JP3324868B2 - Orbital axis displacement compensation type magnetic field generator used for undulator for hybrid insertion light source - 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 used in an undulator for a hybrid insertion light source for generating radiation or a free electron laser.

[0002]

2. Description of the Related Art As is well known, when high-energy electrons are moved in a periodic magnetic field as shown in FIG. 4, radiation having high directivity and extremely high brightness can be obtained. An apparatus for obtaining such emitted light is an insertion light source. A light source that forms a magnetic circuit using only permanent magnets is called a pure insertion light source, while a light source that combines a permanent magnet with a high magnetic permeability and a high saturation magnetic material for a magnetic pole is called a hybrid insertion light source. For example, "Permanent" Magnet
Undulators ", K. Halbach, JOU
RNAL DE PHYSIQUE (Paris), 4
As described in U.S. Pat. No. 4,1983, C1-211 to 215, the hybrid type generally generates a stronger magnetic field.

FIG. 4 is a diagram schematically showing an example of a conventional magnetic field generator used for an undulator for a hybrid insertion light source. In FIG. 4, reference numeral 110 denotes a permanent magnet, and 112 denotes a magnetic pole. Permanent magnet 110 and magnetic pole 1
12 are alternately combined and arranged, and a pair of magnet rows having both ends ending with the magnetic pole 112 are provided to face each other with a certain magnetic pole interval. The arrow shown on the permanent magnet 110 indicates the magnetic direction. Usually, each magnetic pole 112 has substantially the same shape, and the permanent magnets 110 have the same shape except for those at both ends. In a normal insertion light source, one permanent magnet 114 disposed at both ends of the magnetic field generator is substantially half as high as the other permanent magnets 110 constituting the main part, as shown in FIG. It is configured to be. The other components such as materials and dimensions are as shown in FIG. The unit of the dimension is mm. The magnetic field generator configured as described above generates a periodic magnetic field in the direction of the magnet row. The central axis of the so-called magnetic circuit of this magnetic field generator is a permanent magnet 110 and a magnetic pole 11 in a direction orthogonal to the direction of the magnet row, that is, in the x-axis direction shown in FIG.
2 is an axis extending substantially half way along its length and in the direction of the magnet row. The axis coinciding with the center axis of this magnetic circuit is z
Axis, and the direction shown in FIG.
Axis. In FIG. 4, electrons inserted on the z-axis from the left end of the magnetic field generator move on an electron trajectory meandering in the zx plane due to the periodic magnetic field generated by the magnetic field generator, and Released from the right end. At this time, the emitted light is emitted along the orbit axis of the electron by the electron moving in the meandering electron orbit.

FIG. 5 shows an electron trajectory when the magnetic field generator shown in FIG. 4 is used. In FIG. 5, the horizontal axis indicates the z-axis direction, and the vertical axis indicates the x-axis direction. A line parallel to the z-axis passing through 0 on the vertical axis corresponds to the z-axis (central axis of the magnetic circuit) in FIG. As described above, in a normal insertion light source, the height of the permanent magnets 114 at both ends of the magnetic field generator, which is a magnetic circuit, is reduced to half that of the permanent magnets 110 of the main part, and the volume of the permanent magnets 114 is reduced. By halving 110, electrons inserted on the z-axis at the left end entrance of the magnetic field generator are displaced in the x-axis direction at the entrance of the magnetic field generator, but are displaced again at the exit. The trajectory almost returns to the original trajectory on the z-axis. The purpose of restoring the electron trajectory is to facilitate electron collection and the like.

[0005] As shown in FIG. 5, after being displaced at the entrance, the electrons travel while performing substantially sinusoidal vibration in the substantially x-axis direction by the periodic magnetic field generated by the magnetic field generator. The average position of the trajectory in which electrons move with substantially sinusoidal oscillation is called the electron trajectory axis. As can be seen from FIG. 5, since the electron orbit axis in the magnetic field is displaced from the central axis of the magnetic circuit (the z-axis of the horizontal line passing through 0 in FIG. 5), the radiation emitted along the electron orbit axis is magnetic. It will deviate from the circuit center axis. Since the magnetic field strength, that is, the magnetic flux density integrated twice along the z-axis corresponds to the electron orbit, the vertical axis of the graph shown in FIG. G · cm
The size of the double integration value of the magnetic flux density, expressed in ² units is shown.

