heat is generated and adversely affects it. To prevent this, a slit equipped with a cooling device, an absorber 116, etc. are usually placed upstream so as to remove unnecessary light 114.

[0005]

However, the light 114 impinging on the slit / absorber 116 is converted into a large amount of heat there, and beyond the cooling capacity, there is a risk of damage. Therefore, the length of the system using the slit / absorber 116 is long. Driving on time and using high power light will be limited. It is desired to reduce these wasteful and troublesome lights 114 as much as possible.

Therefore, it is an object of the present invention to provide a magnetic field generator for an insertion light source which emits white light having a narrower divergence angle and a method of emitting white light having a narrower divergence angle than before.

[0007]

In order to achieve the above object, one of the inventions used in an insertion light source emitting white light.
One magnetic field generator has a pair of basic permanent magnet rows,
A magnetic field generation device configured by a Halbach type magnetic circuit in which permanent magnets in each basic magnet array are arranged so that the magnetization direction of the permanent magnets periodically changes in the electron movement direction, By arranging one or more other permanent magnet rows having an odd number of times the number of cycles of the basic permanent magnet row in parallel to each of the basic permanent magnet rows, And the magnetic field strength is low
Areas where the magnetic field strength increases in a pulsed manner
It is characterized by generating a pulse wave type magnetic field distribution.

In order to achieve the above-mentioned object, another magnetic field generator of the present invention used for an insertion light source that emits white light has a pair of magnet rows, and a magnetic pole and a permanent magnet are provided in each magnet row. a magnetic field generating device constituted by a magnetic circuit of a hybrid type in which the magnetization direction of electron motion direction and alternately the permanent magnets are arranged to vary periodically, the permanent between the magnetic poles adjacent magnet
Is composed of two permanent magnets , and by providing an air gap that does not generate a magnetic field between the two permanent magnets , the magnetic field strength increases periodically and in a region where the magnetic field strength is low.
It is characterized by generating a pulse wave type magnetic field distribution in which regions alternately appear . To achieve the above object, there is a pair of permanent magnet rows, and in each magnet row, the permanent magnets are arranged so that the magnetization direction of the permanent magnets periodically changes in the electron movement direction. the method of the present invention, periodic and and field strength is lower region and pulse to magnetic direction of movement of the electron emitting white light using the insertion device comprising a composed magnetic field generator by the magnetic circuit
It is characterized by including a step of generating a pulse wave type magnetic field distribution in which regions in which the field strength becomes high appear alternately .
In order to achieve the above object, a pair of magnet rows is provided, and in each of the magnet rows, magnetic poles and permanent magnets are arranged alternately in the electron movement direction and the magnetization direction of the permanent magnets is periodically changed. The method of the present invention for emitting white light by using an insertion light source provided with a magnetic field generator configured by a hybrid type magnetic circuit includes a region having a low magnetic field strength , which is periodic in the moving direction of the electron, and a pulsed light. Magnetic field
The method is characterized by including a step of generating a pulse wave type magnetic field distribution in which regions of high strength appear alternately .

[0009]

In one magnetic field generating device of the present invention, each of the basic permanent magnets has one or more other permanent magnet examples having a number of cycles that is an odd multiple of the number of cycles of the basic permanent magnet example. Due to the configuration arranged in parallel to the example, a pulsed wave-like periodic magnetic field is generated on the central axis of the magnetic circuit.

In another magnetic field generator of the present invention, a pulse wave-like periodic magnetic field is generated on the central axis of the magnetic circuit by providing a gap that does not generate a magnetic field between the adjacent magnetic poles.

Therefore, the deflection angle of electrons obtained by integrating the generated pulse wave-like periodic magnetic field by half a period along the magnetic circuit axis is much smaller than the deflection angle of electrons in the case of the conventional magnetic field generator, for example, , It is reduced to about 1/3 of the deflection angle of electrons in the case of the conventional sinusoidal periodic magnetic field having the same period and the same magnetic field peak value.

[0012]

EXAMPLES First, the principle of the present invention will be described.

FIG. 1 is a diagram for explaining the divergence angle of the emitted light emitted from the magnetic field generator of the insertion light source. FIG. 1 is a view of the magnetic field generator shown in FIG. 7 viewed from the bottom including a plane including x-axis and z-axis, in which 102 denotes a lower magnet array and 104 denotes a permanent magnet. The symbol shown on the permanent magnet 104 represents the magnetization direction. Among the symbols, a symbol with a dot in the circle represents the direction of magnetization from the back side of the paper to the front, and a symbol with a cross in the circle represents the direction from the front to the back of the paper.