The magnetic field generator shown in FIG. 4 can change the magnetic field intensity on the electron orbit axis by changing the magnetic pole interval in FIG. 4 to obtain emitted light of various wavelengths. In that case, the position in the x-axis direction of the optical axis of the emitted light substantially coincident with the electron orbit axis and the inclination in the z-x plane, that is, z
It is desirable that the angular displacement with respect to the axis be unchanged. That is, it is desirable that the position of the electron orbit axis does not change even if the magnetic pole interval is changed. In the pure insertion light source described above, “Pure Permanent Magnet” is used.
End-Configurations ", B. Di
viacco and R.A. P. Walker, SINCRO
TRON TRIESTE, internal rep
ort, ST / M-TN-92 / 5 already shows an undulator magnetic circuit in which the position and inclination of the optical axis of the emitted light do not change.

[0007]

However, FIG. 5 showing the electron trajectory of a magnetic field generator for an undulator of a conventional hybrid insertion light source is shown in FIG.
When the distance is changed to 0 mm, the displacement of the electron orbital axis changes, indicating that the electron orbital axes do not match. in this way,
The magnetic field generator used for the undulator of the conventional hybrid insertion light source does not pay attention to the displacement of the electron orbit axis, and if the magnetic field strength changes by changing the magnetic pole interval, the displacement amount of the electron orbit axis does not change Did not get. For this reason, for example, a sample placed on an optical path in an experimental station for X-ray crystal analysis or the like has to change its position in accordance with a change in the magnetic pole interval. Was a problem.

Accordingly, the present invention provides a magnetic field generator used in an undulator for a hybrid insertion light source for generating radiation light or generating a free electron laser,
It is an object of the present invention to provide a magnetic field generator in which the position and inclination of the optical axis of the emitted light do not change even if the magnetic pole interval is changed to obtain emitted light of various wavelengths.

[0009]

In order to achieve the above-mentioned object, a magnetic field generator of the present invention used in an undulator for a hybrid insertion light source comprises a pair of permanent magnets and magnetic poles periodically combined. A magnet row is provided to face each other, and at least two permanent magnets and at least two magnetic poles are further alternately arranged at both ends of each of the pair of magnet rows, and the at least two permanent magnets are arranged. Is
The intensity of the magnetic field generated by the pair of magnet rows along the central axis of the magnetic circuit in a direction along the magnet rows;
It is characterized in that it has a shape and dimensions and is arranged such that the integration value generates a magnetic field distribution that is a single oscillation centered on a zero value at a main portion except for the end of the magnet row.

That is, according to the present invention, the shape, size and arrangement of at least two permanent magnets at the ends of the magnetic circuit corresponding to the entrance and exit of the electrons are adjusted, and the main part of the magnetic field excluding the end of the magnetic field generator has a magnetic field of two. The present inventors have found a magnet configuration in which the central axis of the integration value, that is, the electron orbit axis coincides with the central axis of the magnetic circuit, and the electron orbit axis does not move even if the magnetic pole interval is changed. That is, the above problem is solved by optimizing the magnetic field distribution at both ends of the magnetic circuit.

[0011]

In a periodic magnetic field close to a sine wave, the electron trajectory also becomes close to a sine wave, and the position of the orbital axis of the meandering electron in the x-axis direction and the angular deviation from the z-axis direction in the zx plane. The slope is determined by the entrance field until the field reaches a sine wave. Therefore, by finely adjusting the shape, size, and arrangement position of at least two permanent magnets near the entrance forming the entrance magnetic field, the electron orbit axis can be corrected and made to coincide with the central axis of the magnetic circuit. The electron orbit is represented by integrating the value of the magnetic field, that is, the value of the magnetic flux density of the magnetic field twice along the center axis of the magnetic circuit. If the value becomes a simple oscillation centering on the zero value, in that state,
The electron trajectory meanders on the center axis of the magnetic circuit.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows an embodiment of the present invention of a magnetic field generator used in an undulator for a hybrid insertion light source for generating radiation light or generating a free electron laser, only for an upper row of magnets. It is sectional drawing. In FIG. 1A, the lower magnet row is
It is omitted because it has the same configuration as the upper one. (A) of FIG.
In the magnetic field generator, the magnet array includes an inlet 10 provided on the side where electrons are inserted, a main portion 12 in which electrons are meandered by being sine-wave oscillated, and an outlet where electrons are emitted. And fourteen. The entrance 10
Two magnetic poles 20 and two permanent magnets 22, 24 are alternately arranged in this order from the side where electrons are inserted. The main part 12 includes a plurality of magnetic poles 26 and permanent magnets 28 which are alternately arranged in this order from the inlet part 10 toward the outlet part 14 so that the number of cycles becomes 52 in the entire magnet row described later.
It is arranged to end with. In the outlet section 14, two permanent magnets 30, 32 and two magnetic poles 34 are alternately arranged in this order toward the side from which electrons are emitted from the main section 12. The arrows shown in FIG. 1A for the permanent magnets 22, 24, 28, 30, and 32 indicate the direction of magnetism.

One cycle of a periodic magnetic field in the z-axis direction is formed by two permanent magnets and two magnetic poles alternately arranged in these order. As will be described later, the permanent magnets 22 and 24 of the inlet 10 and the permanent magnets 30 and 3 of the outlet 14 are provided.
2 is different from the width of the permanent magnet 28 of the main part 12, the period length of the magnetic field of the inlet 10 and the outlet 14 is different from that of the main part 12.

FIG. 1B shows the detailed dimensions of the magnetic pole 26 and the permanent magnet 28 provided on the main part 12. The unit of the dimension shown in FIG. 1 and the unit of the period length λ _u in the main part 12 are mm. The material is permanent magnet 2
For 2, 24, 28, 30, and 32, Nd-Fe-
B (Br = 12.1 kG), and the magnetic poles 20, 26 and 34 are vanadium permendas having high permeability and high saturation magnetic properties. Permanent magnet 28 and magnetic pole 26 of main part 12
Has a wedge shape as shown in the figure, and both are nested.
The shape and dimensions of the permanent magnets 28 are the same, and the shapes and dimensions of the magnetic poles 26 are the same as those of the inlet 10 and the outlet 14.
Are identical except for the magnetic pole 26 adjacent to each of them. Regarding the shape and dimensions of the magnetic poles 26 adjacent to the inlet 10 and the outlet 14, respectively, except that the side surfaces adjacent to the permanent magnets 24 and 30 having a rectangular cross-sectional shape are not inclined but parallel to the y-axis. , Are substantially the same as the other magnetic poles 26. The positions of the top surfaces of the permanent magnets 28 perpendicular to the y-axis are all at the same height, and the top surfaces of the magnetic poles 26 perpendicular to the y-axis are all 6.5 mm below the top surface of the permanent magnet 26. is there.

The two magnetic poles 20 of the inlet 10 and the outlet 14
Both of the two magnetic poles 34 have the same shape and dimensions. Further, the permanent magnets 22 of the inlet 10 and the outlet 14,
Since the cross-sectional shapes of the sections 24, 30 and 32 are rectangular, the magnetic poles 20, 34 of the entrance section 10 and the exit section 14 adjacent thereto are also rectangular, so that the main section 1
2 and slightly different in shape and size (note that y
The magnetic poles 20, 34 of the inlet 10 and the outlet 14 may be regarded as substantially the same as the magnetic pole 26 of the main part 12. For example, the present invention relates to the main part 12
Naturally, the sectional shape of the permanent magnet 28 and the magnetic pole 26 can be applied to a rectangular shape as in the prior art shown in FIG. 1, but in that case, the same shape and size are used for the magnetic poles in each case. .

In this embodiment, the permanent magnet (M1) 2
4 have the values shown in FIG. 1, and the dimensions of the permanent magnet 30 are the same as those of the permanent magnet 24. The dimensions of the permanent magnet (M2) 22 have the numerical values shown in FIG. 1, and the dimensions of the permanent magnet 32 are the same as those of the permanent magnet 22.

The positions of the top surfaces of the magnetic poles 20 and 34 orthogonal to the y-axis are the same as those of the top surface of the magnetic pole 26. Entrance 10
Permanent magnets 22, 24 and the permanent magnet 30,
32, the position of the top surface perpendicular to the y-axis is
Of the top surface of the permanent magnet 28 of FIG.