Radiation light 11 from the magnetic field generator of the insertion light source
The divergence angle 10 of 0 is determined by the electron trajectory 12, and the electron trajectory 12 is determined by the magnetic field distribution generated by the magnetic field generator. As described above, the conventional magnetic field generator as shown in FIG. 7 generally has a sinusoidal periodic magnetic field distribution, and the electrons emit radiated light while meandering in a sinusoidal wave as shown in FIG. . Since the emitted light is emitted in the tangential direction 14 of the electron orbit 12, the divergence angle coincides with the maximum deflection angle of the electron orbit 12, and thus the divergence angle 10 becomes larger as the emitted light 110 from the meandering electron swings greatly. That is, if the deflection angle of the electron orbit 12 is reduced, unnecessary light (114 in FIG. 8) is not emitted.

The deflection angle value Δθ (z) of the electron orbit 12
Is obtained by integrating the magnetic field value felt when electrons pass along the electron passage direction, as shown in equation (1).

[0016]

[Equation 1] Here, e is the charge amount of electrons, m is the mass of electrons, c is the speed of light, γ is the gamma factor, and By (z) is the magnetic field strength in the y-axis direction at the z-axis position z. .

Therefore, in order to reduce the deflection angle of the electron orbit 12 in order to reduce unnecessary light emission, the magnetic field strength B
It suffices to reduce y (z). However, since the synchrotron radiation characteristic is determined by the peak magnetic field strength, the magnetic field strength B
When y (z) is reduced, the emitted light characteristics change and it becomes impossible to obtain the necessary white light. Therefore, by keeping the peak magnetic field strength as it is and reducing the magnetic field strength between the peaks of the magnetic field strength in the z-axis direction as much as possible,
The deflection angle of the electron can be reduced without changing the emitted light characteristic. This is done by, for example, keeping the period of the magnetic field distribution constant and making the magnetic field distribution not a sinusoidal waveform as in the past, but a pulse wave shape in which an extra magnetic field other than the peak portion of the magnetic field distribution is eliminated. It is possible.

Since the magnetic field distribution is periodic, the value of the maximum deflection angle Δθ _MAX of the electron should start from the point of the magnetic field 0 and integrate the half cycle of the magnetic field along the magnetic circuit axis, that is, the z axis in this case. Is obtained by As described above, the characteristic of the radiated light radiated on the axis of the wiggler, that is, the z-axis, is determined only by the magnetic field peak value. Therefore, the peak value of the conventional sinusoidal magnetic field distribution remains constant with the magnetic field period kept constant. If the pulse wave magnetic field distribution is the same and the integration value is small, light having the same radiated light characteristics and a small divergence angle can be obtained.

An embodiment to which the above-described principle of the present invention is applied will be described with reference to FIG. Of course, the invention is not limited to the embodiment shown in FIG.

FIG. 2 shows a magnetic circuit for generating a pulse wave periodic magnetic field when applied to a so-called Halbach type magnetic circuit using only permanent magnets, that is, a configuration of a pair of magnet rows of a magnetic field generator, (A) is a top view,
(B) shows a front view. Symbols such as arrows shown in FIG. 2 represent the magnetization directions of the permanent magnets and have the same meanings as the symbols shown in FIG.

In FIG. 2A, 20 indicates the upper magnet row, and 22 indicates the conventional magnet rows 100 and 1 shown in FIG.
02 shows a permanent magnet part corresponding to one of the permanent magnets 104 constituting the No. 02. The permanent magnet portion 22 is first divided into three in the width direction (x-axis direction). Reference numeral 24 denotes end permanent magnets that are on both sides with respect to the z-axis of the three divisions. As shown in FIGS. 2A and 2B, the arrangement of the magnetization directions of the end permanent magnets 24 of the upper magnet row 20 arranged in the z-axis direction is the upper magnet row 100 shown in FIG. The arrangement is the same as that of the permanent magnets 104 in the magnetization direction, and is rotated clockwise by 90 ° in the direction in which the electrons travel. Permanent magnet part 22
The central portion 26 of the three divided parts is further in the width direction (x axis).
It is divided into three parts. Out of the central portion 26 divided into three, both central end portions 28 are divided into three in the longitudinal direction (z axis) of the magnet array. Reference numeral 30 denotes a first permanent magnet element formed by dividing the central both ends 28 into three. Like the arrangement of the magnetization directions of the end permanent magnets 24, the arrangement of the first permanent magnet elements 30 arranged in the z-axis direction in the magnetization direction is rotated clockwise by 90 ° in the direction in which the electrons travel, In addition, the magnetization direction of the first permanent magnet element 30 located at the center of the center both ends 28 is made to be the same as the magnetization direction of the end permanent magnet 24. A central portion 32 of the central portion 26 divided into three is divided into five in the longitudinal direction of the magnet array (z axis). 34
Shows a second permanent magnet element formed by dividing the central portion 32 into five parts. Like the arrangement of the magnetization directions of the end permanent magnets 24, the arrangement of the second permanent magnet elements 34 arranged in the z-axis direction in the magnetization direction is rotated clockwise by 90 ° in the direction in which the electrons travel, In addition, the magnetization direction of the second permanent magnet element 34 located at the center of the central portion 32 is set to be the same as the magnetization direction of the end permanent magnet 24. End permanent magnet 24, first and second
Both the permanent magnet elements 30 and 34 are composed of only permanent magnets.