In the case of the configuration of the magnetic field generator described above with reference to FIG. 1, the gap between the magnetic poles (gap) is set to 15 mm and 20 mm by an existing calculation method using a computer based on the law of electromagnetism. calculated magnetic field strength i.e. the magnetic flux density B _y when the FIG further the magnetic flux density B _y result of integrating twice along the magnetic circuit center axis (z-axis) with respect to, the displacement of the corresponding electronic orbital axis to it 2 and FIG. FIG. 2 shows the case where the magnetic pole interval is 15 mm, and FIG. 3 shows the case where the magnetic pole interval is 20 mm. 2 and 3
As can be seen from FIG.
Has changed, so that the amplitude of the second integral (ie, representing the electron orbit) has changed, but the electron orbit axis does not change and coincides with the central axis of the magnetic circuit. Therefore, in the hybrid insertion light source in which the magnetic field generator shown in FIG. 1 is applied to the undulator, the position and inclination of the optical axis of the emitted light do not change in the range of the magnetic pole interval of 15 to 20 mm.

As described above, the preferred embodiment has been described in detail by way of example in which the present invention is applied to a wedge-shaped cross section of the permanent magnet and the magnetic pole of the main part 12. Indicates that the invention can be applied to such a special shape, and can also be applied to a permanent magnet and a magnetic pole having a rectangular cross-sectional shape used in the conventional magnetic field generator shown in FIG. Needless to say, The present invention is not limited to a specific shape of the sectional shape of the permanent magnet and the magnetic pole of the main part 12.

In the above embodiment, the number of the permanent magnets and the number of the magnetic poles in the inlet portion 10 or the outlet portion 14 is two. However, the present invention is not limited to two, and the number may be larger. May be used. Further, the present invention provides a shape of the permanent magnet at the entrance 10 or the exit 14,
The dimensions or the arrangement position are not limited to those in the above embodiment.

[0022]

According to the present invention, as described above, in a hybrid insertion light source that generates a higher magnetic field strength than a pure type, the electron orbit is changed by changing the magnetic pole interval in order to change the wavelength of emitted light. Even when the intensity of the magnetic field is changed, the center axis of the meandering trajectory of electrons, that is, the electron trajectory axis does not move, so that it is possible to obtain radiation light in which the optical axis does not shift.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing an embodiment of the present invention of a magnetic field generator used for an undulator for a hybrid insertion light source for generating synchrotron radiation or generating a free electron laser only with respect to an upper magnet row. is there.

In the magnetic field generating apparatus shown in FIG. 1. FIG, a diagram showing the calculation results of the magnetic flux density B _y and double integration i.e. electron orbit thereof generated along the magnetic circuit center axis when the pole spacing 15mm is there.

In the magnetic field generating apparatus shown in FIG. 3 FIG. 1, a diagram showing the calculation results of the magnetic flux density B _y and double integration i.e. electron orbit thereof generated along the magnetic circuit center axis when the pole spacing 20mm is there.

FIG. 4 is a diagram schematically illustrating an example of a conventional magnetic field generator used in an undulator for a hybrid insertion light source.

FIG. 5 is a diagram showing an electron trajectory when the conventional magnetic field generator shown in FIG. 4 is used.

[Explanation of symbols]

 10: Inlet part 12: Main part 14: Outlet part 20, 26, 34: Magnetic pole 22, 24, 28, 30, 32: Permanent magnet

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-269700 (JP, A) JP-A-4-134299 (JP, A) JP-A-6-140195 (JP, A) JP-A-6-140195 203997 (JP, A) JP-A-6-204900 (JP, A) JP-A-6-188096 (JP, A) JP-A-5-343200 (JP, A) JP-A-6-188100 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05H 7/04 G21K 1/093 H05H 13/04

Claims (1)

(57) [Claims] 1. A magnetic field generator for use in an undulator for a hybrid insertion light source, wherein a pair of magnet rows, which periodically combines a plurality of permanent magnets and magnetic poles, are provided to face each other. , At least two permanent magnets and at least two magnetic poles are further alternately arranged at both ends of each of the pair of magnet rows,
The at least two permanent magnets each have a twice integral value of the strength of the magnetic field generated by the pair of magnet rows along a central axis of a magnetic circuit in a direction along the magnet rows . magnetic field generating system characterized in that it is has a shape and dimensions that occur a single vibration becomes magnetic field distribution around the zero value at the portion sandwiched between the ends and arranged.