The permanent magnet portion 22 of the lower magnet row 21 is also constructed similarly to the upper magnet row 20. However, the magnetization directions of the end permanent magnets 24, the first and second permanent magnet elements 30 and 34 (in a hidden position in FIG. 2B) arranged side by side are 90 ° counterclockwise rotation, and Figure 2
As shown in (B) of FIG.
The respective end permanent magnets 24 are aligned and the corresponding end permanent magnets 24 having the y-axis magnetization direction are arranged so that the magnetization directions are the same.

The thickness of the upper and lower magnet rows 20 and 21 is 50 m.
m, the magnet row spacing is 20 mm. The length of the permanent magnet portion 22 in the z-axis direction is 37.5 mm, and the width (in the x-axis direction).
Is 90 mm. Therefore, the magnetic field cycle length is
It is 150 mm, which is four times the length of 2. End permanent magnet 24
Has a width of 30 mm, and the first and second permanent magnet elements 3
The width of 0 and 34 is 10 mm. End permanent magnet 24,
The respective lengths of the first permanent magnet element 30 and the second permanent magnet element 34 in the z-axis direction are 37.5 mm, 37.5 / 3 mm, and 37.5 / 5 mm. The material of these permanent magnets is N
d-Fe-B system, whose Br is 12.1 kGau
It's ss.

A computer based on the law of electromagnetism in the case where the magnetic field peak value on the z-axis through which electrons pass is 7,000 Gauss in the configuration specifications of the magnetic field generator described so far with reference to FIG. By the existing calculation method used, the magnetic field strength By in the y-axis direction is calculated for z, and the calculated magnetic field strength By is 1 along the z-axis direction.
Integral value Int indicating the deflection angle of the electron obtained by integrating twice
FIG. 3 shows the distributions of 1 and the twice-integrated value Int2 indicating the electron orbit. The vertical axis in FIG. 3 indicates I
A scale obtained by converting nt1 into an electron deflection angle is also shown.

For comparison, the calculation result in the case of the conventional sinusoidal periodic magnetic field having the same peak magnetic field strength and the same periodic length is shown in FIG.
Shown in. In the embodiment shown in FIG. 2, the magnetic field has a distribution close to a pulse wave as seen from FIG. 3, and the maximum value of the deflection angle of the electron is 0.22 mrad (milliradian). On the other hand, in the case of the conventional sinusoidal magnetic field, the maximum value of the deflection angle of the electron is 0.64 mrad from FIG. Therefore, the maximum value of the deflection angle of electrons by the magnetic field generator of the embodiment shown in FIG. 2 is about 1/3 of that of the conventional type, and as a result, the divergence angle of emitted light is also reduced to 1/3. Furthermore,
Since the deflection angle of the electron is small, the amplitude of the electron orbit is also small, which is advantageous for utilizing synchrotron radiation.

The case where the present invention is applied to the Hullback type magnetic circuit using only permanent magnets used for so-called pure insertion light sources has been described above. However, the present invention is applied to the magnetic poles with high permeability and high saturation magnetic material. A case where the present invention is applied to a so-called hybrid type insertion light source combined with a permanent magnet will be described below.

FIG. 5 shows an embodiment in which the present invention is applied to a hybrid type magnetic circuit in which a high magnetic permeability material is used for a magnetic pole, in the form of a sectional view including az axis through which electrons pass. In FIG. 5, the magnet row 40 on the upper side and the magnet row 41 on the lower side are arranged so as to be separated from each other by a predetermined magnet row interval (here, 20 mm). The thickness (length in the y-axis direction) of each magnet array 40 and 41 is 55 mm, and the width (length in the x-axis direction (not shown)) is 100 mm. In the upper magnet row 40, the first members 42 and the second members 44 are alternately arranged at a predetermined interval (60 mm in the present embodiment), and the lower magnet row 41 includes the third member 46. And the fourth member 48 are arranged at the same spacing as the spacing between the first member 42 and the second member 44 of the upper magnet row 40, and the third member
The fourth and fourth members 46 and 48 are aligned with the first and second members 42 and 44, respectively. As a result, gaps 60 are provided between the first member 42 and the second member 44 and between the third member 46 and the fourth member 48, respectively. In the first to fourth members 42 to 48, as shown in FIG.
(Thickness 55mm), but thinner than that (thickness 40m
m) It closely adheres to the magnetic pole 52 and sandwiches it. A permanent magnet 54 is sandwiched by the permanent magnet 50 without a gap in the space where the magnetic pole 52 is absent. The individual dimensions of the above components are shown in FIG.
(Unit is mm). In addition,
In this embodiment, the magnetic pole 52 has a wedge shape, but this may have a normal rectangular parallelepiped shape, which is not directly related to the present invention.

The arrow mark on the permanent magnets 50 and 54 indicates the magnetization direction. First member 42 and fourth member 4
The magnetizing directions of the permanent magnet 50 of No. 8 are both toward the magnetic pole 52, and the magnetizing directions of the second member 44 and the third member 46 are both away from the magnetic pole 52. The magnetization directions of the permanent magnets 54 of the first and third members 42 and 46 are from the upper side to the lower side, and the second and fourth members 44,
The magnetization direction of the permanent magnet 54 of 48 is the direction from the lower side to the upper side.

In a conventional hybrid type magnetic circuit having a sinusoidal magnetic field distribution, permanent magnets and magnetic poles are alternately arranged in close contact with each other, whereas in the embodiment shown in FIG. A feature is that a gap is provided in the permanent magnet 50 sandwiched between them.

The material of these permanent magnets 50, 54 is Nd.
-Fe-B type, whose Br is 12.1kGaus
s. The material of the magnetic pole is vanadium permendur having high permeability saturation characteristics.

FIG. 6 shows the result of calculating the magnetic field distribution in the same manner as in the first embodiment in the case of the above-mentioned configuration specifications.
From FIG. 6, even in the hybrid type magnetic field circuit,
It can be seen that a pulsed magnetic field distribution can be achieved.

In the embodiment shown in FIG. 5,
The permanent magnet 54 is provided, but this is to assist the generated magnetic field distribution in a more pulsed form, and it is not always necessary to provide the permanent magnet 54, that is, a gap is provided between the adjacent permanent magnets 50. A pulse-shaped magnetic field distribution is generated only by providing it.

In the embodiment shown in FIGS. 2 and 5,
Compared to the conventional wiggler having a sinusoidal magnetic field shape with the same magnetic field cycle, the magnetic field area within one cycle of the magnetic circuit is approximately 1/3, and the divergence angle of the radiation is also as described above. Although it is 1/3, the magnetic field area may be further reduced in order to further reduce the divergence angle of radiation. As a method for this purpose, the magnetic field period is lengthened, but the ratio of the magnetic field area per period is reduced by separating the magnet structure at the portion indicated by the alternate long and short dash line in FIG. 2 and providing a gap. Further, in FIG. 5, if the distance between the magnetic poles is increased, the ratio of the magnetic field area per cycle becomes smaller.

[0034]

Since the present invention is configured as described above, a pulsed magnetic field distribution is generated, which reduces the divergence angle of emitted light and suppresses the generation of unnecessary light. Therefore, the heat load on each component can be significantly reduced without changing the radiated light characteristics.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a divergence angle of emitted light emitted from a magnetic field generator of an insertion light source.

FIG. 2 shows a configuration of a magnetic circuit that generates a pulse-wave periodic magnetic field, that is, a pair of magnet rows of a magnetic field generator, when the present invention is applied to a so-called Hullback type magnetic circuit that uses only permanent magnets. , (A) is a top view,
(B) shows a front view.

FIG. 3 is a magnetic field intensity By in the y-axis direction obtained by calculation of a magnetic field distribution generated by the magnetic field generator shown in FIG.
FIG. 3 is a diagram showing respective distributions of a once-integrated value Int1 showing the deflection angle of an electron obtained by integrating the obtained magnetic field strength By once along the z-axis direction and a twice-integrated value Int2 showing an electron orbit. is there.

FIG. 4 is a diagram showing calculation results in the case of a conventional sinusoidal periodic magnetic field having the same peak magnetic field strength and the same periodic length for comparison with the embodiment of the present invention shown in FIG. 3.

FIG. 5 shows an embodiment in which the present invention is applied to a hybrid type magnetic circuit in which a high magnetic permeability material is used for a magnetic pole, in the form of a sectional view including az axis through which electrons pass.

6 is a diagram showing a distribution of magnetic field strength By in the y-axis direction obtained by calculation of a magnetic field distribution generated by the magnetic field generator shown in FIG.

FIG. 7 is a schematic view of a conventional magnetic field generator used as an insertion light source for obtaining emitted light.

FIG. 8: The angular divergence of the emitted light 110 from the wiggler, which is an insertion light source device for obtaining white emitted light, is larger than necessary, and is outside the emitted light 112 near the center to be used at an angle away from the center. It is a figure which shows that there exists unnecessary emitted light 114 which diverges.

[Explanation of symbols]

20, 21, 40, 41 Magnet row 22 Permanent magnet part 24 End permanent magnet 26 Central part 28 Both central ends 30 First permanent magnet element 32 Central part 34 Second permanent magnet element 42 First member 44 Second member 46 Third member 48 Fourth member 50 Permanent magnet 52 Magnetic pole 60 Air gap

Front page continuation (72) Inventor Takeo Takada 2-15-5 Kitafu, Takefu City, Fukui Prefecture Shin-Etsu Chemical Co., Ltd. Magnetic Materials Research Laboratory (56) Reference JP-A-6-140195 (JP, A) JP-A 5-182791 (JP, A) JP-A-2-215177 (JP, A) JP-A-5-258896 (JP, A) JP-A-4-269700 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05H 3/00-15/00

Claims (5)

(57) [Claims] 1. An insertion light source that emits white light, and has a pair of basic permanent magnet rows, and in each of the basic magnet rows, the permanent magnet has a magnetizing direction in the electron movement direction. A magnetic field generator configured by a Halbach type magnetic circuit arranged so as to change periodically, wherein one or more having a number of cycles that is an odd multiple of the number of cycles of the basic permanent magnet array. By arranging a large number of different permanent magnet rows in parallel with each of the basic permanent magnet rows, the magnetic field strength is periodic and the magnetic field strength is periodic and low.
A magnetic field generator characterized in that it generates a pulse wave type magnetic field distribution in which regions of increasing height appear alternately . 2. An insertion light source that emits white light, and has a pair of magnet rows, and in each magnet row, magnetic poles and permanent magnets alternate in the movement direction of electrons and the magnetization directions of the permanent magnets. A magnetic field generator configured by a hybrid type magnetic circuit in which the magnetic poles are arranged to change periodically, wherein the permanent magnets between the adjacent magnetic poles are two permanent magnets.
The magnetic field strength is low and the magnetic field strength is low by providing a gap that does not generate a magnetic field between the two permanent magnets.
Areas and areas where the magnetic field strength increases in a pulsed manner appear alternately.
That the pulse wave magnetic field generator, characterized in that to generate a magnetic field distribution. 3. The magnetic field generator according to claim 2, wherein the auxiliary permanent magnets are arranged in series with each of the magnetic poles in a plane orthogonal to the movement direction of electrons and in a direction in which the pair of magnet rows face each other. A magnetic field generator, wherein a magnet is provided, and the auxiliary permanent magnets are magnetized in a direction in which the pair of magnet rows face each other, and adjacent auxiliary permanent magnets are magnetized in opposite directions. 4. A hull-back type magnetic circuit having a pair of permanent magnet rows, in which the permanent magnets are arranged so that the magnetization direction of the permanent magnets periodically changes in the electron movement direction. In the method of emitting white light using an insertion light source including a magnetic field generator configured by, a region having a low magnetic field intensity that is periodic in the electron movement direction.
And a pulse wave type magnetic field distribution in which regions where the magnetic field strength increases in a pulsed manner alternate . 5. A hybrid having a pair of magnet rows, wherein magnetic poles and permanent magnets in each magnet row are arranged alternately in the electron movement direction and the magnetization direction of the permanent magnets is periodically changed. In a method of emitting white light using an insertion light source equipped with a magnetic field generator configured by a magnetic circuit of a type, a region having a low magnetic field intensity that is periodic in the electron movement direction.
And a pulse wave type magnetic field distribution in which regions where the magnetic field strength increases in a pulsed manner alternate .